Fig. 6. Roof plate and early cerebellar anlage defects in dreher mouse embryos. (A-F) Dorsal views of whole-mount in situ-stained E10.5 embryos with genotypes and markers as indicated. In dreher, the anterior roof plate (a) is expanded at the expense of the posterior roof plate domain (p). IsO is still maintained (C,D). (E,F) The anterior limit of Math1 expression is found at the isthmus (broken line) in wild-type embryos. It is positioned more posteriorly in dreher. Open arrowheads show Math1-negative domain in dreher embryos. (I-P) Whole-mount in situ analysis reveals the anterior Math1 gene expression limit is still abnormal in E12.5 dreher embryos. The anterior limits of other genes, however, are normal in dreher embryos. Despite morphological changes in the roof plate a normal negative (neg) zone of gene expression is maintained adjacent to the isthmus (broken line in I-P). Open arrow points to Math1-negative domain in anterior r1 of dreher embryo. Solid arrowheads show pc2, c2 and c3 cells. (G,H,Q,R) Schematic illustrations summarize gene expression changes.