In vitro expression of neural tube pathology in the vl mutant mouse

The pathogenesis of lumbosacral spinal dysraphism was analyzed in vitro in early homozygous embryos of the vl (vacuolated lens) mutant mouse, and comparisons were made between the lag in closure of the posterior neuropore at the beginning of culture and the degree of severity in the spinal defect at the end of culture for each embryo. In the majority of abnormal (vl/vl) embryos, the neural tube closed completely in culture, although mild defects were observed in the spinal roofplate comparable to those that occur in vivo. Although some abnormal embryos did exhibit small openings in the caudal neural tube at the end of the culture period, in none of the cultured embryos was the extent and severity of the defect as great as that observed in some abnormal embryos of comparable age obtained in vivo. Moreover, the degree of delay in closure of the posterior neuropore at the outset of culture did not necessarily correlate with the severity of the defect obtained at the end of culture. Thus, the expression of the neural tube defect in this mutant appears to be modulated and attenuated by biochemical and/or mechanical factors which may be peculiar to the culture milieu.