Alterations in the neuroepithelial basal lamina in a neurological mutant with prenatal hydrocephalus

The neuroepithelial basal lamina (BL) appears to be crucial in controlling cell-cell interactions during the early histogenesis of the nervous system. In this investigation we examined the changes in the BL in a neurological mutant of the rat previously characterized as having BL anomalies which progress to aqueductal stenosis and prenatal hydrocephalus. Embryos were obtained from matings of rats homozygous for the prenatal hydrocephalus gene or from controls, both originally derived from the same Wistar albino stock. On days 12 and 13 of development, embryos were processed for indirect immunofluorescence localization of BL components type IV collagen or laminin. Additional whole litters were processed for ultrastructural analysis of neuroepithelial and BL morphology. In control embryos, neuroepithelial BL components formed a smooth linear boundary to the basal surface of the neuroepithelium. This unbroken border was interrupted only in regions of active neural crest cell migration (day 12), and in areas of imminent vascularization (day 13). In hydrocephalic embryos on the 12th day there were gaps in the continuity of the BL and an apparent reduction in deposition of type IV collagen. By day 13, blood vessels had prematurely colonized the neuroepithelium, few BL breaks were observed, and deposition of type IV collagen appeared similar to that seen in control embryos. Ultrastructurally, a similar pattern of change was observed. The neuroepithelium of control embryos was uniformly bounded by an organized BL consisting of a lamina lucida subjacent to the plasma membrane, and a lamina densa which merged with scattered collagen fibrils in the mesenchymal compartment. On day 12, the BL of hydrocephalic embryos had large gaps through which neuroepithelial cells projected.(ABSTRACT TRUNCATED AT 250 WORDS)