Intron sliding in tetraspanins.

Specific questions about intron evolution are precisely addressed applying a phylogenomic approach to suitable gene families. With this approach we have recently reported that the appearance of most human tetraspanins occurred in the common ancestor of vertebrates and coincides in nearly all cases with the concomitant acquisition of new introns. We observed that indels at the ends of the DNA exonic sequences with no involvement of the corresponding intronic sequence, were the cause of two discordant intron positions between orthologous tetraspanins. Here, we discuss a putative intron sliding occurrence in which a new acquired intron junction (intron 1a) in the ancestor of chordates could have been shifted to new positions (introns 1b and 1c) during the expansion of the tetraspanin family in vertebrates. Such a mechanism could be responsible for generating some of the variation of function in this important family of membrane spanning proteins.