Sex-reversed mice: XX and XO males

Abstract

An autosomally inherited condition is described in the mouse which causes genetic females to develop as phenotypic males. XX males are phenotypically normal with the exception of small testes, which, in the adult, are devoid of germ cells. During late fetal and early postnatal development, male-type germ cells are present but progressively become lost, so that none is present by 10 days of age. XO males are also phenotypically normal, but spermatogenesis is active in the testis, and spermatozoa are produced. Cytological evidence of a Y-autosome translocation was completely lacking, and it is proposed that an autosomal dominant gene mutation, analogous to that found in other mammalian species, is responsible for the sex reversal.