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Dev Dyn
2008 Feb 01;2372:354-65. doi: 10.1002/dvdy.21419.
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Comparison of molecular and cellular events during lower jaw regeneration of newt (Cynops pyrrhogaster) and West African clawed frog (Xenopus tropicalis).
Kurosaka H
,
Takano-Yamamoto T
,
Yamashiro T
,
Agata K
.
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When mammals, including humans, lose a major part of their lower jaw, they are unable to regenerate the lost structures. Urodele amphibians, especially newts, can regenerate their lower jaw after amputation, whereas most anuran amphibians, including the West African clawed frog, can not. In the present study, we investigated the difference between newts and frogs during lower jaw regeneration. One difference was the distribution of myosin heavy chain (MHC) mRNA after lower jaw amputation: MHC mRNA was immediately expressed at the tip of the amputated lower jaw in newts but not in frogs. Moreover, there were proliferating cells that expressed Pax7 in newts but not in frogs, although proliferating cells were present in both animals. These results suggest that the difference of the jaw-regenerating abilities between newts and frogs depends on the expression of MHC mRNA at the tip of the amputated jaw and the contribution of Pax7-positive cells.
Figure 6. Comparison of newt and frog in situ hybridization using MHC mRNA riboprobe. A-C: Newt lower jaw. Bright field image of in situ hybridization of MHC mRNA with the signal shown as brown in A, black in B,C. Newt lower jaw in intact newt (A), and 7 days after amputation (B,C). MHC protein is shown as green, and counterstaining with Hoechst is shown as blue (C). D-F: Frog lower jaw. Bright field image of in situ hybridization of MHC mRNA with the signal shown as brown in D and black in E,F. Frog lower jaw in intact frog (D), and 7 days after amputation. MHC protein is shown as green, and counterstaining with Hoechst is shown as blue (F). Note that MHC mRNA was expressed at the tip of the newt regenerating jaw, but that such expression was not detected in frogs. Scale bars = 200 mu m in A, B, D, E; 100 mu m in C, F.
Figure 7. Distribution of MHC mRNA during newt lower jaw regeneration. A-D, F: MHC mRNA is shown as red, MHC protein is shown as green, and counterstaining with Hoechst is shown as blue. Before amputation (A). Four days after amputation (B). Seven days after amputation (C-G). There were cells that strongly expressed MHC mRNA but not MHC protein (white arrowheads) and expressed both MHC mRNA and protein (white arrows) (C). Multinucleate cells strongly expressed MHC mRNA (white arrows) (D) and in addition myofibers (white dotted line) strongly expressed MHC mRNA at their tips (F, white arrow) (F). E,G: MHC mRNA is shown as black, MHC protein is shown as green, BrdU is shown as magenta, and Hoechst used for counterstaining is shown as blue. There were multinucleate cells expressing MHC mRNA and incorporating BrdU (white arrows) (E). Some nuclei at the tip of myofibers that strongly expressed MHC mRNA incorporated BrdU (white arrows) (G). Scale bars = 100 mu m in A-C; 50 mu m in D, E; 30 mu m in F, G.
Figure 9. Comparison of newt and frog by in situ hybridization using Col2 mRNA riboprobe. A,B: Newt lower jaw. Col2 mRNA is shown as black, Col2 protein is shown as green, and counterstaining with Hoechst is shown as blue. Before amputation, the signal of Col2 mRNA could not be detected in the periosteum or Meckel's cartilage (A). Seven days after amputation, a strong Col2 mRNA signal could be detected at the amputation surface (red arrow) (B). White arrows show toothmesenchyme cells (B). C,D: Frog lower jaw. Col2 mRNA is shown as black, and counterstaining with Hoechst is shown as blue. Before amputation, there were already detectable signals of Col2 mRNA in the periosteum (red arrow) and Meckel's cartilage (white arrows) in the intact lower jaw (C). Seven days after amputation, the region showing a Col2 mRNA signal extended into the periosteum (red arrows) and Meckel's cartilage was still expressing Col2 mRNA (white arrow) (D). Scale bars = 200 mu m in A,B; 100 mu m in C,D.
