Metaphase-specific cell death in meiotic spermatocytes in mice

Apoptosis of male germ cells is a widespread but little-understood phenomen on in many animal species. The elucidation of its mechanisms could be usefu l in the understanding of male infertility. We have examined the distributi on of dying cells with the terminal transferase-mediated nick-end labeling (TUNEL) method and by an electron-microscopic procedure in the testes of 10 mouse strains, viz., C57BL/10 (B10), SL/NiA (SL), C57BL/6 (B6), C3H/He (C3 H), BALB/c (BALB), DBA2 (DBA), CBA/J (CBA), MRL/MpJ-+/+ (M+), MRL/MpJ-lpr/l pr (lpr), and wild-type NJL mice (Mus musculus musculus). In the testes of the B10, NJL, SL, B6, C3H, BALE, DBA, and CBA mice, very few TUNEL-positive cells are distributed in the seminiferous tubules, whereas in the testes o f the M+ and lpr mice, many TUNEL-positive cells, which are restricted to s tage XII seminiferous tubules, have been identified. The most important fin ding is that many metaphases of meiotic spermatocytes show a marked TUNEL-p ositive reaction. Some metaphases show apoptotic morphology electron-micros copically. These results suggest that the testes of MRL strains will provid e a useful model for the study of the mechanism of metaphase-specific apopt osis in meiotic spermatocytes.