Molybdenum cofactor deficiency: Mutations in GPHN, MOCS1, and MOCS2

Area of Science:

• Biochemistry
• Genetics
• Human Physiology

Background:

• Molybdenum cofactor (MoCo) is essential for the function of four key human molybdoenzymes: aldehyde oxidase, mitochondrial amidoxime reducing component (mARC), xanthine oxidoreductase, and sulfite oxidase.
• MoCo is synthesized through a conserved pathway across organisms, termed the "universal molybdenum cofactor."
• Mutations in genes responsible for MoCo biosynthesis lead to combined MoCo deficiency, clinically resembling isolated sulfite oxidase deficiency.

Purpose of the Study:

• To elucidate the genetic basis of molybdenum cofactor deficiency.
• To highlight the clinical similarities between combined MoCo deficiency and isolated sulfite oxidase deficiency.
• To identify the genes associated with different types of MoCo deficiency.

Main Methods:

• Genetic analysis of patients with MoCo deficiency.
• Review of literature on molybdoenzyme function and MoCo biosynthesis.
• Clinical correlation of genotype with phenotype.

Main Results:

• Mutations in MOCS1 (Type A) and MOCS2 (Type B) are the primary causes of combined MoCo deficiency.
• A single case of MoCo deficiency was linked to mutations in GPHN.
• Combined MoCo deficiency presents with severe neurological damage and often early childhood death.
• Isolated sulfite oxidase deficiency shares clinical features due to mutations in the corresponding apoenzyme gene.

Conclusions:

• Combined MoCo deficiency results from defects in the universal MoCo biosynthesis pathway.
• Genetic defects in MOCS1, MOCS2, and GPHN cause combined MoCo deficiency.
• Recent advancements show promising substitution therapy for Type A deficiency.