No abstract

Neurulation transforms the neuroectoderm into the neural tube. This transformation relies on reorganising the configurational relationships between the orientations of intrinsic polarities of neighbouring cells. These orientational intercellular relationships are established, maintained, and modulated by orientational cell adhesions (OCAs). Here, using zebrafish (Danio rerio) neurulation as a major model, we propose a new perspective on how OCAs contribute to the parallel, antiparallel, and opposing intercellular relationships that underlie the neural plate–keel–rod–tube transformation, a stepwise process of cell aggregation followed by cord hollowing. We also discuss how OCAs in neurulation may be regulated by various adhesion molecules, including cadherins, Eph/Ephrins, Claudins, Occludins, Crumbs, Na+/K+‐ATPase, and integrins. By comparing neurulation among species, we reveal that antiparallel OCAs represent a conserved mechanism for the fusion of the neural tube. Throughout, we highlight some outstanding questions regarding OCAs in neurulation. Answers to these questions will help us understand better the mechanisms of tubulogenesis of many tissues.

By using the techniques of partial digestion of cell wall and selective extraction, we examined the cytoskeleton of wheat young leaf cells under scanning electron microscope(SEM). A 3-dimensional cytoskeletal system, showing some new features, was observed. The cortical network located beneath the cross wall was an anastomosing organization. The association of nucleus with the cell wall by some skeletal filaments was also found. It is noticeable that there were cytoskeletal filaments, which passed through cell wall and connected together with cytoskeletal arrays of adjacent cells. Thus, it is possible that an integral skeletal network existed within the young leaf tissue of wheat.