Fig. 6. mes and r1 cells behave differently in En1^-/+;En2^-/- mutants. (A-J) Tamoxifen was administered to mouse embryos carrying the indicated alleles at 18.00 h on E10.5. (A,B) Coronal sections of E12.5 brains and (C,D) horizontal and (E,F) midline sagittal sections of E16.5 brains stained for ß-gal activity. (G,H) Dorsal views of ß-gal-stained adult brains. (I,J) Sagittal sections of adult brains taken at the level of the vermis and stained for ß-gal. The domain of marked cells was comparable in the En1^CreERT1/+;En2^-/- and En1^CreERT1/+;R26R/+ embryos at E12.5, but decreased in the tectum and increased in the Cb of En1^CreERT1/-;En2^-/-;R26R/+ embryos by E16.5. CbP, cerebellar primordium; EGL and associated bar, external granule layer. Ist, isthmus; Mb, midbrain; VZ, ventricular zone; A, anterior; P, posterior; M, medial; L, lateral. Red asterisks indicate truncation of the isthmus/inferior colliculus. CbP is outlined by a purple dashed line in C,D; in I,J, the IC and SC are outlined by dashed red and green lines, respectively. The red bar in A,B indicates the size of the CbP domain with marked cells.