Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China.
Cell Death Dis. 2013 May 2;4(5):e617. doi: 10.1038/cddis.2013.138.
Our previous studies have shown that microRNA-383 (miR-383) expression is downregulated in the testes of infertile men with maturation arrest (MA). Abnormal testicular miR-383 expression may potentiate the connections between male infertility and testicular germ cell tumors. However, the mechanisms underlying the targeting and functions of miR-383 during spermatogenesis remain unknown. In this study, we found that fragile X mental retardation protein (FMRP) was associated with 88 miRNAs in mouse testis including miR-383. Knockdown of FMRP in NTERA-2 (NT2) (testicular embryonal carcinoma) cells enhanced miR-383-induced suppression of cell proliferation by decreasing the interaction between FMRP and miR-383, and then affecting miR-383 binding to the 3'-untranslated region of its target genes, including interferon regulatory factor-1 (IRF1) and Cyclin D1 both in vivo and in vitro. On the other hand, FMRP levels were also downregulated by overexpression of miR-383 in NT2 cells and GC1 (spermatogonia germ cell line). miR-383 targeted to Cyclin D1 directly, and then inhibited its downstream effectors, including phosphorylated pRb and E2F1, which ultimately resulted in decreased FMRP expression. Reduced miR-383 expression, dysregulated cyclin-dependent kinase 4 expression (one of the downstream genes of miR-383) and increased DNA damage were also observed in the testes of Fmr1 knockout mice and of MA patients with a downregulation of FMRP. A potential feedback loop between FMRP and miR-383 during spermatogenesis is proposed, and FMRP acts as a negative regulator of miR-383 functions. Our data also indicate that dysregulation of the FMRP-miR-383 pathway may partially contribute to human spermatogenic failure with MA.
我们之前的研究表明，在患有成熟阻滞（MA）的不育男性的睾丸中，miR-383（微小 RNA-383）的表达下调。睾丸中异常的 miR-383 表达可能增强了男性不育症与睾丸生殖细胞肿瘤之间的联系。然而，miR-383 在精子发生过程中的靶向和功能的机制仍不清楚。在这项研究中，我们发现脆性 X 智力低下蛋白（FMRP）与包括 miR-383 在内的 88 种小鼠睾丸中的 miRNA 相关。在 NTERA-2（NT2）（睾丸胚胎癌细胞）细胞中敲低 FMRP 可通过减少 FMRP 与 miR-383 之间的相互作用来增强 miR-383 诱导的细胞增殖抑制作用，进而影响 miR-383 结合到其靶基因的 3'-非翻译区，包括干扰素调节因子-1（IRF1）和细胞周期蛋白 D1，无论是在体内还是在体外。另一方面，在 NT2 细胞和 GC1（精原细胞系）中过表达 miR-383 也会下调 FMRP 水平。miR-383 靶向 Cyclin D1 直接抑制其下游效应物，包括磷酸化的 pRb 和 E2F1，最终导致 FMRP 表达减少。在 Fmr1 敲除小鼠和 FMRP 下调的 MA 患者的睾丸中也观察到 miR-383 表达降低、细胞周期蛋白依赖性激酶 4 表达失调（miR-383 的下游基因之一）和 DNA 损伤增加。提出了在精子发生过程中 FMRP 和 miR-383 之间存在潜在的反馈回路，并且 FMRP 作为 miR-383 功能的负调节剂。我们的数据还表明，FMRP-miR-383 通路的失调可能部分导致 MA 患者的人类精子发生失败。
