Diminished microtubules in fibroblast cells derived from inherited dystrophic muscle explants.

Abstract

MUSCULAR DYSTROPHY of the Duchenne type is inherited in a recessive, sex-linked fashion. The aetiology of the disease is still unclear but biochemical and morphological studies strongly suggest a cell surface membrane abnormality in Duchenne muscular dystrophy1–7. Even though there are artefacts due to surface condensation of water, freeze-fracture studies of skeletal muscle from patients with Duchenne dystrophy show a depletion of intramembrane particles in the protoplasmic and environmental faces of the muscle Plasma membrane8,9. In contrast, Ketelsen's freeze-fracture studies indicated that the number of particles in the inner membrane fracture face in muscular dystrophy increased two- or threefold beyond normal10. In other studies, it was demonstrated that patients and carriers of Duchenne muscular dystrophy exhibited diminished cap formation in their lymphocytes11,12. Although these experiments clearly support a membrane defect in muscular dystrophy, whether this is related to the aetiology of the disease is not yet clear. Several of these studies indicate that this membrane defect is an early and perhaps primary one in the aetiology of Duchenne's muscular dystrophy7. Even though the primary lesion in muscular dystrophy is usually thought to be myogenic or neurogenic the reported abnormalities in the lymphocyte11,12 and erythrocyte membrane13 indicate that the expression of muscular dystrophy may not necessarily be restricted to these tissues. There have been many studies on the dynamic interrelationships between cytoplasmic structures and the cell surface14,15 and models have been proposed which suggest that changes in the state of the cytoplasmic microfilaments and microtubules can alter the mobility and distribution of membrane surface receptors16. In an attempt to determine if the membrane defect in muscular dystrophy might be correlated with a cytoskeletal alteration, we have studied the distribution of cytoplasmic microfilaments (actin) and micro-tubules (tubulin) in fibroblasts derived from muscle expiants of both normal and dystrophic inbred chickens using indirect immunofluorescence methods with monospecific antibodies directed against actin and tubulin. We report here that fibroblasts from expiants of cardiac and skeletal muscle of dystrophic chickens show a dramatic reduction in the appearance of intact interphase microtubules compared with those from normal chickens.