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Roudgari H, Farndon PA, Murray AD, Hardy C, Miedzybrodzka Z. Is PATCHED an important candidate gene for neural tube defects? Cranial and thoracic neural tube defects in a family with Gorlin syndrome: a case report. Clin Genet 2011; 82:71-6. [PMID: 21651513 DOI: 10.1111/j.1399-0004.2011.01725.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
. The relationship of mutations in the patched gene PTCH and nevoid basal cell carcinoma (NBCC) or Gorlin syndrome is well established. Animal studies have implicated the hedgehog-patched signalling pathway in neurulation and neural tube defects (NTDs). Spina bifida occulta and bifid vertebrae are well recognized in NBCCS, but there appears to be only one report of open spina bifida. We report a father and two sons with a truncating PTCH mutation and the major features of NBCCS. One son had open thoracic spina bifida and the other had an occipital meningocoele. We believe this to be the first report of cranial NTD in NBCCS and suggest that consideration be given to including PTCH analysis in genetic association studies in NTDs as the hedgehog pathway is integral to normal human neurulation.
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Affiliation(s)
- H Roudgari
- Division of Applied Medicine, College of Life Sciences & Medicine, University of Aberdeen, Foresterhill, Aberdeen, UK.
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202
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Potter KA, Weston JF, Munday JS, Johnstone AC. Spina bifida with associated malformations of the central nervous system in Dorper-cross sheep. N Z Vet J 2011; 58:315-8. [PMID: 21151219 DOI: 10.1080/00480169.2010.69763] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
CASE HISTORY In 2008, six lambs within a flock of Dorper-cross sheep were born with musculoskeletal and neurological disease. Clinical signs included hindlimb weakness, and urinary incontinence. CLINICAL FINDINGS All lambs had focal, inverted areas of alopecic skin over the caudal sacrum, and short, often kinked tails. Four affected lambs were subject to euthanasia, and necropsied. On gross examination, the arches of sacral vertebrae were absent, and spinal nerves and meninges were adherent to the overlying subcutis. Other gross lesions included narrow, elongated skulls, herniation of the occipital lobes into the caudal fossas, hydrocephalus, and syringomyelia. One lamb had coning of the cerebellar vermis, but cerebellar herniation through the foramen magnum was not identified. DIAGNOSIS Spina bifida, with associated malformations of the central nervous system. CLINICAL RELEVANCE Examination of breeding records suggested either an autosomal recessive or partially penetrant autosomal dominant pattern of inheritance. Because of the associated tail lesions it is proposed that the pathogenesis of this syndrome involves a defect in development of the tail bud (secondary neurulation), that tethering of the spinal cord resulted in the clinical signs, and abnormal pressure of the cerebral spinal fluid resulted in the defects in the skull and brain.
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Affiliation(s)
- K A Potter
- Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North 4442, New Zealand.
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203
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Wansleeben C, Meijlink F. The planar cell polarity pathway in vertebrate development. Dev Dyn 2011; 240:616-26. [PMID: 21305650 DOI: 10.1002/dvdy.22564] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/05/2010] [Indexed: 12/29/2022] Open
Abstract
Directing the orientation of cells in three dimensions is a fundamental aspect of many of the processes underlying the generation of the appropriate shape and function of tissues and organs during embryonic development. In an epithelium, this requires not only the establishment of apicobasal polarity, but also cell arrangement in a specific direction in the plane of the cell sheet. The molecular pathway central to regulating this planar cell polarity (PCP) was originally discovered in the fruit fly Drosophila melanogaster and has more recently been shown to act in a highly analogous way in vertebrates, involving a strongly overlapping set of genes. Mutant studies and molecular analyses have led to insights into the role of ordered planar cell polarity in the development of a wide variety of organs and tissues. In this review, we give an overview of recent developments in the study of planar polarity signaling in vertebrates.
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204
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Feng Q, Kalari K, Fridley BL, Jenkins G, Ji Y, Abo R, Hebbring S, Zhang J, Nye MD, Leeder JS, Weinshilboum RM. Betaine-homocysteine methyltransferase: human liver genotype-phenotype correlation. Mol Genet Metab 2011; 102:126-33. [PMID: 21093336 PMCID: PMC3053054 DOI: 10.1016/j.ymgme.2010.10.010] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2010] [Accepted: 10/15/2010] [Indexed: 01/31/2023]
Abstract
Betaine-homocysteine methyltransferase (BHMT) catalyzes the remethylation of homocysteine. BHMT is highly expressed in the human liver. In the liver, BHMT catalyzes up to 50% of homocysteine metabolism. Understanding the relationship between BHMT genetic polymorphisms and function might increase our understanding of the role of this reaction in homocysteine remethylation and in S-adenosylmethionine-dependent methylation. To help achieve those goals, we measured levels of BHMT enzyme activity and immunoreactive protein in 268 human hepatic surgical biopsy samples from adult subjects as well as 73 fetal hepatic tissue samples obtained at different gestational ages. BHMT protein levels were correlated significantly (p<0.001) with levels of enzyme activity in both fetal and adult tissues, but both were decreased in fetal tissue when compared with levels in the adult hepatic biopsies. To determine possible genotype-phenotype correlations, 12 tag SNPs for BHMT and the closely related BHMT2 gene were selected from SNPs observed during our own gene resequencing studies as well as from HapMap. These SNPs data were used to genotype DNA from the adult hepatic surgical biopsy samples, and genotype-phenotype association analysis was performed. Three SNPs (rs41272270, rs16876512, and rs6875201), located 28kb upstream, in the 5'-UTR and in intron 1 of BHMT, respectively, were significantly correlated with both BHMT activity (p=3.41E-8, 2.55E-9 and 2.46E-10, respectively) and protein levels (p=5.78E-5, 1.08E-5 and 6.92E-6, respectively). We also imputed 230 additional SNPs across the BHMT and BHMT2 genes, identifying an additional imputed SNP, rs7700790, that was also highly associated with hepatic BHMT enzyme activity and protein. However, none of the 3 genotyped or one imputed SNPs displayed a "shift" during electrophoretic mobility shift assays. These observations may help us to understand individual variation in the regulation of BHMT in the human liver and its possible relationship to variation in methylation.
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Affiliation(s)
- Qiping Feng
- Division of Clinical Pharmacology, Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA
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205
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Brouns MR, De Castro SCP, Terwindt-Rouwenhorst EA, Massa V, Hekking JW, Hirst CS, Savery D, Munts C, Partridge D, Lamers W, Köhler E, van Straaten HW, Copp AJ, Greene NDE. Over-expression of Grhl2 causes spina bifida in the Axial defects mutant mouse. Hum Mol Genet 2011; 20:1536-46. [PMID: 21262862 PMCID: PMC3063985 DOI: 10.1093/hmg/ddr031] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cranial neural tube defects (NTDs) occur in mice carrying mutant alleles of many different genes, whereas isolated spinal NTDs (spina bifida) occur in fewer models, despite being common human birth defects. Spina bifida occurs at high frequency in the Axial defects (Axd) mouse mutant but the causative gene is not known. In the current study, the Axd mutation was mapped by linkage analysis. Within the critical genomic region, sequencing did not reveal a coding mutation whereas expression analysis demonstrated significant up-regulation of grainyhead-like 2 (Grhl2) in Axd mutant embryos. Expression of other candidate genes did not differ between genotypes. In order to test the hypothesis that over-expression of Grhl2 causes Axd NTDs, we performed a genetic cross to reduce Grhl2 function in Axd heterozygotes. Grhl2 loss of function mutant mice were generated and displayed both cranial and spinal NTDs. Compound heterozygotes carrying both loss (Grhl2 null) and putative gain of function (Axd) alleles exhibited normalization of spinal neural tube closure compared with Axd/+ littermates, which exhibit delayed closure. Grhl2 is expressed in the surface ectoderm and hindgut endoderm in the spinal region, overlapping with grainyhead-like 3 (Grhl3). Axd mutants display delayed eyelid closure, as reported in Grhl3 null embryos. Moreover, Axd mutant embryos exhibited increased ventral curvature of the spinal region and reduced proliferation in the hindgut, reminiscent of curly tail embryos, which carry a hypomorphic allele of Grhl3. Overall, our data suggest that defects in Axd mutant embryos result from over-expression of Grhl2.
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Affiliation(s)
- Madeleine R Brouns
- Department of Anatomy and Embryology, Maastricht University Medical Center, University of Maastricht, PO Box 616, 6200 MD, Maastricht, The Netherlands
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206
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Fbxl10/Kdm2b deficiency accelerates neural progenitor cell death and leads to exencephaly. Mol Cell Neurosci 2011; 46:614-24. [PMID: 21220025 DOI: 10.1016/j.mcn.2011.01.001] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2010] [Revised: 11/27/2010] [Accepted: 01/03/2011] [Indexed: 10/18/2022] Open
Abstract
Histone methylation is the important transcription regulatory system that affects mammalian development and cell differentiation. Alterations in epigenetic gene regulation are associated with disease. Fbxl10 (F-box and leucine-rich repeat protein 10) is a JmjC domain-containing histone demethylase. Although Fbxl10 has been implicated in cell cycle regulation, cell death, senescence, and tumorigenesis, these functions are controversial and its physiological function is unclear. To determine the in vivo function of Fbxl10, in this study, we generated a homozygous mutation in the mouse Fbxl10 gene. About half of Fbxl10-deficient mice exhibit failure of neural tube closure, resulting in exencephaly and die shortly after birth. Fbxl10 deficiency also causes retinal coloboma and a curled tail with low penetrances. Fbxl10 mRNA is specifically expressed in the cranial neural folds at E8.5 embryos, and apoptosis increased in the neuroepithelium and mesenchyme of Fbxl10-deficient E9.5 embryos, consistent with neural tube defects found in Fbxl10-deficient mice. Depletion of Fbxl10 induced the increased expression of p19ARF, an inducer of apoptosis, in E8.5 embryos and mouse embryonic fibroblast cells. In addition, the number of mitotic neural progenitor cells is significantly increased in the mutant E14.5 brain. Our findings suggest that the Fbxl10 gene makes important contributions to embryonic neural development by regulating cell proliferation and cell death in mice.
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207
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Danzer E, Adzick NS. Fetal Surgery for Myelomeningocele: Patient Selection, Perioperative Management and Outcomes. Fetal Diagn Ther 2011; 30:163-73. [DOI: 10.1159/000329785] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2011] [Accepted: 05/31/2011] [Indexed: 11/19/2022]
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208
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Tran PX, Au KS, Morrison AC, Fletcher JM, Ostermaier KK, Tyerman GH, Northrup H. Association of retinoic acid receptor genes with meningomyelocele. BIRTH DEFECTS RESEARCH. PART A, CLINICAL AND MOLECULAR TERATOLOGY 2011; 91:39-43. [PMID: 21254357 PMCID: PMC3044482 DOI: 10.1002/bdra.20744] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2010] [Revised: 08/31/2010] [Accepted: 09/03/2010] [Indexed: 11/06/2022]
Abstract
BACKGROUND Neural tube defects (NTDs) occur in as many as 0.5-2 per 1000 live births in the United States. One of the most common and severe neural tube defects is meningomyelocele (MM) resulting from failed closure of the caudal end of the neural tube. MM has been induced by retinoic acid teratogenicity in rodent models. We hypothesized that genetic variants influencing retinoic acid (RA) induction via retinoic acid receptors (RARs) may be associated with risk for MM. METHODS We analyzed 47 single nucleotide polymorphisms (SNPs) that span across the three retinoic acid receptor genes using the SNPlex genotyping platform. Our cohort consisted of 610 MM families. RESULTS One variant in the RARA gene (rs12051734), three variants in the RARB gene (rs6799734, rs12630816, rs17016462), and a single variant in the RARG gene (rs3741434) were found to be statistically significant at p < 0.05. CONCLUSION RAR genes were associated with risk for MM. For all associated SNPs, the rare allele conferred a protective effect for MM susceptibility.
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Affiliation(s)
- Phong X. Tran
- Department of Pediatrics, University of Texas Medical School at Houston, Houston, Texas
| | - Kit Sing Au
- Department of Pediatrics, University of Texas Medical School at Houston, Houston, Texas
| | - Alanna C. Morrison
- Human Genetics Center, Division of Epidemiology, Human Genetics and Environmental Science, School of Public Health, University of Texas Health Sciences Center at Houston, Texas
| | | | | | | | - Hope Northrup
- Department of Pediatrics, University of Texas Medical School at Houston, Houston, Texas
- Shriners Hospital for Children, Houston, Texas
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209
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Cao S, Bay BH, Yip GW. Transcriptome profiling of murine spinal neurulation using laser capture microdissection and high-density oligonucleotide microarrays. Methods Mol Biol 2011; 755:375-84. [PMID: 21761320 DOI: 10.1007/978-1-61779-163-5_31] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Neurulation is a critical process in the formation of the central nervous system during embryonic -development. Closure of the neural tube is driven by forces that originate from both the neuroepithelium and the surrounding tissues. In this chapter, we describe the use of laser capture microdissection to -isolate and separately collect cells from the neuroepithelium and the underlying mesenchyme. We provide protocols for processing of samples for downstream comparison of the transcriptomes of two cell populations using high-density oligonucleotide microarrays, with an emphasis on important technical issues that are to be borne in mind when carrying out these experiments.
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Affiliation(s)
- Shoufeng Cao
- Department of Anatomy, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
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210
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O'Byrne MR, Au KS, Morrison AC, Lin JI, Fletcher JM, Ostermaier KK, Tyerman GH, Doebel S, Northrup H. Association of folate receptor (FOLR1, FOLR2, FOLR3) and reduced folate carrier (SLC19A1) genes with meningomyelocele. ACTA ACUST UNITED AC 2010; 88:689-94. [PMID: 20683905 DOI: 10.1002/bdra.20706] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
BACKGROUND Meningomyelocele (MM) results from lack of closure of the neural tube during embryologic development. Periconceptional folic acid supplementation is a modifier of MM risk in humans, leading toan interest in the folate transport genes as potential candidates for association to MM. METHODS This study used the SNPlex Genotyping (ABI, Foster City, CA) platform to genotype 20 single polymorphic variants across the folate receptor genes (FOLR1, FOLR2, FOLR3) and the folate carrier gene (SLC19A1) to assess their association to MM. The study population included 329 trio and 281 duo families. Only cases with MM were included. Genetic association was assessed using the transmission disequilibrium test in PLINK. RESULTS A variant in the FOLR2 gene (rs13908), three linked variants in the FOLR3 gene (rs7925545, rs7926875, rs7926987), and two variants in the SLC19A1 gene (rs1888530 and rs3788200) were statistically significant for association to MM in our population. CONCLUSION This study involved the analyses of selected single nucleotide polymorphisms across the folate receptor genes and the folate carrier gene in a large population sample. It provided evidence that the rare alleles of specific single nucleotide polymorphisms within these genes appear to be statistically significant for association to MM in the patient population that was tested.
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Affiliation(s)
- Michelle R O'Byrne
- Department of Pediatrics, The University of Texas Medical School at Houston, Houston, Texas 77030, USA
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211
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Abstract
Anencephaly is easily diagnosed by sonography. This article presents images and a discussion of embryology, maternal serum testing, and management.
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Affiliation(s)
- Lisa Moore
- University of New Mexico, Albuquerque, NM, USA,
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212
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Behunova J, Klimcakova L, Zavadilikova E, Potocekova D, Sykora P, Podracka L. Methylenetetrahydrofolate reductase gene polymorphisms and neural tube defects epidemiology in the Slovak population. ACTA ACUST UNITED AC 2010; 88:695-700. [DOI: 10.1002/bdra.20692] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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213
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Au KS, Ashley-Koch A, Northrup H. Epidemiologic and genetic aspects of spina bifida and other neural tube defects. ACTA ACUST UNITED AC 2010; 16:6-15. [PMID: 20419766 DOI: 10.1002/ddrr.93] [Citation(s) in RCA: 187] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The worldwide incidence of neural tube defects (NTDs) ranges from 1.0 to 10.0 per 1,000 births with almost equal frequencies between two major categories: anencephaly and spina bifida (SB). Epidemiological studies have provided valuable insight for (a) researchers to identify nongenetic and genetic factors contributing to etiology, (b) public health officials to design and implement policies to prevent NTD pregnancies, and (c) individuals to take precautions to reduce the chance of having an NTD-affected pregnancy. Despite extensive research, our knowledge of the genetic etiology of human NTDs is limited. Although more than 200 small animal models with NTDs exist, most of these models do not replicate the human disease phenotype. Over a hundred candidate genes have been examined for risk association to human SB. The candidate genes studied include those important in folic acid metabolism, glucose metabolism, retinoid metabolism, and apoptosis. Many genes that regulate transcription in early embryogenesis and maintain planar cell polarity have also been tested as candidates. Additionally, genes identified through mouse models of NTDs have been explored as candidates. We do not know how many genes in the human genome may confer risk for NTDs in human. Less than 20% of the studied candidate genes have been determined to confer even a minor effect on risk association. Many studies have provided conflicting conclusions due to limitations in study design that potentially affect the power of statistical analysis. Future directions such as genomewide association studies (GWAS) and whole exome or even whole genome sequencing are discussed as possible avenues to identify genes that affect risk for human NTDs.
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Affiliation(s)
- Kit Sing Au
- Division of Medical Genetics, Department of Pediatrics, The University of Texas, Medical School at Houston, Houston, Texas 77030, USA
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214
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De Castro SCP, Leung KY, Savery D, Burren K, Rozen R, Copp AJ, Greene ND. Neural tube defects induced by folate deficiency in mutant curly tail (Grhl3) embryos are associated with alteration in folate one-carbon metabolism but are unlikely to result from diminished methylation. BIRTH DEFECTS RESEARCH. PART A, CLINICAL AND MOLECULAR TERATOLOGY 2010; 88:612-8. [PMID: 20589880 PMCID: PMC3634156 DOI: 10.1002/bdra.20690] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND Folate one-carbon metabolism has been implicated as a determinant of susceptibility to neural tube defects (NTDs), owing to the preventive effect of maternal folic acid supplementation and the higher risk associated with markers of diminished folate status. METHODS Folate one-carbon metabolism was compared in curly tail (ct/ct) and genetically matched congenic (+(ct)/+(ct)) mouse strains using the deoxyuridine suppression test in embryonic fibroblast cells and by quantifying s-adenosylmethionine (SAM) and s-adenosylhomocysteine (SAH) in embryos using liquid chromatography tandem mass spectrometry. A possible genetic interaction between curly tail and a null allele of 5,10-methylenetetrahydrofolate reductase (MTHFR) was investigated by generation of compound mutant embryos. RESULTS There was no deficit in thymidylate biosynthesis in ct/ct cells, but incorporation of exogenous thymidine was lower than in +(ct)/+(ct) cells. In +(ct)/+(ct) embryos the SAM/SAH ratio was diminished by dietary folate deficiency and normalized by folic acid or myo-inositol treatment, in association with prevention of NTDs. In contrast, folate deficiency caused a significant increase in the SAM/SAH ratio in ct/ct embryos. Loss of MTHFR function in curly tail embryos significantly reduced the SAM/SAH ratio but did not cause cranial NTDs or alter the frequency of caudal NTDs. CONCLUSIONS Curly tail fibroblasts and embryos, in which Grhl3 expression is reduced, display alterations in one-carbon metabolism, particularly in the response to folate deficiency, compared to genetically matched congenic controls in which Grhl3 is unaffected. However, unlike folate deficiency, diminished methylation potential appears to be insufficient to cause cranial NTDs in the curly tail strain, nor does it increase the frequency of caudal NTDs.
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Affiliation(s)
| | - Kit-yi Leung
- Neural Development Unit, UCL Institute of Child Health, London, UK
| | - Dawn Savery
- Neural Development Unit, UCL Institute of Child Health, London, UK
| | - Katie Burren
- Neural Development Unit, UCL Institute of Child Health, London, UK
| | | | - Andrew J. Copp
- Neural Development Unit, UCL Institute of Child Health, London, UK
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215
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Steinlein OK. Gene polymorphisms and their role in epilepsy treatment and prognosis. Naunyn Schmiedebergs Arch Pharmacol 2010; 382:109-18. [PMID: 20556360 DOI: 10.1007/s00210-010-0531-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2010] [Accepted: 05/27/2010] [Indexed: 12/16/2022]
Abstract
The human genome carries an enormous number of genetic variants, many of them of functional consequence. In epilepsy, they are likely to be involved in drug-specific treatment efficacy, unwanted or even toxic drug reactions, teratogenic risks in pregnancy as well as in the long-term prognosis of patients with epilepsy. As in many other disorders with a complex genetic background, the associated genetic variants that could be verified successfully in replication studies are still only a few. However, new techniques and improved research strategies are likely to increase their number in the foreseeable future, although at a much slower pace as initially expected.
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Affiliation(s)
- Ortrud K Steinlein
- Institute of Human Genetics, University Hospital, Ludwig-Maximilians-University of Munich, Goethestr. 29, 80336, Munich, Germany.
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216
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217
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Abstract
Congenital defects of neural tube closure (neural tube defects; NTDs) are among the commonest and most severe disorders of the fetus and newborn. Disturbance of any of the sequential events of embryonic neurulation produce NTDs, with the phenotype (eg anencephaly, spina bifida) varying depending on the region of neural tube that remains open. While mutation of > 200 genes is known to cause NTDs in mice, the pattern of occurrence in humans suggests a multifactorial polygenic or oligogenic aetiology. This emphasizes the importance of gene-gene and gene-environment interactions in the origins of these defects. A number of cell biological functions are essential for neural tube closure, with defects of the cytoskeleton, cell cycle and molecular regulation of cell viability prominent among the mouse NTD mutants. Many transcriptional regulators and proteins that affect chromatin structure are also required for neural tube closure, although the downstream molecular pathways regulated by these proteins is unknown. Some key signalling pathways for NTDs have been identified: over-activation of sonic hedgehog signalling and loss of function in the planar cell polarity (non-canonical Wnt) pathway are potent causes of NTD, with requirements also for retinoid and inositol signalling. Folic acid supplementation is an effective method for primary prevention of a proportion of NTDs in both humans and mice, although the embryonic mechanism of folate action remains unclear. Folic acid-resistant cases can be prevented by inositol supplementation in mice, raising the possibility that this could lead to an additional preventive strategy for human NTDs in future.
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Affiliation(s)
- Andrew J Copp
- Neural Development Unit, UCL Institute of Child Health, London WC1N 1EH, UK.
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