Department of Cell and Developmental Biology, University of East Anglia, Norwich NR4 7TJ, United Kingdom.
Proc Natl Acad Sci U S A. 2011 Jul 19;108(29):11936-41. doi: 10.1073/pnas.1105362108. Epub 2011 Jul 5.
Commitment of progenitors in the dermomyotome to myoblast fate is the first step in establishing the body musculature. Pax3 is a crucial transcription factor, important for skeletal muscle development and expressed in myogenic progenitors in the dermomyotome of developing somites and in migratory muscle progenitors that populate the limb buds. Down-regulation of Pax3 is essential to ignite the myogenic program, including up-regulation of myogenic regulators, Myf-5 and MyoD. MicroRNAs (miRNAs) confer robustness to developmental timing by posttranscriptional repression of genetic programs that are related to previous developmental stages or to alternative cell fates. Here we demonstrate that the muscle-specific miRNAs miR-1 and miR-206 directly target Pax3. Antagomir-mediated inhibition of miR-1/miR-206 led to delayed myogenic differentiation in developing somites, as shown by transient loss of myogenin expression. This correlated with increased Pax3 and was phenocopied using Pax3-specific target protectors. Loss of myogenin after antagomir injection was rescued by Pax3 knockdown using a splice morpholino, suggesting that miR-1/miR-206 control somite myogenesis primarily through interactions with Pax3. Our studies reveal an important role for miR-1/miR-206 in providing precision to the timing of somite myogenesis. We propose that posttranscriptional control of Pax3 downstream of miR-1/miR-206 is required to stabilize myoblast commitment and subsequent differentiation. Given that mutually exclusive expression of miRNAs and their targets is a prevailing theme in development, our findings suggest that miRNA may provide a general mechanism for the unequivocal commitment underlying stem cell differentiation.
先驱细胞向成肌细胞命运的分化是建立体节肌肉的第一步。Pax3 是一个关键的转录因子，对于骨骼肌的发育非常重要，并在发育中的体节真皮肌节中的成肌前体细胞和在支配肢体的迁移肌肉前体细胞中表达。Pax3 的下调对于引发成肌程序至关重要，包括上调成肌调节因子 Myf-5 和 MyoD。microRNAs（miRNAs）通过对与前一个发育阶段或替代细胞命运相关的遗传程序进行转录后抑制，赋予发育时间的稳健性。在这里，我们证明了肌肉特异性 miRNAs miR-1 和 miR-206 直接靶向 Pax3。用反义寡核苷酸抑制 miR-1/miR-206 导致发育中的体节中成肌分化延迟，如肌生成素表达的短暂丧失所示。这与 Pax3 的增加相关，并使用 Pax3 特异性靶标保护剂进行表型模拟。反义寡核苷酸注射后的肌生成素丢失可以通过剪接形态发生素来挽救 Pax3 敲低，这表明 miR-1/miR-206 通过与 Pax3 的相互作用主要控制体节成肌作用。我们的研究揭示了 miR-1/miR-206 在提供体节成肌时间精度方面的重要作用。我们提出，miR-1/miR-206 下游的 Pax3 转录后控制对于稳定成肌细胞的分化是必需的。鉴于 miRNA 和它们的靶标的相互排斥表达是发育中的一个普遍主题，我们的发现表明 miRNA 可能为干细胞分化所必需的明确承诺提供了一种普遍机制。
