title: Formate supplementation enhances folate-dependent nucleotide biosynthesis and prevents spina bifida in a mouse model of folic acid-resistant neural tube defects.
abstract: The curly tail mouse provides a model for neural tube defects (spina bifida and exencephaly) that are resistant to prevention by folic acid. The major ct gene, responsible for spina bifida, corresponds to a hypomorphic allele of grainyhead-like 3 (Grhl3) but the frequency of NTDs is strongly influenced by modifiers in the genetic background. Moreover, exencephaly in the curly tail strain is not prevented by reinstatement of Grhl3 expression. In the current study we found that expression of Mthfd1L, encoding a key component of mitochondrial folate one-carbon metabolism (FOCM), is significantly reduced in ct/ct embryos compared to a partially congenic wild-type strain. This expression change is not attributable to regulation by Grhl3 or the genetic background at the Mthfd1L locus. Mitochondrial FOCM provides one-carbon units as formate for FOCM reactions in the cytosol. We found that maternal supplementation with formate prevented NTDs in curly tail embryos and also resulted in increased litter size. Analysis of the folate profile of neurulation-stage embryos showed that formate supplementation resulted in an increased proportion of formyl-THF and THF but a reduction in proportion of 5-methyl THF. In contrast, THF decreased and 5-methyl THF was relatively more abundant in the liver of supplemented dams than in controls. In embryos cultured through the period of spinal neurulation, incorporation of labelled thymidine and adenine into genomic DNA was suppressed by supplemental formate, suggesting that de novo folate-dependent biosynthesis of nucleotides (thymidylate and purines) was enhanced. We hypothesise that reduced Mthfd1L expression may contribute to susceptibility to NTDs in the curly tail strain and that formate acts as a one-carbon donor to prevent NTDs.
authors.affiliation: Newlife Birth Defects Research Centre and Developmental Biology & Cancer Programme, Institute of Child Health, University College London, London, WC1N 1EH, UK.
authors.forename: Sonia
authors.initials: S
authors.lastname: Sudiwala
authors.affiliation: Newlife Birth Defects Research Centre and Developmental Biology & Cancer Programme, Institute of Child Health, University College London, London, WC1N 1EH, UK.
authors.forename: Sandra C P
authors.initials: SC
authors.lastname: De Castro
authors.affiliation: Newlife Birth Defects Research Centre and Developmental Biology & Cancer Programme, Institute of Child Health, University College London, London, WC1N 1EH, UK.
authors.forename: Kit-Yi
authors.initials: KY
authors.lastname: Leung
authors.affiliation: Department of Biochemistry, Memorial University of Newfoundland, St John's, NL, A1B3X9, Canada.
authors.forename: John T
authors.initials: JT
authors.lastname: Brosnan
authors.affiliation: Department of Biochemistry, Memorial University of Newfoundland, St John's, NL, A1B3X9, Canada.
authors.forename: Margaret E
authors.initials: ME
authors.lastname: Brosnan
authors.affiliation: Genetics & Genomic Medicine Programme, Institute of Child Health, University College London, London, WC1N 1EH, UK.
authors.forename: Kevin
authors.initials: K
authors.lastname: Mills
authors.affiliation: Newlife Birth Defects Research Centre and Developmental Biology & Cancer Programme, Institute of Child Health, University College London, London, WC1N 1EH, UK.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Copp
authors.affiliation: Newlife Birth Defects Research Centre and Developmental Biology & Cancer Programme, Institute of Child Health, University College London, London, WC1N 1EH, UK. Electronic address: n.greene@ucl.ac.uk.
authors.forename: Nicholas D E
authors.initials: ND
authors.lastname: Greene
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D005492:Folic Acid / Q000378:metabolism*; D005561:Formates / Q000494:pharmacology*; D051379:Mice; D009711:Nucleotides / Q000096:biosynthesis*; D016135:Spinal Dysraphism / Q000378:metabolism / Q000517:prevention & control
chemical_list: D005561:Formates; D009711:Nucleotides; C030544:formic acid; D005492:Folic Acid
keywords: Folate one-carbon metabolism; Folic acid; Formate; Grainyhead-like 3; Neural tube defects; mthfd1L