Fig. 5.

Summary of gene expression patterns with respect to the cortical hem. Schematic coronal sections through an E12.5 cerebral hemisphere at midrostral (A) and caudal (B) levels. At E12.5, the ventricular zone of the embryonic cerebral cortex expresses Emx2. The territories of Emx1, Wnt2b,Wnt3a, and Wnt5a expression are nested within the region of Emx2 expression.Wnt2b, Wnt3a, and Wnt5aare expressed in the cortical hem only; expression ofEmx1 fills most of the cortical neuroepithelium, but not the cortical hem. Expression of at least two other transcription factors, BF-1 and Lhx2, resembles that ofEmx1 in avoiding the cortical hem. Selectively low expression of these genes may in part reflect the fate of the cortical hem to shrink with respect to the rest of the cortical neuroepithelium (see Discussion). cpe, Choroid plexus epithelium;hem, cortical hem; je, junctional epithelium adjacent to the differentiating cpe.