Scientific background:

Summary: Mutations are associated with several cardio-vascular diseases.

Gene: Then gene MTHFR is about 3kb in size. Its locus is on chromosome 1 (1p36.3). It consists of 11 exons.

Pathology: The enzyme methylenetetrahydrofolate reductase is important to the metabolism of the amino acid cysteine. A mutation in this gene leads to elevation of the homocysteine level in plasma.

Clinical signs: Hyperhomocysteinemia is discussed as a cause of accelerated arteriosclerosis. Thrombophilia seems to be associated with MTHFR mutations too. In dialysis patients there is the homocysteine level elevated partly due to uremia and further increased by MTHFR mutations. Folic acid substitution can decrease this level and this might be associated with a lover risk for cardiovascular diseases.

Epidemiology: The frequency of homozygous C677T mutation in Caucasian population is about 4-10% a heterozygous state is found in about 40-50%. There is a gradient in frequency from North to South.

Interpretation: Carriers of this mutation have a greater risk for cardiovascular diseases and could be treated with folic acid.

Test strategy: Patient with higher risk for cardiovascular disease to decide folic acid substitution. This test is much easier to perform than measuring homocysteine levels in plasma.

Methodology:

	clinical test	Method		Genomic sequencing of the entire coding region
		Turn-around time		25 working days
		Effort		medium
		Specimen		DNA
		Quality assessment		Internal quality control only
	All known and new missense, nonsense and splice mutations can be detected.
	clinical test	Method		Hotspot sequencing
		Turn-around time		5 working days
		Effort		little
		Specimen		DNA
		Quality assessment		Internal and in some aspects external quality control
	Only in the region of interest, known and new missense, nonsense and splice mutations can be detected.
	clinical test	Method		Fragment analysis
		Turn-around time		5 working days
		Effort		little
		Specimen		DNA
		Quality assessment		Full external quality control
	Only the target mutation is detected all other genetic variations, though possibly important they may be, are missed.
	clinical test	Method		Carrier testing
		Turn-around time		5 working days
		Effort		little
		Specimen		DNA
		Quality assessment		Internal quality control only
	The test is only specific about the mutation already known in this kindred.

Literature: 

Födinger M et al. (1997) Mutation (677 C to T) in the methylenetetrahydrofolate reductase gene aggravates hyperhomocysteinemia in hemodialysis patients.
Peng F et al. (2001) Single nucleotide polymorphisms in the methylenetetrahydrofolate reductase gene are common in US Caucasian and Hispanic American populations.
Pallaud C et al. (2001) Candidate gene polymorphisms in cardiovascular disease: a comparative study of frequencies between a French and an Italian population.