Fig. S1

Patterning gene expression is normal in sly mutants during MHBC formation. (A–H) Wild type and sly mutants were analyzed by in situ hybridization for pax2a and krox20 at 17, 20, and 24 hpf. Gene expression at 17 hpf was normal in sly compared to wild type shown in (A and B). At 20 hpf gene expression remained normal, shown dorsally (C and D) and laterally (E and F). At 24 hpf pax2a and krox20 are still expressed normally in sly mutants compared to wild type (G and H). (I–J) Wild type and sly mutants were analyzed for expression of engrailed 3 (eng3) and krox20 at 24 hpf. In sly mutants, the eng3 expression domain appeared to be extended along the neural tube around the MHB relative to wild type. This is because the MHB tissue in the mutant is also elongated due to the lack of a sharp MHBC and MHB fold, indicating that gene expression in the MHB at the time of MHBC formation is the same in wild type embryos and in sly mutants. The bracket marks the MHB region in each embryo. Anterior is to the left in all images.