Flexibility within Myosin Heads Revealed by Negative Stain and Single-Particle Analysis
Open Access
- 3 November 1997
- journal article
- research article
- Published by Rockefeller University Press in The Journal of cell biology
- Vol. 139 (3), 675-681
- https://doi.org/10.1083/jcb.139.3.675
Abstract
Pattern in the developing limb depends on signaling by polarizing region mesenchyme cells, which are located at the posterior margin of the bud tip. Here we address the underlying cellular mechanisms. We show in the intact bud that connexin 43 (Cx43) and Cx32 gap junctions are at higher density between distal posterior mesenchyme cells at the tip of the bud than between either distal anterior or proximal mesenchyme cells. These gradients disappear when the apical ectodermal ridge (AER) is removed. Fibroblast growth factor 4 (FGF4) produced by posterior AER cells controls signaling by polarizing cells. We find that FGF4 doubles gap junction density and substantially improves functional coupling between cultured posterior mesenchyme cells. FGF4 has no effect on cultured anterior mesenchyme, suggesting that any effects of FGF4 on responding anterior mesenchyme cells are not mediated by a change in gap junction density or functional communication through gap junctions. In condensing mesenchyme cells, connexin expression is not affected by FGF4. We show that posterior mesenchyme cells maintained in FGF4 under conditions that increase functional coupling maintain polarizing activity at in vivo levels. Without FGF4, polarizing activity is reduced and the signaling mechanism changes. We conclude that FGF4 regulation of cell–cell communication and polarizing signaling are intimately connected.Keywords
This publication has 23 references indexed in Scilit:
- Electron Tomography of Insect Flight Muscle in Rigor and AMPPNP at 23°CJournal of Molecular Biology, 1996
- A 35-Å movement of smooth muscle myosin on ADP releaseNature, 1995
- Tilting of the light-chain region of myosin during step length changes and active force generation in skeletal muscleNature, 1995
- The ribosome at improved resolution: New techniques for merging and orientation refinement in 3D cryo-electron microscopy of biological particlesUltramicroscopy, 1994
- Visualization of domains in native and nucleotide-trapped myosin heads by negative stainingJournal of Muscle Research and Cell Motility, 1988
- Domain structure of the myosin head in correlation-averaged images of shadowed moleculesJournal of Muscle Research and Cell Motility, 1988
- Electron microscope study of the effect of temperature on the length of the tail of the myosin moleculeJournal of Molecular Biology, 1986
- Negative staining of myosin moleculesJournal of Molecular Biology, 1985
- Electron microscopy of thin filaments decorated with a Ca2+-regulated myosinJournal of Molecular Biology, 1980
- Electron microscopy of the stacked disk aggregate of tobacco mosaic virus protein: II. The influence of electron irradiation on the stain distributionJournal of Molecular Biology, 1974