Figure 2.

Loss of Pax6 Causes Increasingly Widespread Rapid-Onset Proliferative Defects after E13.5

(A–C) Expression of Pax6 protein in parasagittal sections from E13.5–E15.5 WT embryos (all oriented the same way; scale bars, 100 μm).

(D–E″) BrdU and YFP immunohistochemistry on brain sections from E15.5 iKO and control embryos after tamoxifen administration on E10.5. (D and E) More BrdU-labeled cells were present in iKO cortex. (D′ and E′) Almost all cortical cells were YFP positive. (D″ and E″) Merged images: BrdU-positive cells were counted in radially arranged 100-μm-wide boxes, as illustrated.

(F–I) PH3 immunohistochemistry on sections from E15.5 and E16.5 iKO and control embryos after tamoxifen administration on E10.5 or E13.5. Increased numbers of PH3-positive cells were observed in iKOs. PH3-positive cells were counted in 200-μm-wide boxes, as illustrated. Scale bars = 100 μm.

(J–Q) Average numbers (±SEM) of BrdU-YFP double-labeled cells or nonapical PH3-labeled cells in counting boxes (see D”, E”, and F–I) from rostral, central, and caudal cortical areas in E13.5, E15.5, or E16.5 iKO or control embryos injected with tamoxifen on E10.5 or E13.5. (J) ^∗p < 0.003, Student’s t test. (K) ^∗p < 0.002 rostrally, ^∗p < 0.001 centrally, ^∗p < 0.02 caudally. (L) ^∗p < 0.04. (M) ^∗p < 0.001 rostrally, ^∗p < 0.002 centrally, ^∗p < 0.001 caudally. (O) ^∗p < 0.002 rostrally, ^∗p < 0.004 centrally, ^∗p < 0.006 caudally. (Q) ^∗p < 0.003 rostrally, ^∗p < 0.03 centrally. In all cases, n = 3 embryos per genotype.

(R–U) Measurements of mean Ts and Tc (±SEM) in four cortical areas in control and iKO E14.5 embryos after tamoxifen administration at E9.5 (n = 3 embryos per genotype; ^∗p < 0.0001, Sidak’s multiple-comparisons test).

See also Figures S2 and S3.