Nonobstructive azoospermia (NOA) is a common cause of infertility and is defined as the complete absence of sperm in ejaculation due to defective spermatogenesis. The aim of this study was to identify the genetic etiology of NOA in an infertile male from a Chinese consanguineous family. A homozygous missense variant of the membrane-bound O-acyltransferase domain-containing 1 (MBOAT1) gene (c.770C>T, p.Thr257Met) was found by whole-exome sequencing (WES). Bioinformatic analysis also showed that this variant was a pathogenic variant and that the amino acid residue in MBOAT1 was highly conserved in mammals. Quantitative polymerase chain reaction (Q-PCR) analysis showed that the mRNA level of MBOAT1 in the patient was 22.0% lower than that in his father. Furthermore, we screened variants of MBOAT1 in a broader population and found an additional homozygous variant of the MBOAT1 gene in 123 infertile men. Our data identified homozygous variants of the MBOAT1 gene associated with male infertility. This study will provide new insights for researchers to understand the molecular mechanisms of male infertility and will help clinicians make accurate diagnoses.

Keywords: male infertility; membrane-bound O-acyltransferase domain-containing 1; nonobstructive azoospermia; whole-exome sequencing

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