Staff Events
Tiana Kohlsdorf

Why snakes are so unique. Some insights from developmental pathways.

This talk will focus on analyses of coding (Hoxa13) and non-coding (CsB and H1- Myf5) regions of genes expressed during embryo development, combining evaluation of molecular signatures in snakelike lineages with functional assays. Analyses of coding regions were performed as models of molecular evolution between lineages using PAML, while non-coding regions were compared between clades based on predicted transcription factor binding sites (TFBS). Our analyses identified in the three fragments of snakes some molecular signatures that are either absent in amphisbaenians or in caecilians. The most striking one is a polymorphism in H1-Myf5 described in the literature as being responsible for lack of identity in trunk vertebrae of snakes. Analyses based on prediction of TFBSs show one substitution that occurred in different snakelike lineages, but also reveal regulatory haplotypes in CsB and H1-Myf5 that are exclusive to Serpentes. Finally, evidence for directional selection in the exon-1 of Hoxa13 is identified in snakes but not amphisbaenians or caecilians.

The five mutations identified in snakes as evolving under positive selection result in differential expression of several genes involved in the processes that terminate somitogenesis, suggesting that molecular signatures that are unique to snakes affect developmental pathways involved in axial elongation.