Analysis of an allelic series of conditional En1/2 mutants in VZ-derived and RL-derived cells highlights the predominant role for En2 in regulating foliation. H&E-stained sagittal sections of the vermis (A, C, E, G, I, K, M & O) and hemispheres (B, D, F, H, J, L, N & P) of mice with the genotypes indicated. a, ansoparamedian; pc, preculminate; po, posterolateral; prc, precentral; ppy, prepyramidal; pr, primary; sec, secondary; black arrowheads, vermal anterior fissures; white arrowheads, vermal posterior fissures; white arrow, hemisphere fissure. Stars denote fissures with developmental defects and yellow highlighted areas denote regions with defects in mutants compared to same region in the control. Genotypes colored blue represent conditional mutants with one functional allele of En1 and genotypes colored red represent conditional mutants with one functional allele of En2. Scale bar: 600μm.