Morriss-Kay G, Wood H, Chen W H
Department of Human Anatomy, University of Oxford, UK.
Ciba Found Symp. 1994;181:51-63; discussion 63-9. doi: 10.1002/9780470514559.ch4.
During mammalian neurulation regional differences are evident between the cranial region, in which neurulation is most complex, the trunk as far as the caudal neuropore and the secondary neurulation region of the caudal trunk plus tail. Differences among these three regions are characterized by specific patterns of morphogenesis and by specific patterns of gene expression. During cranial neurulation distinct regions develop in the brain and the presomitic hindbrain forms seven rhombomeric divisions. The first clear morphological boundary is the preotic sulcus (later transformed into the gyrus between rhombomeres 2 and 3), which may limit cell movement as neuroepithelial cells rostral to it flow towards and into the rapidly expanding forebrain region. The formation of rhombomeres as morphological entities and the development of a normal rhombomere-specific pattern of homeobox and other gene expression domains depend on relatively low levels of retinoic acid. Retinoic acid receptors, which are retinoic acid-activated transcription factors, and retinoid binding proteins, which control the availability of retinoic acid to the receptors, show regional patterns of expression in the cranial, trunk and caudal regions of the neuroepithelium during neurulation. These patterns suggest a possible mechanism for region-specific gene expression during neurulation.
在哺乳动物神经胚形成过程中，颅区、直至尾神经孔的躯干以及尾侧躯干加尾部的次级神经胚形成区域之间存在明显的区域差异。这三个区域之间的差异表现为特定的形态发生模式和特定的基因表达模式。在颅神经胚形成过程中，脑内形成了不同的区域，前体节后脑形成了七个菱脑节段。第一个明显的形态学边界是耳前沟（后来转变为菱脑节2和3之间的脑回），当位于其前方的神经上皮细胞流向并进入快速扩展的前脑区域时，它可能会限制细胞运动。菱脑节作为形态学实体的形成以及同源盒和其他基因表达域的正常菱脑节特异性模式的发育取决于相对较低水平的视黄酸。视黄酸受体是视黄酸激活的转录因子，类视黄醇结合蛋白控制视黄酸向受体的可用性，在神经胚形成过程中，它们在神经上皮的颅区、躯干区和尾区呈现出区域表达模式。这些模式提示了神经胚形成过程中区域特异性基因表达的一种可能机制。
