Gadd45g Is Essential for Primary Sex Determination, Male Fertility and Testis Development

Heiko Johnen,Laura Carramolino,Jesús M Salvador,Juana Maria Flores,Miguel Torres,Laura González-Silva,Yann Herault

doi:10.1371/journal.pone.0058751

Abstract

In humans and most mammals, differentiation of the embryonic gonad into ovaries or testes is controlled by the Y-linked gene SRY. Here we show a role for the Gadd45g protein in this primary sex differentiation. We characterized mice deficient in Gadd45a, Gadd45b and Gadd45g, as well as double-knockout mice for Gadd45ab, Gadd45ag and Gadd45bg, and found a specific role for Gadd45g in male fertility and testis development. Gadd45g-deficient XY mice on a mixed 129/C57BL/6 background showed varying degrees of disorders of sexual development (DSD), ranging from male infertility to an intersex phenotype or complete gonadal dysgenesis (CGD). On a pure C57BL/6 (B6) background, all Gadd45g−/− XY mice were born as completely sex-reversed XY-females, whereas lack of Gadd45a and/or Gadd45b did not affect primary sex determination or testis development. Gadd45g expression was similar in female and male embryonic gonads, and peaked around the time of sex differentiation at 11.5 days post-coitum (dpc). The molecular cause of the sex reversal was the failure of Gadd45g−/− XY gonads to achieve the SRY expression threshold necessary for testes differentiation, resulting in ovary and Müllerian duct development. These results identify Gadd45g as a candidate gene for male infertility and 46,XY sex reversal in humans.

Highlights

The Gadd45 family members Gadd45a, -b and -g are small nuclear and cytoplasmic proteins that bind to and modify the activity of other intracellular proteins, including p21 [1,2], PCNA [1,2], CRIF [3], CDK1 [4] and the MAP kinases p38 [5] and MAP3K4 [6]
Gadd45g deletion did not result in a male-specific lethal phenotype, but the majority of XY Gadd45g2/2 mice on the 129/B6 background and all XY Gadd45g2/2 mice on the pure B6 background were born as sex-reversed XY females (XY-F) (Fig. 1)
We evaluated the role of Gadd45a and/or Gadd45b in testis development and sex determination

Summary

Introduction

The Gadd (growth arrest and DNA-damage-inducible protein 45) family members Gadd45a, -b and -g are small nuclear and cytoplasmic proteins that bind to and modify the activity of other intracellular proteins, including p21 [1,2], PCNA [1,2], CRIF [3], CDK1 [4] and the MAP kinases p38 [5] and MAP3K4 [6]. It was suggested that loss of an enhancer region that drives brainspecific Gadd45g expression leads to increased growth of brain regions in humans compared to chimpanzees [8]. Another group studied the expression pattern during mouse embryonic development up to 10.5 dpc and proposed a conserved role for Gadd45g in vertebrate neurogenesis [9] as well as involvement in embryonic neural cell development and exit from pluripotency in Xenopus [10]

Methods

Results

Conclusion