Deletion of Mthfd1l causes embryonic lethality and neural tube and craniofacial defects in mice

Department of Chemistry and Biochemistry, Institute for Cellular and Molecular Biology, Section of Molecular Cell and Developmental Biology, and Dell Pediatric Research Institute, The University of Texas at Austin, Austin, TX 78712.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 12/2012; 110(2). DOI: 10.1073/pnas.1211199110
Source: PubMed


Maternal supplementation with folic acid is known to reduce the incidence of neural tube defects (NTDs) by as much as 70%. Despite the strong clinical link between folate and NTDs, the biochemical mechanisms through which folic acid acts during neural tube development remain undefined. The Mthfd1l gene encodes a mitochondrial monofunctional 10-formyl-tetrahydrofolate synthetase, termed MTHFD1L. This gene is expressed in adults and at all stages of mammalian embryogenesis with localized regions of higher expression along the neural tube, developing brain, craniofacial structures, limb buds, and tail bud. In both embryos and adults, MTHFD1L catalyzes the last step in the flow of one-carbon units from mitochondria to cytoplasm, producing formate from 10-formyl-THF. To investigate the role of mitochondrial formate production during embryonic development, we have analyzed Mthfd1l knockout mice. All embryos lacking Mthfd1l exhibit aberrant neural tube closure including craniorachischisis and exencephaly and/or a wavy neural tube. This fully penetrant folate-pathway mouse model does not require feeding a folate-deficient diet to cause this phenotype. Maternal supplementation with sodium formate decreases the incidence of NTDs and partially rescues the growth defect in embryos lacking Mthfd1l. These results reveal the critical role of mitochondrially derived formate in mammalian development, providing a mechanistic link between folic acid and NTDs. In light of previous studies linking a common splice variant in the human MTHFD1L gene with increased risk for NTDs, this mouse model provides a powerful system to help elucidate the specific metabolic mechanisms that underlie folate-associated birth defects, including NTDs.

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Available from: Jordan Lewandowski, Aug 08, 2015
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    • "It is therefore not surprising that a gene-disruption of Mthfd1 is embryonically lethal in mice (MacFarlane et al 2009). Deletion of Mthfd1l and Mthfd2, two mitochondrial homologs of Mthfd1, the first of which catalyses only the synthetase reaction and the second both the cyclohydrolase and dehydrogenase in the developing embryo, are also embryonically lethal in murine models (Di Pietro et al 2002; Momb et al 2013), underlining the requirement of this activity for the growing organism. Thus far, only one patient with MTHFD1 deficiency has been identified (Keller et al 2013; Watkins et al 2011). "
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    ABSTRACT: In the folate cycle MTHFD1, encoded by MTHFD1, is a trifunctional enzyme containing 5,10-methylenetetrahydrofolate dehydrogenase, 5,10-methenyltetrahydrofolate cyclohydrolase and 10-formyltetrahydrofolate synthetase activity. To date, only one patient with MTHFD1 deficiency, presenting with hyperhomocysteinemia, megaloblastic anaemia, hemolytic uremic syndrome (HUS) and severe combined immunodeficiency, has been identified (Watkins et al J Med Genet 48:590-2, 2011). We now describe four additional patients from two different families. The second patient presented with hyperhomocysteinemia, megaloblastic anaemia, HUS, microangiopathy and retinopathy; all except the retinopathy resolved after treatment with hydroxocobalamin, betaine and folinic acid. The third patient developed megaloblastic anaemia, infection, autoimmune disease and moderate liver fibrosis but not hyperhomocysteinemia, and was successfully treated with a regime that included and was eventually reduced to folic acid. The other two, elder siblings of the third patient, died at 9 weeks of age with megaloblastic anaemia, infection and severe acidosis and had MTFHD1 deficiency diagnosed retrospectively. We identified a missense mutation (c.806C > T, p.Thr296Ile) and a splice site mutation (c.1674G > A) leading to exon skipping in the second patient, while the other three harboured a missense mutation (c.146C > T, p.Ser49Phe) and a premature stop mutation (c.673G > T, p.Glu225*), all of which were novel. Patient fibroblast studies revealed severely reduced methionine formation from [(14)C]-formate, which did not increase in cobalamin supplemented culture medium but was responsive to folic and folinic acid. These additional cases increase the clinical spectrum of this intriguing defect, provide in vitro evidence of disturbed methionine synthesis and substantiate the effectiveness of folic or folinic acid treatment.
    Journal of Inherited Metabolic Disease 01/2015; 38(5). DOI:10.1007/s10545-015-9810-3 · 3.37 Impact Factor
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    • "Understanding the molecular and developmental mechanisms by which dietary supplementation affects neural tube development is critical to reducing the impact of one of the most common birth defects, especially since some NTDs appear to be resistant to the beneficial effects of FA [1]–[6],[21]–[23]. Animal models are essential for studying experimentally the ways that these dietary factors modulate protein functions, biochemical pathways, and developmental processes during neural tube formation [21]–[26],[28],[34]. In the present study, we found that parental FA supplementation did not protect embryos either from exencephaly in Apob −/− embryos or from craniorachischisis and looped-tail phenotypes in Lp −/− and Lp +/− embryos (Table 1). "
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    ABSTRACT: Background Neural tube defects (NTDs) are the second most common birth defect in humans. Dietary folic acid (FA) supplementation effectively and safely reduces the incidence of these often debilitating congenital anomalies. FA plays an established role in folate and homocysteine metabolism, but the means by which it suppresses occurrence of NTDs is not understood. In addition, many cases remain resistant to the beneficial effects of folic acid supplementation. To better understand the molecular, biochemical and developmental mechanisms by which FA exerts its effect on NTDs, characterized mouse models are needed that have a defined genetic basis and known response to dietary supplementation.ResultsWe examined the effect of FA supplementation, at 5-fold the level in the control diet, on the NTD and vertebral phenotypes in Apob tm1Unc and Vangl2 Lp mice, hereafter referred to as Apob and Lp respectively. The FA supplemented diet did not reduce the incidence or severity of NTDs in Apob or Lp mutant homozygotes or the loop-tail phenotype in Lp mutant heterozygotes, suggesting that mice with these mutant alleles are resistant to FA supplementation. Folic acid supplementation also did not affect the rate of resorptions or the size of litters, but instead skewed the embryonic genotype distribution in favor of wild-type alleles.Conclusion Similar genotypic biases have been reported for several NTD models, but were interpreted as diet-induced increases in the incidence and severity of NTDs that led to increased embryonic lethality. Absence of differences in resorption rates and litter sizes argue against induced embryonic lethality. We suggest an alternative interpretation, namely that FA supplementation led to strongly skewed allelic inheritance, perhaps from disturbances in polyamine metabolism that biases fertilization in favor of wild-type gametes.
    BMC Genetics 08/2014; 15(1):91. DOI:10.1186/s12863-014-0091-x · 2.40 Impact Factor
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    • "The G allele, associated with an increased risk, provides more efficient binding that is likely to alter the expression level of MTHFD1L. Recent reports indicate that mthfd1l knockout mice develop NTD with 100% penetrance [Momb et al., 2013]. Thus, the impact of SNP rs7646 on the binding of miR-197 to the 3 UTR of MTHFD1L provides a mechanistic explanation of the previous association of this SNP with NTD risk [Parle-McDermott et al., 2009]. "
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    ABSTRACT: Maternal folate levels and polymorphisms in folate-related genes are known risk factors for Neural Tube Defects (NTD). Single Nucleotide polymorphisms (SNP) in the mitochondrial folate gene MTHFD1L are associated with the risk of NTDs. We investigated whether different alleles of SNP rs7646 in the 3' UTR of MTHFD1L can be differentially regulated by microRNAs affecting MTHFD1L expression. We previously reported that miR-9 targets MTHFD1L and now we identify miR-197 as an additional miRNA regulator. Both of these miRNAs have predicted binding sites in the MTHFD1L 3' UTR in the region containing SNP rs7646. We have determined whether the alleles of SNP rs7646 (A/G) and miRNA expression levels affect miRNA binding preferences for the MTHFD1L 3' UTR and consequently MTHFD1L expression. Our results indicate that miR-9 and miR-197 specifically downregulate MTHFD1L levels in HEK293 and MCF-7 cells and that SNPrs7646 significantly affects miR-197 binding affinity to the MTHFD1L 3' UTR, causing more efficient post-transcriptional gene repression in the presence of the allele that is associated with increased risk of NTDs. These results reveal that the association of SNP rs7646 and NTD risk involves differences in microRNA regulation and, highlights the importance of genotype-dependent differential microRNA regulation in relation to human disease risk. This article is protected by copyright. All rights reserved.
    Human Mutation 01/2014; 35(1). DOI:10.1002/humu.22459 · 5.14 Impact Factor
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