To remove Zfhx1b in the early progenitors of the MGE, we used the Nkx2.1-Cre allele (Xu et al., 2008), which drives Cre expression in the ventricular zone (VZ) of the MGE beginning around E9.5 [later it also drives expression in the subventricular and mantle zones (SVZ and MZ)]. To differentiate between the role of Zfhx1b in the VZ and the SVZ/MZ, we used the DlxI1/2b-Cre allele (Potter et al., 2008), which drives Cre expression in the SVZ and MZ of the entire subpallium beginning around E10.5. To examine the pattern of recombination, we used an antisense riboprobe designed against Zfhx1b exon 7.
