OV-A-1Methylenetetrahydrofolate reductase (MTHFR) molecular pharmacogenetics: Isoform characterization and human liver expression

Abstract

BACKGROUND MTHFR genetic variation is a risk factor for cardiovascular disease and fetal neural tube defects. In fetal liver, MTHFR exists as 70 and 77 kDa isoforms. Gene resequencing studies revealed a nonsynonymous cSNP in the 77 kDa isoform, an isoform which has never been successfully expressed or characterized. We expressed the 77kDa isoform with the E2 and V222 polymorphisms and performed functional genomic studies. We also studied patterns of isoform expression during fetal growth and development. METHODS The two isoforms and the variant allozymes were expressed using bacterial and mammalian systems and their biochemical properties were studied. Expression of both isoforms in 73 human fetal livers was measured using Western blots. RESULTS Recombinant wild-type (WT) 77 kDa isoform and the D2E allozyme showed no significant differences in activity or substrate kinetics as compared to the recombinant 70 kDa isoform. However, the V222 77 kDa allozyme had 26% of WT activity. 77 kDa isoform expression decreased during fetal development, while this trend was less evident for the 70 kDa isoform. Both isoforms showed large individual variation in expression at comparable gestational age. CONCLUSIONS These studies represent the first successful expression and characterization of the 77 kDa MTHFR isoform and variant allozymes and provide insight into MTHFR pharmacogenetics as well as variation in expression during fetal growth and development. Clinical Pharmacology & Therapeutics (2005) 79, P34–P34; doi: 10.1016/j.clpt.2005.12.122