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Fig. 1.
AChE plays a non-neuronal, non-esterase role in intestine organogenesis. Normal intestinal elongation and rotation are observed in DMSO-exposed control tadpoles (A,A′). Exposure to malathion (MTH; B,B′), chlorpyrifos-methyl (CPF; C,C′) or Huperzine A (HupA; D,D′) increases the percentage (E) of tadpoles with short/malrotated intestines. AChE activity assays (F) confirm that the applied compounds inhibit AChE in vivo. RT-PCR (G) indicates that isolated intestinal endoderm (indicated by the expression of ifabp, but not foxf1) expresses ache. −RT, control lacking reverse transcriptase. At NF 41, AChE (red) colocalizes with E-cadherin (green) at endoderm cell membranes (H-H′, arrows). By NF 46, AChE is apically enriched (I-I′, arrowheads), with reduced lateral membrane expression (arrows). Intestinal development is normal in control MO-injected embryos (J,J′,N), whereas microinjection of AChE MO results in short/malrotated intestines (K,K′,N). Intestinal malformations are rescued by co-injection of RNA encoding wt AChE (L,L′,N) or mutAChE that lacks catalytic activity (M,M′,N). AChE activity assays (O) confirm that AChE MO knocks down AChE, that wt AChE mRNA increases activity, and that mutAChE mRNA has no effect on AChE activity, relative to controls (uninjected, control MO, GFP mRNA). Higher magnification views of the boxed regions in A-D,H-M are shown in A′-D′,H′-M′, respectively. The number of tadpoles with the phenotype shown among the total number of tadpoles in that experimental group is indicated (A-D,J-M). Bar charts show mean±s.e.m. Significant differences between the percentage of tadpoles with abnormal gut phenotypes or between AChE activities from n=3-16 independent experiments (16-30 embryos per condition per experiment) are indicated by lowercase letters (P<0.05). Scale bars: 1000 μm in A-D′,J-M′; 100 μm in H,I; 25 μm in H′-I′. |
