Fig. 2. Identification of an enhancer to drive lacZ expression in the dorsal spinal cord. (A) Schematic representation of the genomic structure of Mbh1 and Mbh1/lacZ transgenes. The orange boxes indicate exons, and translation start site (ATG) is designated as nucleotide number 1. The blue and green boxes represent lacZ and the ß-globin promoter/lacZ construct (BGZA), respectively. The 3' fragment was reversed in Tg6. The number of transgenic (#TgM) and ß-gal⁺ (#expression) embryos are shown in the table; ^athe two embryos expressed lacZ at low levels in the midbrain. Lateral (B) and dorsal (C-E) views of representative ß-gal⁺ embryos harboring Tg2 (B,C), Tg4 (D) and Tg5 (E). Transverse sections of the embryos carrying Tg2 (F) and Tg4 (G). Arrowheads indicate ß-gal⁺ ventral funiculi. (H) Transverse section of the embryo carrying Tg4 was immunostained with antibodies against Math1 (red) and ß-gal (green). Scale bars: in B, 1 mm for B-E; in F, 100 µm for F,G; in H, 50 µm.