Formation and function of neural networks in the mouse spinal cord dorsal horn

我们分析了小鼠脊髓背角神经网络形成和功能的分子机制。脊髓连合神经元的轴突投射已经得到了很好的研究。然而，调控它们分化的分子和机制在很大程度上仍不清楚。我们建立了一种基于小鼠中枢神经系统体内电穿孔的高效基因转移方法，用于基因功能分析。通过使用这种方法的获得和功能丧失的分析，结合转基因和基因敲除小鼠，我们揭示了连合神经元的命运是由从原神经基因Math1到同源框基因Mbh1的转录级联决定的，并且Mbh1是连合神经元分化所必需的。染色质免疫沉淀分析表明，Math1蛋白通过其增强子直接激活Mbh1的表达。我们已经开展了微阵列分析，使用来自Mbh1错误表达的脊髓的RNA来寻找级联的下游基因。Mbh1基因的错误表达激活了许多基因。它们中的一些，如Netrin和Sit受体、Doc和Robs，已被认为在轴突的投射中起着关键作用。它们的表达受到从Math1到Mbh1的级联的时空组织方式的调控，这表明该级联对于连合轴突的投射是必不可少的。

We have analyzed molecular mechanisms underlying the formation and function of neural networks in the mouse spinal cord dorsal horn. Axon projection of commissural neurons in the spinal cord has been well studied. However, molecules and mechanisms to regulate their differentiation remained largely unknown. We have established a highly efficient gene transfer method based on in vivo elechroporation in the mouse central nervous system for functional analysis of genes. By gain- and loss-of-function analyses using this method, in combination with transgenic and knockout mice, we have revealed that the fate of commissural neurons is determined by the transcriptional cascade from a proneural gene, Math1, to a homeobox gene, Mbh1, and that Mbh1 is required for the differentiation of commissural neurons. Moreover, chromatin immunoprecipitation assays showed that the Math1 protein directly activates expression of Mbh1 through its enhancer. We have curried out microarray analyses to find downstream genes of the cascade using RNAs from the Mbh1-misexpressed spinal cord. Many genes were activated by misexpression of Mbh1. Some of them, such as Netrin and Slit receptors, Doc and Robes, have been known to play pivotal roles in the projection of axons. Their expressions were regulated in a spatiotemporally organized manner by the cascade from Math1 to Mbhl, suggesting that the cascade is essential for the projection of commiecnral axons.