Stem Cells & Development, Department of Developmental Biology Pasteur Institute, Centre National de la Recherche Scientifique (CNRS) URA 2578, 75724 Paris Cedex 15, France.
Stem Cells. 2009 Nov;27(11):2769-80. doi: 10.1002/stem.220.
Multiple cell types arise from cells in the dermomyotome of the somite that express Pax3 and Pax7, and myogenesis is regulated by Notch signaling. The asymmetric cell fate determinant Numb is thought to promote differentiation of skeletal muscle and other lineages by negatively regulating Notch signaling. We used transgenesis to overexpress Numb spatiotemporally in Pax3(+)/Pax7(+) somitic stem and progenitor cells in mouse embryos using a spatiotemporally regulated enhancer element from the Myf5 locus that can target muscle progenitor cells prior to cell commitment. Molecular analyses as well as examination of dermal and skeletal muscle cell fates in vivo show that although Numb is thought to be associated with muscle differentiation, unexpectedly the common stem/progenitor pool size for these lineages is increased in Numb-transgenic embryos. Prospective isolation of the relevant transgenic cells and analysis by quantitative reverse-transcription polymerase chain reaction demonstrated that, in this context, canonical Notch targets are not significantly downregulated. These findings were corroborated using a Notch reporter mouse during the formation of somites and prior to lineage segregation. Thus, we propose that Numb can regulate the self-renewal of dermal and muscle progenitors during a lineage progression.
多种细胞类型起源于体节中的真皮肌节细胞，这些细胞表达 Pax3 和 Pax7，并且肌发生受 Notch 信号的调节。不对称细胞命运决定因子 Numb 被认为通过负向调节 Notch 信号来促进骨骼肌和其他谱系的分化。我们使用转基因技术，通过使用来自 Myf5 基因座的时空调节增强子元件，在小鼠胚胎中的 Pax3(+) / Pax7(+) 体节干细胞和祖细胞中时空表达 Numb。分子分析以及体内真皮和骨骼肌细胞命运的检查表明，尽管 Numb 与肌肉分化有关，但出人意料的是，在 Numb 转基因胚胎中，这些谱系的常见干细胞/祖细胞池大小增加。对相关转基因细胞的前瞻性分离和定量逆转录聚合酶链反应分析表明，在这种情况下，典型的 Notch 靶标没有显著下调。在体节形成和谱系分离之前，使用 Notch 报告基因小鼠对这些发现进行了证实。因此，我们提出 Numb 可以在谱系进展过程中调节真皮和肌肉祖细胞的自我更新。
