Muscle Research Unit, Dept. Anatomy & Histology, The University of Sydney, *Clinical Chemistry Dept. Prince of Wales Hospital, Randwick, and +Heart & Lung Transplant Unit, St. Vincent's Hospital, Darlinghurst
Introduction: Dilated Cardiomyopathy (DCM) is a disorder where the cause is entirely unknown. It involves a chronic and progressive weakening of myocardial contraction. Several recent reports1-2 have suggested that DCM is associated with a reduction or loss of dystrophin, a protein known to be defective in Duchenne and related muscular dystrophies. Dystrophin is a large (427kD), very low abundance protein, which can not be detected on SDS PAGE gels and can only be detected by Western blot methods.
Aim: To determine if Dilated Cardiomyopathy is associated with dystrophin deficiency
Methods: Electrophoresis was performed on a linear (4-7%) gradient, SDS PAGE gel with a 3% stacking gel and run on a horizontal Pharmacia Multiphore system. Semi-dry blotting was performed onto 0.45m nitrocellulose membranes, blocked in 5% skim milk, washed in Tris-buffered saline and incubated with an anti-dystrophin monoclonal Ab, second Ab was IgG-biotin followed by streptavidin-alk.phos. & visualized by a NBT/BCIP detection system. Dystrophin was estimated by volume integration of densitometer-scans using serial dilutions of a control dystrophin. 3 monoclonal anti-dystrophin Abs were specific for the N- & C-treminal and mid-rod portions of dystrophin.
Sample No. % Dystrophin
(normalized to
myosin content per
lane)
Means +/-SDs Ranges
Controls 5 97 8 86-107
Non-familial 29 96 9 82-108
Familial 3 104 4 100-108
Conclusion: We find no evidence that either the familial or non-familial form of human dilated cardiomyopathy is associated with a loss or deficiency of dystrophin.
References:
(1) Michels, V.V. (1993) New Engl. J. Med. 329: 9960-61
(2) Oldfors, A. et al. (1994) Br. Heart J. 72: 344-48
(3) Antibodies from: Novacastra Labs. Newcastle-upon-Tyne, UK