Analysis of Saliva DNA Suggested for Screening Stroke-Linked Mutation

The MTHFR nucleotide at position 677 in the gene has two possibilities: C (cytosine) or T (thymine). C at position 677 (leading to an alanine at amino acid 222) is the normal allele. The 677T allele (leading to a valine substitution at amino acid 222) encodes a thermolabile enzyme with reduced activity. Individuals with two copies of 677C (677CC) have the "normal" or "wildtype" genotype. 677TT individuals (homozygous) have mild MTHFR deficiency. 677CT individuals (heterozygotes) are almost the same as normal individuals, since the one copy of normal MTHFR compensates for the other, thermolabile copy of MTHFR. Individuals with 677TT are predisposed to mild hyperhomocysteinemia (high blood homocysteine levels), as they have less active MTHFR available to produce 5-methyltetrahydrofolate.

Investigators at Peking University Shenzhen Hospital (Shenzhen, China) extracted DNA from saliva samples obtained from 70 stroke patients and 70 healthy controls using a magnetic nanoparticles-based method and from blood using conventional methods. Real-time PCR results revealed that the C677T polymorphism was genotyped by PCR using DNA extracted from both saliva and blood samples. The genotype results were confirmed by gene sequencing, and results for saliva and blood samples were consistent. The mutation TT genotype frequency was significantly higher in the stroke group than in controls. Homocysteine levels were significantly higher than controls in both TT genotype groups.

Based on these results, the authors proposed that, "This noninvasive magnetic nanoparticles-based method using saliva samples could be used to screen for the MTHFR C677T polymorphism in target populations."

The study was published in the November 15, 2013, issue of the journal Neural Regeneration Research.

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Peking University Shenzhen Hospital