Towards defining the stage of differentiation when Zfhx1b is required for programming interneurons to migrate to the cortex, and not the striatum, we used the DlxI12b-Cre allele (Potter et al., 2008). DlxI1/2b-Cre expression begins in subpallial SVZ cells that express the mitotic marker Ki67 (Figures S1T-S1T”), suggesting that Cre recombination occurs in secondary progenitor cells that are mitotically active. Thus, DlxI12b-Cre induces recombination beginning in the SVZ of the entire subpallium, whereas Nkx2.1-Cre induces recombination in the VZ of the MGE and preoptic area (Figures 1D-1F’).
