Synaptic defects at meiosis I and non-obstructive azoospermia.

Background: Recent advances in immunofluorescence methodology have made it possible to directly monitor protein localization patterns in germ cells undergoing meiosis. We used this technology to examine the early stages of meiosis in testicular material obtained from men presenting for evaluation at infertility clinics.

Methods: Specifically, we compared meiotic progression, synapsis and recombination in 34 individuals with obstructive azoospermia ('controls') to 26 individuals with non-obstructive azoospermia (NOA) ('cases').

Results: In 9 of the 26 cases, no germ cells were identified, but in the remaining 17, there was at least some progression through meiosis. Most of these individuals appeared to have normal levels of spermatogenic activity, with little evidence of meiotic impairment. However, in three individuals, we observed either complete or partial meiotic arrest associated with abnormalities in synapsis.

Conclusions: This suggests that >10% of cases of unexplained NOA may be attributable to severe meiotic defects. The characterization of these meiotic arrest phenotypes may guide further research into the molecular basis of unexplained infertility.