Novel Variants in HFM1 Lead to Male Infertility Due to Non-obstructive Azoospermia

Abstract Background Non-obstructive azoospermia (NOA) is the most severe form of male infertility. More than half of the NOA patients were idiopathic for their etiology, in whom it’s difficult to retrieve sperm despite the application of microsurgical testicular sperm extraction (microTESE). Therefore, we conducted to this study to identify the potential genetic factors responsible for NOA, and investigate the sperm retrieval rate of microTESE for the genetic defected NOA.Methods One NOA patient from a consanguineous family (F1-II-1) and fifty NOA patients from non-consanguineous families were included in the study. Semen analyses, chromosome karyotypes, screening of Y chromosome microdeletions, sex hormone testing, and subsequent testicular biopsy were performed to categorize NOA or obstructive azoospermia. Potentialgenetic variants were identified by whole exome sequencing (WES),and confirmed by Sanger sequencing in F1 II-1. The candidate genes were screened in the other fifty NOA patients. Further experiments including quantitative real time-polymerase chain reaction and western blotting were performed to verify the effects of gene variation on gene expression.Results Normal somatic karyotypes and Y chromosome microdeletions were examined in all patients. Hematoxylin and eosin staining (H&E) of the testicular tissues suggested meiotic arrest, and a novel homozygous HFM1 variant (c.3490C>T: p.Q1164X) was identified in F1 II-1. Furthermore, another homozygous HFM1 variant (c.3470G>A: p.C1157Y) was also verified in F2 II-1 from the fifty NOA patients. Significantly decreased expression levels of HFM1 mRNA and protein were observed in the testicular tissues of these two mutants compared with controls. MicroTESE was performed in these two patients, while no sperm were retrieved. Conclusions Our study identified two novel homozygous variants of HFM1 that are responsible for spermatogenic failure and NOA, even microTESE can not contribute to retrieve sperm in these patients.