There is genetic evidence for at least three parallel (although interacting) transcriptional pathways in the MGE that are required for cortical interneuron development: the 1) Ascl1 (Mash1); 2) Dlx; and 3) Nkx2-1 pathways (Long et al., 2009a,b). The Nkx2-1 pathway is the core mediator of MGE regional and cell identity (Butt et al., 2007; Sussel et al., 1999); it functions through induction of Lhx6 and Lhx8 (Sussel et al., 1999). Lhx6 is essential for induction of Mafb and Shh in neurons, maintaince of Sox6 in interneurons, and the differentiation of Sst and Parvalbumin cortical interneurons (Lhx6) (Liodis et al., 2007; Zhao et al., 2008); Lhx8 is required in cholinergic striatal interneurons (Lhx8) (Fragkouli et al., 2009).
