DAILY RHYTHMS IN MALE-MICE MEIOSIS

Various processes associated with mammalian reproduction exhibit circa dian rhythms, yet no information is available concerning the presence of rhythmicity in meiosis-the crucial process of the production of sex cells. Following meiosis in cells derived from male mice exposed in v ivo to daily light-dark cycles (LD), we were able to demonstrate the e xistence of a clear 24h rhythmic pattern in the overall meiotic proces s, as well as in the production of spermatids, the immediate products of male meiosis and the precursors of male sex cells. On the other han d, cells of free-running male mice exposed to constant external condit ions (light-light, LL) revealed a 12h rhythmic pattern in the overall meiotic process, indicating the endogenous nature of this rhythm. The existence of a 24h rhythm component in a long-lasting (approximately 1 2 days) process like meiosis suggests a time-dependent gating mechanis m that controls the dynamics of miocyte arrest and release. The 12h rh ythms observed in LL may indicate the presence of either a 12h rhythm component or of two 24h endogenous components, phased 12h from each ot her, that are coupled in daily LD cycles and split up in the free-runn ing condition (LL). The rhythmic pattern observed in the course of mal e meiosis might have significant implications for male reproduction.