Figure 5.

The translation of a gradient-based neocortical map in stem cells into spatially discrete patterns of neuronal gene expression in the neocortex. (A) In the developing spinal cord, an initial graded pattern of transcription factor expression along the dorsoventral axis is progressively resolved into clearly delineated, molecularly distinct stem cell domains. Each spatially defined group of stem cells goes on to produce different classes of spinal cord neurons. (B) In contrast, in the developing neocortex, gradients of expression in the ventricular zone do not resolve into discrete spatial domains. Instead, those gradients appear to be translated into discrete spatial expression in the neurons generated by those stem cells. Furthermore, the spacial expression of specific genes often differs between different neuronal layers, as shown here for the gene Epha7.