Repeated evolutionary turnover of vertebrate skeletal muscle myosins

Myosin heavy chain proteins are essential for muscle contraction and nearly every physiological function in animals, but their diversity and evolution outside mammals is largely unknown. Here, we analyze over 1,000 myosin protein sequences and dozens of skeletal muscle expression profiles to comprehensively model the evolutionary history of heavy-chain myosins and understand common themes of their tissue-specific expression. We show that even though skeletal muscle myosins are located in the same tandem gene cluster across vertebrate species, repeated gene duplication-loss turnover has resulted in each major vertebrate group now having an independently evolved set of core skeletal muscle myosins. Despite these separate derivations of skeletal myosins, each major vertebrate group exhibits tissue-specific patterns of expression, includes diverse myosin molecular properties, and employs different myosins in extreme muscles. Our results suggest that muscle evolution across vertebrates involves a repeated and multifaceted process of gene family diversification of sarcomeric myosin proteins, with shifting expression of myosins in different muscle types as a general theme of their evolution across vertebrates.