Zebrafish Nedd8 facilitates ovarian development and the maintenance of female secondary sexual characteristics via suppression of androgen receptor activity

Nedd8 is a ubiquitin-like protein that covalently conjugates to target proteins through neddylation. In addition to cullin-RING ligases, neddylation also modifies non-cullin proteins to regulate protein activity, stability and localization. However, the roles of NEDD8 remain largely unknown in vivo. Here, we found that loss of nedd8 in female zebrafish led to defects in oogenesis, disrupted oocyte maturation and stimulated growth of the breeding tubercles (BTs) on the pectoral fins. The BTs are normally present in males, not females. However, the loss of one copy of ar can partially rescue the phenotypes displayed by nedd8-null female zebrafish. Further assays indicated that Nedd8 conjugates to Ar and Ar is neddylated at lysine 475 and lysine 862. Moreover, Nedd8 conjugation efficiently suppressed Ar transcriptional activity. Lysine 862 (K862) of Ar is the key site modified by neddylation to modulate Ar transcriptional activity. Thus, our results not only demonstrated that Nedd8 modulates ovarian maturation and the maintenance of female secondary sexual characteristics of female zebrafish in vivo, but also indicated that androgen signaling is strictly regulated by nedd8.