Tropomyosin - Evolution of Isoform Generation

Evolution of Isoform Generation

Structurally the genes are very similar, suggesting that they arose through gene duplication of an ancestral gene. The most highly related genes are the α- and γ-genes, utilizing two promoters and differing only with the presence of the unique 2a exon in the α-gene. Although substantial differences between alternative exons from the same gene have been revealed by sequence comparison (1a and 1b, 6a and 6b, and the exon 9s), most exons are, however, highly conserved between the different genes. For example, exon 1a and 1b from the α-gene vary considerably in sequence, however the sequence from exon 1a from the α-, β-, γ-, and δ-genes is highly conserved.

Due to the conservative nature of the genes, it is believed that the genes evolved from a common ancestral gene, giving rise to over 40 functionally distinct isoforms. The expression of these isoforms is highly regulated and variable throughout development. The diversity of tropomyosin expression, both in space and time provides the potential to not only regulate actin filament function, but to create specialised actin filament populations.