Scientists at the Institute of Molecular Biology (IMB) in Mainz have identified a protein essential for initiating the development of male sex organs. Loss of the gene Gadd45g results in complete sex reversal of male mice, making them appear female. The researchers' finding uncovers a novel signaling cascade, which acts early in development to determine the gonads in males. This discovery sheds light on the genetic network that controls how embryos develop as males or females. The research has just been published in the high-impact journal Developmental Cell.
Research carried out in the laboratory of IMB Director Professor Christof Niehrs uncovered that the deletion of just one gene, Gadd45g, results in male mice with external genitalia that are indistinguishable from those of female mice. Furthermore, the internal reproductive organs of the mutant male mice look like those of females, indicating that a complete sex reversal has occurred. Says Christof Niehrs, "when breeding Gadd45g mutant mice we were puzzled why we got only females, until we discovered that some of these females actually carry a Y-chromosome."
The researchers further showed that Gadd45g exerts its effect by regulating signaling cascades that control the gene Sry, which had previously shown to be a master regulator of male sex development. This study both identifies a new role for Gadd45g and suggests a novel signaling pathway that could have important implications for research into disorders of sexual development.