Premature separation of sister chromatids in human male meiosis.

BACKGROUND Meiotic disorders result in meiotic arrest and aneuploid spermatozoa, leading to male infertility, spontaneous abortions or affected offspring. We carried out meiotic studies in an infertile male to detect meiotic nondisjunction mechanisms leading to aneuploidy in spermatogenesis. METHODS AND RESULTS Meiotic studies were performed in testicular and semen samples from a 38-year-old teratozoospermic male with normal somatic karyotype and a history of spontaneous abortions. We analysed 262 spermatocytes (69 pachytene cells, 106 metaphases I (MI), 87 metaphases II (MII)) by multiplex-fluorescence in situ hybridization and 20,193 spermatozoa by multicolour-FISH with probes for chromosomes 9, 10, 15, 21, X and Y. The results indicate high increase of 21 and XY disomies, as well as diploidy in both spermatocytes at MII and spermatozoa (P < 0.0001). Achiasmate segregation of sex chromosomes was found in 3.4% of spermatocytes II, preceded by early-dissociated XY bivalent at MI (41.5% of cells). We also detected premature separation of sister chromatids (PSSC) in 4.6% of MII. CONCLUSIONS This individual presents high levels of numerical abnormalities in germ cells, caused by two different nondisjunction mechanisms during meiosis I. To our knowledge, this work represents the first time that PSSC has been demonstrated in human male germ cells.