P-021 A novel SNP in HUWE1 promoter confers increased risk of NOA by affecting the RA/RARα pathway in Chinese individuals

Abstract

Abstract Study question The present study aimed to investigate the role of HUWE1 in non-obstructive azoospermia (NOA) etiology and germ cell differentiation. Summary answer An SNP mutation in HUWE1 promoter region downregulates HUWE1 expression in NOA patients, the genetic polymorphisms of HUWE1 are related to the pathogenesis of NOA. What is known already HUWE1, a ubiquitin ligase, is crucial to the development of male reproductive system and embryonic development. However, the specific role of HUWE1 in regulating germ cell differentiation is unclear, and clinical evidence for the relationship between HUWE1 and the pathogenesis of male infertility is lacking. Study design, size, duration 190 NOA Chinese patients were recruited and analyzed single nucleotide polymorphisms (SNPs) in HUWE1 gene. Participants/materials, setting, methods Regulation of HUWE1 gene expression by RARα factor was evaluated by performing ChIP assay, EMSA, and siRNA-mediated RARα knockdown. We used C18-4 cells to determine whether HUWE1 participated in RA-mediated RARα signaling and performed luciferase assay, CCK-8 assay, immunofluorescence staining, RT-qPCR, and western blot analysis. The expression level of HUWE1 and RARa was evaluated in clinical samples obtained from NOA or obstructive azoospermia (OA) patients using RT-qPCR. Main results and the role of chance We explored the mechanism by which polymorphism of the HUWE1 promoter leads to spermatogenesis disorders, and focused on the identification of mutations in the SNP site of the HUWE1 regulatory sequence among patients with NOA, which may influence HUWE1 expression. The results of in vitro experiments showed that RARα binds to the HUWE1 promoter region and regulates its expression. However, the regulatory effect of RARα weakened following introduction of the mutation into the HUWE1 regulatory sequence. The expression of spermatogonial differentiation-related gene STRA8 was impaired, and γH2AX foci accumulated following inhibition of HUWE1 gene expression using siRARα. Finally, to determine whether HUWE1 expression was important in patients with NOA, its expression was verified using testicular puncture samples collected from patients with NOA and the results revealed that HUWE1 expression was abnormal (P < 0.01). In addition, RARα expression was significantly downregulated (P < 0.001). Overall, our result support the hypothesis that HUWE1 expression is induced by the RA/RARα signaling pathway and it inhibit γH2AX foci accumulation, thereby considerably promoting sperm differentiation and meiotic prophase. Limitations, reasons for caution The effect of SNPs in HUWE1 on male infertility is further studied in a wider population. Wider implications of the findings Our study of HUWE1 and RA/RARα signaling pathway provides new information on the regulatory mechanism of spermiogenesis, suggesting that SNPs in HUWE1 promoter are etiological factors in patients with NOA and providing a rationale for further drug development to target HUWE1 in these patients. Trial registration number the National Key Research and Development Program of China (2018YFC1003603)