Conditional loss of Notch1 in the early embryonic cerebellum results in precocious differentiation at the expense of the progenitor pool. (a) Whole mount β-galactosidase staining of an E9.5 En1cre; Rosa-stopLacZ reveals the extent of recombination across the mid-hindbrain region. (b-g) In situ hybridization with antisense probes for (b, c) Notch1, (d, e) Mash1, and (f, g) Math1 on sagittal cryosections of the cerebellar primordia from E10.5 floxNotch1 (b, d, f) and En1cre; floxNotch1 (c, e, g) embryos. (h, i) Immunohistochemistry for Math1 on E10.5 floxNotch1 (h) and En1cre; floxNotch1 (i) tissue cryosections. (j-o) In situ hybridization with antisense probes for (j, k) Notch1, (l, m) Mash1, and (n, o) Math1 on sagittal cryosections of the embryonic cerebella from E12.5 floxNotch1 (j, l, n) and Engrailed1-cre; floxNotch1 (k, m, o) embryos. The r1/r2 boundary is indicated by the arrow in (k). Brackets in (m, n) indicate the extent of Math1 induction in the VZ. (p, q) Immunohistochemistry for Math1 (white arrows) on E12.5 floxNotch1 (p) and En1cre; floxNotch1 (q) tissue cryosections. Scale bars in (g, o) represent 300 μm.