Decreased activity of cytochrome c oxidase in the macular mottled mouse: an immuno-electron microscopic study

The macular mottled mouse is a murine model of the kinky hair syndrome, characterized by a deficiency in copper transport. Cytochrome c oxidase (CCO), a respiratory enzyme, is located in the inner mitochondrial membrane and consists of seven subunits, along with copper and iron. Biochemical and histochemical findings indicated that CCO activity was decreased in the cerebellum of the macular mottled mice but not in that of the controls. Immunocytochemical analysis, using anti-CCO and anti-complex III rabbit sera, revealed that CCO in the macular mottled mice was stained more weakly than that in the controls. Immuno-electron microscopic examination of CCO and complex III, using a method of gold labeling, was also performed. In the control mice, a high concentration of gold particles present over CCO and complex III could be seen in the inner mitochondrial membrane. The number of CCO-labeled gold particles was remarkably less, however, in the macular mottled mice, while no significant difference was found in the labeling of complex III between the two groups. It may be concluded that the very low CCO enzyme content in the macular mottled mouse results not only from a copper transport disorder but also from a CCO protein synthesis disorder which impairs the localization of CCO protein in the cerebellum.