Development of the enteric nervous system

肠神经系统由于其神经细胞类型的数量和多样性，通常被称为第二大脑。肠道神经元和神经胶质组织在神经节相互连接的网络中，控制关键的胃肠道功能，如消化运动和选择性上皮通透性。******肠道神经系统在产前发育期间由神经管迁移的神经嵴细胞形成。在进入前肠间质后，所谓的肠神经嵴来源细胞（ENCCs）随后向后迁移，定植在中肠和后肠。不完全定植（由于迁移缺陷或ENCCs数量不足）导致远端肠道不同长度的神经节缺失，从而导致功能性肠梗阻，这在出生后不久就会致命。在小鼠中，这种表型被称为神经节巨结肠，并允许鉴定肠神经系统发育的关键调节因子（例如Gdnf/Ret通路成员）。神经发生和胶质瘤发生是在定植阶段开始的，然而这些过程中的缺陷通常会导致更微妙的表型。这可能就是为什么与控制ENCC迁移/增殖/存活的机制相比，肠内神经发生和胶质瘤发生的分子机制仍然不明确的原因。******利用转基因插入突变筛选中的小鼠神经节巨结肠表型，我们产生了三个突变小鼠系，命名为TashT， Holstein和Spot。这些突变使我们对ENCC迁移和增殖的调控有了重大发现。在Spot中，我们发现这两个过程都因过早的胶质细胞分化而受损。Spot插入突变破坏了沉默元件与Nr2f1-A830082K12Rik重叠基因对之间的远程相互作用，导致这两个基因在Spot ENCCs中过表达。我们进一步发现Nr2f1直接调控胶质生成线索下游胶质标记物的表达，而A830082K12Rik是顺式调节基因表达的lncRNA。所有这些数据为研究提供了一个坚实的框架，旨在阐明目前在肠道胶质形成过程中发挥作用的神秘分子机制。******启动于10年前，这个nserc资助的基础研究项目旨在揭示控制肠道神经系统发育的分子机制。在接下来的5年里，这项工作将集中在肠道胶质发生上。我们的目标是：***1)阐明斑点相关沉默元件A830082K12Rik和Nr2f1之间的调控相互作用；***2)确定Nr2f1相对于肠道胶质形成的其他调节因子的等级地位；***3)确定肠道胶质形成的新调控因子。***这项工作预计将对肠道神经系统领域以及更广泛的神经生物学领域产生重大而持久的影响

***The enteric nervous system is often referred to as the second brain due to the number and diversity of its neural cell types. Enteric neurons and glia are organized in interconnected networks of ganglia, which control key gastrointestinal functions such as digestive motility and selective epithelial permeability. ******The enteric nervous system forms during prenatal development from neural crest cells that migrate from the neural tube. Following their entry in the foregut mesenchyme, the so-called enteric neural crest-derived cells (ENCCs) then migrate posteriorly to colonize the midgut and hindgut. Incomplete colonization (due to defective migration or insufficient number of ENCCs) leads to a lack of neural ganglia over varying lengths of the distal gut, and consequently to functional bowel obstruction, which is lethal soon after birth. In mice, this phenotype is known as aganglionic megacolon and has allowed the identification of key regulators of enteric nervous system development (e.g. Gdnf/Ret pathway members). Neurogenesis and gliogenesis are initiated during the colonization phase, yet defects in these processes generally result in more subtle phenotypes. This is likely why, compared to the mechanisms governing ENCC migration/proliferation/survival, the molecular mechanisms underlying enteric neurogenesis and gliogenesis remain poorly defined. ******Taking advantage of the murine aganglionic megacolon phenotype in a transgenic insertional mutation screen, we generated three mutant mouse lines, named TashT, Holstein and Spot. These mutants allowed us to make major discoveries about the regulation of ENCC migration and proliferation. In Spot, we found that both processes are impaired because of premature glial differentiation. The Spot insertional mutation disrupts a long-range interaction between a silencer element and the Nr2f1-A830082K12Rik overlapping gene pair, resulting in overexpression of both genes in Spot ENCCs. We further discovered that Nr2f1 directly regulates the expression of glial markers downstream of gliogenic cues, whereas A830082K12Rik is a lncRNA regulating gene expression in cis. All these data provide a solid framework for studies aimed at elucidating the currently enigmatic molecular mechanisms at play during enteric gliogenesis.******Initiated 10 years ago, this NSERC-funded basic research program is aimed at unravelling the molecular mechanisms that control enteric nervous system development. For the next 5 years, this work will be focused on enteric gliogenesis. Our aims are to: ***1) Elucidate the regulatory interactions between the Spot-associated silencer element, A830082K12Rik and Nr2f1; ***2) Determine the hierarchical position of Nr2f1 relative to other regulators of enteric gliogenesis; ***3) Identify new regulators of enteric gliogenesis. ***This work is expected to have a significant and long-lasting impact on the enteric nervous system field as well as on the wider field of neurobiology.**