Reproductive Technology

The Expression of nrOb1 and nr5a4 During Gonad Development and Sex Change in Protandrous Black Porgy Fish, Acanthopagrus schlegeli

Abstract
Protandrous black porgy fish, Acanthopagrus schlegeli, have a striking life cycle with a mono-male sex differentiation at the juvenile stage and male-to-female sex change at 3 yrs of age. We report for the first time an integrative molecular data on these interesting phenomena. Sex differentiation occurred between 4- to 5-months of age. Testicular nr5a4 (Sf-1) transcripts increased to high levels during sex differentiation (5-months age), while nrOb1 (Dax-1) did not increase until the age of 8 months. High nr5a4 and nrOb1 expression in testicular tissue, in contrast to low nr5a4 and high nrOb1 expression in ovarian tissue were found in the male phase of 0⁺- to 2-yr-old fish (before sex change). Increased nr5a4, decreased nrOb1 and increased cyp19a1a were found in the ovarian tissues undergoing development from primary oocytes to vitellogenic oocytes during the natural sex change in 2⁺-yr-old fish. Removal of testicular tissue in 1⁺-yr-old fish resulted in increased ovarian nr5a4 and genes in steroidogenic pathway, and decreased nrOb1 together with the appearance of vitellogenic oocytes. Ovary developed into the active stage with the increased expression of star and steroidogenic enzymes including aromatase in concordance with the decreased expressions of nrOb1 in the testis-excised fish. Long-term estradiol (E2)-administration resulted in early sex change, but the ovaries were mainly with primary oocytes. Low nr5a4, high nrOb1 and low steroidogenic enzymes including cyp19a1a expression were also observed in these E2-fed ovarian tissues. Thus, nr5a4 but not nrOb1 was associated with male sex differentiation. Testicular development required cooperative functions of both nr5a4 and nrOb1. The present study suggests that nr5a4 and nrOb1 have an antagonistic interaction for the oocyte development. Testicular tissue exerted inhibitory effects on ovarian development. nrOb1 probably regulates the timing of vitellogenic development and sex change in black porgy.

Key words: Ovary • Testis • Early development • Gene regulation • Oocyte development

This article has been cited by other articles:

				G.-C. Wu, S. Tomy, M. Nakamura, and C.-F. Chang Dual Roles of cyp19a1a in Gonadal Sex Differentiation and Development in the Protandrous Black Porgy, Acanthopagrus schlegeli Biol Reprod, December 1, 2008; 79(6): 1111 - 1120. [Abstract] [Full Text] [PDF]