Molecular expression of genes related to sex differentiation and their response to sex steroid hormones in the clam Chinese cyclina (Cyclina sinensis)

This study investigated the tissue-specific expression and subcellular localization of sex differentiation-related genes of Cyclina sinensis, and then analyzed the effects of hormone treatment (1 and 50 μg/L estradiol treatment (E-1, E-50), 1 and 50 μg/L testosterone (T-1, T-50), and a control group (C)) on the sex ratio, gonadosomatic index, hepatosomatic index, hormone content, and expression of sex differentiation-related genes of juvenile C. sinensis. Vitellogenin (Vg), testis-specific serine kinase 1 (Tssk1), doublesex and mab-3 related transcription factor 1 (Dmrt1), and Wnt family member 4 (Wnt4) were significantly expressed in the gonads of adult C. sinensis, and the in situ hybridization signals of forkhead box L2 (Foxl2) and SRY-box transcription factor 9 (Sox9) were localized in nuclei of oogonia and oocytes and in spermatogonia, spermatocytes, and sperm, respectively. The male to female ratio was 7:3 in group T-1 after 60 days of hormone treatment, but this effect was not statistically significant. In the E-1 group, Vg was highly expressed in the ovary at days 30 and 120. TSSK1 was highly expressed in the testes of the T-1 and T-50 groups at 120 days (60 days after the cessation of hormone treatment). The expression of Foxl2 was significantly higher in the ovaries of the T-1 group at 60 days, relative to the control and other hormone-treated groups. Sox9 was highly expressed in the testes at 120 days. The concentrations of testosterone and estradiol in the gonad of C. sinensis increased initially and then decreased. Overall, these results revealed that hormones caused disruption of sex determination and expression of sex-differentiation genes in juvenile C. sinensis.