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Wilfred Denetclaw
Cell Biology |
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| Research Interests: Myogenic specification (myoD expression) and myotome formation (skeletal muscle expression) in somites of chicken embryos are dependent on regulatory signaling molecules secreted into the somite environment by adjacent tissues such as the overlying ectoderm. This mode for signaling is problematic because proliferation and differentiation promoting signals are released into the same somite region. And, it is not clear how cells distinguish these signals during somite development. However, we have investigated epithelial cells in the somite and dermomyotome for their role in mediating the signaling process using lipophilic membrane dyes coupled with confocal laser scanning microscopy imaging. Live somite cross-sections labeled by Bodipy-FL sphingomyelin revealed the presence of membrane microdomains in dermomyotome and ectoderm tissues and an extensive network of filopodia connecting the dermomyotome with ectoderm. Membrane microdomains suggest lipid rafts. Briefly, the Fluid Mosaic Model describes cellular membranes as liquid crystalline structures due to their amphiphilic chemical structure and to their presence in the membrane in liquid order and disorder forms. Membrane microdomains (lipid rafts?) are examples of the former and are formed because they are enriched in cholesterol and glycosphingolipids and are thought to act as platforms for protein insertion to mediate activities such as in the attachment of cytoplasmic microfilaments with plasma membrane for filopodial extension. Membrane microdomains also have roles in signal transduction for cellular proliferation and differentiation. However, membrane microdomains depend on cholesterol for their organization into lipid platforms. Therefore, drugs that reduce membrane cholesterol inhibit membrane microdomain function. We investigate somite cellular behaviors during key times when external signals for myogenesis occur. Our findings show that filopodia establish stable contact with ectoderm and develop in a spatio-temporal pattern to correlate with epaxial myotome development. Furthermore, specific labeling of the ectoderm with DiIC18 and FM 4-64 lipophilic dyes result in progressive movements of membrane microdomains through filopodia into the dermomyotome. And, ectoderm treatment with a cholesterol removing drug inhibited myogenesis in somites. Therefore, we propose that the somites are proactive in the process of myogenic signaling through development of filopodia and that ectoderm membrane microdomains (lipid rafts?) are regulators of myotome development. |
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| Recent Publications & Presentations (** = grad student): Denetclaw, W.F. Jr., Berdougo, E., Venters, S.J., and Ordahl, C.P. (2001). Precursor cell movement in primary myotome growth and morphogenesis. (manuscript submitted). Ordahl, C.P., Berdougo, E., Venters, S.J., and Denetclaw, W.F. Jr. (2001). The dermomyotome dorso-medial lip drives growth and morphogenesis of both the primary myotome and dermomyotome epithelium. (manuscript submitted). Denetclaw, W.F. Jr. and Ordahl, C.P. (2000). The growth of the dermomyotome and formation of early myotome lineages in thoraco-lumbar somites of chicken embryos. Development 127:893-905. Denetclaw, W.F. Jr. (2000). DiI and diO confocal imaging of chicken embryos. Microscopy Today. January 2000:24. Ordahl, C.P., Williams, B., and Denetclaw, W.F. Jr. (2000). Lineage and determination in the myotome. Current Topics in Developmental Biology, Vol. 47:Somitogenesis. Dettman, R. W., Denetclaw, W. Jr., Ordahl, C.P., and Bristow, J. (1998). Common epicardial origin of coronary vascular smooth muscle, perivascular fibroblasts, and intermyocardial fibroblasts in the avian heart. Developmental Biology. 193:169-181. Denetclaw, W.F. Jr., Christ, B., and Ordahl, C.P. (1997). Location and growth of epaxial myotome precursor cells. Development. 124(8):1601-1610. McCarter, G.C., Denetclaw, W.F., Reddy, P., and Steinhardt, R.A. (1997). Lipofection of a cDNA plasmid containing the dystrophin gene lowers intracellular free calcium and calcium leak channel activity in mdx myotubes. Gene Therapy. 4(5):483-487. Hopf, F.W., Turner, P.R., Denetclaw, W.F. Jr., Reddy, P., and Steinhardt, R.A. (1996). A critical evaluation of resting intracellular free calcium regulation in dystrophic mdx muscle. American Journal of Physiology. 271(Cell Physiology 40):C1325-1339. Garrison, E.R., Denetclaw, W.F. Jr., and Scott, O.T. (1995). Navajo scientists of the next century -- Laanaa Daniidzin. Journal of Navajo Education. 12(3):11-15. Denetclaw, T.H. and Denetclaw, W.F. Jr. (1994). Hantavirus Pulmonary Syndrome in New England and Europe. New England Journal of Medicine. 331(8):545-548. Denetclaw, W.F. Jr., and Denetclaw, T.H. (1994). Is "south-west US mystery disease" caused by hantavirus? The Lancet. 343(8888):53-54. Denetclaw, W.F. Jr., Hopf, F.W., Cox, G.A., Chamberlain, J.S., and Steinhardt, R.A. (1994). Myotubes from transgenic mdx mice expressing full-length dystrophin show normal calcium regulation. Molecular Biology of the Cell. 5:1159-1167. Denetclaw, W.F. Jr., Bi, G., Pham, D.V., and Steinhardt, R.A. (1993). Heterokaryon myotubes with normal mouse and Duchenne nuclei exhibit sarcolemmal dystrophin staining and efficient intracellular free calcium control. Molecular Biology of the Cell. 4:963-972. Turner, P.R., Fong, P., Denetclaw, W.F., and Steinhardt, R.A. (1991). Increased calcium influx in dystrophic muscle. Journal of Cell Biology. 115(6):1701-12. Fong, P., Turner, P.R., Denetclaw, W.F., and Steinhardt, R.A. (1990). Increased activity of calcium leak channels in myotubes of Duchenne human and mdx mouse origin. Science. 250:673-676. |
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