BACKGROUND In the vertebrate spinal cord, motor neurons (MN) are generated in stereotypical numbers from a pool of dedicated progenitors (pMN) whose number depends on signals that control their specification but also their proliferation and differentiation rates. Although the initial steps of pMN specification have been extensively studied, how pMN numbers are regulated over time is less well characterized. RESULTS Here, we show that ephrinB2 and ephrinB3 are differentially expressed in progenitor domains in the ventral spinal cord with several Eph receptors more broadly expressed. Genetic loss-of-function analyses show that ephrinB2 and ephrinB3 inversely control pMN numbers and that these changes in progenitor numbers correlate with changes in motor neuron numbers. Detailed phenotypic analyses by immunostaining and genetic interaction studies between ephrinB2 and Shh indicate that changes in pMN numbers in ephrin mutants are due to alteration in progenitor identity at late stages of development. CONCLUSIONS Altogether our data reveal that Eph:ephrin signaling is required to control progenitor identities in the ventral spinal cord.

中文翻译：

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Eph / Ephrin信号控制腹脊髓中的祖细胞身份。

背景技术在脊椎动物的脊髓中，从专用祖细胞（pMN）中以定型数量产生运动神经元（MN），其数量取决于控制其规格以及其增殖和分化速率的信号。尽管已经对pMN规范的初始步骤进行了广泛的研究，但如何对pMN数随时间进行调节仍不太清楚。结果在这里，我们显示了ephrinB2和ephrinB3在腹侧脊髓的祖细胞域中差异表达，并且一些Eph受体表达更为广泛。遗传功能丧失分析表明，ephrinB2和ephrinB3反向控制pMN数量，并且祖细胞数量的这些变化与运动神经元数量的变化相关。通过在ephrinB2和Shh之间进行的免疫染色和遗传相互作用研究进行的详细表型分析表明，ephrinB2突变体中pMN数量的变化是由于发育后期祖细胞身份的改变所致。结论总的来说，我们的数据表明，Eph：ephrin信号是控制腹脊髓中祖细胞身份所必需的。