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Lookup NU author(s): Martin Picard, Dr Kathryn White, Emeritus Professor Doug Turnbull
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Dynamic remodeling of mitochondrial morphology through membrane dynamics are linked to changes in mitochondrial and cellular function. Although mitochondrial membrane fusion/fission events are frequent in cell culture models, whether mitochondrial membranes dynamically interact in postmitotic muscle fibers in vivo remains unclear. Furthermore, a quantitative assessment of mitochondrial morphology in intact muscle is lacking. Here, using electron microscopy (EM), we provide evidence of interacting membranes from adjacent mitochondria in intact mouse skeletal muscle. Electron-dense mitochondrial contact sites consistent with events of outer mitochondrial membrane tethering are also described. These data suggest that mitochondrial membranes interact in vivo among mitochondria, possibly to induce morphology transitions, for kiss-and-run behavior, or other processes involving contact between mitochondrial membranes. Furthermore, a combination of freeze-fracture scanning EM and transmission EM in orthogonal planes was used to characterize and quantify mitochondrial morphology. Two subpopulations of mitochondria were studied: subsarcolemmal (SS) and intermyofibrillar (IMF), which exhibited significant differences in morphological descriptors, including form factor (means +/- SD for SS: 1.41 +/- 0.45 vs. IMF: 2.89 +/- 1.76, P < 0.01) and aspect ratio (1.97 +/- 0.83 vs. 3.63 +/- 2.13, P < 0.01) and circularity (0.75 +/- 0.16 vs. 0.45 +/- 0.22, P < 0.01) but not size (0.28 +/- 0.31 vs. 0.27 +/- 0.20 mu m(2)). Frequency distributions for mitochondrial size and morphological parameters were highly skewed, suggesting the presence of mechanisms to influence mitochondrial size and shape. In addition, physical continuities between SS and IMF mitochondria indicated mixing of both subpopulations. These data provide evidence that mitochondrial membranes interact in vivo in mouse skeletal muscle and that factors may be involved in regulating skeletal muscle mitochondrial morphology.
Author(s): Picard M, White K, Turnbull DM
Publication type: Article
Publication status: Published
Journal: Journal of Applied Physiology
Year: 2013
Volume: 114
Issue: 2
Pages: 161-171
Print publication date: 01/10/2012
ISSN (print): 8750-7587
ISSN (electronic): 1522-1601
Publisher: American Physiological Society
URL: http://dx.doi.org/10.1152/japplphysiol.01096.2012
DOI: 10.1152/japplphysiol.01096.2012
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