Specific miRNA-GPCR networks regulate Sox9a/Sox9b activities to promote gonadal renewal in zebrafish

Abstract

14Fertility and endocrine function rely on a tightly regulated synchronicity within the hypothalamic-pituitary 15 gonadal (HPG) axis. FSH/cAMP/MAPK/ Sox9 axis signaling and its regulated specific miRNAs are thought 16 to regulate vertebrate gonadal development and sex differentiation, and yet the regulatory networks are largely 17 unknown. Here we construct small RNA and mRNA libraries from sexually matured ovary and testis of 18 zebrafish to identify specific miRNA-target pairs. Integration of Targetscan prediction and in vivo induced 19 gene expression highlight four specific miRNAs that conditionally target three G protein-coupled receptor 20 (GPCR) -Sox9 signaling genes, and implicate two regulatory circuits of miR430a-Sox9a in the testis and 21 miR218a-Sox9b in the ovary. Co-injected Sox9a-miR430a mixture increases the proportion of spermatogonia 22 but degenerates primary oocyte, while Sox9b-miR218a mixture induces renewal of ovarian follicles. 23Co-immunoprecipitation and mass-spectrometry analyses further reveal that miR430a and Sox9a 24 synergistically activate testicular PKC/Rock1 signals while miR218a and Sox9b constrict ovary 25 PKC/PI3K/Rock1 signaling. These results clarify specific miRNAs-GPCR regulatory networks of 26 Sox9a/Sox9b switch, and also provide mechanistic insight into gonadal rejuvenation and plasticity. 27 28