The sensitive period for male‐to‐female sex reversal begins at the embryonic stage in the Nile tilapia and is associated with the sexual genotype. Issue 12 (5th December 2014)

• Record Type: Journal Article
• Authors: Gennotte, Vincent; Mélard, Charles; D'Cotta, Helena; Baroiller, Jean‐François; Rougeot, Carole
• Is Part Of: Molecular reproduction and development. Volume 81:Issue 12(2014:Dec.)
• Page Start: 1146
• Page End: 1158
• Publication Date: 2014-12-05
• Subjects: Reproduction -- Periodicals; Molecular biology -- Periodicals; Molecular genetics -- Periodicals; Embryology -- Periodicals; 571.8
• DOI: 10.1002/mrd.22436
• Languages: English
• ISSNs: 1040-452X

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>SUMMARY</title> <sec id="mrd22436-sec-0001" sec-type="section"> <p>In this study, we sought to determine the mechanism of early sex reversal in a teleost by applying 4 hr feminization treatments to XY (17α‐ethynylestradiol 2000 μg L<sup>−1</sup>) and YY (6500 μg L<sup>−1</sup>) Nile tilapia embryos on the first day post‐fertilization (dpf). We then searched for changes in the expression profiles of some sex‐differentiating genes in the brain (c<italic>yp19a1b</italic>, <italic>foxl2</italic>, and <italic>amh</italic>) and in sex steroids (testosterone, 17β‐estradiol, and 11‐ketotestosterone) concentrations during embryogenesis and gonad differentiation. No sex reversal was observed in YY individuals, whereas sex‐reversal rates in XY progeny ranged from 0–60%. These results, together with the clearance profile of 17α‐ethynylestradiol, confirmed the existence of an early sensitive period for sex determination that encompasses embryonic and larval development and is active prior to any sign of gonad differentiation. Estrogen treatment induced elevated expression of c<italic>yp19a1b</italic> and higher testosterone and 17β‐estradiol concentrations at 4 dpf in both XY and YY individuals. <italic>foxl2</italic> and <italic>amh</italic> were repressed at 4 dpf and their expression levels were not different between treated and control groups at 14 dpf, suggesting that <italic>foxl2</italic> did not control <italic>cyp19a1b</italic> in the brains of tilapia embryos. Increased <italic>cyp19a1b</italic> expression in treated embryos could reflect early brain sexualization, although this difference alone cannot account for the observed sex reversal as the treatment was ineffective in YY individuals. The differential sensitivity of XY and YY genotypes to embryonic induced‐feminization suggests that a sex determinant on the sex chromosomes, such as a Y repressor or an X activator, may influence sex reversal during the first steps of tilapia embryogenesis. <italic>Mol. Reprod. Dev. 81: 1146–1158, 2014. © 2014 Wiley Periodicals, Inc</italic>.</p> </sec> </abstract>