Hingepoints and neural folds reveal conserved features of primary neurulation in the zebrafish forebrain

Primary neurulation is the process by which the neural tube, the central nervous system precursor, is formed from the neural plate. Incomplete neural tube closure occurs frequently, yet underlying causes remain poorly understood. Developmental studies in amniotes and amphibians have identified hingepoint and neural fold formation as key morphogenetic events and hallmarks of primary neurulation, the disruption of which causes neural tube defects. In contrast, the mode of neurulation in teleosts like zebrafish has remained highly debated. Teleosts are thought to have evolved a unique pattern of neurulation, whereby the neural plate infolds in absence of hingepoints and neural folds, at least in the hindbrain/trunk where it has been studied. We report here on zebrafish forebrain morphogenesis where we identify these morphological landmarks. Our findings reveal a deeper level of conservation of neurulation than previously recognized and establish the zebrafish as a model to understand human neural tube development.