XB-ART-39658Dev Biol July 1, 2009; 331 (1): 89-98.
Cell-cell interactions during remodeling of the intestine at metamorphosis in Xenopus laevis.
Amphibian metamorphosis is accompanied by extensive intestinal remodeling. This process, mediated by thyroid hormone (TH) and its nuclear receptors, affects every cell type. Gut remodeling in Xenopus laevis involves epithelial and mesenchymal proliferation, smooth muscle thickening, neuronal aggregation, formation of intestinal folds, and shortening of its length by 75%. Transgenic tadpoles expressing a dominant negative TH receptor (TRDN) controlled by epithelial-, fibroblast-, and muscle-specific gene promoters were studied. TRDN expression in the epithelium caused abnormal development of virtually all cell types, with froglet guts displaying reduced intestinal folds, thin muscle and mesenchyme, absence of neurons, and reduced cell proliferation. TRDN expression in fibroblasts caused abnormal epithelia and mesenchyme development, and expression in muscle produced fewer enteric neurons and a reduced inter-muscular space. Gut shortening was inhibited only when TRDN was expressed in fibroblasts. Gut remodeling results from both cell-autonomous and cell-cell interactions.
PubMed ID: 19409886
PMC ID: PMC2712884
Article link: Dev Biol
Species referenced: Xenopus
Genes referenced: acta2 acta4 actc1 actl6a fabp2 mmp11 thibz trdn tubb2b
Antibodies: Acta2 Ab1 Cdh1 Ab1 Fabp2 Ab1 Tubb2b Ab1
Article Images: [+] show captions
|Fig. 4. The IFABP-TRDN-GFP transgene specifically inhibits TH direct-response genes in the epithelium, but not in the mesenchyme. Cross sections of duodenums from (A, B) wild-type NF54 tadpoles treated with either 0 nM T3; (C, D) 5 nM T3 for 48 h. Cross sections of duodenums from (E, F) sibling tadpoles transgenic for IFABP-TRDN-GFP treated with 5 nM T3 for 48 h. (A, C, E) Expression of the TH direct-response gene, bZip, mRNA in the epithelium. (B, D, F) Expression of the TH direct-response gene, stromelysin-3 (ST3), mRNA in the mesenchyme. mRNA localized by in situ hybridization (purple stain). Scale bar in F denotes 0.2 mm length.|
|Fig. 7. Both The ST3-TRDN-GFP and Col-TRDN-GFP transgenes inhibit epithelial development and thickening of the sub-epithelial mesenchyme. (A) GFP is expressed specifically in the intestinal mesenchyme of tadpoles transgenic for ST3-GFP in an NF48 tadpole induced with T3 (10 nM) for 48 h. (B) Cross sections of the intestine from an untreated NF48 wild-type tadpole; (C) an NF48 wild-type tadpole treated for 7 days with 5 nM T; (D) an NF48 tadpole transgenic for ST3-TRDN-GFP treated for 7 days with 5 nM T3. (E) GFP is expressed in the mesenchyme and smooth muscle layers (but not in the epithelium) of an NF48 tadpole transgenic for Col-GFP. Cross sections of intestine from (F) an untreated NF54 wild-type tadpole; (G) an NF54 wild-type tadpole treated for 7 days with 5 nM T3; (H) an NF54 tadpole transgenic for Col-TRDN-GFP treated for 7 days with 5 nM T3. Immunoreactivity against GFP in A and E is green, and nuclei are counterstained white with dapi. Tissues in B–D and F–H are stained with hematoxylin and eosin. Scale bar in E denotes 20 μm length; scale bars in D and H denote 50 μm length.|
|Fig. 8. The pCar-TRDN-GFP transgene inhibits smooth muscle separation, thickening of the inter-muscular mesenchyme, and aggregation of enteric neurons. (A) The whole-mounted duodenum of an NF57 tadpole transgenic for pCar-GFP expresses GFP (green) specifically in the longitudinal (oriented left–right) and circular (oriented top–bottom) muscle fibers. Cross sections from the duodenum of (B) NF63 tadpole transgenic for pCar-GFP stained for immunoreactivity against GFP (green) and counterstained for nuclei with dapi (white); (C, D) stained with smooth muscle actin antibody; (E, F) stained with smooth muscle actin and neural beta-tubulin antibodies. (C, E) Control NF63 tadpole; (D, F) NF63 tadpole transgenic for pCar-TRDN-GFP. Circular (c) and longitudinal (l) smooth muscle fibers. Scale bar in A denotes 20 μm length; scale bar in B denotes 100 μm length; scale bar in F denotes 40 μm length.|
|Fig. 1. Virtually every tissue is affected during spontaneous metamorphic remodeling of the duodenum. Cross sections of the duodenum from (A–C) wild-type prometamorphic tadpoles NF57; (D–F), metamorphic climax NF61; (G–I), and the end of metamorphosis NF66. (C, F, and I) Cross sections of the duodenum from tadpoles transgenic for IFABP-GFP. The GFP antibody reaction is green; smooth muscle actin antibody is red. (A, D, and G) Hematoxylin and eosin. (B, E and H) Immunoreactivity against endogenous intestinal fatty acid binding protein (IFABP; blue), muscle-specific smooth muscle actin (red), enteric neuron-specific neural beta-tubulin (green); and a nuclear counter-stain (dapi; white) is shown for half of each section. t = typhlosole, c = circular muscle, l = longitudinal muscle. Scale bar in C denotes 0.2 mm length.|
|Fig. 6. The IFABP-TRDN-GFP transgene inhibits circular muscle thickening and aggregation of enteric neurons. (A) Duodenal cross sections from a wild-type NF66+ froglet; (B), from a transgenic froglet. Tissues were stained for immunoreactivity against smooth muscle actin (red) and neural beta-tubulin (green). Sections are counterstained for nuclei with dapi (white). Circular muscle fibers (c); longitudinal muscle fibers (l). Inset in B is a magnification of the region encompassed by the dashed yellow rectangle. Scale bar denotes 0.1 mm length.|
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