Genetic cascade governing cortical interneuron generation. Corticolimbic interneurons originate in the medial and caudal ganglionic eminences (MGE and CGE). The homeobox transcription factors Dlx5/6, Dlx1/2 and the proneural gene Mash1 (not shown) are expressed throughout the ganglionic eminences and are required for the generation of all GABAergic interneurons. The MGE generates parvalbumin-positive (PV) basket cells and chandelier cells, as well as somatostatin-positive (SST) cells (including Martinotti cells). These rely on the sequential expression of Nkx2.1, Lhx6, and Sox6 for proper specification and maturation (see text). The genetic cascade governing the specification of CGE-derived interneurons has not been fully elucidated yet, but Nkx6.2 and Gsh2 are expressed in the CGE and might be important players (see text).