Smooth muscle persists in the muscularis externa of developing and adult mouse esophagus |
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Authors: | Mark Rishniw Pat W Fisher Robert M Doran Eric Meadows William H Klein Michael I Kotlikoff |
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Institution: | (1) Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, T4 018 VRT, Box 11, Ithaca, NY 14853, USA;(2) Department of Biochemistry and Molecular Biology, MD Anderson Cancer Center, University of Texas, Houston, TX 77030, USA |
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Abstract: | Following initial patterning as differentiated smooth muscle (SM) cells, the muscularis externa of the murine esophagus is replaced by skeletal muscle, but the mechanism underlying this process is controversial. The hypothesis
that committed SM cells transdifferentiate into striated muscle is not consistent with fate mapping studies. Similarly, apoptosis
does not fully explain the process. Using immunohistochemical techniques and transgenic mice that express eGFP and Cre-recombinase
exclusively in SM, we have identified a population of remnant SM cells that persist throughout the developing and mature murine
esophagus. These cells display an atypical phenotype, are not associated with microvasculature, but are often apposed to cKit
positive, interstitial cells of Cajal. The absolute length of the SM component of the developing esophagus remains constant
during a period when total esophageal length increases 4-fold, resulting in a small maintained distal segment of smooth muscle.
Esophageal SM cells fail to express myogenin during development, and striated muscle cell precursors expressing myogenin fail
to express specific SM cell markers, indicating that they did not transdifferentiate from SM cells. Moreover, smooth muscle-specific
myogenin inactivation has no effect on esophageal skeletal myogenesis. Taken together, our results provide an alternative
hypothesis regarding the fate of SM cells in the developing murine esophagus, which does not invoke apoptosis or transdifferentiation. |
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Keywords: | Transdifferentiation Esophagus Development Muscle |
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