Abstract
BackgroundThe threespine stickleback (Gasterosteus aculeatus) has a characteristic reproductive mode; mature males build nests using a secreted glue-like protein called spiggin. Although recent studies reported multiple occurrences of genes that encode this glue-like protein spiggin in threespine and ninespine sticklebacks, it is still unclear how many genes compose the spiggin multi-gene family.ResultsGenome sequence analysis of threespine stickleback showed that there are at least five spiggin genes and two pseudogenes, whereas a single spiggin homolog occurs in the genomes of other fishes. Comparative genome sequence analysis demonstrated that Muc19, a single-copy mucous gene in human and mouse, is an ortholog of spiggin. Phylogenetic and molecular evolutionary analyses of these sequences suggested that an ancestral spiggin gene originated from a member of the mucin gene family as a single gene in the common ancestor of teleosts, and gene duplications of spiggin have occurred in the stickleback lineage. There was inter-population variation in the copy number of spiggin genes and positive selection on some codons, indicating that additional gene duplication/deletion events and adaptive evolution at some amino acid sites may have occurred in each stickleback population.ConclusionA number of spiggin genes exist in the threespine stickleback genome. Our results provide insight into the origin and dynamic evolutionary process of the spiggin multi-gene family in the threespine stickleback lineage. The dramatic evolution of genes for mucous substrates may have contributed to the generation of distinct characteristics such as "bio-glue" in vertebrates.
Highlights
The threespine stickleback (Gasterosteus aculeatus) has a characteristic reproductive mode; mature males build nests using a secreted glue-like protein called spiggin
Identification of the spiggin multi-gene family and homologs in genome sequences We identified seven putative spiggin genes in linkage group (LG) IV of the threespine stickleback genome sequence
When we focused on the genes from the threespine stickleback genome sequence (Gaac_spg1, 3, 4, 5, and 7), the phylogenetic relationships of the genes were not congruent with their chromosomal locations (Figs. 1, 3), indicating that the genes that showed close relationships in the phylogenetic tree were not necessarily located close to each other on the chromosome
Summary
The threespine stickleback (Gasterosteus aculeatus) has a characteristic reproductive mode; mature males build nests using a secreted glue-like protein called spiggin. CNVs contribute to inter-individual variation in responses to drugs, immune defence, and susceptibility to certain diseases in humans and mice [2,3]. These findings suggest that variation in gene copy number is sometimes under selection and that it is one of the driving forces for evolution in these species. Because these studies focused on certain human and mouse diseases, it is unclear whether CNVs and these features of CNVs are common phenomena in vertebrates. Threespine stickleback (Gasterosteus aculeatus), which inhabits marine, brackish, and freshwaters of the Northern hemisphere, is a classical model organism in ethology (page number not for citation purposes)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
