Defects in early meiotic events are thought to play a critical role in male infertility; however, little is known regarding the relationship between early meiotic events and the chromosomal constitution of human sperm. Thus, we analyzed testicular tissue from 26 men (9 fertile and 17 infertile men), using immunofluorescent techniques to examine meiotic chromosomes, and fluorescent in situ hybridization to assess sperm aneuploidy. Based on a relatively small sample size, we observed that 42% (5/12) of men with impaired spermatogenesis displayed reduced genome-wide recombination when compared to the fertile men. Analysis of individual chromosomes showed chromosome-specific defects in recombination: chromosome 13 and 18 bivalents with only a single crossover and chromosome 21 bivalents lacking a crossover were more frequent among the infertile men. We identified two infertile men who displayed a novel meiotic defect in which the sex chromosomes failed to recombine: one man had an absence of sperm in the testes, while the other displayed increased sex chromosome aneuploidy in the sperm, resulting in a 45,X abortus after intracytoplasmic sperm injection. When all men were pooled, we observed an inverse correlation between the frequency of sex chromosome recombination and XY disomy in the sperm. Recombination between the sex chromosomes may be a useful indicator for identifying men at risk of producing chromosomally abnormal sperm. An understanding of the molecular mechanisms that contribute to sperm aneuploidy in infertile men could aid in risk assessment for couples undergoing assisted reproduction.
Male factor infertility has been associated with abnormal DNA methylation at imprinted genes. Little information is available on the status of imprinting in the sperm of men with azoospermia, including the association between aberrant imprinting and obstructive azoospermia (OA) or non-OA (NOA). Analysis of DNA methylation at imprinted genes in the sperm of men undergoing vasectomy reversal would aid determination of whether aberrant imprinting is associated with obstruction. Testicular sperm was retrieved from testicular biopsies obtained from men with azoospermia (NZ18), including OA (NZ10), NOA (NZ5), and unknown pathology (NZ3), and from men undergoing vasectomy reversal (NZ17). Sperm was also obtained from proven fertile men (NZ9). DNA methylation was investigated at multiple CpG sites within the differentially methylated regions (DMRs) of three imprinted genes, H19, IG-GTL2 and MEST, using bisulphite sequencing. Unique clones representative of single cells were analyzed. We found a significant decrease in DNA methylation at the H19 DMR in testicular sperm of azoospermic men compared with proven fertile men. The decrease was also significant between OA and proven fertile men, and between men undergoing vasectomy reversal and proven fertile men, suggesting that aberrant DNA methylation may be associated with obstruction. Changes in DNA methylation at IG-GTL2 and MEST DMRs among groups were not significant. Our data suggest that imprinting abnormalities may be associated with obstruction and may occur in response to changes in testicular environment and not only spermatogenesis failure, as previously reported. Methylation at the H19 DMR was particularly prone to modification in testicular sperm.
The fidelity of synapsis is a critical factor in determining the outcome of gametogenesis in humans, as the transcriptional inactivation of asynapsed regions may silence meiotic genes, leading to meiotic arrest and infertility.
The level of germ cell moscaicism and their meiotic sex chromosome configurations may determine sperm aneuploidy rate and fertility status in 47,XYY men. Our approach of immunostaining meiotic cells in the ejaculate is a novel method for investigating spermatogenesis in infertile men.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.