Each vertebrate species appears to have a unique timing mechanism for forming somites along the vertebral column, and the process in human remains poorly understood at the molecular level due to technical and ethical limitations. Here, we report the reconstitution of human segmentation clock by direct reprogramming. We first reprogrammed human urine epithelial cells to a presomitic mesoderm (PSM) state capable of long-term self-renewal and formation of somitoids with an anterior-to-posterior axis. By inserting the RNA reporter Pepper into HES7 and MESP2 loci of these iPSM cells, we show that both transcripts oscillate in the resulting somitoids at ~5 h/cycle. GFP-tagged endogenous HES7 protein moves along the anterior-to-posterior axis during somitoid formation. The geo-sequencing analysis further confirmed anterior-to-posterior polarity and revealed the localized expression of WNT, BMP, FGF, and RA signaling molecules and HOXA-D family members. Our study demonstrates the direct reconstitution of human segmentation clock from somatic cells, which may allow future dissection of the mechanism and components of such a clock and aid regenerative medicine.

中文翻译：

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体外体节中人类节段时钟的再生

每个脊椎动物物种似乎都有独特的沿脊柱形成体节的计时机制，但由于技术和伦理的限制，人类的这一过程在分子水平上仍然知之甚少。在这里，我们报告了通过直接重编程重建人类分段时钟。我们首先将人尿液上皮细胞重新编程为体前中胚层（PSM）状态，能够长期自我更新并形成具有前后轴的体节。通过将 RNA 报告基因 Pepper 插入这些 iPSM 细胞的 HES7 和 MESP2 基因座，我们发现两种转录物在生成的体节中以约 5 小时/周期振荡。GFP 标记的内源 HES7 蛋白在体细胞形成过程中沿前后轴移动。地理测序分析进一步证实了前后极性，并揭示了 WNT、BMP、FGF 和 RA 信号分子以及 HOXA-D 家族成员的局部表达。我们的研究证明了从体细胞直接重建人类分段时钟，这可能允许未来剖析这种时钟的机制和组件，并有助于再生医学。