Immunofluorescent analysis of the spinal cord in dysraphic mice.

Development of the spinal cord was analyzed immunocytochemically at 10-12 days of gestation in normal and dysraphic embryos of the loop-tail mutant mouse, using an anti-neural cell adhesion molecule (NCAM) and the lectin concanavalin A (Con A) as histological markers for evaluating neural cell organization and distribution. The normal and abnormal embryos showed similar patterns of reactivity to anti-NCAM and Con A, even though the neural folds were open and everted in the abnormal embryos, with displacement of the dorsal root ganglia. In the abnormal embryos the floor plate was similar to that in normal embryos, as evidenced by its increased anti-NCAM and Con A labeling relative to that in the rest of the neuroepithelium. Moreover, each lateral end of the everted abnormal neuroepithelium developed an attenuated 'roof plate' that appeared to be structurally similar to the normal roof plate. However, some of these 'roof plates' exhibited prominent clusters of labeled and nonlabeled cells, especially in the 10-day embryos. In addition, whereas normal embryos showed strong luminal labeling of the neuroepithelial cells with Con A, comparable regions in the abnormals were spotty and poorly defined except for the 'roof plate' and floor plate. The results indicate that dorsoventral polarity in the spinal cord, as assessed structurally and histochemically, develops essentially normally in abnormal dysraphic embryos, even though the topographic relationships of the abnormal neural tube are disturbed.