Molecular characterization of myosin heavy chain and its involvement in muscle growth and development in the Yesso scallop Patinopecten yessoensis

Myosin found in scallop adductor muscles is a regulatory protein that is responsible for muscle contraction. Myosin heavy chains (MyHCs) form the core component of myosin and play important roles in myofibril assembly and maintenance. In the present study, we obtained the full-length cDNA sequences encoding MyHC from the Yesso scallop Patinopecten yessoensis and investigated its expression patterns as well as regulatory functioning in muscle growth and development. Py-MyHC was 6054 bp in length and was comprised of a 5′-untranslated region (51 bp), a 3′-untranslated region (180 bp), and an open reading frame (5823 bp) encoding 1940 amino acids. Analysis of the MyHC sequences in bivalves revealed that they were closely homologous to each other, with identities ranging from 74.48% to 95.16%. qPCR analysis and immunohistochemistry staining revealed the existence of tissue-specific expression patterns for Py-MyHC with maximal expression occurring in the striated adductor muscles. Whole-mount in situ hybridization showed that during larval development, Py-MyHC mRNA was mainly expressed in the velum retractor muscles, and in the anterior and posterior adductor muscles. Furthermore, noticeable defects in myofibril structure were found in the striated adductor muscles following the application of RNA interference. Based on the above, it is considered that MyHCs play a crucial role in myofibril assembly and maintenance in both larvae and adults. These findings are considered to provide useful information with regard to the functional basis of muscle growth and muscle production with potential implications for actual aquaculture production. •The maximum expression of Py-MyHC was found in the striated adductor muscle.•The developmental expression indicates the dynamics of scallop myogenesis.•The defective muscle structure was observed after RNAi knockdown of MyHC.