Identification and functional characterization of Pomstna in Japanese flounder (Paralichthys olivaceus)

Myostatin (MSTN) as a negative regulator of muscle growth has been identified in Japanese flounder. Yet, most fish experienced the teleost specific genome duplication and possess at least two mstn genes. In current study, the second mstn gene named Pomstna is identified in Japanese flounder. Pomstna is clustered with other mstn2 of teleosts and owned highly conserved TGF-beta domain. In addition to muscle, Pomstna also highly expressed in brain and spleen. Using the primarily cultured muscle cells of Japanese flounder, we found that Pomstna could inhibit the proliferation and differentiation of muscle cells in vitro. As a ligand of TGF-beta signaling pathway, Pomstnb could regulate the expression of p21 and myod by activating the TGF-beta signaling pathway. Different from the function of Pomstnb, Pomstna could not activate the TGF-beta signaling pathway in vitro. During the differentiation of PoM cells, the expression of Pomstnb decreased significantly but the expression of Pomstna showed no change. Our study suggests that Pomstna could negatively regulate the growth and differentiation of muscle like Pomstnb yet through a different regulatory mechanism than Pomstnb. The present study suggests that muscle proliferation and differentiation were regulated by mstn not only through the TGF-beta signaling pathway but also other unknown mechanisms.