Relationship Between Polymorphism of Methylenetetrahydrofolate Dehydrogenase and Congenital Heart Defect

To investigate the relationship between G1958A gene polymorphism of methylenetetrahydrofolate dehydrogenase (MTHFD) and occurrence of congenital heart disease (CHD) in North China. Methods One hundred and ninety-two CHD patients and their parents were included in this study as case group in Liaoning Province by birth defect registration cards, and 124 healthy subjects (age and gender matched) and their parents were simultaneously selected from the same geographic area as control. Their gene polymorphism of MTHFD G1958A locus was examined with PCR-RFLP, and serum folic acid and homocysteine (Hcy) levels were tested with radio-immunoassay and fluorescence polarization immunoassay (FPIA). Results There existed gene polymorphism at MTHFD G1958A locus in healthy subjects living in North China. The percentages of GG, GA, and AA genotype were 57.98%, 35.57%, and 6.45% respectively, and the A allele frequency was 24.23%, which was significantly different from Western population. No difference was observed when comparing genotype distribution and allele frequency between the case and control groups, so was the result from the comparison between genders. The A allele frequency of arterial septal defect patients’ mothers (10.87%) was significantly lower than that of controls (28.15%) (P=0.014), with OR=0.31 (95% CI: 0.09-0.84), and no difference in the other subgroups. The percentage of at least one parent carrying A allele in arterial septal defect subgroup (43.48%) was significantly lower than that in controls (69.64%) (P=0.017), with OR=0.34 (95% CI: 0.12-0.92). The analysis of genetic transmission indicated that there was no transmission disequillibrium in CHD nuclear families. Their serum folic acid level was significantly higher than that of controls (P=0.000), and Hcy level of the former was higher than that of the latter with no statistical significance (P>0.05). Serum Hcy and folic acid levels of mothers with gene mutation were lower than those of mothers with no mutation. Conclusion No significant difference of genotype distribution and allele frequency existed between CHD patients and healthy population. MTHFD G1958A mutation in parents (particularly in mother) can decrease the risk of arterial septal defect in offspring. The possible mechanism of protection might be mutation, which can increase MTHFD enzyme activity, folic acid metabolism and homocysteine remethylation, and decrease Hcy level.

Molecular Modeling and Molecular Dynamics Simulation Studies on the Selective Binding Mechanism of MTHFD2 Inhibitors

Methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) is a mitochondrial enzyme that plays an important role in purinecarbon metabolism and thymidine biosynthesis. It has attracted broad interest as a novel therapeutic target for cancer. However, a major problem of current MTHFD2 inhibitors is their lack of selectivity and reactivity with its closest isoform, MTHFD1. Recently, the first selective MTHFD2 inhibitor, DS44960156, has been reported and it exhibits a more than 18-fold selectivity for MTHFD2 over MTHFD1. However, mechanism of DS44960156 selective binding to MTHFD2 over MTHFD1 is unknown. In this study, molecular docking, molecular dynamics (MD) simulations, molecular mechanics generalized born/surface area (MM_GBSA) binding free energy calculations, and analysis of the decomposition of binding free energies were used to investigate the selective binding mechanism of DS44960156 to the folate-binding site of MTHFD2 over MTHFD1. The results revealed that contributions from residues Gln100/Gln132, Val55/Asn87, and Gly237/Gly310 in the binding pocket of MTHFD1/MTHFD2 are the key factors responsible for the binding selectivity. These findings explain the selectivity of DS44960156 to MTHFD2 over MTHFD1, and may provide guidance for the future study and design of novel MTHFD2 inhibitors.