Fig. 2. Pancreas development is dependent on RAR function. (A) rara2a expression in dorsal view at 10 hpf. (B) rara2b expression in dorsal view at 10 hpf; arrowhead indicates the approximate AP position where the pancreas will develop. (C) insulin is expressed at 24 hpf following morpholino knock-down of RAR2b (indistinguishable from controls; data not shown). (D-F) rara2b expression in endoderm cells; examples are indicated by asterisks. Confocal images of rara2b expression (red) at 10 hpf, SOX32-positive donor-derived endoderm is labeled with fluorescein (green). Approximate area of image is boxed in B. (G) DN-RAR2a mRNA blocks insulin expression in a dose-dependent fashion (concentrations injected in ng/µl). (H) Histogram showing number of insulin-expressing cells in uninjected control embryos (n=44) compared with embryos injected with RAR2a-MO (n=11), RAR2b-MO (n=12), RAR-MO (n=12), RAR2a-MO plus RAR2b-MO (n=10), RAR2b-MO plus RAR-MO (n=7), DN-RAR2a mRNA (125 ng/ml; n=11) and DN-RAR2a mRNA (125 ng/ml) plus RAR2b-MO (RAR knock-down, RKD; n=85). Error bars indicate standard deviation. (I) Co-injection of DN-RAR2a mRNA and RAR2b-MO blocks insulin expression.