Immortalized germ cells undergo meiosis in vitro.

Establishing mammalian germ-cell lines capable of differentiation in vitro would greatly facilitate the study of gametogenesis and the meiotic process that is so fundamental for reproduction and the maintenance of genetic diversity of the species. We have established two germ-cell lines [GC-2spd(ts) and GC-3spc(ts)] by cotransfecting primary mouse testicular germ cells with the simian virus 40 large tumor antigen gene and the gene coding for a temperature-sensitive mutant of p53. Both cell lines express the germ cell-specific lactate dehydrogenase C4 isozyme and cytochrome ct isoform. At the permissive temperature of 37 degrees C, the GC-2spd(ts) line generates cells with a haploid DNA content and morphologic and biochemical features of round spermatids, including the appearance of an acrosomic granule. The identification of a flagellar axoneme when these cells are cultured at 32 degrees C further indicates that these cells correspond to the early spermatid stages of spermiogenesis.