Fig. 2. Expression of Fgfr3 and Olig2. Transverse sections through stage 35 (E9) chicken spinal cords were subjected to in situ hybridisation for Fgfr3 (A) or double in situ for Fgfr3 and Olig2 (B). At this age, Fgfr3 expression is confined to the VZ and a few scattered cells outside the VZ. The two spatially separated domains of Fgfr3 expression are clearly visible (A). Olig2 is expressed predominantly within the ventral `gap' of Fgfr3 expression (B). This suggests that pMN (brackets), which generates Pdgfra⁺ oligodendrocyte progenitors (OLPs), does not also generate Fgfr3⁺ putative astrocyte progenitors. Scale bar: 50 µm.