Systematic molecular analyses for 115 karyotypically normal men with isolated non-obstructive azoospermia.

Area of Science:

• Human Genetics
• Reproductive Medicine
• Molecular Biology

Background:

• Isolated non-obstructive azoospermia (NOA) is a significant cause of male infertility.
• Previous studies implicated sex chromosomal abnormalities, AZF-linked microdeletions, and monogenic mutations in NOA.
• Over 160 genes have been identified as potentially causative or susceptibility genes for NOA.

Purpose of the Study:

• To investigate the role of copy-number variations (CNVs) in azoospermia factor (AZF) regions and monogenic mutations in Japanese men with isolated NOA and a normal 46,XY karyotype.
• To determine the frequency and spectrum of genetic causes contributing to NOA in this population.

Main Methods:

• Systematic molecular analyses were performed on 115 unrelated Japanese male patients with isolated NOA.
• AZF-linked CNVs were assessed using sequence-tagged PCR and multiplex ligation-dependent probe amplification.
• Whole exome sequencing (WES) was employed to screen for nucleotide variants, followed by an optimized sequence kernel association test (SKAT-O) for novel gene discovery.

Main Results:

• Thirteen types of AZF-linked CNVs were identified in 54.8% of patients, with a significant frequency (30.7%) even after excluding common polymorphisms.
• Known NOA-causative AZF-linked CNVs were found in 7.8% of cases.
• Rare damaging variants in known causative or spermatogenesis-associated genes were identified in another 7.8% of patients, suggesting oligogenicity in some cases.

Conclusions:

• Various AZF-linked CNVs are prevalent in Japanese NOA patients, expanding the understanding of structural variations in spermatogenic failure.
• The findings underscore the etiological heterogeneity of isolated NOA, with CNVs and monogenic mutations playing substantial roles.
• These genetic variations should be considered in the molecular diagnosis of male infertility and spermatogenic failure.