Abstract:Chinese tongue sole (Cynoglossus semilaevis) growth exhibits clear sex dimorphism, and the weight of mature female fish is significantly greater than that of male fish. In fish, muscle accounts for 40%-60% of body weight, and muscle growth is the core growth trait. Myostatin (mstn), also known as GDF-8, is a member of the transcriptional growth factor (TGF-β) superfamily. mstn is a negative regulator of muscle growth and development and has an inhibitory effect on myoblast proliferation. mstn gene deletion can lead to an increase in skeletal muscle mass. In recent years, research on the mstn gene has primarily focused on the aspects of gene cloning, expression pattern analysis, and RNA interference. Minimal studies have reported the differential expression of the mstn gene between male and female fish with sex dimorphism. The aim of this study was to explore the spatiotemporal expression pattern of the mstn gene in different sexes of Chinese tongue sole during muscle growth and development. The results showed that mstn expression was detected in the liver, spleen, intestine, kidney, gonad, gill, heart, brain, and muscle of 1-year-old fish, and mstn expression was the highest in muscle. The quantitative results of muscle tissue at different developmental stages showed that the expression levels in one- and two-year-old males were significantly higher than those in females (P<0.05), however, there was no significant difference in expression levels between males and females in other selected stages. Tissue section staining showed that the muscle fiber cross sections presented an irregular polygonal shape. The results of in situ hybridization showed that mstn gene expression was found at the edge of the muscle fiber, where myoblasts proliferate and differentiate. In this study, the spatial and temporal expression patterns of mstn were systematically studied in different sexes of Chinese tongue sole, which provides a basis for further studies on the growth differences between male and female Chinese tongue sole.
