Detection of four germ cell markers in rats during testis morphogenesis: differences and similarities with mice.

Germ cells are the only cells capable of transmitting genetic information from generation to generation. Germ cell development has been widely studied in different species. Among mammals, the mouse is the model used in the majority of studies on germ cell differentiation, sex determination and genetics. In the present study, we suggest that the rat is also a very important model for the investigation of the mechanisms of germ cell development. To study rat germ cell development and compare it with that of mouse, the germ cell markers germ cell nuclear antigen 1 (GCNA1), OCT4, mouse vasa homologue (MVH) and specific surface embryonic antigen 1 (SSEA1) were immunolabeled at different phases of embryonic and postnatal development. SSEA1 and GCNA1 were not detected in rat primordial germ cells and fetal gonocytes. GCNA1 was detected postnatally and was present only in leptotene, zygotene and early pachytene spermatocytes. On the other hand, in mice, these markers were detected in germ cells as soon as 11.5 days postcoitum (dpc). MVH was detected in migrating rat primordial germ cells as well as in those that have already colonized the gonads, whereas in mice, MVH is detected only in germ cells that have reached the gonads. In rats, OCT4-positive germ cells were detected from 13 to 17 dpc, but not at 19 dpc or in postnatal testes. This is in contrast with mice that show OCT4 labeling in both embryonic and adult testes. These data suggest that primordial germ cell development in rats and mice shows considerable differences and that the rat may also be an important model to study the embryonic development of germ cells.