论文部分内容阅读
During vertebrate neurulation, extensive cell movements transform the flat neural plate into the neural tube.This dynamic morphogenesis requires the tissue to bear a certain degree of plasticity to accommodate shape and position changes of individual cells as well as intercellular cohesiveness to maintain tissue integrity and architecture.The proper balance between tissue plasticity and cohesiveness relies on modulations of cell-cell adhesion.Although it is known that apicobasal polarity plays essential roles in modulating coordinated cell-cell adhesion, the mechanisms of the modulations are not yet fully understood.In this study, we analyzed the spatial-temporal dynamics of apicobasal polarity at the genetic, biophysical, and ultrastructural levels during zebrafish neural development.We show that the expressions of apical polarity genes follow delicate spatial-temporal orders that are conserved among different vertebrate species.For example, the expression ofN-Cad/ZO-1 complex is required to precede that of Lin7c/Nok/Crumbs complex, and disturbance of this spatial-temporal order results in deleterious consequences in neurulation.We also show that the Crumbs polarity proteins directly mediate physical cell-cell adhesion, which underlie the late-onset enhancement of apicobasal polarity and intercellular cohesion during neurulation as well as the maintenance of geometric organization of cone photoreceptor mosaics in developed retina.In addition, these transcriptional and biophysical adhesion modulations correlate well with the modifications of the ultrastructural features of the cell-cell adhesion complexes.Together, the stepwise modulations ofapicobasal polarity and cell-cell adhesion play critical roles in the morphogenesis of the neuroepithelium from a more plastic and less cohesive tissue to a less plastic and more cohesive tissue.Such modulations may underlie the dynamic-to-stable morphogenesis of other epithelium-derived tissues as well.