TY - JOUR
T1 - Mechanical function of dystrophin in muscle cells
AU - Pasternak, Carmela
AU - Wong, Scott
AU - Elson, Elliot L.
PY - 1995/2
Y1 - 1995/2
N2 - We have directly measured the contribution of dystrophin to the cortical stiffness of living muscle cells and have demonstrated that lack of dystrophin causes a substantial reduction in stiffness. The inferred molecular structure of dystrophin, its preferential localization underlying the cell surface, and the apparent fragility of muscle cells which lack this protein suggest that dystrophin stabilizes the sarcolemma and protects the myofiber from disruption during contraction. Lacking dystrophin, the muscle cells of persons with Duchenne muscular dystrophy (DMD) are abnormally vulnerable. These facts suggest that muscle cells with dystrophin should be stiffer than similar cells which lack this protein. We have tested this hypothesis by measuring the local stiffness of the membrane skeleton of myotubes cultured from mdx mice and normal controls. Like humans with DMD mdx mice lack dystrophin due to an x-linked mutation and provide a good model for the human disease. Deformability was measured as the resistance to identation of a small area of the cell surface (to a depth of 1 μm) by a glass probe 1 μm in radius. The stiffness of the membrane skeleton was evaluated as the increment of force (mdyne) per μm of indentation. Normal myotubes with an average stiffness value of 1.23 ± 0.04 (SE) mdyne/μm were about fourfold stiffer than myotubes cultured from mdx mice (0.34 ± 0.014 mdyne/μm). We verified by immunofluorescence that both normal and mdx myotubes, which were at a similar developmental stage, expressed sarcomeric myosin, and that dystrophin was detected, diffusely distributed, only in normal, not in mdx myotubes. These results confirm that dystrophin and its associated proteins can reinforce the myotube membrane skeleton by increasing its stiffness and that dystrophin function and, therefore, the efficiency of therapeutic restoration of dystrophin can be assayed through its mechanical effects on muscle cells.
AB - We have directly measured the contribution of dystrophin to the cortical stiffness of living muscle cells and have demonstrated that lack of dystrophin causes a substantial reduction in stiffness. The inferred molecular structure of dystrophin, its preferential localization underlying the cell surface, and the apparent fragility of muscle cells which lack this protein suggest that dystrophin stabilizes the sarcolemma and protects the myofiber from disruption during contraction. Lacking dystrophin, the muscle cells of persons with Duchenne muscular dystrophy (DMD) are abnormally vulnerable. These facts suggest that muscle cells with dystrophin should be stiffer than similar cells which lack this protein. We have tested this hypothesis by measuring the local stiffness of the membrane skeleton of myotubes cultured from mdx mice and normal controls. Like humans with DMD mdx mice lack dystrophin due to an x-linked mutation and provide a good model for the human disease. Deformability was measured as the resistance to identation of a small area of the cell surface (to a depth of 1 μm) by a glass probe 1 μm in radius. The stiffness of the membrane skeleton was evaluated as the increment of force (mdyne) per μm of indentation. Normal myotubes with an average stiffness value of 1.23 ± 0.04 (SE) mdyne/μm were about fourfold stiffer than myotubes cultured from mdx mice (0.34 ± 0.014 mdyne/μm). We verified by immunofluorescence that both normal and mdx myotubes, which were at a similar developmental stage, expressed sarcomeric myosin, and that dystrophin was detected, diffusely distributed, only in normal, not in mdx myotubes. These results confirm that dystrophin and its associated proteins can reinforce the myotube membrane skeleton by increasing its stiffness and that dystrophin function and, therefore, the efficiency of therapeutic restoration of dystrophin can be assayed through its mechanical effects on muscle cells.
UR - http://www.scopus.com/inward/record.url?scp=0028929061&partnerID=8YFLogxK
U2 - 10.1083/jcb.128.3.355
DO - 10.1083/jcb.128.3.355
M3 - Article
C2 - 7844149
AN - SCOPUS:0028929061
SN - 0021-9525
VL - 128
SP - 355
EP - 361
JO - Journal of Cell Biology
JF - Journal of Cell Biology
IS - 3
ER -