Fig. 1. The I12b intergenic enhancer targets the expression of a lacZ reporter construct to the developing mouse forebrain. (A) The convergently transcribed (arrows) mouse Dlx1 and Dlx2 genes. Exons are shown as blue boxes. Two enhancers, I12a and I12b, are located in the intergenic region. The reporter construct used for the production of mouse transgenic lines is shown beneath. (B) The I12b enhancer targets expression of the reporter gene to the ventral telencephalon (VT), the diencephalon (Di) and the frontonasal prominence (FN), in an E11.5 mouse embryo (whole-mount preparation). (C-F) Transverse sections (half a section is shown in E,F) through the telencephalon of E11.5 (C) and E13.5 (D) transgenic embryos and rostral brain of P0 (E) and P25 (F) transgenic mice. Scale bars: 1 mm in B; 500 µm in C-F.