Dlx1 and Dlx2 are necessary for subpallial development, including interneuron migration to the cortex (Anderson et al., 1997a; Long et al., 2009a; Long et al., 2009b; Yun et al., 2002a); thus we examined Zfhx1b RNA expression in Dlx1/2 constitutive null mutants using in situ hybridization (Figures 5A-B’). In control brains at E12.5 and E15.5, Zfhx1b was expressed in the VZ and SVZ of the subpallium, in addition to its previous described expression in the cortical plate and SVZ (Miquelajauregui et al., 2007; Seuntjens et al., 2009). Zfhx1b expression in the subpallial MZ was restricted to dispersed cells in the LGE and to a nucleus forming near the ventral medial ganglionic eminence (MGE) (Figures 1A; 5A, 5B). In Dlx1/2-/- mutants, Zfhx1b expression was strongly and specifically decreased in the SVZ of the entire subpallium; expression in the subpallial VZ was maintained, albeit perhaps reduced (Figures 5A-B’).
