Department of Genetics, Ribeirão Preto Medical School, University of São Paulo (USP), Ribeirão Preto, SP, Brazil.
Institute of Human Genetics, University of Münster, Münster, Germany.
Andrology. 2020 Mar;8(2):434-441. doi: 10.1111/andr.12704. Epub 2019 Nov 22.
The routine genetic analysis for diagnosing male infertility has not changed over the last twenty years, and currently available tests can only determine the etiology of 4% of unselected infertile patients. Thus, to create new diagnostic assays, we must better understand the molecular and genetic mechanisms of male infertility. Although next-generation sequencing allows for simultaneous analysis of hundreds of genes and the discovery of novel candidates related to male infertility, so far only a few gene candidates have enough sound evidence to support the gene-disease relationship.
Since complementary studies are required to validate genes, we aimed to analyze the presence of potentially pathogenic rare variants in a set of candidate genes related to azoospermia in a hitherto understudied South American population.
We performed whole exome sequencing in a group of 16 patients with non-obstructive azoospermia from Ribeirão Preto, Brazil. Based on a recent systematic review of monogenic causes of male infertility, we selected a set of 37 genes related to azoospermia, Sertoli-Cell-Only histology, and spermatogenic arrest to analyze. The identified variants were confirmed by Sanger sequencing, and their functional consequence was predicted by in silico programs.
We identified potential pathogenic variants in seven genes in six patients. Two variants, c.671A>G (p.(Asn224Ser)) in DMRT1 and c.91C>T (p.(Arg31Cys)) in REC8, have already been described in association with azoospermia. We also found new variants in genes that already have moderate evidence of being linked to spermatogenic failure (TEX15, KLHL10), in genes with limited evidence (DNMT3B, TEX14) and in one novel promising candidate gene that has no evidence so far (SYCE1L).
Although this study included a small number of patients, the process of rationally selecting genes allowed us to detect rare potentially pathogenic variants, providing supporting evidence for validating candidate genes associated with azoospermia.
过去二十年来，男性不育症的常规基因分析并未改变，目前可用的检测方法只能确定 4%未选择的不育患者的病因。因此，要创建新的诊断检测方法，我们必须更好地了解男性不育的分子和遗传机制。尽管下一代测序允许同时分析数百个基因，并发现与男性不育相关的新候选基因，但迄今为止，只有少数几个基因候选者有足够的可靠证据支持基因-疾病关系。
由于需要互补研究来验证基因，我们旨在分析一组与巴西里贝朗普雷图非梗阻性无精子症相关的候选基因中潜在致病性罕见变异的存在。
我们对来自巴西里贝朗普雷图的 16 名非梗阻性无精子症患者进行了全外显子组测序。基于最近对男性不育单基因病因的系统评价，我们选择了一组与无精子症、Sertoli 细胞仅组织学和精子发生停滞相关的 37 个候选基因进行分析。通过 Sanger 测序证实了鉴定出的变体，并通过计算机程序预测了其功能后果。
我们在 6 名患者的 7 个基因中发现了潜在的致病性变体。两个变体，c.671A>G(p.(Asn224Ser))在 DMRT1 中和 c.91C>T(p.(Arg31Cys))在 REC8 中，已经与无精子症相关联。我们还在与精子发生失败相关的基因（TEX15、KLHL10）、证据有限的基因（DNMT3B、TEX14）和一个目前尚无证据的新的有前途的候选基因（SYCE1L）中发现了新的变体。
尽管这项研究纳入的患者数量较少，但合理选择基因的过程使我们能够检测到罕见的潜在致病性变异，为验证与无精子症相关的候选基因提供了支持证据。
