Sertoli Cell-Specific Gene Expression in Conditionally Immortalized Cell Lines

Abstract

A set of conditionally immortalized Sertoli cell lines has recently been established in this laboratory from H-2K ^h-tsA58 transgenic mice (Walther et al., 1996). These cell lines have conserved the expression of a number of important Sertoli cell marker genes, and therefore provide ideal tools for detailed studies on the regulation of Sertoli cell-specific gene expression. The Н-2K ^h-tsA58 transgenic mice (Jat et al., 1991) carry a temperature-sensitive SV40 T antigen in their germline. Primary cell cultures derived from these mice can easily be grown at the permissive temperature of 33°C in the presence of γ-interferon in order to induce SV40 T antigen expression, and immortalized cell lines can be isolated from these cultures. Upon transfer to the non-permissive temperature of 39.5°C the temperature-sensitive SV40 T antigen is inactivated. The temperature-sensitive growth of the Sertoli cell lines was characterized by shifting one of two parallel cultures to 39.5°C and observing the effects on growth and expression of Sertoli cell-specific genes. After two days of culture at 39.5°С the cells begin to show a flat morphology and cell growth stops as shown for the immortalized cell line SK11 (Fig. 1). At this temperature the cells cannot be passaged and die after prolonged culture. SK11 cells were infected with a recombinant retrovirus expressing a mutant (175 His) of the cell cycle control protein p53 (Morgenstern and Land, 1990; Hollstein et al., 1991). The expréssion of the mutant p53 inactivates the cellular p53 and should result in unconditional immortalization of the cells. However, colonies of retrovirus-infected SK11 cells could not continue growth after shift from 33°C to 39.5°С. This experiment suggests that the immortalizing effect of SV40 T antigen on the Sertoli cells is not only due to inactivation of the cellular p53, but that other, possibly transcriptional, actions of SV40 T antigen (Damania and Alwine, 1996) contribute to Sertoli cell immortalization.