NEURULATION ABNORMALITIES SECONDARY TO ALTERED GENE-EXPRESSION IN NEURAL-TUBE DEFECT SUSCEPTIBLE SPLOTCH EMBRYOS

The murine mutant Splotch (Sp) is a well-established model for studyin g neural tube closure defects. In the current investigation, the progr ession through neural tube closure (NTC) as well as the expression pat terns of 12 developmentally regulated genes were examined in the neura l tissue of wildtype (+/+), Splotch heterozygous (Sp/+), and Splotch h omozygous (Sp/Sp) embryos during neurulation. The overall growth of th e embryos, as measured by the number of somite pairs, did not differ s ignificantly between the three genotypes at any of the collection time -points. There was, however, a significant delay in the progression th rough NTC for both the Sp/+ and Sp/Sp embryos. A univariate analysis o n the expression of the 12 candidate genes (bcl-2, FBP-2, Hmx-2, Msx-3 , N-cam, N-cad, noggin, p53, Pax-3, Shh, Wee-1, wnt-1) revealed that a lthough 11 were statistically altered, across time or by genotype, the re were no significant interactions between gestation age and genotype for any of these genes during NTC. However, a multivariate statistica l analysis on the simultaneous expression of these genes revealed inte ractions at both gestation day (GD) 8:12 (day:hour) and 9:00 among Pax -3, N-cam, N-cad, bcl-2, p53, and Wee-1 that could potentially explain the aberrant NTC. The data from these studies suggest that a disrupti on in the genes that govern the cell cycle or extracellular matrices o f the developing neural tube might play a critical role in the occurre nce of the NTDs observed in Splotch embryos. (C) 1998 Wiley-Liss, Inc.