Different expression of sox17 gene during gametogenesis between scallop Chlamys farreri and vertebrates

•Cf-SOX17 lacks the conservative C-terminal region of vertebrate SOX17.•Cf-sox17 mRNA exhibited a tissue differential distribution, in which the abundance was the highest in gonads.•Cf-sox17 mRNA and Cf-SOX17 protein were located in all germ cells, while vertebrate sox17 mRNA is only in partial germ cells.

SOX17, a member of SRY-related high-mobility-group box (SOX) family, involves in endoderm formation, angiogenesis and carcinogenesis, and its expression characteristics are different in spermatogenesis among several vertebrates. In this study, we cloned a full-length cDNA sequence of sox17 from Zhikong scallop Chlamys farreri, and determined its expression characteristics in gonad at mRNA and protein levels. The cDNA sequence was 2802 bp in length, predicted to encode a protein of 511 amino acids and contained a conservative HMG-box of SOX family, while lacked the C-terminal region of SOX17 comparing to vertebrates. Semi-quantitative RT-PCR showed that C. farreri sox17 (Cf-sox17) mRNA exhibited a different tissue distribution, and the transcript abundance was the highest in the gonads. In situ hybridization determined that the Cf-sox17 mRNA was located in various germ cells in testis and ovary. Similar result of Cf-SOX17 protein was also observed by immunohistochemical detection. The location in gonad is different from that of mammals and fish in which SOX17 is only located in some specific germ cells. Our finding revealed a different characteristic of sox17 expression in gametogenesis between scallop and vertebrates, which implied that Cf-sox17 may involve in gametogenesis of bivalves and the function may differ from that in vertebrates.