dbx1 and nkx6 overexpression blocks Prdm12 activity, and their knockdown upregulates En1. (A) RT-PCR analysis of en1 in neuralized animal caps overexpressing mouse Prdm12 mRNA (250 pg/blastomere), dbx1, dbx2, nkx6-1 or nkx6-2 mRNA (50 and 250 pg/blastomere) and treated with RA as indicated. (B) RT-PCR analysis of en1 and prdm12 in neuralized animal caps derived from embryos injected with MO against dbx1, nkx6-1 and nkx6-2 as indicated.