A folate receptor alpha double-mutated haplotype 1816delC-1841A is distributed throughout Eurasia and associated with lower erythrocyte folate levels.

Folate is crucial for various cellular functions. Several transport mechanisms allow folate to enter the intracellular compartment with folate receptor-α being the major high-affinity receptor. Rare genetic variations in exons of the FR-α gene, FOLR1, were recently shown to cause severe folate deficiency accompanied by neurological and other disturbances. So far, similar effects by genetic variation in noncoding parts of the FOLR1 gene have not been identified. The aim of our study was to determine biochemically the haplotype structure of two linked polymorphisms in the FOLR1 gene, 1816delC and 1841G>A, the prevalences of the mutated alleles across Eurasia, and their possible effects on physiological folate levels in vivo. For this purpose we employed allele-specific PCR and Pyrosequencing technology and performed genotyping in 738 subjects from Spain, 387 from Sweden, 952 from Estonia, and 47 from Korea. We demonstrate the presence of an ancient double-mutated haplotype 1816delC-1841A in the FOLR1 gene, with the prevalence of the mutated allele being highest among Koreans (q = 0.074), lower in Estonians (q = 0.017), Spaniards (q = 0.0061), and the lowest among Swedes (q = 0.0026). Erythrocyte folate levels were studied in the Spanish population sample, where subjects carrying the double-mutated FOLR1 haplotype had significantly reduced levels by 27% (P = 0.039), adjusted for serum vitamin B(12) levels and MTHFR 677C>T genotype, while the mean serum folate levels were only 20% lower among the carriers (P = 0.11). Plasma homocysteine and cobalamin levels did not differ. Thus, we have demonstrated by molecular haplotyping an ancient double-mutated haplotype 1816delC-1841A in the FOLR1 gene, spread over the whole Eurasian continent, which may be of functional importance for uptake of folate in red blood cells.

Androgen receptor epigenetic variations influence early follicular phase gonadotropin levels.

OBJECTIVE: we examined the influence of the androgen receptor gene (AR) CAG microsatellite (AR-CAG) repeat polymorphism and X-chromosome inactivation (XCI) pattern on ovarian reserve markers (follicle stimulating hormone (FSH) and antral follicle count on menstrual cycle day 3-5) and disease etiology in patients with polycystic ovarian syndrome (PCOS) or premature ovarian failure (POF). DESIGN: case-control study. Population. In all, 32 women with PCOS, 26 women with POF and 79 controls were investigated. METHODS: AR-CAG and XCI were analyzed using polymerase chain reaction-based assays following DNA digestion with the methylation-sensitive restrictase HpaII. MAIN OUTCOME MEASURES: distribution of AR-CAG alleles and XCI patterns. RESULTS: POF patients had shorter AR-CAG microsatellites than controls. AR-CAG microsatellite length was negatively associated with serum dehydroepiandrosterone sulfate level. The magnitude of XCI skewing was negatively and positively correlated with luteinizing hormone (LH) and FSH serum levels, respectively, during the early follicular phase, but showed no correlation with the number of early antral follicles. CONCLUSIONS: our results suggest that AR-CAG variations and XCI pattern exert an effect on FSH and LH values, and also have the potential to influence the etiopathogenesis of POF.

Folate-mediated one-carbon metabolism and its effect on female fertility and pregnancy viability.

This review summarizes current knowledge of the effect of folate-mediated one-carbon metabolism and related genetic variants on female fertility and pregnancy viability. Insufficient folate status disrupts DNA methylation and integrity and increases blood homocysteine levels. Elevated levels of follicular fluid homocysteine correlate with oocyte immaturity and poor early embryo quality, while methylenetetrahydrofolate reductase (MTHFR) gene variants are associated with lower ovarian reserves, diminished response to follicular stimulation, and reduced chance of live birth after in vitro fertilization. Embryos carrying multiple MTHFR variants appear to have a selective disadvantage; however, the heterozygous MTHFR 677CT genotype in the mother and fetus provides the greatest chance for a viable pregnancy and live birth, possibly due to a favorable balance in folate cofactor distribution between methyl donor and nucleotide synthesis. The results of previous studies clearly emphasize that imbalances in folate metabolism and related gene variants may impair female fecundity as well as compromise implantation and the chance of a live birth.

Variations in folate pathway genes are associated with unexplained female infertility.

OBJECTIVE: To investigate associations between folate-metabolizing gene variations, folate status, and unexplained female infertility. DESIGN: An association study. SETTING: Hospital-based IVF unit and university-affiliated reproductive research laboratories. PATIENT(S): Seventy-one female patients with unexplained infertility. INTERVENTION(S): Blood samples for polymorphism genotyping and homocysteine, vitamin B12, and folate measurements. MAIN OUTCOME MEASURE(S): Allele and genotype frequencies of the following polymorphisms: 5,10-methylenetetrahydrofolate reductase (MTHFR) 677C/T, 1298A/C, and 1793G/A, folate receptor 1 (FOLR1) 1314G/A, 1816delC, 1841G/A, and 1928C/T, transcobalamin II (TCN2) 776C/G, cystathionase (CTH) 1208G/T and solute carrier family 19, member 1 (SLC19A1) 80G/A, and concentrations of plasma homocysteine, vitamin B12, and serum folate. RESULT(S): MTHFR genotypes 677CT and 1793GA, as well as 1793 allele A were significantly more frequent among controls than in patients. The common MTHFR wild-type haplotype (677, 1298, 1793) CAG was less prevalent, whereas the rare haplotype CCA was more frequent in the general population than among infertility patients. The frequency of SLC19A1 80G/A genotypes differed significantly between controls and patients and the A allele was more common in the general population than in infertile women. Plasma homocysteine concentrations were influenced by CTH 1208G/T polymorphism among infertile women. CONCLUSION(S): Polymorphisms in folate pathway genes could be one reason for fertility complications in some women with unexplained infertility.