Reproliferation and relocation of mouse male germ cells (gonocytes) during prespermatogenesis

Abstract

In the prespermatogenesis period, male germ cells (gonocytes) begin to reproliferate and move to the basement membrane of the seminiferous tubule. Although these two events-reproliferation and relocation-are important for establishment of spermatogenesis, they have not been greatly analyzed both in a mechanical and in an endocrine or paracrine aspect. In this study, the relationship between reproliferation and relocation of gonocytes was examined, using the thymidine analog bromodeoxyuridine (BrdU) labeling method and transmission electron microscopy (TEM). BrdU was injected into the fetuses [day 13.5 post coitus (dpc) to 18.5 dpc] and pups [day 0. 5 post partum (dpp) to 6.5 dpp] of C57BL/6J mice. Two hours later, BrdU positive gonocytes were examined immunohistochemically and these data were analyzed. TEM and LM observation was carried out as well. Gonocytes began to relocate on the basement membrane from 18.5 dpc (1.4%) while BrdU-labeled gonocytes were first detected on 1.5 dpp (13.6%). Relocated BrdU-negative gonocytes were recognized from 18.5 dpc (1.4%), and relocated BrdU-labeled gonocytes were recognized from 1.5 dpp (8.4%). On the other hand, non-relocated BrdU-labeled gonocytes were detected from 1.5 dpp (5.2%). Gonocyte relocation began 2 days earlier than reproliferation during the late fetal period. After birth, the two events occurred at random. These results indicate that the reproliferation of the gonocyte does not correlate with relocation. The two events may be regulated by different mechanisms.

Neonatal Gonocyte Differentiation in Mongolian GerbilMeriones unguiculatusInvolves Asynchronous Maturation of Seminiferous Cords and Rapid Formation of Transitional Cell Stage

“…Mitotic and PCNA-positive Gn were found near or in the basement of the seminiferous cords even before the relocation peak, indicating that relocation to the epithelial base is not a requirement for Gn to resume the mitotic cycle. Then, similarly to other rodents, neonatal Gn proliferation in gerbils is not dependent on adhesion to basement membrane (McGuinness and Orth, 1992a;Nagano et al, 2000). Whereas in mice and rats Gn disappears during the first week of age (Clermont and Perey, 1957;Sakai et al, 2004), in gerbils they were observed up 14 d. In addition, cells with a transitional phenotype between Gn and spermatogonia, namely the prospermatogonia, were also found adhering to the basement membrane early into the postnatal period.…”

“…There is much disagreement about the behavior, properties and nomenclature of prespermatogenic germ cell populations. The term gonocyte was originally proposed by Clermont and Perey (1957) and it currently refers to the fetal germ cells derived from primordial germ cells that exhibit distinctive morphological characteristics as well as stages of quiescence and mitotic activity (de Rooij and Russell, 2000;Nagano et al, 2000;Culty 2009). Other authors employed the terms prospermatogonia and prespermatogonia to define the cells derived from primordial germ cells (Hilscher et al, 1974;Wartenberg, 1976;Byskov, 1986).…”

SMAD expression in the testis: An insight into BMP regulation of spermatogenesis

“…After birth, gonocytes relocate to the basement membrane of the seminiferous cord, concomitant with their transition into spermatogonia (Nagano et al, 2000). In all gonocytes at birth, uniform staining for SMAD6, which inhibits BMP as well as activin/TGF␤ signaling (Imamura et al, 1997;Shi and Massague, 2003), indicates a global repression of TGF␤ superfamily signaling.…”

Heat-shock protein HSPA4 is required for progression of spermatogenesis

“…After colonizing the primordial germ cells in mouse testis, gonocytes proliferate until day 15.5 and arrest in the G1 of cell cycle (Vergouwen et al 1991, Nagano et al 2000. Shortly after birth, gonocytes resume mitotic activity and develop into type A spermatogonia (Mclean et al 2003).…”