Fig. 4

Close relationship between gbx2 and regionalization genes. A. Closely associated expression of gbx2 and its target genes around the MHB. The expression of gbx2 and three candidate target genes (otx1b, otx2, and her5) was detected by fluorescence in situ hybridization (FISH) in wild-type embryos at the bud stage (left three columns) or 4-somite stage (right three columns). Dorsal views with anterior to the top. The expression of the candidate target genes (magenta), gbx2 (green), and their merged views are shown for each gene and stage. Scale bars, 100 µm. B. The expression of her5 was examined in embryos obtained by crossing double gbx heterozygotes (gbx1^+/–;gbx2^+/–) at the 4-somite stage (a, b, a', b') and 24 hpf (c, c'). Right three panels (a'–c') show her5 expression in double homozygotes and the left three (a–c) show expression in the rest of the offspring. The genotypes of the stained embryos were confirmed by PCR. Images show dorsal views with anterior to the top (a, a') and left (c, c'), and lateral views with anterior to the top and dorsal to the right (b, b'). fb, forebrain; mb, midbrain; op, otic placode; r1/2/4, rhombomere 1/2/4; arrowhead, midbrain-hindbrain boundary (MHB). Scale bars, 200 µm.