Fig. 11
From: FGF signaling controls Shh-dependent oligodendroglial fate specification in the ventral spinal cord
Model for FGF functions in OPC specification. At stage of ongoing neuronal generation (t1), the Olig2 (pMN, green) and Nkx2.2 (p3, red) progenitor domains do not overlap due to the repressive activity of Nkx2.2 on Olig2 expression. Olig2 progenitor cells generate motor neurons while Shh secreted by MFP cells activates low level of intracellular signaling (blue) to maintain expression of Olig2. As development proceeds (t2), Nkx2.2 progenitor cells become exposed to FGFs, possibly provided by ventral neurons. These cells subsequently up-regulate Shh expression to form the LFP. Soon after (t3), Olig2 progenitors, because they are submitted to higher Shh signaling activity, up-regulate Nkx2.2. At that time, Olig2 expression is no more repressed by Nkx2.2 thanks to joint exposure of these cells to FGFs. Olig2 and Nkx2.2 coexpressing progenitor cells, included in the p* domain (yellow), then start generating OPCs