Haploinsufficiency of SF 1 Causes Female to Male Sex Reversal in Nile Tilapia, Oreochromis niloticus.
Steroidogenic factor 1 (Sf 1) (officially designated nuclear receptor subfamily 5 group A member 1 [NR5A1] is a master regulator of steroidogenesis and reproduction in mammals. However, its function remains unclear in nonmammalian vertebrates. In the present study, we used immunohistochemistry to detect expression of Sf 1 in the steroidogenic cells, the interstitial, granulosa, and theca cells of the ovary, and the Leydig cells of the testis, in Nile tilapia. Clustered regularly interspaced short palindromic repeats/CRISPR associated protein 9 (Cas9) cleavage of sf 1 resulted in a high mutation rate in the F0 generation and a phenotype of gonadal dysgenesis and reduced steroidogenic cells in XX and XY fish. Sf 1 deficiency also resulted in decreased cytochrome P450, family 19, subfamily A, polypeptide 1a, forkhead box L2 expression, and serum estradiol 17b in XX fish. In XY fish, Sf 1 deficiency increased cytochrome P450, family 19, subfamily A, polypeptide 1a and forkhead box L2 expression but decreased cytochrome P450, family 11, subfamily B, polypeptide 2 expression and serum 11 ketotestosterone levels. 17a methyltestosterone treatment successfully rescued the gonadal phenotype of Sf 1 deficient XY fish, as demonstrated by normal spermatogenesis and production of F1 mutants. In contrast, estradiol 17b treatment only partially rescued the gonadal phenotype of Sf 1 deficient XX fish, as demonstrated by the appearance of phase II oocytes. Furthermore, both sf 1( F1 XX and XY mutants developed as fertile males, although spermatogenesis was delayed and efferent duct formation was disordered. Our data suggest that Sf 1 is a major regulator of steroidogenesis and reproduction in fish, as it is in mammals. Sf 1 deficiency resulted in gonadal dysgenesis and feminization of XY gonads. However, unlike in mammals, Sf 1 deficiency also resulted in female to male sex reversal in 8.1% of F0 and 92.1% of sf 1( F1 in XX fish.
Endocrinology