Pros and Cons of Male Fertility

Abstract

DEVELOPMENT The male testis and female ovary arise from a common bipotential gonad during mammalian embryogenesis. Abnormal testis development and resulting infertility are hallmarks of a human disorder called adrenal hypoplasia congenita (AHC), an X-linked syndrome associated with mutations in an orphan nuclear receptor called DAX1. Mouse models of this condition have suggested contrasting roles of DAX1 in gonad development. Adult male mice deficient in DAX1 exhibit pathology similar to that of AHC patients, yet DAX1 has also been called an “anti-testis” gene because overexpression in mice supports female sex determination. Two studies by Meeks et al. argue for a “pro-testis” DAX1 in early gonad development. Testes of DAX1-deficient mice were smaller in size as compared to those of wild-type mice, with incomplete formation of testis cords, which are the earliest structural feature that discriminates testes from ovaries and are the precursors of seminiferous tubules. In particular, DAX1 regulates the differentiation and organization of the peritubular myoid cells that define testis cord boundaries. The appearance of ovary-like gonads in DAX1-deficient male mice was only observed in a genetic background that sensitized mice to sex reversal. The influence of DAX1 on gene expression may provide further information on testicular development, degeneration, and infertility.— LDC Development 130 , 1029 (2003); Nature Genet. 10.1038/ng1441 (2003).