PL 30. Screening and identification of the genes related to idiopathic azoospermia

Azoospermia is the medical condition of a male not having any measurable level of sperm in his semen, which affects about 1% of the male population and may be seen in up to 20% of male infertility situations. Genetic factors are the main reason for non-obstructive azoospermia, but the exact causes for most of the patient are unknown. The present study is to detect the mutations in the genes related to spermatogenesis in the patients with idiopathic azoospermia by massively parallel sequencing.

The peripheral blood samples from 766 patients with idiopathic azoospermia and 221 men with proven fertility were collected from Peking University Shenzhen Hospital and The Center of Reproductive Medicine, Tongji Medical College. Genomic DNA was isolated from the blood sample. The exons of 656 genes, which are reported to relate to spermatogenesis and male infertility, were selectively captured by NimbleGen custom array, and followed by the standard Illumina-based resequencing procedures. Mutation analysis for all the exons of the genes was performed with novoSNP. Novel coding mutations in the genes were defined as those variants that had not been annotated in dbSNP or in the publicly available database. PCR and sequencing were used to validate the novel mutation from the Illumina-based resequencing.

Functional or causative mutations accounting for idiopathic azoospermia are assumed to be under strong negative selection in the general health population. Therefore, here we focused most of the analysis on the rare non-silent variants and identified a total of 84 genes showing substantial enrichment of novel mutations in the patients. The percentages of individuals harboring novel nonsilent mutations in four or more highlighted genes that showed substantial trend of mutation enrichment in the patients and the men with proven fertility are 44.77% and 6.78%, respectively. The mean number of highlighted genes in the patients and the men with proven fertility are 3.4 and 1.7, respectively.

The patients with idiopathic azoospermia harbored more rare non-silent mutations in multiple genes, which may confer risk to idiopathic azoospermia.