Metabolic cooperation between Tfm and wild-type cells in mosaic mice after induction of DNA synthesis

Abstract

Mosaic mice composed of androgen-insensitive Tfm and androgen-sensitive wild-type cells are constructed by virtue of the natural X inactivation: XX mice heterozygous for X-linked testicular feminization ( Tfm) are reverted to males by the sex reversal ( Sxr) mutation. After stimulation with testosterone, in the epididymis of the mosaic mice, the incorporation of 3H-thymidine is compared in both cell fractions. The labeling index of Tfm and wild-type cells is in the same order of magnitude. The result indicates that the stimulus for DNA synthesis exerted by testosterone is conveyed from the androgen-sensitive wild-type to the androgen-insensitive Tfm cells by metabolic cooperation on tissue level. On the other hand, the proportion of Tfm cells in the epididymal mosaic is far less than expected from X inactivation. The reason is that in the mosaic, in spite of normal proliferation, the undifferentiated Tfm cells die off steadily. Typical dense bodies are observed as signs of physiological cell death.