Restricted expression of FGFR3 in cortical progenitors in the ventricular zone of the developing neocortex. Coronal sections of E12.5 (A), E13.5 (B), E14.5 (C), and E16.5 (D) cerebral cortex, showing the expression patterns of FGFR3, determined by in situ hybridization. In situ hybridization analyses revealed the exclusive expression of FGFR3 in the ventricular zone with the spatial and temporal expression patterns that are tightly linked with the expression of Pea3-Ets transcription factors (Fig. 1). Scale bars: A, 0.37; B, 0.41 mm; C, 0.48 mm; D, 0.5 mm.