Immunofluorescent analysis of fibronectin and laminin distribution in the vl mutant mouse

The distribution of fibronectin and laminin was determined in the basement membrane surrounding the caudal neural tube and at the site of initial apposition of the caudal neural folds by means of indirect immunofluorescence histochemistry on 9.0- to 10.5-day mouse embryos fixed in Carnoy's solution and serially sectioned in paraffin. At early phases of development of normal (+/+) and abnormal (vl/vl) embryos the dorsolateral neural basement membrane overlying putative neural crest cells caudal to the hindlimb shows a patchy fibronectin reaction, with laminin virtually absent. In older embryos, both components are present but are discontinuous overlying the neural crest. The results suggest that since discontinuities occur in the basement membrane of abnormal as well as normal embryos, the neutral crest cells are not prevented from emigrating from the abnormal neural tube; thus the faulty neural fold fusion that characterizes vl/vl embryos does not appear to be due to a suppression of emigration by the basement membrane. The results also demonstrate the advantages and reliability of embedding in paraffin for analysis of serially sectioned pathological material by means of indirect immunofluorescence, provided that normal controls and abnormals are processed simultaneously.