Wu Limin1,， Yang Peng2,， Wang Deshou1,， Zhou Linyan1,*
（ 1、Key labotrary of Freshwater Fish Reproduction and Development (Ministry of Education), Key Laboratory of Aquatic Science of Chongqing, School of Life Sciences, Southwest University, Chongqing 400715, China； 2、 College of Fisheries, Henan Normanl University, Xinxiang, 453007, China.； ）
Abstract： The furin-domain-containing peptide R-spondin1 (RSPO1) has recently emerged as an important regulator of ovarian development, upregulating the WNT/β-catenin pathway to oppose testis formation in mammals. However, little information has been reported on the Rspo1 signaling pathway in teleosts. In this study, Rspo1 was isolated from the gonads of the Nile tilapia, Oreochromis niloticus. An in situ hybridization analysis demonstrated that Rspo1 is expressed in the germ cells of the ovary and the testis. An ontogenic analysis demonstrated that Rspo1 expression is upregulated just before meiotic initiation in both the ovary and testis during the early developmental stages of the tilapia. The expression pattern is sexually dimorphic from 20 days after hatching, with higher expression in the ovary. The reduction of Rspo1 expression by tranｓｃｒｉｐｔion activator-like (TAL) effector nuclease (TALEN) caused retarded ovarian development, the ectopic expression of male-dominant genes, and increased serum 11-ketotestosterone. Intriguingly, a deficiency of Rspo1 in XY fish caused a delay in spermatogenesis, the inhibition of igf3 and amh expression and a reduction in serum 11-ketotestosterone. Furthermore, FH535, an inhibitor of the Rspo1/Wnt pathway, decreased β-catenin, while increased cyp11c1 and dmrt1 expression in the in vitro culture ovaries; decreased cyp11c1, amh and igf3 expression in the in vitro cultured testes. Taken together, our data suggest that the fish Rspo1 signaling pathway is involved in both ovarian and testicular development in the tilapia.
Keywords： Rspo1; ovarian and testicular development; retardation; impaired spermatogenesis