Ongoing tardigrade antimicrobial peptide research is supported by intramural funding from the Midwestern University Office of Research and Sponsored Programs (ORSP). The ORSP had no role in study design, data collection, analysis, interpretation, or manuscript preparation.

1. Determine the Defining Features of the Protein Group of Interest
<ol>
	<li>Consult previous publications to determine if there is a consensus regarding the features that are necessary to be considered part of the group. Take note of any inconsistencies or differences in opinion between research groups, and include characteristics that may serve to differentiate one subgroup from another.</li>
	<li>If previous literature does not address defining characteristics, use sequences that are considered representative of the group as a starting point to identify conserved features.</li>
</ol>
2. Collect Relevant Sequences
<ol>
	<li>If reviews have been written that include analyses of sequences that are representing the group, include these sequences in the raw dataset. Retrieve sequences using accession numbers referenced in the literature and save in a standard sequence editing program (e.g., EditSeq in the Lasergene suite or one of many available for free online).</li>
	<li>If the group in question has been defined in one of the structural databases, include the sequences the database lists as being part of the group.&#160;Retrieve sequences using accession numbers provided in the database and save in a standard sequence editing program, as above. 
	NOTE: For example, the sequences categorized in the CS-&#945;&#946; (scorpion toxin-like) superfamily in the SCOP database can be found here: http://scop.mrc-lmb.cam.ac.uk/scop/data/scop.b.h.c.h.html.&#160;</li>
	<li>Perform Basic Local Alignment Search Tool (BLAST)14 searches of public, online databases available through the National Center for Biotechnology Information (NCBI) to find sequences that may have not been included in the literature or structural databases. For the most complete results, use both the protein BLAST (blastp) and translated blast with protein query (tblastn) programs; these are both available at: https://blast.ncbi.nlm.nih.gov/Blast.cgi.
	<ol>
		<li>Use sequences known to be part of the group of interest as query sequences. Copy and paste the sequence into the search box at the top, or provide a GenBank accession number or gi identifier, if available.</li>
		<li>Choose the database from the dropdown menu. Choose non-redundant protein sequences (nr) for blastp and expressed sequence tags for tblastn.</li>
		<li>Search for results in specific taxa in the organism setting by typing the organism or taxon name and choosing from the list that appears while typing. To add additional organisms or taxa to exclude, click the &#34;+&#34; button and another field will appear. Exclude any unwanted taxa in the organism box by typing the organism or taxon name, choosing from the list that appears while typing, and checking the &#34;Exclude&#34; box on the right.</li>
		<li>Access additional parameters by clicking on &#34;Algorithm parameters&#34; near the bottom of the page. Leave at default unless there is a rationale for changing a parameter.</li>
		<li>Click the &#34;BLAST&#34; button to run the analysis; it may take some time for the results to appear. In general, retrieve hits with an expect value (or e-value) of &#34;-05&#34; or better and save in a standard sequence editing program.
		<ol>
			<li>If all hits are above this threshold, rerun the search with an increased number of target sequences (in the algorithm parameters section) to obtain all relevant sequences.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>If necessary, trim the sequences to exclude irrelevant information (e.g., the CS-&#945;&#946; fold only applies to the mature peptide). Identify signal peptides and pro-peptides for removal using ProP15 (available online), or SignalP for more sophisticated signal peptide prediction16 (available online).</li>
</ol>
3. Generate a Reference in a Spreadsheet Based on the Important Features That Were Identified
<ol>
	<li>Identify the defining characteristics of the group of interest. For example, use the CS-&#945;&#946; fold definitively established by the solution structure of insect defensin A from Phormia terraenovae (Figure 1)8.
	<ol>
		<li>This fold includes a smaller motif called the cysteine-stabilized helix (CSH)17; identify this motif by a CXXXC (where X is any amino acid) upstream of a CXC that form two disulfide bonds (Figure 1, solid pink lines). 
		NOTE: To complete the CS-&#945;&#946; motif, a third disulfide bond is formed from additional cysteines placed before each half of the CSH motif (Figure 1, dotted pink lines).</li>
	</ol>
	</li>
	<li>Enter these defining features into a spreadsheet. See Figure 2.
	<ol>
		<li>Use columns for the conserved features and to represent the spaces between these features. Keep the columns wide enough to fit numbers and ensure that they have a consistent width. Set the width using the &#34;Format| Column Width&#34; function (Figure 2, pink arrow).</li>
		<li>Use the rows for the sequence names.</li>
		<li>When a sequence has the feature, fill in the box using the fill function (Figure 2, pink square). For spacing between features, enter the number of amino acids in the box between and leave it unfilled. For example, using the insect defensin sequence gives a reference that includes six cysteines, with defined spacings between C2 and C3 and between C5 and C6.</li>
	</ol>
	</li>
	<li>Add representative sequences that have been previously established as members of the group based on the structural databases and literature. 
	NOTE: For example, previous literature and the SCOP database identify several groups for inclusion: insect defensins, short-chain scorpion toxins, long-chain scorpion toxins, MGD-1, plant defensins, nematode ABFs, drosomycins from Drosophila, and macins. The literature also identifies a bacterial sequence with only four cysteines that might represent the ancestor of this superfamily18. Adding these sequences increases the number of cysteines in the reference from six to ten but maintains the alignment of the important structural features (Figure 3).
	<ol>
		<li>To add a feature that is likely to define a subgroup of sequences (for example, an extra cysteine), use the &#34;Insert&#34; function (Figure 3, pink arrow).</li>
		<li>If there are features missing from a given sequence, leave the box unfilled and combine it with boxes representing intervening amino acids. If necessary, merge the cells using the merge and center feature (Figure 3, pink box).</li>
	</ol>
	</li>
	<li>Continue adding sequences to the groups to gain a better picture of the variation in each group of the larger superfamily. Summarize the group characteristics to facilitate comparisons (Figure 4).
	<ol>
		<li>When the number of amino acids between major features varies, use a hyphen to indicate a range, such as 6 - 12 (6 to 12 amino acids), and a slash to indicate either/or, such as 7/10 (7 or 10 amino acids).</li>
		<li>Choose a way to annotate features of sequences that may be relevant but do not occur often enough to include in the reference. For example, since cysteines are important in this superfamily, label additional cysteines (Figure 4, pink boxes).</li>
	</ol>
	</li>
	<li>Add newly-identified sequences to the spreadsheet using the established sequences as a guide. For example, adding sequences from tardigrades (yellow) shows that the tardigrade sequences fall into several different groups of the superfamily (Figure 5 shows summaries instead of a row per sequence for space purposes).</li>
	<li>Show variability within a taxonomic group by rearranging the rows (Figure 6).</li>
</ol>
4. Use the Reference to Refine Amino Acid Alignments
NOTE: There are many programs that can be used for multiple sequence alignments, but this demonstration will use Molecular Evolutionary Genetics Analysis (MEGA6)19 because it is available to download for free.
<ol>
	<li>Download and install the software.</li>
	<li>Begin a new alignment in MEGA by selecting &#34;Edit/Build Alignment&#34; under the Align tab. Select &#34;Create a new alignment&#34; in the box that appears and click &#34;OK.&#34; Then select &#34;Protein.&#34;</li>
	<li>Select &#34;Insert Sequence from File&#34; in the &#34;Edit&#34; menu to import the sequences. 
	NOTE: Sequences will need to be in FASTA format for import into MEGA. Background colors that reflect different amino acid types are used by default, but this option can be turned off under the &#34;Display&#34; menu.</li>
	<li>Once all sequences are entered, click the flexing arm icon and then &#34;Align Protein&#34; to align the sequences using the MUSCLE algorithm20. 
	NOTE: ClustalW is also available.
	<ol>
		<li>If a message saying that nothing has been selected pops up and asks to select all, click &#34;OK.&#34;</li>
		<li>NOTE: This opens a window that allows one to change some parameters, but they should only be changed there is reason to do so. This analysis uses a subset of the sequences analyzed in a previous paper12.</li>
	</ol>
	</li>
	<li>Check the alignment based on the important features; note that the top bar above the sequences will show any columns where the amino acid is completely conserved (*). See Figure 7. See that the initial alignment shows only three of the four conserved cysteines (Figure 7, pink boxes); looking down the column, the AlCRP sequence is clearly misaligned (Figure 7, pink arrow).</li>
	<li>To get rid of the large gap between the I and the conserved C, highlight the dashes and press the &#34;delete&#34; key. Do not highlight any amino acids, or they will be deleted as well.</li>
	<li>To move amino acids to the right, highlight and press the space bar.
	<ol>
		<li>Note that the AlCRP now has the structural cysteines aligned and that the last C of the CXXXC motif is conserved throughout the alignment (Figure 8). Adjust the alignment as necessary to prioritize the most important features of the sequences.</li>
	</ol>
	</li>
</ol>
5. Compare the Groups Identified Using the Reference with Results from Phylogenetic Analyses
<ol>
	<li>From preliminary alignments, determine which sequences should be included in a phylogenetic analysis; for a small number of sequences, this step may be unnecessary.
	<ol>
		<li>Keep an alignment file that includes all sequences, but for a phylogenetic analysis, remove redundant sequences (Figure 9, pink boxes show pairs of redundant sequences).</li>
		<li>If the data set includes a large number of sequences, run a preliminary analysis and select representatives from groups that always form a clade.</li>
	</ol>
	</li>
	<li>Determine the best amino acid substitution model.
	<ol>
		<li>Export the alignment in MEGA format (under the data tab).</li>
		<li>Go to the Models menu and select &#34;Find Best DNA/Protein Model.&#34; Choose the file just saved and open it; this will open a window that has some parameters that can be changed.</li>
		<li>Use the default parameters unless there is a reason to change them. Click &#34;Compute&#34; to begin the analysis.</li>
	</ol>
	</li>
	<li>Run a maximum likelihood (ML) analysis in MEGA.
	<ol>
		<li>Choose &#34;Construct/Test Maximum Likelihood Tree&#34; from the Phylogeny menu.</li>
		<li>Choose the model determined to be the best fit for the data from step 5.2 (the output will give the substitution model as well as the best &#34;rates among sites&#34; parameter).</li>
		<li>Choose 1,000 bootstrap replicates to obtain the measures of support for the tree.</li>
		<li>Click &#34;Compute&#34; to run the analysis; MEGA has a &#34;Tree Explorer&#34; to visualize the tree.</li>
	</ol>
	</li>
	<li>Run a Bayesian analysis in MrBayes open-source software21. 
	NOTE: A MrBayes manual is also available from this site. This is intended to provide basic steps and is not a comprehensive guide to conducting Bayesian phylogenetic analysis.
	<ol>
		<li>Export the MEGA alignment in PAUP (Nexus) format to the same folder as the MrBayes program.</li>
		<li>Open MrBayes and type &#34;exe Filename&#34; (e.g., &#34;exe Alignment.nex&#34;).</li>
		<li>Specify the model and analysis parameters. Choose either the model specified in step 5.2 or choose the &#34;mixed&#34; setting that will try various models and report the frequency of the model in the trees with the best posterior probabilities (prset aamodelpr=mixed). Type &#34;showmodel&#34; to report the current model settings and &#34;help mcmc&#34; to show current parameter settings, with a brief explanation of each.</li>
		<li>Set the number of generations using the &#34;mcmcp ngen=&#34; command (1 million is typical).</li>
		<li>Type &#34;mcmc&#34; to begin the analysis.</li>
		<li>When the number of generations has completed, the program will ask to add more generations. If the average standard deviation of split frequencies is less than 0.1, type no. If it is above 0.1, the analysis should be allowed to continue, or some parameters should be changed (see the manual).</li>
		<li>Use the &#34;sumt&#34; command to generate the tree files.</li>
		<li>After the analysis is complete and a consensus tree is generated, the tree can be viewed in FigTree (available online).</li>
	</ol>
	</li>
	<li>Compare the trees to see if the methods generate consistent results. 
	NOTE: Some sequences do not provide a lot of information: the trees may not be well resolved and the branches may have minimal support (Figure 10).</li>
	<li>Compare trees to the groups identified using the reference to see if the phylogenetic analyses support these groups.</li>
</ol>

<ol>
	<li>Matsuyama, K., Natori, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Purification+of+Three+Antibacterial+Proteins+from+the+Culture+Medium+of+NIH-Sape-4,+an+Embryonic+Cell+Line+of+Sarcophaga+peregrina.">Purification of Three Antibacterial Proteins from the Culture Medium of NIH-Sape-4, an Embryonic Cell Line of Sarcophaga peregrina.</a> J Biol Chem. 263 (32), 17112-17116 (1988).</li><li>Lambert, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Insect+immunity:+Isolation+from+immune+blood+of+the+dipteran+Phormia+terranovae.+of+two+insect+antibacterial+peptides+with+sequence+homology+to+rabbit+lung+macrophage+bactericidal+peptides.">Insect immunity: Isolation from immune blood of the dipteran Phormia terranovae. of two insect antibacterial peptides with sequence homology to rabbit lung macrophage bactericidal peptides.</a> PNAS. 86 (262-266), (1989).</li><li>Dimarcq, J. -. L., Bulet, P., Hetru, C., Hoffmann, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cysteine-rich+antimicrobial+peptides+in+invertebrates.">Cysteine-rich antimicrobial peptides in invertebrates.</a> Biopolymers. 47, 465-477 (1998).</li><li>Shafee, T. M. A., Lay, F. T., Hulett, M. D., Anderson, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Defensins+Consist+of+Two+Independent,+Convergent+Protein+Superfamilies.">The Defensins Consist of Two Independent, Convergent Protein Superfamilies.</a> Mol Biol Evol. 33 (9), 2345-2356 (2016).</li><li>Zhu, S., Gao, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nematode-derived+drosomycin-type+antifungal+peptdies+provide+evidence+for+plant-to-ecdysozoan+horizontal+transfer+of+a+disease+resistance+gene.">Nematode-derived drosomycin-type antifungal peptdies provide evidence for plant-to-ecdysozoan horizontal transfer of a disease resistance gene.</a> Nat Commun. 5, (2014).</li><li>Zhu, S., Gao, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evolutionary+origin+of+b-defensins.">Evolutionary origin of b-defensins.</a> Dev. Comp. Immunol. 39, 79-84 (2013).</li><li>Bonmatin, J. -. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two-dimensional+1H+NMR+study+of+recombinant+insect+defensin+A+in+water:+Resonance+assignments,+secondary+structure+and+global+folding.">Two-dimensional 1H NMR study of recombinant insect defensin A in water: Resonance assignments, secondary structure and global folding.</a> J Biomol NMR. 2 (3), 235-256 (1992).</li><li>Cornet, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Refined+three-dimensional+solution+structure+of+insect+defensin+A.">Refined three-dimensional solution structure of insect defensin A.</a> Structure. 3 (5), 435-448 (1995).</li><li>Murzin, A. G., Brenner, S. E., Hubbard, T., Chothia, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=SCOP:+a+structural+classification+of+proteins+database+for+the+investigations+of+sequences+and+structures.">SCOP: a structural classification of proteins database for the investigations of sequences and structures.</a> J Mol Biol. 247, 536-540 (1995).</li><li>Sillitoe, I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CATH:+comprehensive+structural+and+functional+annotations+for+genome+sequences.">CATH: comprehensive structural and functional annotations for genome sequences.</a> Nucleic Acids Res. 43, 376-381 (2015).</li><li>Lam, S. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gene3D:+expanding+the+utility+of+domain+assignments.">Gene3D: expanding the utility of domain assignments.</a> Nucleic Acids Res. 44, 404-409 (2016).</li><li>Tarr, D. E. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Establishing+a+reference+array+for+the+CS-ab+superfamily+of+defensive+peptides.">Establishing a reference array for the CS-ab superfamily of defensive peptides.</a> BMC Res Notes. 9, 490 (2016).</li><li>Shafee, T. M. A., Robinson, A. J., van der Weerden, N., Anderson, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structural+homology+guided+alignment+of+cysteine+rich+proteins.">Structural homology guided alignment of cysteine rich proteins.</a> SpringerPlus. 5 (27), (2016).</li><li>Altschul, S. F., Gish, W., Miller, W., Myers, E. W., Lipman, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Basic+Local+Alignment+Search+Tool.">Basic Local Alignment Search Tool.</a> J Mol Biol. 215 (3), 403-410 (1990).</li><li>Duckert, P., Brunak, S., Blom, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prediction+of+proprotein+convertase+cleavage+sites.">Prediction of proprotein convertase cleavage sites.</a> Protein Eng Des Sel. 17 (1), 107-112 (2004).</li><li>Petersen, T. N., Brunak, S., von Heijne, G., Nielsen, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=SignalP+4.0:discriminating+signal+peptides+from+transmembrane+regions.">SignalP 4.0:discriminating signal peptides from transmembrane regions.</a> Nat Methods. 8, 785-786 (2011).</li><li>Kobayashi, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+cysteine-stabilized+a-helix:+A+common+structural+motif+of+ion-channel+blocking+neurotoxic+peptides.">The cysteine-stabilized a-helix: A common structural motif of ion-channel blocking neurotoxic peptides.</a> Biopolymers. 31, 1213-1220 (1991).</li><li>Gao, B., del Carmen Rodriguez, M., Lanz-Mendoza, H., Zhu, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=AdDLP,+a+bacterial+defensin-like+peptide,+exhibits+anti-Plasmodium.+activity.">AdDLP, a bacterial defensin-like peptide, exhibits anti-Plasmodium. activity.</a> Biochem Biophys Res Commun. 387, 393-398 (2009).</li><li>Tamura, K., Stecher, G., Peterson, D., Filipski, A., Kumar, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MEGA6:+Molecular+Evolutionary+Genetics+Analysis.">MEGA6: Molecular Evolutionary Genetics Analysis.</a> Mol Biol Evol. 30 (12), 2725-2729 (2013).</li><li>Edgar, R. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MUSCLE:+multiple+sequence+alignment+with+high+accuracy+and+high+throughput.">MUSCLE: multiple sequence alignment with high accuracy and high throughput.</a> Nucleic Acids Res. 32 (5), 1792-1797 (2004).</li><li>Ronquist, F., Huelsenbeck, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MrBayes+3:+Bayesian+phylogenetic+inference+under+mixed+models.">MrBayes 3: Bayesian phylogenetic inference under mixed models.</a> Bioinformatics. 19 (12), 1572-1574 (2003).</li><li>Altschul, S. F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gapped+BLAST+and+PSI-BLAST:+a+new+generation+of+protein+database+search+programs.">Gapped BLAST and PSI-BLAST: a new generation of protein database search programs.</a> Nucleic Acids Res. 25 (17), 3389-3402 (1997).</li><li>Zhang, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protein+sequence+similarity+searches+using+patterns+as+seeds.">Protein sequence similarity searches using patterns as seeds.</a> Nucleic Acids Res. 26 (17), 3986-3990 (1998).</li></ol>

The author has nothing to disclose.

The criteria for naming a protein within a group should be clear, but this is not always the case. Sequences that have the CS-&#945;&#946; fold have been studied in many labs using a variety of organisms, resulting in different systems of nomenclature, as well as varying levels of characterization. Attempting to impose a completely new nomenclature is not reasonable and would result in a great deal of confusion when consulting previous literature. A reference numbering system can be used in addition to the name of a protein to clarify its characteristics relative to the superfamily. 
Groups of proteins with clear criteria for naming and classification will not likely benefit from generating a reference in a spreadsheet, although it may be useful for summarizing large numbers of sequences and visualizing important characteristics. Sequence alignments and logos are useful for investigating the level of conservation at each site, but do not actively prioritize sequence features important for structure or function. The CS-&#945;&#946; example focused on the structure, but specific amino acids that form a binding site could also be incorporated as a defining feature. As sequence features that confer specific antimicrobial/toxic activities of CS-&#945;&#946; peptides are identified, these could be added to the reference to clarify groups based on activity. Although only the predicted mature peptides were used in this example, if the presence of a signal peptide or pro-peptide is important, that information can be added for each sequence. Specific insertion or deletion events, as well as intron locations, can also be included if they are thought to be informative. An advantage of using MrBayes for the phylogenetic analysis is that it is not limited to molecular data-it can analyze data coding for other characteristics that may have evolutionary importance. These can be coded as present or absent, providing more information than the sequence alone.
Collecting the relevant sequences is a critical step of the protocol. Depending on the scope of the study and the distribution of the group members, this may span broad taxonomical groups. If the goal is to understand an entire group of proteins, consider that some sequences may be found outside the species that they are usually reported from. If a taxon is already well represented and additional sequences are unlikely or redundant, excluding them from the search may be appropriate. A basic rule-of-thumb for retrieving hits in a BLAST search is to use a cutoff of -05 for the e-value. The e-value is the number of hits expected by chance. While this is suitable for some situations, if there is a group of sequences that is highly divergent but shares specific characteristics, it can be less reliable-it may retrieve sequences that are similar but do not have the specific features wanted, and it may not return sequences that have the key characteristics but that are highly divergent. There are some potential ways of addressing this issue. The first is to look at the sequences identified in the search that are below the -05 cut-off to see if they meet the inclusion criteria. Second, if there is enough information, use Position-Specific Iterated BLAST (PSI-BLAST)22 or Pattern-Hit Initiated BLAST (PHI-BLAST)23. PSI-BLAST uses the results from an initial search to generate a new model for the next round and can sometimes find divergent sequences that the initial search did not identify. PHI-BLAST requires a pattern to be submitted along with the query sequence. This restricts the retrieved sequences to those containing the pattern of interest. This tool is especially useful if a motif unique to the group can be clearly identified.
An accurate alignment is critical for phylogenetic analysis; interpretations of trees are only valid if they are generated using good alignment. Using the reference to inform the alignment can help to avoid errors that are only obvious when the structure or activity are considered. Sequence redundancy will need to be defined for the project. Two sequences that seem redundant may not be for phylogenetic purposes if they are from widely divergent taxa or are nearly identical in sequence but have different structural or functional properties. If there is ambiguity regarding which sequences should be included, multiple alignments can be generated and analyzed separately to see how alignment changes impact phylogenetic inferences. The method presented here does not eliminate the need for the manual adjustment of alignments, but it can help to clarify how the sequences should align and could possibly be used in conjunction with a more sophisticated barcoding technique than has been described previously13.
For the reference to be useful, it is important to identify defining characteristics that are not currently obvious from the sequence alone. For example, consider the inability to compare cysteine bonding patterns between sequences with different numbers of cysteines when each sequence is numbered with respect to itself. The goal is to facilitate comparison and discussion, not to add another layer of confusion. This may involve several iterations of the reference and judgment calls in deciding which features to include. It is hoped that adopting a common method of discussing divergent sequences in a group will increase the understanding of the group as a whole.

A protein&#39;s name should reflect is characteristics and relationship to other proteins. Unfortunately, names are generally assigned at the time of discovery and, as research continues, the understanding of the larger context may change. This can lead to multiple names if a protein was independently identified by more than one lab, to changes in nomenclature or in the characteristics thought to be definitive when assigning the name, and to the name no longer sufficiently differentiating the protein from others.
Invertebrate defensins provide a good example of degeneration in nomenclature and classification. The first invertebrate defensins were reported from insects, and the name &#34;insect defensin&#34; was proposed based on the perceived homology to mammalian defensins1,2. The term defensin is still used, even though it is now clear that invertebrate and mammalian defensins do not share a common ancestor3,4. Depending on the species, an invertebrate &#34;defensin&#34; may have six or eight cysteines (that form three or four disulfide bonds) and a variety of antimicrobial activities. To complicate the situation, proteins with the same characteristics as defensins are not always called &#34;defensins,&#34; such as the recently identified cremycins from Caenorhabditis remanei5. In addition, invertebrate big defensins are more likely to be evolutionarily related to vertebrate &#946;-defensins than to other invertebrate defensins6. Despite this, researchers sometimes rely on the name &#34;defensin&#34; when determining which sequences should be included in analyses.
Structural studies revealed the similarity between insect defensins and scorpion toxins7, and the CS-&#945;&#946; fold was subsequently established as the defining structural characteristic of insect defensins8. This fold defines the scorpion toxin-like (CS-&#945;&#946;) superfamily in the Structural Classification of Proteins (SCOP) database9, which currently includes five families: insect defensins, short-chain scorpion toxins, long-chain scorpion toxins, MGD-1 (from a mollusk), and plant defensins. This superfamily is synonymous with the recently described cis-defensins4 and Superfamily 3.30.30.10 in the CATH/Gene 3D database10,11. Studies from a variety of invertebrate taxa, plants, and fungi show that the names of proteins that contain this fold are not clearly related to cysteine number or bonding pattern, antimicrobial activity, or evolutionary history12.
The lack of consistency and clear criteria make it challenging to name and classify newly-identified sequences in this superfamily. A major obstacle to comparing proteins in this superfamily is that cysteines are numbered with respect to each individual sequence (the first cysteine in each sequence is C1), with no way to account for the structural role. This means that only sequences with the same number of cysteines can be compared. There is little sequence conservation other than the cysteines forming the CS-&#945;&#946; fold, which makes alignments and phylogenetic analyses difficult. By developing a numbering system that prioritizes structural features, superfamily sequences can be more easily compared and aligned. Conserved features, as well as those defining subgroups, can be visualized quickly, and new sequences can be more easily placed into the appropriate context.
This paper uses a spreadsheet software (e.g., Excel) to generate a reference numbering system for the CS-&#945;&#946; superfamily. It shows how this clarifies comparisons between sequences and applies it to new CS-&#945;&#946; sequences identified from tardigrades. Using the CS-&#945;&#946; superfamily as an example, the protocol was written to provide guidance when using sequences of interest; however, it is not intended to be specific to this superfamily or to cysteine-rich sequences. This method will likely be most useful for groups of proteins that have been researched independently in divergent taxa and/or have little overall sequence homology, with discrete characteristics that may not be easily recognized by molecular analysis software. This method requires some a priori decisions regarding important features, so it will be of limited utility if no important features have been identified. The primary goal is to show how a simple visualization of the sequence relationships can be achieved. This can then be used to inform sequence alignment and analysis, but if alignment and analysis are the primary goals, a barcode method would be a suitable alternative that has more capacity for automation13. The current method displays the features of each peptide in a linear form, so it will not be helpful for the direct visualization of 3D structure.

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			<td height="42" style="width:216px;height:42px;">BLAST webpage</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td style="width:167px;">https://blast.ncbi.nlm.nih.gov/Blast.cgi</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:216px;height:21px;">EditSeq (Lasergene suite)</td>
			<td style="width:71px;">DNASTAR</td>
			<td style="width:119px;"></td>
			<td style="width:167px;">https://www.dnastar.com/t-allproducts.aspx</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:216px;height:21px;">Excel 2013</td>
			<td style="width:71px;">Microsoft</td>
			<td style="width:119px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="63">
			<td height="63" style="width:216px;height:63px;">FigTree</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td style="width:167px;">&#160;http://tree.bio.ed.ac.uk/software/figtree/</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:216px;height:21px;">MEGA</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td>www.megasoftware.net</td>
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			<td height="42" style="width:216px;height:42px;">MrBayes</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td style="width:167px;">http://mrbayes.sourceforge.net/</td>
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			<td height="42" style="width:216px;height:42px;">SCOP database</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td style="width:167px;">http://scop.mrc-lmb.cam.ac.uk/scop/</td>
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</table>

creating and applying a reference to facilitate the discussion and classification of proteins in a diverse group

Related proteins that have been studied in different labs using varying organisms may lack a uniform system of nomenclature and classification, making it difficult to discuss the group as a whole and to place new sequences into the appropriate context. Developing a reference that prioritizes important sequence features related to structure and/or activity can be used in addition to established names to add some coherency to a diverse group of proteins. This paper uses the cysteine-stabilized alpha-helix (CS-&#945;&#946;) superfamily as an example to show how a reference generated in&#160;spreadsheet software can clarify relationships between existing proteins in the superfamily, as well as facilitate the addition of new sequences. It also shows how the reference can help to refine sequence alignments generated in commonly used software, which impacts the validity of phylogenetic analyses. The use of a reference will likely be most helpful for protein groups that include highly divergent sequences from a broad spectrum of taxa, with features that are not adequately captured by molecular analyses.

Groups of sequences in the CS-&#945;&#946; superfamily reported in the literature are shown in Figure 4. The cysteine pairings based on the numbering for each sequence suggest five basic groups (Table 1, middle column). Group 1 has six cysteines that from three disulfide bonds and includes sequences from insects, arachnids, mollusks, nematodes, and fungi. Groups 2, 3, and 4 have 8 cysteines that form four disulfide bonds. Group 2 includes insect, arachnid, and plant sequences; group 3 includes arachnid, mollusk, and nematode sequences; and group 4 includes sequences from cnidarians, annelids, mollusks, and fungi. Group 5 includes the 10 cysteine macins. Some sequences did not quite fit these patterns but were generally closer to one group than the others.
Groups 1 and 2 seem to share two bonds: C2-C5 and C3-C6; however, beginning the numbering of each sequence with its first cysteine does not acknowledge the structural context of the bonds. C2-C5 in Group 1 sequences forms one of the two bonds in the CSH motif, while C2-C5 in Group 2 sequences forms the final bond needed to stabilize the CS-&#945;&#946; fold. The homologous bond to the Group 1 C2-C5 is Group2 C3-C6, which is not obvious from the numbering. It is also not obvious that in Group 3, the C2-C6 bond plays the same structural role.
Using sequences from the literature generated a reference with a total of ten cysteines. The CSH motif is formed from bonds C3-C8 and C4-C9, with C2-C6 completing the CS-&#945;&#946; fold. Renumbering the cysteine pairs based on the reference numbers clarifies the bonds present in each sequence (Table 1, right column). It is now obvious that all the sequences have C2-C6, C3-C8, and C4-C9, reflecting the structural fold that defines the superfamily. The use of a reference allows for easy comparison between sequences that have inconsistent nomenclature and ambiguous classification criteria. It can also help to identify features that define a subgroup of sequences. For example, the C1-C7 bond may differentiate macins from other superfamily members, making it appropriate to classify sequences with this bond as &#34;macins&#34; rather than &#34;defensins&#34; (Table 1 and Figure 4).
Searches of public online databases revealed sixteen sequences from tardigrades that clearly have the CS-&#945;&#946; fold, eight each from Hypsibius dujardini and Milnesium tardigradum. Four of the new sequences have six cysteines, nine have eight, one has nine, and two have ten. This gives very little information, but by aligning the sequences to the reference, it becomes clear that tardigrade sequences with the same number of cysteines do not always have the structurally-important cysteines at the same place within the sequence (Figure 5 and Figure 6). The alignment with the reference also allows for the inference of bonding patterns (Table 2, inferred bonding patterns shown in parentheses). Some of the tardigrade sequences clearly fit patterns 1 - 4. Others are most similar to the proposed bacterial ancestor, scorpion Cl- toxin, or a family of fungal defensin-like peptides. Pattern 2 may have two subgroups, one represented by scorpion Na+ toxins, drosomycin, and plant defensins, and the other by scorpion Cl- toxins. Further work investigating the function of the tardigrade proteins is needed to determine if some should be considered toxins rather than defensins.
Phylogenetic analyses are often used to study how a group of proteins may have evolved. The sequences in the CS-&#945;&#946; superfamily are generally short and highly divergent; resulting trees are often poorly resolved and offer little insight. Both the ML and Bayesian trees for the subset of sequences analyzed here were poorly resolved, with low support for many clades (Figure 10, Supplementary Files 1 - 4). It is common practice to only show bootstrap levels over 70 (or posterior probabilities over 0.7), but Figure 10 retains all numbers to demonstrate the overall low levels of support. Five groups were supported above 70/0.7 in at least one of the two trees: (a) a 6C and an 8C scorpion toxin; (b) macins; (c) tick and scorpion defensins; (d) plant defensins; and (e) 6C defensins from insects, arachnids, and mollusks. In the ML tree, clade e also includes an 8C toxin and an 8C tardigrade defensin, but support was very low (Figure 10A). In general, these reflect the categories identified using the reference cysteine numbering but also show that sequences with different cysteine numbers within a large taxonomical group may be more closely related than sequences with the same pattern from different groups. While only a small number of sequences were used in this study, a larger analysis of 250 sequences did not eliminate the lack of resolution (Supplementary Files 5 - 8)12. The spreadsheet reference alignment may offer easier visualization of similarities with structural or functional relevance compared to phylogenetic trees.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56107/56107fig1.jpg" /> 
Figure 1: Defining Sequence and Structural Features of the CS-&#945;&#946; Superfamily. Amino acids and 3D structure are color coded: loop (blue), alpha-helix (green), beta-sheets (gold), and disulfide bonds (pink). <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56107/56107fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56107/56107fig2.jpg" /> 
Figure 2: Preliminary Six-cysteine Reference Based on the Sequence of Insect Defensin. Columns indicate the conserved cysteines (C1-C6) and, for the CSH motif, the number of conserved amino acids between the cysteines. The filled boxes indicate that the sequence has the given cysteine and the numbers indicate amino acids between the cysteines. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56107/56107fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/56107/56107fig3.jpg" /> 
Figure 3: Refined Ten-cysteine Reference Based on Representative Sequences from Groups of the CS-&#945;&#946; Superfamily. The columns indicate conserved cysteines and the amino acids between them. Cysteines contributing to the CSH motif (C3, C4, C8, and C9) and to the CS-&#945;&#946; fold (C2 and C6) are labeled. Sequences are color-coded by taxonomic group: Arachnida (light orange), Bacteria (black), Cnidaria (grey), Hexapoda (orange), Mollusca (blue), Nematoda (purple), and Plantae (green). <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56107/56107fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/56107/56107fig4.jpg" /> 
Figure 4: Summary of CS-&#945;&#946; Superfamily Sequences Aligned with Reference by Group Characteristics. The columns indicate conserved cysteines and the amino acids between them. Cysteines contributing to the CSH motif (C3, C4, C8, and C9) and to the CS-&#945;&#946; fold (C2 and C6) are labeled. Sequences are color-coded by taxonomic group: Annelida (dark red), Arachnida (light orange), Bacteria (black), Cnidaria (grey), Fungi (light green), Hexapoda (orange), Mollusca (blue), Nematoda (purple), and Plantae (green). Numbers separated by a dash indicate a range of intervening amino acids; numbers separated by a slash represent either/or. A &#34;C&#34; indicates an additional cysteine that does not occur with enough frequency to warrant addition to the reference. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56107/56107fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/56107/56107fig5.jpg" /> 
Figure 5: Addition of Tardigrade CS-&#945;&#946; Sequences to Superfamily Alignment with Reference by Group Characteristics. The columns indicate conserved cysteines and the amino acids between them. Cysteines contributing to the CSH motif (C3, C4, C8, and C9) and to the CS-&#945;&#946; fold (C2 and C6) are labeled. Sequences are color-coded by taxonomic group: Annelida (dark red), Arachnida (light orange), Bacteria (black), Cnidaria (grey), Fungi (light green), Hexapoda (orange), Mollusca (blue), Nematoda (purple), Plantae (green), and Tardigrada (yellow). Numbers separated by a dash indicate a range of intervening amino acids; numbers separated by a slash represent either/or. A &#34;C&#34; indicates an additional cysteine that does not occur with enough frequency to warrant addition to the reference. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56107/56107fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/56107/56107fig6.jpg" /> 
Figure 6: Addition of Tardigrade CS-&#945;&#946; Sequences to Superfamily Alignment with Reference by Taxonomic Group. The columns indicate conserved cysteines and the amino acids between them. Cysteines contributing to the CSH motif (C3, C4, C8, and C9) and to the CS-&#945;&#946; fold (C2 and C6) are labeled. Sequences are color-coded by taxonomic group: Annelida (dark red), Arachnida (light orange), Bacteria (black), Cnidaria (grey), Fungi (light green), Hexapoda (orange), Mollusca (blue), Nematoda (purple), Plantae (green), and Tardigrada (yellow). Numbers separated by a dash indicate a range of intervening amino acids; numbers separated by a slash represent either/or. A &#34;C&#34; indicates an additional cysteine that does not occur with enough frequency to warrant addition to the reference. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56107/56107fig6large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 7" class="xfigimg" src="/files/ftp_upload/56107/56107fig7.jpg" /> 
Figure 7: Misaligned Sequence Using Automated Alignment. Amino acids conserved in all sequences are indicated by * in the row above the first sequence (outlined in pink boxes). AlCRP is misaligned. The gap needs to be removed to correctly align the C (pink arrow). <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56107/56107fig7large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 8" class="xfigimg" src="/files/ftp_upload/56107/56107fig8.jpg" /> 
Figure 8: Manual Refinement of the Alignment Preserves the Structurally Important Features of the Sequences. AlCRP is now aligned correctly (pink arrow), and the CXXXC motif is fully conserved for the sequences (pink boxes). <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56107/56107fig8large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 9" class="xfigimg" src="/files/ftp_upload/56107/56107fig9.jpg" /> 
Figure 9: Redundant Sequences in an Alignment. If there are pairs of nearly identical sequences (pink boxes), one can be removed, since these will likely always cluster together in and contribute little to the overall topology of the tree. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56107/56107fig9large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 10" class="xfigimg" src="/files/ftp_upload/56107/56107fig10.jpg" /> 
Figure 10: Comparison of Trees Generated from Phylogenetic Analyses. (A) Maximum likelihood analysis in MEGA, with 1,000 bootstrap replicates using the WAG+G+I model. (B) Bayesian analysis with 1,000,000 generations using the mixed-model setting. Clades supported at 70/0.7 are shown in solid pink lines; dashed pink lines show clades supported at 70/0.7 in the other tree. (a) A 6C and an 8C scorpion toxin; (b) macins; (c) tick and scorpion defensins; (d) plant defensins; and (e) 6C defensins from insects, arachnids, and mollusks. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56107/56107fig10large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Table 1" src="/files/ftp_upload/56107/56107table1.jpg" /> 
Table 1: Groups within the CS-&#945;&#946; Superfamily Based on Cysteine-pairing Patterns. Five basic patterns of bond formation are shown using internal numbers (middle column) or reference numbers (right column). Scorpion Cl- toxins, ASABF 6Cys-alpha, and a group of fungal peptides are placed with the pattern that most closely matches. A cysteine not included in the reference is indicated by a superscript of the cysteines before/after (e.g., C3/4 is between C3 and C4).
<img alt="Table 2" src="/files/ftp_upload/56107/56107table2.jpg" /> 
Table 2: Addition of Tardigrade CS-&#945;&#946; Sequences to Cysteine-pairing Pattern Groups. Tardigrade defensins and macins (bold) are put into the previously established groups where possible. Some tardigrade sequences may show a group-specific pattern. A cysteine not included in the reference is indicated by a superscript of the cysteines before/after (e.g., C3/4 is between C3 and C4). The notation &#34;2C/1&#34; indicates there are two cysteines upstream of reference C1.
Supplementary File 1 (S1): Alignment of this Dataset in MEGA. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56107/S1_MEGAalignment.mas" target="_blank">Please click here to download this file.</a>
Supplementary File 2 (S2): Maximum-likelihood Tree MEGA File for This Dataset. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56107/S2_MLtree.mts" target="_blank">Please click here to download this file.</a>
Supplementary File 3 (S3): Alignment of This Dataset in Nexus Format for MrBayes. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56107/S3_MrBayesalignment.nexus" target="_blank">Please click here to download this file.</a>
Supplementary File 4 (S4): Consensus File from the MrBayes Analysis of This Dataset. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56107/S4_Consensus_MrBayes.con" target="_blank">Please click here to download this file.</a>
Supplementary File 5 (S5): Alignment of 250 CS-&#945;&#946; Sequences in MEGA. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56107/S5_MEGA_250.mas" target="_blank">Please click here to download this file.</a>
Supplementary File 6 (S6): Maximum Likelihood tree of 250 CS-&#945;&#946; Sequences. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56107/S6_MLtree_250.nwk" target="_blank">Please click here to download this file.</a>
Supplementary File 7 (S7): Alignment of 250 CS-&#945;&#946; Sequences in Nexus Format for MrBayes. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56107/S7_MrBayesalignment_250.nexus" target="_blank">Please click here to download this file.</a>
Supplementary File 8 (S8): Consensus File from the MrBayes Analysis of 250 CS-&#945;&#946; Sequences. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56107/S8_Consensus_MrBayes_250.tre" target="_blank">Please click here to download this file.</a>

Watch this Scientific Journal Video about Creating and Applying a Reference to Facilitate the Discussion and Classification of Proteins in a Diverse Group at JoVE.com

Creating and Applying a Reference to Facilitate the Discussion and Classification of Proteins in a Diverse Group

The goal of this protocol is to develop a reference for divergent proteins in a group that lacks coherent criteria for nomenclature and classification. This reference will facilitate analyses and discussion of the group as a whole and can be used in addition to established names.

Related proteins that have been studied in different labs using varying organisms may lack a uniform system of nomenclature and classification, making it ...

creating-applying-reference-to-facilitate-discussion-classification

Nanyang Technological University

Research

JoVE Journal

Behavior

7.0K Views.  Midwestern University. The goal of this protocol is to develop a reference for divergent proteins in a group that lacks coherent criteria for nomenclature and classification. This reference will facilitate analyses and discussion of the group as a whole and can be used in addition to established names.

Video: Creating and Applying a Reference to Facilitate the Discussion and Classification of Proteins in a Diverse Group

The Crossmodal Congruency Task as a Means to Obtain an Objective Behavioral Measure in the Rubber Hand Illusion Paradigm

The rubber hand illusion (RHI) is a popular experimental paradigm. Participants view touch on an artificial rubber hand while the participants' own hidden hand is touched. If the viewed and felt touches are given at the same time then this is sufficient to induce the compelling experience that the rubber hand is one's own hand. The RHI can be used to investigate exactly how the brain constructs distinct body representations for one's own body. Such representations are crucial for successful interactions with the external world. To obtain a subjective measure of the RHI, researchers typically ask participants to rate statements such as "I felt as if the rubber hand were my hand". Here we demonstrate how the crossmodal congruency task can be used to obtain an objective behavioral measure within this paradigm.
The variant of the crossmodal congruency task we employ involves the presentation of tactile targets and visual distractors. Targets and distractors are spatially congruent (i.e. same finger) on some trials and incongruent (i.e. different finger) on others. The difference in performance between incongruent and congruent trials - the crossmodal congruency effect (CCE) - indexes multisensory interactions. Importantly, the CCE is modulated both by viewing a hand as well as the synchrony of viewed and felt touch which are both crucial factors for the RHI.
The use of the crossmodal congruency task within the RHI paradigm has several advantages. It is a simple behavioral measure which can be repeated many times and which can be obtained during the illusion while participants view the artificial hand. Furthermore, this measure is not susceptible to observer and experimenter biases. The combination of the RHI paradigm with the crossmodal congruency task allows in particular for the investigation of multisensory processes which are critical for modulations of body representations as in the RHI.

We demonstrate how an objective measure can be employed in the widely employed rubber hand illusion paradigm. This measure is obtained by modifying the well-established crossmodal congruency task. This task allows the investigation of multisensory processes which are critical for modulations of body representations as in the rubber hand illusion.

The rubber hand illusion (RHI) is a popular experimental paradigm. Participants view touch on an artificial rubber hand while the participants' own hidden ...

Uncovering Beat Deafness: Detecting Rhythm Disorders with Synchronized Finger Tapping and Perceptual Timing Tasks

A set of behavioral tasks for assessing perceptual and sensorimotor timing abilities in the general population (i.e., non-musicians) is presented here with the goal of uncovering rhythm disorders, such as beat deafness. Beat deafness is characterized by poor performance in perceiving durations in auditory rhythmic patterns or poor synchronization of movement with auditory rhythms (e.g., with musical beats). These tasks include the synchronization of finger tapping to the beat of simple and complex auditory stimuli and the detection of rhythmic irregularities (anisochrony detection task) embedded in the same stimuli. These tests, which are easy to administer, include an assessment of both perceptual and sensorimotor timing abilities under different conditions (e.g., beat rates and types of auditory material) and are based on the same auditory stimuli, ranging from a simple metronome to a complex musical excerpt. The analysis of synchronized tapping data is performed with circular statistics, which provide reliable measures of synchronization accuracy (e.g., the difference between the timing of the taps and the timing of the pacing stimuli) and consistency. Circular statistics on tapping data are particularly well-suited for detecting individual differences in the general population. Synchronized tapping and anisochrony detection are sensitive measures for identifying profiles of rhythm disorders and have been used with success to uncover cases of poor synchronization with spared perceptual timing. This systematic assessment of perceptual and sensorimotor timing can be extended to populations of patients with brain damage, neurodegenerative diseases (e.g., Parkinson&#8217;s disease), and developmental disorders (e.g., Attention Deficit Hyperactivity Disorder).

Behavioral tasks that allow for the assessment of perceptual and sensorimotor timing abilities in the general population (i.e., non-musicians) are presented. Synchronization of finger tapping to the beat of an auditory stimuli and detecting rhythmic irregularities provides a means of uncovering rhythm disorders.

A set of behavioral tasks for assessing perceptual and sensorimotor timing abilities in the general population (i.e., non-musicians) is presented here ...

Using the Threat Probability Task to Assess Anxiety and Fear During Uncertain and Certain Threat

Fear of certain threat and anxiety about uncertain threat are distinct emotions with unique behavioral, cognitive-attentional, and neuroanatomical components. Both anxiety and fear can be studied in the laboratory by measuring the potentiation of the startle reflex. The startle reflex is a defensive reflex that is potentiated when an organism is threatened and the need for defense is high. The startle reflex is assessed via electromyography (EMG) in the orbicularis oculi muscle elicited by brief, intense, bursts of acoustic white noise (i.e., &#8220;startle probes&#8221;). Startle potentiation is calculated as the increase in startle response magnitude during presentation of sets of visual threat cues that signal delivery of mild electric shock relative to sets of matched cues that signal the absence of shock (no-threat cues). In the Threat Probability Task, fear is measured via startle potentiation to high probability (100% cue-contingent shock; certain) threat cues whereas anxiety is measured via startle potentiation to low probability (20% cue-contingent shock; uncertain) threat cues. Measurement of startle potentiation during the Threat Probability Task provides an objective and easily implemented alternative to assessment of negative affect via self-report or other methods (e.g., neuroimaging) that may be inappropriate or impractical for some researchers. Startle potentiation has been studied rigorously in both animals (e.g., rodents, non-human primates) and humans which facilitates animal-to-human translational research. Startle potentiation during certain and uncertain threat provides an objective measure of negative affective and distinct emotional states (fear, anxiety) to use in research on psychopathology, substance use/abuse and broadly in affective science. As such, it has been used extensively by clinical scientists interested in psychopathology etiology and by affective scientists interested in individual differences in emotion.

Potentiation of the startle reflex is measured via electromyography of the orbicularis oculi muscle during low (uncertain) and high (certain) probability electric shock threat in the Threat Probability Task. This provides an objective measure of distinct negative emotional states (fear/anxiety) for research on psychopathology, substance use/abuse, and broad affective science.

Fear of certain threat and anxiety about uncertain threat are distinct emotions with unique behavioral, cognitive-attentional, and neuroanatomical ...

The Modified Hole Board - Measuring Behavior, Cognition and Social Interaction in Mice and Rats

This protocol describes the modified hole board (mHB), which combines features from a traditional hole board and open field and is designed to measure multiple dimensions of unconditioned behavior in small laboratory mammals (e.g., mice, rats, tree shrews and small primates). This paradigm is a valuable alternative for the use of a behavioral test battery, since a broad behavioral spectrum of an animal&#8217;s behavioral profile can be investigated in one single test.
The apparatus consists of a box, representing the &#8216;protected&#8217; area, separated from a group compartment. A board, on which small cylinders are staggered in three lines, is placed in the center of the box, representing the &#8216;unprotected&#8217; area of the set-up. The cognitive abilities of the animals can be measured by baiting some cylinders on the board and measuring the working and reference memory. Other unconditioned behavior, such as activity-related-, anxiety-related- and social behavior, can be observed using this paradigm. Behavioral flexibility and the ability to habituate to a novel environment can additionally be observed by subjecting the animals to multiple trials in the mHB, revealing insight into the animals&#8217; adaptive capacities.
Due to testing order effects in a behavioral test battery, na&#239;ve animals should be used for each individual experiment. By testing multiple behavioral dimensions in a single paradigm and thereby circumventing this issue, the number of experimental animals used is reduced. Furthermore, by avoiding social isolation during testing and without the need to food deprive the animals, the mHB represents a behavioral test system, inducing if any, very low amount of stress.

This protocol describes the modified hole board, which is a behavioral test set-up that comprises the characteristics of an open field and a traditional hole board. This set-up enables the differential analysis of unconditioned behavior of small laboratory mammals as well as the analysis of cognitive abilities.

This protocol describes the modified hole board (mHB), which combines features from a traditional hole board and open field and is designed to measure ...

Applying Stereotactic Injection Technique to Study Genetic Effects on Animal Behaviors

Stereotactic injection is a useful technique to deliver high titer lentiviruses to targeted brain areas in mice. Lentiviruses can either overexpress or knockdown gene expression in a relatively focused region without significant damage to the brain tissue. After recovery, the injected mouse can be tested on various behavioral tasks such as the Open Field Test (OFT) and the Forced Swim Test (FST). The OFT is designed to assess locomotion and the anxious phenotype in mice by measuring the amount of time that a mouse spends in the center of a novel open field. A more anxious mouse will spend significantly less time in the center of the novel field compared to controls. The FST assesses the anti-depressive phenotype by quantifying the amount of time that mice spend immobile when placed into a bucket of water. A mouse with an anti-depressive phenotype will spend significantly less time immobile compared to control animals. The goal of this protocol is to use the stereotactic injection of a lentivirus in conjunction with behavioral tests to assess how genetic factors modulate animal behaviors.

Stereotactic injection of lentiviruses expressing cDNAs or shRNAs can modulate gene expression in specific brain areas of mice. Here, we present a protocol to combine stereotactic injections with behavioral tasks, such as the Open Field Test (OFT) and the Forced Swim Test (FST).

Stereotactic injection is a useful technique to deliver high titer lentiviruses to targeted brain areas in mice. Lentiviruses can either overexpress or ...

The Social Dimension of Stress: Experimental Manipulations of Social Support and Social Identity in the Trier Social Stress Test

In many situations humans are influenced by the behavior of other people and their relationships with them. For example, in stressful situations supportive behavior of other people as well as positive social relationships can act as powerful resources to cope with stress. In order to study the interplay between these variables, this protocol describes two effective experimental manipulations of social relationships and supportive behavior in the laboratory. In the present article, these two manipulations are implemented in the Trier Social Stress Test (TSST)&#8212;a standard stress induction paradigm in which participants are subjected to a simulated job interview. More precisely, we propose (a) a manipulation of the relationship between different protagonists in the TSST by making a shared social identity salient and (b) a manipulation of the behavior of the TSST-selection committee, which acts either supportively or unsupportively. These two experimental manipulations are designed in a modular fashion and can be applied independently of each other but can also be combined. Moreover, these two manipulations can also be integrated into other stress protocols and into other standardized social interactions such as trust games, negotiation tasks, or other group tasks.

Previous research on the social dimension of stress has focused on two important variables: social identity and social support. This protocol introduces an effective experimental manipulation of these two social variables and describes their implementation in a standard stress induction paradigm (Trier Social Stress Test).

In many situations humans are influenced by the behavior of other people and their relationships with them. For example, in stressful situations ...

Psychophysical Tracking Method to Measure Taste Preferences in Children and Adults

The Monell two-series, forced-choice, paired-comparison tracking method provides a reliable measure of sweet taste preferences from childhood to adulthood. The method, which is identical for children, adolescents, and adults, is of short duration (&#60; 15 min), does not rely on sustained attention or place demands on memory (which would yield spurious age differences), and minimizes the impact of language development, making this method amenable to the cognitive limitations of pediatric populations. In this whole-mouth tasting method, subjects are asked to taste (without swallowing) pairs of solutions of different sucrose concentrations and to point to the solution they prefer. Each subsequent pair contains the participant&#39;s preceding preferred concentration and an adjacent stimulus concentration. The procedure continues until the subject chooses either a given concentration of sucrose when paired with both a higher and a lower concentration, or the highest or lowest concentration two consecutive times. Subjects are prevented from reaching response criteria on the basis of first or second position bias by the two-series design of the method, which counterbalances the order of solution presentation within each pair between the series (the weaker concentration is presented first in Series 1, second in Series 2). The geometric mean of the two sucrose concentrations chosen in Series 1 and 2 is an estimate of the participant&#39;s most preferred level of sucrose. Sucrose preference as determined with this laboratory-based measure has been shown to be associated with preference for sugars in foods and beverages and with taste receptor genotype, family history of alcoholism, and race/ethnicity, as well as depressive symptomatology among pediatric populations. The method has real-world relevance and has been applied to determine most preferred level of other tastes (e.g., salt), making it a valuable psychophysical tool.

Sweet taste has powerful hedonic appeal among people of all ages, particularly children. Described herein is a reliable and valid method that can be used to determine the level of sweetness most preferred, making it a valuable psychophysical tool for scientists.

The Monell two-series, forced-choice, paired-comparison tracking method provides a reliable measure of sweet taste preferences from childhood to ...

Behavioral Disturbances: An Innovative Approach to Monitor the Modulatory Effects of a Nutraceutical Diet

In dogs, diets are often used to modulate behavioral disturbances related to chronic anxiety and stress caused by intense and restless activity. However, the traditional ways to monitor behavioral changes in dogs are complicated and not efficient. In the current clinical evaluation, a new, simple monitoring system was used to assess the effectiveness of a specific diet in positively modulating the intense and restless activity of 24 dogs of different ages and breeds. This protocol describes how to easily and rapidly evaluate improvement in a set of symptoms related to generalized anxiety by using a specific sensor, a mobile phone app, a wireless router, and a computer. The results showed that dogs treated with specific diets showed significant improvement in the times spent active and at rest after 10 days (p &lt; 0.01 and p &lt; 0.05, respectively). These dogs also showed an overall significant improvement in clinical and behavioral symptoms. A specific sensor, along with its related hardware, was demonstrated to successfully monitor behavioral changes relating to movement in dogs.

We report a simple approach to evaluate the effectiveness of a specific diet in positively modulating the daily activity and clinical and behavioral symptoms of dogs with evident behavioral disturbances.

In dogs, diets are often used to modulate behavioral disturbances related to chronic anxiety and stress caused by intense and restless activity. However, ...

Using a Virtual Store As a Research Tool to Investigate Consumer In-store Behavior

People&#39;s responses to products and/or choice environments are crucial to understanding in-store consumer behaviors. Currently, there are various approaches (e.g., surveys or laboratory settings) to study in-store behaviors, but the external validity of these is limited by their poor capability to resemble realistic choice environments. In addition, building a real store to meet experimental conditions while controlling for undesirable effects is costly and highly difficult. A virtual store developed by virtual reality techniques potentially transcends these limitations by offering the simulation of a 3D virtual store environment in a realistic, flexible, and cost-efficient way. In particular, a virtual store interactively allows consumers (participants) to experience and interact with objects in a tightly controlled yet realistic setting. This paper presents the key elements of using a desktop virtual store to study in-store consumer behavior. Descriptions of the protocol steps to: 1) build the experimental store, 2) prepare the data management program, 3) run the virtual store experiment, and 4) organize and export data from the data management program are presented. The virtual store enables participants to navigate through the store, choose a product from alternatives, and select or return products. Moreover, consumer-related shopping behaviors (e.g., shopping time, walking speed, and number and type of products examined and bought) can also be collected. The protocol is illustrated with an example of a store layout experiment showing that shelf length and shelf orientation influence shopping- and movement-related behaviors. This demonstrates that the use of a virtual store facilitates the study of consumer responses. The virtual store can be especially helpful when examining factors that are costly or difficult to change in real life (e.g., overall store layout), products that are not presently available in the market, and routinized behaviors in familiar environments.

This paper describes the use of a desktop virtual store to create virtual shopping environments to investigate in-store consumer behavior. A description of the protocol to build and run experiments, example results from an experiment concerning store layout, and important considerations when conducting virtual store experiments are presented.

People&#39;s responses to products and/or choice environments are crucial to understanding in-store consumer behaviors. Currently, there are various ...

Using the FishSim Animation Toolchain to Investigate Fish Behavior: A Case Study on Mate-Choice Copying In Sailfin Mollies

Over the last decade, employing computer animations for animal behavior research has increased due to its ability to non-invasively manipulate the appearance and behavior of visual stimuli, compared to manipulating live animals. Here, we present the FishSim Animation Toolchain, a software framework developed to provide researchers with an easy-to-use method for implementing 3D computer animations in behavioral experiments with fish. The toolchain offers templates to create virtual 3D stimuli of five different fish species. Stimuli are customizable in both appearance and size, based on photographs taken of live fish. Multiple stimuli can be animated by recording swimming paths in a virtual environment using a video game controller. To increase standardization of the simulated behavior, the prerecorded swimming path may be replayed with different stimuli. Multiple animations can later be organized into playlists and presented on monitors during experiments with live fish.
In a case study with sailfin mollies (Poecilia latipinna), we provide a protocol on how to conduct a mate-choice copying experiment with FishSim. We utilized this method to create and animate virtual males and virtual model females, and then presented these to live focal females in a binary choice experiment. Our results demonstrate that computer animation may be used to simulate virtual fish in a mate-choice copying experiment to investigate the role of female gravid spots as an indication of quality for a model female in mate-choice copying.
Applying this method is not limited to mate-choice copying experiments but can be used in various experimental designs. Still, its usability depends on the visual capabilities of the study species and first needs validation. Overall, computer animations offer a high degree of control and standardization in experiments and bear the potential to &#39;reduce&#39; and &#39;replace&#39; live stimulus animals as well as to &#39;refine&#39; experimental procedures.

Using the FishSim Animation Toolchain to Investigate Fish Behavior: A Case Study on Mate-Choice Copying In Sailfin Mollies

Using the novel FishSim Animation Toolchain, we present a protocol for non-invasive visual manipulation of public information in the context of mate-choice copying in sailfin mollies. FishSim Animation Toolchain provides an easy-to-use framework for the design, animation and presentation of computer-animated fish stimuli for behavioral experiments with live test fish.