Developmental time rather than local environment regulates the schedule of epithelial polarization in the zebrafish neural rod
1 MRC Centre for Developmental Neurobiology, King’s College London, Guy’s Campus, London, SE1 1UL, UK
2 MRC-LMB, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge, CB2 0QH, UK
3 Laboratory of Developmental Biology, Institute of Marine Sciences and Limnology, Faculty of Sciences, Universidad Austral de Chile, Campus Isla Teja s/n, Valdivia, 5090000, Chile
4 Invasive Pathogens Laboratory, Institute of Environmental Science and Research, 34 Kenepuru Drive, Porirua, Wellington, New Zealand
Neural Development 2013, 8:5 doi:10.1186/1749-8104-8-5Published: 24 March 2013
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.