Sha Xuan, Zhang Xin, Geng Hao, Li Yuqian, Xia Xun, Li Guotong, Hua Rong, Li Kuokuo, Gao Yang, Shen Qunshan, Guo Rui, Xu Yuping, He Xiaojin, Cao Yunxia, Liu Mingxi, Wu Huan
Reproductive Medicine Center, Department of Obstetrics and Gynecology, the First Affiliated Hospital of Anhui Medical University, Hefei, 230022, China.
State Key Laboratory of Reproductive Medicine and Offspring Health, The Affiliated Taizhou People's Hospital of Nanjing Medical University, Taizhou School of Clinical Medicine, Nanjing Medical University, Nanjing, 211166, China.
Cell Death Discov. 2025 Jul 1;11(1):292. doi: 10.1038/s41420-025-02581-y.
Non-obstructive azoospermia (NOA) represents the most severe form of male infertility; however, its genetic etiology remains largely elusive. MCM9 is crucial for DNA damage repair in mammalian somatic cells, playing a key role in regulating both homologous recombination (HR) and mismatch repair (MMR) pathways. In mice, MCM9 deficiency leads to spermatogenic failure characterized by progressive germ cell depletion and impaired HR repair. However, the underlying mechanism remains unclear in humans. Our study identified two novel homozygous loss-of-function (LoF) mutations in MCM9 in two unrelated NOA patients presenting with Sertoli cell-only syndrome (SCOS). The absence of testicular MCM9 confirmed the pathogenicity of these LoF mutations. Furthermore, diminished HR-mediated DNA repair capacity observed in HEK293T cells, either lacking MCM9 or overexpressing mutant MCM9 plasmids, highlighted the deleterious impact of these LoF mutations on HR repair. Additionally, the confirmed interaction between human testicular MCM9 and both MSH2 and MLH1, alongside findings that human MCM9 is predominantly expressed in spermatogonial stem cells and spermatogonia, provides compelling evidence for the involvement of the MCM9-mediated MMR pathway in maintaining genomic integrity and supporting the viability and proliferation of spermatogonia in humans. Given the poor outcomes of microdissection testicular sperm extraction (micro-TESE) observed in both probands, we propose that biallelic LoF mutations in MCM9 may serve as non-invasive molecular biomarkers for predicting micro-TESE failure. These findings enhance our understanding of the genetic basis of human NOA, particularly SCOS, and provide valuable insights for genetic counseling and fertility guidance tailored to these patients.
非梗阻性无精子症（NOA）是男性不育最严重的形式；然而，其遗传病因在很大程度上仍不清楚。MCM9对哺乳动物体细胞中的DNA损伤修复至关重要，在调节同源重组（HR）和错配修复（MMR）途径中均发挥关键作用。在小鼠中，MCM9缺陷导致生精失败，其特征为生殖细胞逐渐耗竭和HR修复受损。然而，在人类中其潜在机制仍不清楚。我们的研究在两名患有唯支持细胞综合征（SCOS）的无关NOA患者中鉴定出MCM9的两个新的纯合功能丧失（LoF）突变。睾丸中MCM9的缺失证实了这些LoF突变的致病性。此外，在缺乏MCM9或过表达突变MCM9质粒的HEK293T细胞中观察到HR介导的DNA修复能力降低，突出了这些LoF突变对HR修复的有害影响。此外，已证实人类睾丸MCM9与MSH2和MLH1之间存在相互作用，同时发现人类MCM9主要在精原干细胞和精原细胞中表达，这为MCM9介导的MMR途径参与维持人类基因组完整性以及支持精原细胞的存活和增殖提供了有力证据。鉴于两名先证者的显微切割睾丸取精术（micro-TESE）结果均不佳，我们提出MCM9的双等位基因LoF突变可能作为预测micro-TESE失败的非侵入性分子生物标志物。这些发现加深了我们对人类NOA，尤其是SCOS遗传基础的理解，并为针对这些患者的遗传咨询和生育指导提供了有价值的见解。
