Abstract
Turner syndrome (TS) is an interesting model for investigating the association between methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms and non-disjunction because of the high frequency of chromosomal mosaicism among patients with this syndrome. We determined the frequencies of MTHFR 677C -> T and 1298A -> C polymorphic mutations in 49 patients with TS and 200 control individuals. The frequency of the 677C -> T allele was 0.39 for patients and 0.29 for controls while that of the 1298A -> C allele was 0.28 for patients and 0.25 for controls. Genotype frequencies were shown to be different in patients and controls (chi2 = 12.143; p = 0.033), and this was attributable to the higher frequency of the C677C -> T /677C -> T genotype among TS patients. In homozygotes, this mutation might have an effect on somatic chromosome disjunction by decreasing MTHFR activity.
Highlights
Turner syndrome (TS) is an interesting model for investigating the association between methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms and non-disjunction because of the high frequency of chromosomal mosaicism among patients with this syndrome
The MTHFR gene is located on the short arm of chromosome 1 (1p36.3) and has 11 exons (Goyette et al, 1994) which code for a cytosolic flavoprotein that catalyzes the reduction of 5,10-methylenetetrahydrofolate (5,10-methyleneTHF) to 5-methyltetrahydrofolate (5-methylTHF), the predominant circulating form of folic acid (Weisberg et al, 1998)
Converting an alanine to a valine residue in the gene product and creating a new HinfI restriction site resulting in the MTHFR 677C ® T polymorphism and a reduction in enzyme activity which may lead to a decrease in the levels of SAM, inhibition of methyltransferase and subsequent DNA hypomethylation
Summary
Turner syndrome (TS) is an interesting model for investigating the association between methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms and non-disjunction because of the high frequency of chromosomal mosaicism among patients with this syndrome. Defects in folic acid metabolism because of mutations in the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene have been considered as a possible cause of chromosomal non-disjunction by hypomethylation (James et al, 1999; Hobbs et al, 2000).
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