sox4b is required for the differentiation of α cells. (A–V) Expression of various pancreatic markers in wild-type control embryos (first and third columns) or sox4b knock-down embryos (second and fourth columns), analyzed at 30 hpf (except trypsin that was analyzed at 3 dpf). Compared to the controls (A and I), glucagon expression dramatically decreases in embryos injected with either mo1sox4b or mo2sox4b (B and J). The injection of the mRNA encoding Sox4deltaC leads to the same phenotype (K and L) while the injection of gfp mRNA has not any effect. By contrast, the expression of insulin (C, D), somatostatin (E, F) is not much affected although the cells are scattered. In addition to glucagon decrease, sox4b knock-down causes a similar phenotype on arx expression specifically in the pancreas (panels M and N and arrowhead in O and P), without any effect on the floor plate nor the somites (thin and thick arrows in panels O and P, respectively). By contrast, the levels of expression of pax6.2 (Q, R), neuroD (S, T), pdx-1 (U, V), and trypsin (G, H) are not significantly affected. All the panels present yolk-free embryos. Except panels O and P that are lateral views, all the panels are dorsal views with the anterior to the left. B, N, and P scale bars = 50 μm; H scale bar = 100 μm. In panels O and P, arrowhead: dorsal bud, thin arrow: floor plate, thick arrow: somites. W: quantitative analysis of endocrine markers in mo1mis or mo1sox4b morphant embryos at 30 hpf. The knock-down of sox4b leads, on average, to the loss of 82% and 55% of glucagon and arx cells. The average number of cells of the other markers analyzed is poorly affected. Y bars correspond to the standard error. See Table 1 for embryo numbers.
|
