CYCLIN D1 PROVIDES A LINK BETWEEN DEVELOPMENT AND ONCOGENESIS IN THE RETINA AND BREAST

Mice lacking cyclin D1 have been generated by gene targeting in embryo nic stem cells. Cyclin D1-deficient animals develop to term but show r educed body size, reduced viability, and symptoms of neurological impa irment. Their retinas display a striking reduction in cell number due to proliferative failure during embryonic development. In situ hybridi zation studies of normal mouse embryos revealed an extremely high leve l of cyclin al in the retina, suggesting a special dependence of this tissue on cyclin D1. In adult mutant females, the breast epithelial co mpartment fails to undergo the massive proliferative changes associate d with pregnancy despite normal levels of ovarian steroid hormones, th us, steroid-induced proliferation of mammary epithelium during pregnan cy may be driven through cyclin D1.