RyR Function Is Required for Shh-Dependent Patterning of the Neural Tube
(A) Schematic of Shh-dependent neural tube (NT) patterning. The medial floorplate (MFP), lateral floorplate (LFP), and neighboring motoneurons (mn) are indicated. The notochord (ntc) and MFP are sources of Shh, designated in blue. Approximate gene expression domains of nkx2.2b, isl1, nkx6.1, and pax3 are indicated.
(B–O) Whole-mount in situ hybridization to detect neural tube markers in vehicle-treated (0.5% DMSO) and 200 μM azumolene-treated embryos. (B and C) shha-expression in the notochord (arrowhead) and MFP (arrow) is similar in control and treated embryos. (D–O) Gene expression in the neural tube is shifted upon azumolene treatment in a manner consistent with reduced Shh signaling. (D–G) Whereas foxa and foxa2 are expressed in both the MFP and LFP in control embryos, they are expressed in fewer FP cells in azumolene-treated embryos. (H–K) Expression of nkx2.2b marking the LFP is reduced, but spon1b expression marking the MFP appears unchanged in azumolene-treated embryos. (L–O) The ventral domain of the neural tube, marked by nkx6.1, is reduced, while the dorsal domain of the neural tube, marked by pax3, is expanded in azumolene-treated embryos.
(P–S) Expression of nkx2.2a in the LFP and nkx6.1 in the ventral domain of the neural tube is diminished in MZryr1a(−/−);MZryr2a(−/−);MZryr3(−/−) compared with WT.
(B, C, L–O, R, and S) Lateral views of flat mounted embryos. (D, E, H–K, P, and Q) Dorsal views of flat-mounted embryos. Prime letters, (F), and (G) are transverse cross-sections. Scale bars, 25 μm. Interval bars indicate dorsoventral extents of gene expression domains. See also Figure S3.