Cytochrome oxidase deficiency affecting the structure of the myofibre and the shape of mitochondrial cristae membrane

Abstract

Cytochrome oxidase deficiency was detected in the skeletal muscle of a newborn floppy child. There was a significant decrease in the quantity of subunit 5 and 6 of cytochrome oxidase as showed in Western blot with cytochrome oxidase antibody. By contrast, the NADH: cytochrome c oxidoreductase activity was normal. Electron microscopic studies revealed serious distortion in the myofibres with broken Z-bands and disorganized fibers. The relative molecular mass of actin in the myopathic muscle was smaller than in control. The diffuse actin band in Western blot suggested a proteolytic degradation of F-actin in the myopathic muscle. There was also a serious distortion in the mitochondrial structure. Cytochrome oxidase has a direct role in the formation of cristae and mutation in its components may be directly responsible for the abnormal structure.