Development

Male Order Growth Factor

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Science  06 Apr 2001:
Vol. 292, Issue 5514, pp. 15
DOI: 10.1126/science.292.5514.15d

The mechanisms that determine whether a fetus develops into a male or a female is a central question in embryology and has been debated for centuries. We now know that in mammals the primordial tissue that gives rise to the gonads passes through an “indifferent” stage, during which time it retains the potential to develop into either an ovary or a testis. However, the signaling pathways involved in this developmental decision, which establishes the sexual future of the organism, are not fully understood.

Important progress is reported by Colvin et al., who have identified a new player in sex determination. In the course of characterizing mice deficient in fibroblast growth factor 9 (FGF9), which die at birth of lung abnormalities, the authors noted that a high percentage of the pups were female. Closer inspection revealed that about half of the phenotypically female mice were in fact genotypically XY males that had undergone sex reversal during development. The absence of FGF9 appeared to disrupt several early steps in development of the testis, including Sertoli cell differentiation, gonadal cell proliferation, and mesonephric cell migration. The evolutionary conservation of FGF signaling pathways raises the possibility that they may function in sex determination in many species. — PAK

Cell104, 875 (2001).

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