Correlation between the aberrant human testicular germ-cell gene expression and disruption of spermatogenesis leading to male infertility

Abstract

AbstractSpermatogenesis is characterized by sequential gene-expression at precise stages in progression of differentiation of the germ cells. Any alteration in expression of the critical genes is responsible for arrest of spermatogenesis associated with infertility. Inspite of advances the differential gene expression accompanying spermatogenesis, the corresponding regulatory mechanisms and their correlation to human infertility have not been clearly established. This study aims to identify the gene expression pattern of the human testicular germ cells from the patients either with obstructive azoospermia with complete intra-testicular spermatogenesis or non-obstructive azoospermia with spermatogenesis arrested at different stages and correlate the same to infertility. The testicular transcriptomes of 3 OA and 8 NOA patients and pooled testicular RNA (commercial source) were analyzed for their differential gene expression to identify potential regulators of spermatogenesis and the results were further validated in all of the 44 patients clinically diagnosed with azoospermia undergoing sperm retrieval surgery over the study period and 4 control samples included in this study. Analyses of the differential transcriptome led to identification of genes enriched in a specific testicular cell type and subsequently, several regulators of the diploid-double-diploid-haploid transitions in the human spermatogenesis were identified. Perturbations in the expression of these genes were identified as the potential causes of the spermatogenic arrest seen in azoospermia and thus the potential mediators of human male infertility. Another interesting observation was the increased autophagy in the testes of patients with non-obstructive azoospermia. The present study suggests that the regulation of the diploid-double-diploid-haploid transition is multigenic with the tandem alteration of several genes resulting in infertility. In conclusion, this study identified some of the genetic regulators controlling spermatogenesis using comparative transcriptome analyses of testicular tissues from azoospremic individuals and showed how alterations in several genes results in disruption of spermatogenesis and subsequent infertility. This study also provides interesting insights into the gene expression patterns of the Indian population that were not available earlier.