Regional specific expression of genes identified from the microarray analysis of the VM (A–Q). Regional specific expression of genes identified from the microarray analysis of the VM (A–Q). In situ hybridization in sagittal sections of the mouse embryonic brain (E12) shows restricted expression of 17 genes selected in the distinct layers of VM. Dashed lines indicate the position of the VM. Scales indicate the four-layer laminar structure in the VM. A–E, Ttyh1 and Fabp7 are expressed in layer I, while Hmgb2, Id3, and Ccnb2 are predominantly expressed in layers I and II. F, G, Ccnd2 and Cdc2a show restricted expression in layer II. H–J, Stmn2, Lrrn3, and Dll1 are expressed in layer II/III cells. K–N, Ebf2, Ebf3, Klhl1, and Cdk5r1 are specifically expressed in layer III. O–Q, Nurr1, Chl1, and Foxp2 mRNA are detected in layers III and IV. The prototypical expression profile of each gene is shown in the right panel. The data represent means ± SEM of three independent experiments. Asterisks indicate statistical significance between two adjacent time points (p < 0.05). Scale bar, 100 μm. R, Schematic representation of a potential model for the generation of mDA neurons from neuroepithelial cells. The model shows a four-layer laminar organization in the VM (left), which corresponds to a four-stage mDA neuron development (right). Some genes that are expressed by developing mDA cells, identified by microarray analysis, are indicated at right. Min Yin et al. J. Neurosci. 2009;29:5170-5182 ©2009 by Society for Neuroscience