title: Folate deficiency induces dysfunctional long and short telomeres; both states are associated with hypomethylation and DNA damage in human WIL2-NS cells.
abstract: The essential role of dietary micronutrients for genome stability is well documented, yet the effect of folate deficiency or excess on telomeres is not known. Accordingly, human WIL2-NS cells were maintained in medium containing 30, 300, or 3,000 nmol/L folic acid (FA) for 42 days to test the hypothesis that chronic folate deficiency would cause telomere shortening and dysfunction. After 14 days, telomere length (TL) in FA-deficient (30 nmol/L) cultures was 26% longer than that of 3,000 nmol/L FA cultures; however, this was followed by rapid telomere attrition over the subsequent 28 days (P trend, P < 0.0001); both long and short telomere status was positively correlated with biomarkers of chromosome instability (P ≤ 0.003) and mitotic dysfunction (P = 0.01), measured by the cytokinesis-block micronucleus cytome (CBMN-cyt) assay. The early increase in TL was associated with FA-deficiency-induced global DNA hypomethylation (P = 0.05), with an effect size similar to that induced by the DNA methyltransferase inhibitor, 5-aza-2'-deoxycytidine. Quantitative PCR analysis indicated a negative association between FA concentration and uracil incorporation into telomeric DNA (r = -0.47, P = 0.1), suggesting a possible plausible mechanism for uracil as a cause of folate deficiency-induced telomere dysfunction or deletion. Peptide nucleic acid-FISH (PNA-FISH) analysis showed that FA deficiency resulted in 60% of micronuclei containing acentric terminal fragments, an observation consistent with the 3-fold increase in terminal deletions (P = 0.0001). Together, these results demonstrate the impact of folate deficiency on biomarkers of telomere maintenance and integrity, and provide evidence that dysfunctional long telomeres may be as important as critically short telomeres as a cause of chromosomal instability.
authors.affiliation: CSIRO Animal, Food and Health Sciences, P.O. Box 10041, Adelaide BC, South Australia 5000, Australia. caroline.bull@csiro.au; and Michael F. Fenech, michael.fenech@csiro.au.
authors.forename: Caroline F
authors.initials: CF
authors.lastname: Bull
authors.forename: Graham
authors.initials: G
authors.lastname: Mayrhofer
authors.forename: Nathan J
authors.initials: NJ
authors.lastname: O'Callaghan
authors.forename: Amy Y
authors.initials: AY
authors.lastname: Au
authors.forename: Hilda A
authors.initials: HA
authors.lastname: Pickett
authors.forename: Grace Kah Mun
authors.initials: GK
authors.lastname: Low
authors.forename: Dimphy
authors.initials: D
authors.lastname: Zeegers
authors.forename: M Prakash
authors.initials: MP
authors.lastname: Hande
authors.forename: Michael F
authors.initials: MF
authors.lastname: Fenech
mesh_terms: D001374:Azacitidine / Q000031:analogs & derivatives / Q000737:chemistry; D015415:Biomarkers / Q000378:metabolism; D043171:Chromosomal Instability; D048749:Cytokinesis; D004249:DNA Damage; D019175:DNA Methylation; D000077209:Decitabine; D004032:Diet; D005492:Folic Acid / Q000737:chemistry*; D005494:Folic Acid Deficiency / Q000235:genetics*; D006801:Humans; D019098:Telomerase / Q000378:metabolism; D016615:Telomere / Q000648:ultrastructure*; D014498:Uracil / Q000737:chemistry
chemical_list: D015415:Biomarkers; D014498:Uracil; D000077209:Decitabine; D005492:Folic Acid; C509186:TERT protein, human; D019098:Telomerase; D001374:Azacitidine