Absence of Dorsal Pancreatic Bud Derived β-Cells in smoothened (smo) Mutant Embryos
(A-D) Dorsal views of insulin expression, comparing wildtype (A and B) and smo mutant (C and D) embryos at 18 (A and C) and 24 (B-D) hpf. insulin expression is completely missing in smo mutant embryos at 18 hpf (C) and mostly missing at 24 hpf (D). (E-L) Dorsal (E, G-I and K-L) and lateral (F and J) views of pdx1 expression, comparing wildtype (E-H) and smo mutant (I-L) embryos at 18 (E and I), 24 (F and J), 36 (G and K) and 48 (H and L) hpf. (E) At 18 hpf, pdx1 is expressed at high level in the presumptive pancreatic endocrine cells (asterisks) and at low level in the endodermal cells located laterally. (I) In smo mutants at 18 hpf, the low level expression of pdx1 is present in the endoderm but the high level expression is absent. (F and K) pdx1 is expressed in a broad A-P extent of the developing gut at 24 (F and J) and 36 (G and K) hpf. Dorsal pancreatic endocrine cells bud out from the gut (arrow) in wildtype embryos at 24 (F) and 36 (G) hpf, but this process does not appear to occur in smo mutant embryos at 24 (J) and 36 (K) hpf. (H) At 48 hpf, pdx1 is expressed in the extending ventral pancreas (arrowheads) and intestinal bulb in wildtype embryos. (L) In smo mutant embryos, endodermal organ formation is perturbed and multiple ventral pancreatic buds (arrowheads) can be detected at 48 hpf. (A-E, G-I and K-L) Anterior to the top. (F and J) Anterior to the left and dorsal to the top.
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