FIGURE 2.

Vitamin B12 treatment restores normal expression of cortical markers in Tbx1 heterozygous embryos. Panels show coronal sections of embryonic brains at E13.5. The cartoon, a, indicates the position of the ML-cortex in coronal brain sections (boxed area). The red line indicates the position where all measurements were made. (A,a) In situ hybridization of Pax6 (A–A”’) revealed thinning of the expression domain (yellow brackets) in vehicle-treated Tbx1^lacZ/+ (heterozygous) embryos (A’) compared to vehicle-treated WT embryos (A,a), which was rescued by B12 treatment (A”’,a). (B,b,b’) In situ hybridization of Tis21 (B–B”’) showed increased expression (OD) in the ML-cortex of vehicle-treated Tbx1^lacZ/+ embryos compared to vehicle-treated WT embryos (B), including the VZ and SVZ (B’,b,b’), which was rescued by B12 treatment (B”’,b,b’). (C,c) In situ hybridization of NeuroD2 (C–C”’) showed increased expression in the ML-cortex of vehicle-treated Tbx1^lacZ/+ embryos (C’,c) compared to vehicle-treated WT embryos (C) and extension of the expression domain (yellow brackets), relative to the total ventricular pial thickness (white brackets), which was rescued by B12 treatment (C”’,c). Dashed red line defines the external edge of the cortical plate (CP). Scale bars, 100 μm in all panels except (C), which is 200 μm. *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001, error bars indicate mean ± SD, red horizontal bars with # not significant, n = 5–6 per genotype. VZ, ventricular zone; SVZ, subventricular zone; IZ, intermediate zone; CP, cortical plate; ML-Cx, medio-lateral cortex; D, dorsal; M, medial; ML, medio-lateral; L, lateral; OD, optical density.