Druckenbrod Noah R, Epstein Miles L
Department of Anatomy and Neuroscience Training Program, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA.
Development. 2009 Sep;136(18):3195-203. doi: 10.1242/dev.031302.
The enteric nervous system (ENS) develops from neural crest cells (NCCs) that enter the foregut and hindgut to become enteric neural-crest-derived cells (ENCCs). When these cells of neural crest origin fail to colonize the terminal hindgut, this aganglionic region becomes non-functional and results in a condition in humans known as Hirschsprung's disease (HSCR). One of the genes associated with HSCR is endothelin receptor type B (Ednrb). To study the development of colonic aganglionosis we have utilized a novel knockout mouse (Ednrb(flex3/flex3)), in which the expression of a null Ednrb allele and YFP is confined to NCCs. We have identified two primary cellular defects related to defective EDNRB signaling. First, ENCC advance in Ednrb(flex3/flex3) embryos is delayed shortly after NCCs enter the gut. Apart from this early delay, Ednrb(flex3/flex3) ENCCs advance normally until reaching the proximal colon. Second, as Ednrb(flex3/flex3) ENCCs reach the colon at E14.5, they display migratory defects, including altered trajectories and reduced speed, that are not dependent on proliferation or differentiation. We constructed grafts to test the ability of donor ENCCs to invade a recipient piece of aganglionic colon. Our results indicate that the age of the recipient, and not the age or genotype of donor ENCCs, determines whether the colon is invaded. We identify changes in laminin expression that are associated with the failure of ENCCs to invade recipient tissue. Together, our data suggest that a defect in pre-enteric Ednrb(flex3/flex3) NCCs results in delayed colonic arrival, which, due to environment changes in the colon, is sufficient to cause aganglionosis.
肠神经系统（ENS）由进入前肠和后肠的神经嵴细胞（NCCs）发育而来，这些细胞进而成为肠神经嵴衍生细胞（ENCCs）。当这些神经嵴来源的细胞无法定植于终末后肠时，这个无神经节区域就会失去功能，从而导致人类患上一种名为先天性巨结肠症（HSCR）的疾病。与HSCR相关的基因之一是内皮素B型受体（Ednrb）。为了研究结肠神经节缺如的发育情况，我们利用了一种新型基因敲除小鼠（Ednrb(flex3/flex3)），其中无效的Ednrb等位基因和黄色荧光蛋白（YFP）的表达仅限于NCCs。我们确定了与EDNRB信号缺陷相关的两个主要细胞缺陷。首先，在NCCs进入肠道后不久，Ednrb(flex3/flex3)胚胎中的ENCC推进就会延迟。除了这种早期延迟外，Ednrb(flex3/flex3)的ENCCs在到达近端结肠之前通常会正常推进。其次，当Ednrb(flex3/flex3)的ENCCs在胚胎发育第14.5天到达结肠时，它们会表现出迁移缺陷，包括轨迹改变和速度降低，这些缺陷并不依赖于增殖或分化。我们构建了移植体来测试供体ENCCs侵入受体无神经节结肠段的能力。我们的结果表明，受体的年龄，而非供体ENCCs的年龄或基因型，决定了结肠是否会被侵入。我们确定了层粘连蛋白表达的变化，这些变化与ENCCs无法侵入受体组织有关。总之，我们的数据表明，肠前Ednrb(flex3/flex3) NCCs的缺陷导致结肠到达延迟，由于结肠环境的变化，这足以导致神经节缺如。
