Direct and mediated effects of testosterone: the development of intersexes in sex reversed mosaic mice, heterozygous for testicular feminization.

The X-linked Tfm mutation causes androgen insensitivity in the target cells of testerone. Due to random X-inactivation, XX-mice heterozygous for Tfm are mosaics in respect to androgen sensitivity. By the autosomal "sex reversal" mutation, Tfm-heterozygotes were converted to males during embryonic life so that male sex organs developed in which the mosaic was expressed. The mutual influence of both components of the mosaic is analysed. It is shown that cellular differentiation is directly induced by testosterone, while the formation of organ anlagen and proliferation are locally mediated effects.