magoo mutant cortex has reduced production of progenitors. (A) Pax6 (green) and Tbr2 (red) mark apical and basal progenitors, respectively, in control and magoo mutant cortical sections. Scale bars: 20 μm for each age pair. (B) The number of Tbr2+ progenitors per 100 μm length of ventricle is significantly reduced in magoo mutants at E14.5 and E16.5 compared with controls. Number of brains for +/+ and -/-: E14.5 and E16.5, 3 and 3, n=6 fields each; E18.5, 2 and 2, n=4 fields each. (C) The average thickness of the vz (Pax6+) is slightly reduced in E14.5 and increased in E16.5 mutants. Number of brains for +/+ and -/-: E14.5 and E16.5, 3 and 3, n=6 fields each; E18.5, 2 and 2, n=4 fields each. (D) The vz makes up a larger proportion of the total cortical thickness in magoo mutant cortices at E14.5 and E16.5. Number of brains for +/+ and -/-: E14.5, 3 and 3, n=5 and n=6 fields, respectively; E16.5, 3 and 3, n=4 and n=6 fields, respectively; E18.5, 2 and 2, n=4 fields each. *P<0.05, **P<0.01, ***P<0.001.