Stern H M, Brown A M, Hauschka S D
University of Washington, Department of Biochemistry, Seattle, WA 98195, USA.
Development. 1995 Nov;121(11):3675-86. doi: 10.1242/dev.121.11.3675.
Previous studies have demonstrated that the neural tube/notochord complex is required for skeletal muscle development within somites. In order to explore the localization of myogenic inducing signals within the neural tube, dorsal or ventral neural tube halves were cultured in contact with single somites or pieces of segmental plate mesoderm. Somites and segmental plates cultured with the dorsal half of the neural tube exhibited 70% and 85% myogenic response rates, as determined by immunostaining for myosin heavy chain. This response was slightly lower than the 100% response to whole neural tube/notochord, but was much greater than the 30% and 10% myogenic response to ventral neural tube with and without notochord. These results demonstrate that the dorsal neural tube emits a potent myogenic inducing signal which accounts for most of the inductive activity of whole neural tube/notochord. However, a role for ventral neural tube/notochord in somite myogenic induction was clearly evident from the larger number of myogenic cells induced when both dorsal neural tube and ventral neural tube/notochord were present. To address the role of a specific dorsal neural tube factor in somite myogenic induction, we tested the ability of Wnt-1-expressing fibroblasts to promote paraxial mesoderm myogenesis in vitro. We found that cells expressing Wnt-1 induced a small number of somite and segmental plate cells to undergo myogenesis. This finding is consistent with the localized dorsal neural tube inductive activity described above, but since the ventral neural tube/notochord also possesses myogenic inductive capacity yet does not express Wnt-1, additional inductive factors are likely involved.
先前的研究表明，神经管/脊索复合体对于体节内骨骼肌的发育是必需的。为了探究神经管内成肌诱导信号的定位，将神经管的背侧或腹侧半部分与单个体节或节段板中胚层碎片接触培养。通过对肌球蛋白重链进行免疫染色测定，与神经管背侧半部分一起培养的体节和节段板表现出70%和85%的成肌反应率。这种反应略低于对整个神经管/脊索的100%反应，但远高于对有或没有脊索的腹侧神经管的30%和10%的成肌反应。这些结果表明，背侧神经管发出一种强大的成肌诱导信号，该信号占整个神经管/脊索诱导活性的大部分。然而，当背侧神经管和腹侧神经管/脊索都存在时，诱导出的成肌细胞数量更多，这清楚地表明腹侧神经管/脊索在体节成肌诱导中起作用。为了研究特定背侧神经管因子在体节成肌诱导中的作用，我们测试了表达Wnt-1的成纤维细胞在体外促进轴旁中胚层成肌的能力。我们发现，表达Wnt-1的细胞诱导少量体节和节段板细胞发生成肌作用。这一发现与上述局部背侧神经管诱导活性一致，但由于腹侧神经管/脊索也具有成肌诱导能力但不表达Wnt-1，可能还涉及其他诱导因子。
