Molecular characterization of three muscle alpha actin genes in mud loach (Misgurnus mizolepis; Cypriniformes)

Abstract

Background: Teleosts represent unique features in the regulation of muscle development and growth, with a great deal of myogenic plasticity. Muscle actins are major components to compose muscle fibers, and they play essential roles in cellular mobility and other related functions. In order to understand isoform-dependent roles of muscle actins in the mud loach (Misgurnus mizolepis), this study was aimed to characterize gene structure and expression pattern of the three muscle actin isoforms (α-skeletal, α-cardiac, and α-smooth muscle actins) isolated from this benthic fish species. Results: Mud loach α-actin isoforms (ACTA1, ACTC1, and ACTA2) were fairly conserved in their primary structures and shared a high-sequence identity one another. At genomic level also, all the three isoforms exhibited the same exon-intron organization pattern characterized by eight translated exons. However, in mRNA expression patterns, these three actin isoforms were found to display an apparent isoform-dependency in tissue distribution (i.e., ACTA1 in the skeletal muscles, ACTC1 in the heart, and ACTA2 in the intestines) and developmental regulation (i.e., increased expression of ACTA1 and ACTC1 with the progress of myogenesis, and the significant elevation of ACTA2 during organ development in early larvae). Conclusion: Data from this study suggest that three muscle actin isoforms have undergone certain functional differentiation with regard to their roles in the development and adult musculature, in spite of high structural similarity. Genetic information on muscle actins obtained in this study could provide a useful base to extend our understanding on evolutionary diversification of the myogenic regulation in teleosts.