Wnt7A identifies embryonic γ-motor neurons and reveals early postnatal dependence of γ-motor neurons on a muscle spindle-derived signal.
Wnt7A identifies embryonic γ-motor neurons and reveals early postnatal dependence of γ-motor neurons on a muscle spindle-derived signal.
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DOI：
10.1523/jneurosci.1160-12.2012
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发表时间：
2012-06-20
期刊：
影响因子：
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通讯作者：
Kaltschmidt JA
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文献类型：
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作者：
Ashrafi S;Lalancette-Hébert M;Friese A;Sigrist M;Arber S;Shneider NA;Kaltschmidt JA
运动池由异质的运动神经元群组成，它们支配不同的肌内目标。虽然运动神经元组织成运动池的过程已经得到了很好的描述，但运动池多样化为功能不同类别的时间过程和机制仍不清楚。 γ 运动神经元 (γ-MN) 和 α 运动神经元 (α-MN) 在大小、分子特性、突触输入和外周目标方面有所不同。 α-MN 支配梭外骨骼肌纤维以介导肌肉收缩，而 γ-MN 支配肌梭的梭内纤维，并调节肌梭对拉伸的敏感性。在这项研究中，我们发现分泌的信号分子 Wnt7a 在胚胎第 17.5 天时在小鼠脊髓的 γ-MN 中选择性表达，并在出生后第三周继续从分子上区分 γ;- 和 α-MN。我们的数据表明，Wnt7a 是已知最早的 γ-MN 标记，支持胚胎阶段 α-MN 和 γ-MN 之间的发育差异模型。此外，使用 Wnt7a 表达作为 γ-MN 身份的早期标记，我们证明了 γ-MN 在出生后第一周对肌梭衍生的、不依赖 GDNF 的信号的先前未知的依赖性。
Motor pools comprise a heterogeneous population of motor neurons that innervate distinct intramuscular targets. While the organization of motor neurons into motor pools has been well described, the time course and mechanism of motor pool diversification into functionally distinct classes remains unclear. γ-Motor neurons (γ-MNs) and α-motor neurons (α-MNs) differ in size, molecular identity, synaptic input and peripheral target. While α-MNs innervate extrafusal skeletal muscle fibers to mediate muscle contraction, γ-MNs innervate intrafusal fibers of the muscle spindle, and regulate sensitivity of the muscle spindle in response to stretch. In this study, we find that the secreted signaling molecule Wnt7a is selectively expressed in γ-MNs in the mouse spinal cord by embryonic day 17.5 and continues to molecularly distinguish γ;-from α-MNs into the third postnatal week. Our data demonstrate that Wnt7a is the earliest known γ-MN marker, supporting a model of developmental divergence between α- and γ-MNs at embryonic stages. Furthermore, using Wnt7a expression as an early marker of γ-MN identity, we demonstrate a previously unknown dependence of γ-MNs on a muscle spindle-derived, GDNF-independent signal during the first postnatal week.