Emigration of neural crest cells from macaque optic vesicles is correlated with discontinuities in its basement membrane.

It is established that cranial neural crest cells play critical roles in normal development, but the production of neural crest cells from the prosencephalon has received little attention, especially in primates. We therefore investigated the emigration into adjacent mesenchyme of neuroepithelial cells from macaque optic vesicles. Paraffin sections prepared from 13 embryos (Macaca fascicularis) representing developmental stages 10-14 were examined following standard immunoperoxidase staining for laminin and type IV collagen. At stage 10 the optic vesicle basement membrane was closely applied to that of the surface ectoderm except at its posterior border, where it contacted mesenchyme. The basement membrane was continuous and showed no evidence of cell migration. By stage 11 the optic vesicle basement membrane exhibited numerous gaps along its posterior border. These defects were frequently occupied by cells emigrating from the optic vesicle epithelium, as judged by the deflection of basement membrane fragments. Gaps were also seen along the lateral border, where migrating neuroepithelial cells were positioned between the surface ectoderm and optic vesicle. This cell migration appeared to increase during stage 12, with deterioration of all areas of the optic vesicle basement membrane. Basement membranes of the surface ectoderm, adjacent mesencephalon, and telencephalon anlage remained intact. By stage 13 the basement membranes of the optic vesicles were repaired and nearly continuous, with migrating cells rarely seen. Development of the optic cups at stage 14 indicated a near absence of basement membrane defects and emigrating cells.