Molecular evolution of type VI intermediate filament proteins

Background  

Tanabin, transitin and nestin are type VI intermediate filament (IF) proteins that are developmentally regulated in frogs, birds and mammals, respectively. Tanabin is expressed in the growth cones of embryonic vertebrate neurons, whereas transitin and nestin are found in myogenic and neurogenic cells. Another type VI IF protein, synemin, is expressed in undifferentiated and mature muscle cells of birds and mammals. In addition to an IF-typical α-helical core domain, type VI IF proteins are characterized by a long C-terminal tail often containing distinct repeated motifs. The molecular evolution of type VI IF proteins remains poorly studied.