Extended Data Fig. 20: Ectopic RA signalling leads to enlargement of the lateral region of the frontal cortex and upregulation of Rorb.

a, Representative image and quantification of the ratio of brain width at anterior and posterior cortex to total brain length at PCD 18 in Cyp26b1 KO brain compared WT. Two-tailed Student’s t-test: WT vs. Cyp26b1 KO: ***P = 3e-4; N = 4 per genotype; Errors bars: S.E.M. b, Nissl staining reveals that the cortical wall and cortical plate are grossly normal when analysed in the mPFC and SSp of Cyp26b1 KO. N = 3 per genotype. c, Representative image and quantification of Rorb expression after electroporation of either control pCAG-IRES-Gfp or pCAG-Aldh1a3-IRES-Gfp expression vector plasmid in the dorso-lateral fronto-parietal wall at PCD 14. Brains were dissected out at PD 5. Boxed region represents region of higher magnification to the right. GFP expression as a marker of misexpressing cells are shown in lower panels. Rorb signal intensity in the boxed area in the cortex was quantified. Two-tailed Student’s t-test: ***P = 2e-4; N = 4 per genotype; Errors bars: S.E.M.; Scale bars: 500 μm (a); 200 μm (b); 1 mm (c); 40 μm and 500 μm (d).