Osório Liliana, Teillet Marie-Aimée, Palmeirim Isabel, Catala Martin
UPMC Univ Paris 06, UMR 7622, Laboratoire de Biologie du Développement, Paris, France.
Int J Dev Biol. 2009;53(4):641-8. doi: 10.1387/ijdb.072517lo.
In the prospective lumbo-sacral region of the chick embryo, neurulation is achieved by cavitation of the medullary cord, a process called secondary neurulation. Neural crest cells (NCC) are generated in this region and they give rise to the same types of derivatives as in more rostral parts of the trunk where neurulation occurs by dorsal fusion of the neural plate borders (primary neurulation). However, no molecular data were available concerning the different steps of their ontogeny. We thus performed a detailed expression study of molecular players likely to participate in the generation of secondary NCC in chick embryos between Hamburger and Hamilton stages 18-20 (HH18-20) at the level of somites 30 to 43. We found that specification of secondary NCC involves, as in primary neurulation, the activity of several transcription factors such as Pax3, Pax7, Snail2, FoxD3 and Sox9, which are all expressed in the dorsal secondary neural tube as soon as full cavitation is achieved. Moreover, once specification has occurred, emigration of NCC from the dorsal neuroepithelium starts facing early dissociating somites and involves a series of changes in cell shape and adhesion, as well as interactions with the extracellular matrix. Furthermore, Bmp4 and Wnt1 expression precedes the detection of migratory secondary NCC and is coincident with maturation of adjacent somites. Altogether, this first study of molecular aspects of secondary NCC ontogeny has revealed that the mechanisms of neural crest generation occurring along the trunk region of the chick embryo are generally conserved and independent of the type of neurulation involved.
在鸡胚的腰骶部区域，神经胚形成是通过髓索空化实现的，这一过程称为次级神经胚形成。神经嵴细胞（NCC）在该区域产生，它们产生的衍生物类型与躯干更靠前部位相同，在躯干靠前部位神经胚形成是通过神经板边缘的背侧融合（初级神经胚形成）。然而，关于它们个体发育不同阶段的分子数据尚不可得。因此，我们对可能参与鸡胚在汉伯格和汉密尔顿18-20期（HH18-20）第30至43体节水平次级NCC生成的分子参与者进行了详细的表达研究。我们发现，次级NCC的特化与初级神经胚形成一样，涉及几种转录因子的活性，如Pax3、Pax7、Snail2、FoxD3和Sox9，一旦完全空化完成，它们就在背侧次级神经管中表达。此外，一旦特化发生，NCC从背侧神经上皮的迁出开始面对早期解离的体节，并涉及一系列细胞形状和黏附的变化，以及与细胞外基质的相互作用。此外，Bmp4和Wnt1的表达先于迁移的次级NCC的检测，并且与相邻体节的成熟同时发生。总之，这项关于次级NCC个体发育分子方面的首次研究表明，沿鸡胚躯干区域发生的神经嵴生成机制通常是保守的，且与所涉及的神经胚形成类型无关。
