MTHFR rs1801133 polymorphism in Bangladeshi population – its prevalence and detection

Methylenetetrahydrofolate reductase (MTHFR) has been reported as a key enzyme not only for intracellular folate homeostasis but also for metabolism. A particular variant (G677A) leads to an altered amino acid, which ultimately causes decreased enzyme activity and may modulate the risk of causing several chronic diseases. The purpose of this study was to detect the pervasiveness of this variant MTHFR rs1801133 G677A in the Bangladeshi population. We applied allele-specific polymerase chain reaction (AS-PCR) to determine the genotypes at the rs1801133 in the Bangladeshi population. We performed targeted sequencing of the AS-PCR product of randomly selected samples. Out of the 181 Bangladeshi individuals, 71.8% had homozygous 677GG genotype, while 28.2% comprised of heterozygous 677GA genotype. No individual with the homozygous 677AA genotype was found in this representative Bangladeshi population. The 677G alleles had higher frequency (0.856) compared to 677A alleles (0.144) at the rs1801133 locus. Though the more risky homozygous 677AA genotype at the rs1801133 locus is absent in the Bangladeshi population, further association studies can be performed to identify the role of MTHFR mutation in the susceptibility to different multifactorial diseases.

Genetic and physiological regulation of folate in pak choi (Brassica rapa subsp. Chinensis) germplasm

Folates are one of the essential micronutrients for all living organisms. Due to inadequate dietary intake, folate deficiency remains prevalent in humans. Genetically diverse germplasms can potentially be used as parents in breeding programs and also for understanding the folate regulatory network. Therefore, we investigated the natural genetic diversity of folates and their physiological regulation in pak choi (Brassica rapa subsp. Chinensis) germplasm. The total folate concentration ranged from 52.7 μg 100 gFW–1 to 166.9 μg 100 gFW–1, with 3.2-fold variation. The main folate vitamer was represented by 5-CH3-H4folate, with 4.5-fold variation. The activities of GTP cyclohydrolase I and aminodeoxy chorismate synthase, the first step of folate synthesis, were high in high folate accessions and low in low folate accessions. Analysis of the transcription levels of 11 genes associated with folate metabolism demonstrated that the difference in folate concentrations may be primarily controlled at the post-transcriptional level. A general correlation between total folate and their precursors was observed. Folate diversity and chlorophyll content were tightly regulated through the methyl cycle. The diverse genetic variation in pak choi germplasm indicated the great genetic potential to integrate breeding programs for folate biofortification and unravel the physiological basis of folate homeostasis in planta.

Genetic variant in folate homeostasis is associated with lower warfarin dose in African Americans

Key Points A population-specific genetic variant involved in folate homeostasis is associated with lower warfarin dose in African Americans.

Folate homeostasis of cancer cells affects sensitivity to not only antifolates but also other non-folate drugs: effect of MRP expression

Sensitivity to antifolates can be decreased by endogenous or exogenous folates. Leucovorin protects cancer patients against toxicity of the dihydrofolate reductase inhibitor methotrexate (MTX), while folic acid is used to protect rheumatoid arthritis patients against MTX. Folates and antifolates can be effluxed from the cell by ABC transporters multidrug resistance protein 1 (MRP1), 2 and 3. We previously demonstrated in 2008 ovarian cancer cells that MRP overexpression reduced cellular folate content by 40%, while folate depletion increased expression of MRP1. As MRPs mediate resistance to several unrelated drugs, we investigated whether folate status would affect sensitivity to doxorubicin, daunorubicin, etoposide and vincristine. Ovarian cancer 2008 cells and its MRP1 transfected variant (2008/MRP1) were adapted from normal folate medium [2.3 μM; high folate (HF) cells] to short-term folate depletion (up to 7 days) (low folate cells); drugs were added after 2 days and sensitivity was tested by the MTT test after 3 additional days. The effect on folate homeostasis was evaluated by measurement of intracellular homocysteine using high-performance liquid chromatography and glutathione using a kit. MRP expression of wild-type (WT) 2008 cells did not increase homocysteine pools in 2008/MRP1 cells. Three day folate depletion increased homocysteine pools 23-fold in 2008 cells and 8.6-fold in the MRP variant. Folate depletion increased glutathione 20%–40% in 2008/WT and 2008/MRP1. In 2008 HF cells MRP1 expression did not affect sensitivity to MTX, but induced 4- to 10-fold resistance to doxorubicin, daunorubicin, etoposide and vincristine. Folate depletion decreased 50% growth inhibition (IC50) for MTX in both 2008 variants 25- to 4-fold, but that to doxorubicin and daunorubicin approximately 2-fold. Sensitivity to etoposide and vincristine was not affected. In conclusion, folate depletion markedly increased homocysteine, but moderately increased glutathione. Folate depletion increased MTX sensitivity, but effects on other drugs were most pronounced in WT cells, probably because MRP expression is already high in transfected variants.