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Methylenetetrahydrofolate reductase deficiency is the most common genetic cause of elevated serum levels of homocysteine (hyperhomocysteinemia). It is caused by genetic defects in MTHFR, which is an important enzyme in the methyl cycle. [1] Common variants of MTHFR deficiency are asymptomatic and have only minor effects on disease risk. [2]
Methylenetetrahydrofolate reductase (MTHFR) is the rate-limiting enzyme in the methyl cycle, and it is encoded by the MTHFR gene. [5] Methylenetetrahydrofolate reductase catalyzes the conversion of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, a cosubstrate for homocysteine remethylation to methionine.
Genetic defects in 5-MTHF reductase can consequently lead to hyperhomocysteinemia. The most common polymorphisms are known as MTHFR C677T and MTR A2756G. [23] [24] The homozigote mutation G;G also called C;C (it is equivalent) occurs in about 10% of the population of european ethnicity (white caucasians). [25]
C677T or rs1801133 is a genetic variation—a single nucleotide polymorphism (SNP)—in the MTHFR gene. Among Americans the frequency of T-homozygosity ranges from 1% or less among people of sub-Saharan African descent to 20% or more among Italians and Hispanics. [1] It has been related to schizophrenia [2] Alzheimer's disease [3] depression [4 ...
The following is a list of genetic disorders and if known, type of mutation and for the chromosome involved. Although the parlance "disease-causing gene" is common, it is the occurrence of an abnormality in the parents that causes the impairment to develop within the child. There are over 6,000 known genetic disorders in humans.
A meta-analysis demonstrated that polymorphism of the MTHFR C677T genotype is correlated with an ASD diagnosis in children from countries lacking food fortification. [39] While MTHFR is a proposed genetic factor for ASD, there is limited clinical evidence from testing for MTHFR gene polymorphisms in the diagnostic setting. [40]
A deficiency of folate itself does not cause neural tube defects. The association seen between reduced neural tube defects and folic acid supplementation is due to a gene-environment interaction such as vulnerability caused by the C677T methylenetetrahydrofolate reductase (MTHFR) variant.
Additionally, mutations of the MTHFR gene (A1298C variant) and DHFR can interfere with the recycling of BH4 and lead to less severe, but still clinifically significant, deficiencies of BH4. [citation needed] BH4 is a compound that helps convert several amino acids, including phenylalanine, to other essential molecules in the body.