Fig. 6

hb9 and mnr2a are differentially required in endocrine and exocrine pancreas formation. Expression of insulin at 3.5 dpf (A–C), trypsin at 4 dpf (D–F), and mnr2a (purple) and insulin (red) at 3.5 dpf in higher magnification (G–I) in wild type embryos (A, D, G) and in embryos injected with 2 ng MO^hb9 (B, E, H) or 4 ng MO^mnr2a (C, F, I). (G–I) Expression of insulin is strongly reduced in embryos injected with MO^hb9 (B, H) but not in embryos injection of MO^mnr2a (C, I). In contrast, expression of trypsin is strongly reduced after injection of MO^mnr2a (F) but is not changed after injection of MO^hb9 (E). Similarly, mnr2a expression is only reduced in MO^mnr2a-injected embryos but not in MO^hb9-injected embryos (I); arrow marks mnr2a expression. Embryos are shown from dorsal (A–F) or in a higher magnification from lateral with anterior left (G–I). (J) Summary of morpholino experiments. Indicated numbers of embryos (n) were injected with the indicated type and amount of morpholino and analyzed for expression of insulin, trypsin or mnr2a at indicated stages (hpf). The phenotypes of the embryos were classified relative to the expression level of the marker genes in the un-injected embryos: average wild type level (wt), reduced up to 50% (slightly reduced), reduction up to 10% (reduced), reduced to less than 10% or missing (strongly reduced). While injection of MO^hb9 or MO^mnr2a could result in total loss of insulin or trypsin expression, respectively, we did not find MO^mnr2a embryos entirely lacking endoderm mnr2a expression. Note that the un-injected embryos frequently show different levels of mnr2a and trypsin expression representing natural variations found in zebrafish. (#) All analyzed embryos showed similar level of expression and since only few mnr2a-positive cells can be detected at 54 hpf, the presence of mnr2a-expressing cells was classified as 100%. Scale bars correspond to 100 μm.