Figure 1.

Fgfr1 and Fgfr2, but not Fgfr3, are required for the generation of OL progenitor from the embryonic mouse forebrains. Coronal sections of E12.5 forebrains from control, Fgfr1^−/−, Fgfr2^−/−, or Fgfr3^−/− mutants were analyzed for the expression of OLP markers Pdgfra (A) or Olig2 (B) mRNA by in situ hybridization. Total numbers of scattered Pdgfra+ or Olig2+ cells (arrows) were counted in the whole forebrain sections taken caudally (Pdgfra) or rostrally (Olig2). Three to four matched sections from each littermate control and mutant mice were analyzed. Numbers of animals analyzed were six each of control, Fgfr1^−/−, or Fgfr2^−/−, and two of Fgfr3^−/−. Data are expressed as percentage of control (C). Error bars represent SEM. Scale bars, 200 μm. Pdgfra expression is also visible in the meninges (*). Note that, compared with controls, decreased numbers of OLPs were found in both Fgfr1^−/− and Fgfr2^−/− mutants regardless of abnormal ventral forebrain morphology in the Fgfr1^−/− mutants. All the mutants maintained the expression of Olig2 in the ventral VZ of the MGE and LGE, suggesting normal dorsoventral patterning. The dotted line defines the boundary between the dorsal neocortical (d) and the ventral forebrain (v) regions.