BACKGROUND Non-obstructive azoospermia (NOA) is a multifactorial disorder whose molecular basis remains largely unknown. Circular RNAs (CircRNAs), a novel class of endogenous RNAs, have been recognized to play important roles in many biological processes. However, little is known about the expression patterns and functions of circRNAs in human testes involved in NOA. METHODS In this study, the testicular circRNA expression profile were explored in NOA patients and the controls by high-throughput circRNA microarray. Real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) was performed to confirm the microarray data. Bioinformatics analyses including the circRNA/miRNA/mRNA interaction network, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were used to predict the functions of differentially expressed circRNAs. RESULTS A total of 368 differentially down-regulated and 526 up-regulated circRNAs were detected in NOA patients. These findings have been verified by qRT-PCR on 6 selected circRNAs. Among these differentially expressed circRNAs, the hsa_circRNA_0023313 was obviously up-regulated in testicular tissue of NOA patients. The most likely potential target miRNA for hsa_circRNA_0023313 include hsa-miR-520d-3p, hsa-miR-373-3p, hsa-miR-372-3p, hsa-miR-302c-3p and hsa-miR-130b-5p. Function analysis indicated that hsa_circRNA_0023313 was ubiquitin-protein transferase activity and chromatin binding. KEGG analysis revealed that the top five pathways related to hsa_circRNA_0023313 were endocytosis, meiosis, FoxO signaling pathway, ubiquitin mediated proteolysis and AMPK signaling pathway. CONCLUSIONS This is the first report that the testicular circRNA expression profile is altered in NOA patients indicating circRNAs might play important roles in regulating spermatogenesis and be potential biomarkers for the diagnosis and treatment of NOA.

中文翻译：

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非阻塞性无精子症患者睾丸组织中CircRNA表达谱和功能分析

背景技术非阻塞性无精子症（NOA）是一种多因素疾病，其分子基础仍是未知之数。环状RNA（CircRNA）是一类新型的内源RNA，已被公认在许多生物学过程中起着重要作用。然而，关于参与NOA的人类睾丸中circRNA的表达模式和功能的了解甚少。方法在本研究中，通过高通量circRNA微阵列探索了NOA患者和对照组睾丸circRNA的表达谱。进行实时定量逆转录聚合酶链反应（qRT-PCR）以确认微阵列数据。生物信息学分析，包括circRNA / miRNA / mRNA相互作用网络，基因本体论（GO）和京都基因与基因组百科全书（KEGG）途径分析用于预测差异表达的circRNA的功能。结果在NOA患者中总共检测到368个差异下调的circRNA和526个上调的circRNA。这些发现已通过qRT-PCR对6个选定的circRNA进行了验证。在这些差异表达的circRNA中，hsa_circRNA_0023313在NOA患者的睾丸组织中明显上调。hsa_circRNA_0023313最可能的潜在靶标miRNA包括hsa-miR-520d-3p，hsa-miR-373-3p，hsa-miR-372-3p，hsa-miR-302c-3p和hsa-miR-130b-5p。功能分析表明，hsa_circRNA_0023313具有泛素蛋白转移酶活性和染色质结合能力。KEGG分析显示，与hsa_circRNA_0023313相关的前五个途径是胞吞作用，减数分裂，FoxO信号通路，泛素介导的蛋白水解和AMPK信号通路。结论这是第一篇关于NOA患者睾丸circRNA表达谱发生改变的报道，表明circRNA可能在调节精子发生中起重要作用，并可能成为诊断和治疗NOA的潜在生物标志物。