the developing cortex. To identify such fronto-temporal patterning genes directly, we correlated gene expression in each cortical layer against the angular position of each neocortical region, as illustrated schematically in Figure 5c. All layers contained gradient genes conserved across all four brains (p~0, permutation analysis; FDR<2.4%; Suppl. Methods), and each layer contained distinct sets of gradient genes, particularly when comparing germinal with postmitotic layers (Suppl. Table 9). Gradient genes in VZ likely reflect intrinsic areal specification as VZ does not receive thalamic innervation. Interestingly, rostral and caudal genes that can be identified in grossly dissected cortex3 largely represent gradients in postmitotic cells, as they show significant overlap with gradient genes in MZ, CP, and IZ (Extended Data Fig. 9).
