MRC Centre for Developmental Neurobiology, King's College London, Guy's Campus, London, UK.
Neural Dev. 2013 Mar 24;8:5. doi: 10.1186/1749-8104-8-5.
Morphogenesis requires developmental processes to occur both at the right time and in the right place. During neural tube formation in the zebrafish embryo, the generation of the apical specializations of the lumen must occur in the center of the neural rod after the neural cells have undergone convergence, invagination and interdigitation across the midline. How this coordination is achieved is uncertain. One possibility is that environmental signaling at the midline of the neural rod controls the schedule of apical polarization. Alternatively, polarization could be regulated by a timing mechanism and then independent morphogenetic processes ensure the cells are in the correct spatial location.
Ectopic transplantation demonstrates the local environment of the neural midline is not required for neural cell polarization. Neural cells can self-organize into epithelial cysts in ectopic locations in the embryo and also in three-dimensional gel cultures. Heterochronic transplants demonstrate that the schedule of polarization and the specialized cell divisions characteristic of the neural rod are more strongly regulated by time than local environmental signals. The cells' schedule for polarization is set prior to gastrulation, is stable through several rounds of cell division and appears independent of the morphogenetic movements of gastrulation and neurulation.
Time rather than local environment regulates the schedule of epithelial polarization in zebrafish neural rod.
形态发生需要在正确的时间和正确的地点发生发育过程。在斑马鱼胚胎神经管形成过程中，在神经细胞经过汇聚、内陷和中线交叉后，管腔的顶端特化必须在神经杆的中心产生。这种协调是如何实现的还不确定。一种可能性是神经杆中线的环境信号控制顶端极化的时间表。或者，极化可以通过定时机制来调节，然后独立的形态发生过程确保细胞处于正确的空间位置。
异位移植表明神经中线的局部环境不是神经细胞极化所必需的。神经细胞可以在胚胎的异位部位和三维凝胶培养物中自我组织成上皮样囊肿。异时性移植表明，极化的时间表和神经杆特有的特化细胞分裂受时间的调控要强于局部环境信号。细胞极化的时间表在原肠胚形成之前就已经确定，在经过几轮细胞分裂后仍然稳定，并且似乎独立于原肠胚形成和神经管形成的形态发生运动。
时间而不是局部环境调节斑马鱼神经杆中上皮细胞极化的时间表。
