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Axial distribution of myosin binding protein-C is unaffected by mutations in human cardiac and skeletal muscle.

Vydyanath A, Gurnett CA, Marston S, Luther PK - J. Muscle Res. Cell. Motil. (2012)

Bottom Line: Myosin binding protein-C (MyBP-C), a major thick filament associated sarcomeric protein, plays an important functional and structural role in regulating sarcomere assembly and crossbridge formation.Due to the difficulty of obtaining normal human tissue, we compared the distribution to the A-band structure in normal frog skeletal, rat cardiac muscle and in cardiac muscle of MyBP-C-deficient mice.Very similar overall profile averages were obtained from the C-zones in cardiac HCM samples and skeletal DA-1 samples with MyBP-C gene mutations, suggesting that mutations in MyBP-C do not alter its mean axial distribution along the thick filament.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Medicine, National Heart and Lung Institute, Imperial College London, London, UK. a.vydyanath@imperial.ac.uk

ABSTRACT
Myosin binding protein-C (MyBP-C), a major thick filament associated sarcomeric protein, plays an important functional and structural role in regulating sarcomere assembly and crossbridge formation. Missing or aberrant MyBP-C proteins (both cardiac and skeletal) have been shown to cause both cardiac and skeletal myopathies, thereby emphasising its importance for the normal functioning of the sarcomere. Mutations in cardiac MyBP-C are a major cause of hypertrophic cardiomyopathy (HCM), while mutations in skeletal MyBP-C have been implicated in a disease of skeletal muscle-distal arthrogryposis type 1 (DA-1). Here we report the first detailed electron microscopy studies on human cardiac and skeletal tissues carrying MyBP-C gene mutations, using samples obtained from HCM and DA-1 patients. We have used established image averaging methods to identify and study the axial distribution of MyBP-C on the thick filament by averaging profile plots of the A-band of the sarcomere from electron micrographs of human cardiac and skeletal myopathy specimens. Due to the difficulty of obtaining normal human tissue, we compared the distribution to the A-band structure in normal frog skeletal, rat cardiac muscle and in cardiac muscle of MyBP-C-deficient mice. Very similar overall profile averages were obtained from the C-zones in cardiac HCM samples and skeletal DA-1 samples with MyBP-C gene mutations, suggesting that mutations in MyBP-C do not alter its mean axial distribution along the thick filament.

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Averaged axial density profile plots of skeletal muscle with MYBPC1 mutations and control samples. The profile plot from a frog sartorius muscle is compared with the mean profile plots of b ss-W236R and c ss-Y856H. The left panel shows an example electron micrograph used to calculate the average profile plots in the right panel. The profile plots are aligned at the centre of the M-band and the edge of the A-band (green lines) and 17 red stripes of 43-nm spacing. a Reproduced from Luther et al. (2008) with permission from Elsevier. (Color figure online)
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Fig5: Averaged axial density profile plots of skeletal muscle with MYBPC1 mutations and control samples. The profile plot from a frog sartorius muscle is compared with the mean profile plots of b ss-W236R and c ss-Y856H. The left panel shows an example electron micrograph used to calculate the average profile plots in the right panel. The profile plots are aligned at the centre of the M-band and the edge of the A-band (green lines) and 17 red stripes of 43-nm spacing. a Reproduced from Luther et al. (2008) with permission from Elsevier. (Color figure online)

Mentions: One-dimensional analysis was carried out on human skeletal and cardiac muscle carrying MYBPC1 and MYBPC3 mutations respectively. Axial distribution of MyBP-C in these samples was analysed by averaging profile plots of the A-band over several electron micrographs of half-sarcomere regions by cross-correlation to produce an average axial density profile. The axial density plots for the skeletal and cardiac samples are compared in Figs. 5 and 6, respectively. The averaged half A-band plot was divided into seventeen equally spaced bands of 43 nm intervals, marked by red lines labelled 1–17 in Figs. 5 and 6, although non-myosin protein is known to be present only on stripes 1–11. Luther et al. (2008) have determined previously by immuno-electron microscopy that the C-zone in cardiac muscle is located between stripe 3 and 11, hence the P-zone (proximal) spans stripes 1–3. In these figures, representative electron micrographs of the different samples are shown in the left panel, while in the right panel the plot profiles are arranged to line up at the centre of the M-bands and the edges of the A-band marked by the two green lines. The plots are regular and show peaks of high density in the A-band region. As discussed below, the majority of the peaks within the C-zone coincide with the 43 nm spaced red lines indicating the presence of one layer of myosin crossbridges (crowns) and MyBP-C.Fig. 5


Axial distribution of myosin binding protein-C is unaffected by mutations in human cardiac and skeletal muscle.

Vydyanath A, Gurnett CA, Marston S, Luther PK - J. Muscle Res. Cell. Motil. (2012)

Averaged axial density profile plots of skeletal muscle with MYBPC1 mutations and control samples. The profile plot from a frog sartorius muscle is compared with the mean profile plots of b ss-W236R and c ss-Y856H. The left panel shows an example electron micrograph used to calculate the average profile plots in the right panel. The profile plots are aligned at the centre of the M-band and the edge of the A-band (green lines) and 17 red stripes of 43-nm spacing. a Reproduced from Luther et al. (2008) with permission from Elsevier. (Color figure online)
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Related In: Results  -  Collection

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Fig5: Averaged axial density profile plots of skeletal muscle with MYBPC1 mutations and control samples. The profile plot from a frog sartorius muscle is compared with the mean profile plots of b ss-W236R and c ss-Y856H. The left panel shows an example electron micrograph used to calculate the average profile plots in the right panel. The profile plots are aligned at the centre of the M-band and the edge of the A-band (green lines) and 17 red stripes of 43-nm spacing. a Reproduced from Luther et al. (2008) with permission from Elsevier. (Color figure online)
Mentions: One-dimensional analysis was carried out on human skeletal and cardiac muscle carrying MYBPC1 and MYBPC3 mutations respectively. Axial distribution of MyBP-C in these samples was analysed by averaging profile plots of the A-band over several electron micrographs of half-sarcomere regions by cross-correlation to produce an average axial density profile. The axial density plots for the skeletal and cardiac samples are compared in Figs. 5 and 6, respectively. The averaged half A-band plot was divided into seventeen equally spaced bands of 43 nm intervals, marked by red lines labelled 1–17 in Figs. 5 and 6, although non-myosin protein is known to be present only on stripes 1–11. Luther et al. (2008) have determined previously by immuno-electron microscopy that the C-zone in cardiac muscle is located between stripe 3 and 11, hence the P-zone (proximal) spans stripes 1–3. In these figures, representative electron micrographs of the different samples are shown in the left panel, while in the right panel the plot profiles are arranged to line up at the centre of the M-bands and the edges of the A-band marked by the two green lines. The plots are regular and show peaks of high density in the A-band region. As discussed below, the majority of the peaks within the C-zone coincide with the 43 nm spaced red lines indicating the presence of one layer of myosin crossbridges (crowns) and MyBP-C.Fig. 5

Bottom Line: Myosin binding protein-C (MyBP-C), a major thick filament associated sarcomeric protein, plays an important functional and structural role in regulating sarcomere assembly and crossbridge formation.Due to the difficulty of obtaining normal human tissue, we compared the distribution to the A-band structure in normal frog skeletal, rat cardiac muscle and in cardiac muscle of MyBP-C-deficient mice.Very similar overall profile averages were obtained from the C-zones in cardiac HCM samples and skeletal DA-1 samples with MyBP-C gene mutations, suggesting that mutations in MyBP-C do not alter its mean axial distribution along the thick filament.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Medicine, National Heart and Lung Institute, Imperial College London, London, UK. a.vydyanath@imperial.ac.uk

ABSTRACT
Myosin binding protein-C (MyBP-C), a major thick filament associated sarcomeric protein, plays an important functional and structural role in regulating sarcomere assembly and crossbridge formation. Missing or aberrant MyBP-C proteins (both cardiac and skeletal) have been shown to cause both cardiac and skeletal myopathies, thereby emphasising its importance for the normal functioning of the sarcomere. Mutations in cardiac MyBP-C are a major cause of hypertrophic cardiomyopathy (HCM), while mutations in skeletal MyBP-C have been implicated in a disease of skeletal muscle-distal arthrogryposis type 1 (DA-1). Here we report the first detailed electron microscopy studies on human cardiac and skeletal tissues carrying MyBP-C gene mutations, using samples obtained from HCM and DA-1 patients. We have used established image averaging methods to identify and study the axial distribution of MyBP-C on the thick filament by averaging profile plots of the A-band of the sarcomere from electron micrographs of human cardiac and skeletal myopathy specimens. Due to the difficulty of obtaining normal human tissue, we compared the distribution to the A-band structure in normal frog skeletal, rat cardiac muscle and in cardiac muscle of MyBP-C-deficient mice. Very similar overall profile averages were obtained from the C-zones in cardiac HCM samples and skeletal DA-1 samples with MyBP-C gene mutations, suggesting that mutations in MyBP-C do not alter its mean axial distribution along the thick filament.

Show MeSH
Related in: MedlinePlus