Two-dimensional electrophoretic analysis of muscle contractile proteins in patients with idiopathic scoliosis.

Muscle biopsies from patients with idiopathic scoliosis were analyzed by two-dimensional gel electrophoresis. Both isoelectric focusing and nonequilibrium pH-gradient electrophoresis were used in the first dimension of the separations, to obtain maximum information from each biopsy specimen. The identification of the various contractile proteins and their isoforms was considered, based in part by analogy with studies on animal models. The myosin light chains and the TN-C subunit of troponin were the most useful qualitative markers indicative of the muscle phenotype. Convex and concave paraspinal muscles were analyzed from 13 patients with idiopathic scoliosis. Eight of the patients had light chain and TN-C subunits characteristic of both fast and slow contracting muscle. However, five patients had mixtures of fast and slow proteins only in the concave muscle, the convex muscle being composed exclusively of slow light chains and slow TN-C. Possible mechanisms leading to such a situation and the implications of these results concerning the muscle pathology are discussed.