SCO1

Protein SCO1 homolog, mitochondrial is a protein that in humans is encoded by the SCO1 gene. Mutations in both SCO1 and SCO2 are associated with distinct clinical phenotypes as well as tissue-specific cytochrome c oxidase deficiency. SCO1 localizes predominantly to blood vessels, whereas SCO2 is barely detectable. Expression of SCO2 is also much higher than that of SCO1 in muscle tissue, while SCO1 is expressed at higher levels in liver tissue than SCO2.

Function

Mammalian cytochrome c oxidase (COX) catalyzes the transfer of reducing equivalents from cytochrome c to molecular oxygen and pumps protons across the inner mitochondrial membrane. In yeast, 2 related COX assembly genes, SCO1 and SCO2 (synthesis of cytochrome c oxidase), enable subunits 1 and 2 to be incorporated into the holoprotein. This gene is the human homolog to the yeast SCO1 gene.

Clinical relevance

Mutation in the SCO1 gene are a cause of mitochondrial complex IV deficiency also known as cytochrome c oxidase deficiency. This disorder affects the mitochondrial respiratory chain resulting in a variety of symptoms, ranging from isolated myopathy to severe multisystem disease affecting several tissues and organs. A subset of patients also suffer from Leigh syndrome.

Model organisms

Sco1 knockout mouse phenotype

Characteristic	Phenotype
Homozygote viability	Abnormal
Recessive lethal study	Abnormal
Fertility	Normal
Body weight	Normal
Anxiety	Normal
Neurological assessment	Normal
Grip strength	Normal
Hot plate	Normal
Dysmorphology	Normal
Indirect calorimetry	Normal
Glucose tolerance test	Normal
Auditory brainstem response	Normal
DEXA	Normal
Radiography	Normal
Body temperature	Normal
Eye morphology	Normal
Clinical chemistry	Normal
Haematology	Normal
Peripheral blood lymphocytes	Normal
Micronucleus test	Normal
Heart weight	Normal
Salmonella infection	Normal
All tests and analysis from

Model organisms have been used in the study of SCO1 function. A conditional knockout mouse line, called Sco1^{tm1a(KOMP)Wtsi} was generated as part of the International Knockout Mouse Consortium program — a high-throughput mutagenesis project to generate and distribute animal models of disease.

Male and female animals underwent a standardized phenotypic screen to determine the effects of deletion. Twenty two tests were carried out on mutant mice and two significant abnormalities were observed. No homozygous mutant embryos were identified during gestation, and therefore none survived until weaning. The remaining tests were carried out on heterozygous mutant adult mice; no additional significant abnormalities were observed in these animals.