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Stabler SP, Freehauf C, Allen RH, Thomas J, Gallagher R. Potential Misdiagnosis of Hyperhomocysteinemia due to Cystathionine Beta-Synthase Deficiency During Pregnancy. JIMD Rep 2017; 37:55-61. [PMID: 28275971 DOI: 10.1007/8904_2017_15] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Revised: 02/08/2017] [Accepted: 02/13/2017] [Indexed: 12/23/2022] Open
Abstract
Extreme hyperhomocysteinemia with low cystathionine and cysteine is virtually diagnostic of cystathionine beta-synthase (CBS) deficiency since remethylation defects and hypermethioninemia due to other inborn errors cause elevated serum cystathionine. However, a pregnant CBS deficient patient was found to have elevated cystathionine in addition to elevated total homocysteine and methionine at 23 weeks of gestation and post-delivery cystathionine decreased to the lower level of normal. A second patient with cystathionine values during gestation also showed a rise from the low pre-pregnant value to massive elevation by delivery. Her infant had severe hyperhomocysteinemia in cord blood with a massive elevation of cystathionine, S-adenosylmethionine, and S-adenosylhomocysteine. The infant corrected her homocysteine value by 2 months and is not affected. This data demonstrates that the fetus when exposed to high homocysteine and methionine has increased synthesis of cystathionine which cannot be cleared because the fetus lacks cystathionine gamma-lyase, and thus cystathionine is returned to the mother's circulation. This situation could lead to a misdiagnosis of the cause of hyperhomocysteinemia in a previously undiagnosed pregnant CBS deficient patient. Assays combining homocysteine with cystathionine measurements are commonly available from commercial laboratories in the USA. The recognition of CBS deficiency vs. remethylation disorders is important in order to maximize treatment. The cord blood values revealed a major disturbance in methionine metabolism including a potential for impaired transmethylation reactions in the fetus due to the buildup of S-adenosylhomocysteine. It is possible that monitoring maternal cystathionine during gestation could provide another measure of fetal exposure to homocysteine.
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Affiliation(s)
- Sally P Stabler
- Division of Hematology, Department of Medicine, University of Colorado School of Medicine, 12700 E. 19th Avenue, Room 9122, Bldg. RC2, Campus Box B170, Aurora, CO, USA.
| | - Cynthia Freehauf
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO, USA
| | - Robert H Allen
- Division of Hematology, Department of Medicine, University of Colorado School of Medicine, 12700 E. 19th Avenue, Room 9122, Bldg. RC2, Campus Box B170, Aurora, CO, USA
| | - Janet Thomas
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO, USA
| | - Renata Gallagher
- Department of Pediatrics, University of California at San Francisco, 330 Post Street, 6th Floor, San Francisco, CA, USA
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Akahoshi N, Kamata S, Kubota M, Hishiki T, Nagahata Y, Matsuura T, Yamazaki C, Yoshida Y, Yamada H, Ishizaki Y, Suematsu M, Kasahara T, Ishii I. Neutral aminoaciduria in cystathionine β-synthase-deficient mice, an animal model of homocystinuria. Am J Physiol Renal Physiol 2014; 306:F1462-76. [DOI: 10.1152/ajprenal.00623.2013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The kidney is one of the major loci for the expression of cystathionine β-synthase (CBS) and cystathionine γ-lyase (CTH). While CBS-deficient ( Cbs−/−) mice display homocysteinemia/methioninemia and severe growth retardation, and rarely survive beyond the first 4 wk, CTH-deficient ( Cth−/−) mice show homocysteinemia/cystathioninemia but develop with no apparent abnormality. This study examined renal amino acid reabsorption in those mice. Although both 2-wk-old Cbs−/− and Cth−/− mice had normal renal architecture, their serum/urinary amino acid profiles largely differed from wild-type mice. The most striking feature was marked accumulation of Met and cystathionine in serum/urine/kidney samples of Cbs−/− and Cth−/− mice, respectively. Levels of some neutral amino acids (Val, Leu, Ile, and Tyr) that were not elevated in Cbs−/− serum were highly elevated in Cbs−/− urine, and urinary excretion of other neutral amino acids (except Met) was much higher than expected from their serum levels, demonstrating neutral aminoaciduria in Cbs−/− (not Cth−/−) mice. Because the bulk of neutral amino acids is absorbed via a B0AT1 transporter and Met has the highest substrate affinity for B0AT1 than other neutral amino acids, hypermethioninemia may cause hyperexcretion of neutral amino acids.
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Affiliation(s)
- Noriyuki Akahoshi
- Department of Molecular and Cellular Neurobiology, Gunma University Graduate School of Medicine, Gunma, Japan
- Japan Science and Technology Agency (JST), Exploratory Research for Advanced Technology (ERATO), Suematsu Gas Biology Project, Tokyo, Japan
- Department of Immunology, Akita University Graduate School of Medicine, Akita, Japan; and
| | - Shotaro Kamata
- Department of Biochemistry, Keio University Graduate School of Pharmaceutical Sciences, Tokyo, Japan
| | - Masashi Kubota
- Department of Biochemistry, Keio University Graduate School of Pharmaceutical Sciences, Tokyo, Japan
| | - Takako Hishiki
- Japan Science and Technology Agency (JST), Exploratory Research for Advanced Technology (ERATO), Suematsu Gas Biology Project, Tokyo, Japan
| | - Yoshiko Nagahata
- Japan Science and Technology Agency (JST), Exploratory Research for Advanced Technology (ERATO), Suematsu Gas Biology Project, Tokyo, Japan
| | - Tomomi Matsuura
- Japan Science and Technology Agency (JST), Exploratory Research for Advanced Technology (ERATO), Suematsu Gas Biology Project, Tokyo, Japan
| | - Chiho Yamazaki
- Department of Molecular and Cellular Neurobiology, Gunma University Graduate School of Medicine, Gunma, Japan
| | - Yuka Yoshida
- Department of Molecular and Cellular Neurobiology, Gunma University Graduate School of Medicine, Gunma, Japan
| | - Hidenori Yamada
- Department of Molecular and Cellular Neurobiology, Gunma University Graduate School of Medicine, Gunma, Japan
| | - Yasuki Ishizaki
- Department of Molecular and Cellular Neurobiology, Gunma University Graduate School of Medicine, Gunma, Japan
| | - Makoto Suematsu
- Japan Science and Technology Agency (JST), Exploratory Research for Advanced Technology (ERATO), Suematsu Gas Biology Project, Tokyo, Japan
| | - Tadashi Kasahara
- Department of Biochemistry, Keio University Graduate School of Pharmaceutical Sciences, Tokyo, Japan
| | - Isao Ishii
- Department of Molecular and Cellular Neurobiology, Gunma University Graduate School of Medicine, Gunma, Japan
- Department of Biochemistry, Keio University Graduate School of Pharmaceutical Sciences, Tokyo, Japan
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MEDEIROS JVR, SOARES PMG, BRITO GADC, SOUZA MHLPD. IMMUNOHISTOCHEMICAL APPROACH REVEALS LOCALIZATION OF CYSTATHIONINE-?-LYASE AND CYSTATHIONINE-ß-SYNTHETASE IN ETHANOL-INDUCED GASTRIC MUCOSA DAMAGE IN MICE. Arq Gastroenterol 2013; 50:157-60. [DOI: 10.1590/s0004-28032013000200027] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2013] [Accepted: 03/12/2013] [Indexed: 11/22/2022]
Abstract
Context Hydrogen sulphide (H2S) has been proved to be a neuromodulator and contributes to the maintenance of gastric mucosal integrity in damage caused by anti-inflammatory nonsteroidal drugs. Previously, we demonstrated that H2S synthesis is essential to gastric protection against ethanol. Objective To better understanding the role of H2S and the detailed localization of its production in both normal and injured stomach due to ethanol injection, we studied the expression of cystathionine-γ-lyase (CSE) and cystathionine-β-synthetase (CBS) isoforms in gastric mucosa of mice treated with saline or 50% ethanol. Methods Mice were treated by gavage with saline or 50% ethanol (0.5 mL/25 g). After 1 hour, mice were sacrificed, and gastric tissue was evaluated by histological and immunohistochemical analysis specific for CSE and CBS. Results We have demonstrated a non-specific expression of CBS in the normal gastric mucosa and expression of CSE occurring mainly in the parietal cells of the animals treated with ethanol. Conclusion Thus, we demonstrated that the expression of CBS appears to be constitutive and diffuse across the gastric epithelium, while the expression of CSE appears to be induced in parietal cells by damage agents such as ethanol.
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Ishii I, Akahoshi N, Yamada H, Nakano S, Izumi T, Suematsu M. Cystathionine gamma-Lyase-deficient mice require dietary cysteine to protect against acute lethal myopathy and oxidative injury. J Biol Chem 2010; 285:26358-68. [PMID: 20566639 DOI: 10.1074/jbc.m110.147439] [Citation(s) in RCA: 181] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cysteine is considered a nonessential amino acid in mammals as it is synthesized from methionine via trans-sulfuration. However, premature infants or patients with hepatic failure may require dietary cysteine due to a lack of cystathionine gamma-lyase (CTH), a key trans-sulfuration enzyme. Here, we generated CTH-deficient (Cth(-/-)) mice as an animal model of cystathioninemia/cystathioninuria. Cth(-/-) mice developed normally in general but displayed hypercystathioninemia/hyperhomocysteinemia though not hypermethioninemia. When fed a low cyst(e)ine diet, Cth(-/-) mice showed acute skeletal muscle atrophy (myopathy) accompanied by enhanced gene expression of asparagine synthetase and reduced contents of glutathione in livers and skeletal muscles, and intracellular accumulation of LC3 and p62 in skeletal myofibers; they finally died of severe paralysis of the extremities. Cth(-/-) hepatocytes required cystine in a culture medium and showed greater sensitivity to oxidative stress. Cth(-/-) mice exhibited systemic vulnerability to oxidative injury, which became more prominent when they were fed the low cyst(e)ine diet. These results reveal novel roles of trans-sulfuration previously unrecognized in mice lacking another trans-sulfuration enzyme cystathionine beta-synthase (Cbs(-/-)). Because Cbs(-/-) mice display hyperhomocysteinemia and hypermethioninemia, our results raise questions against the homocysteine-based etiology of CBS deficiency and the current newborn screening for homocysteinemia using Guthrie's method, which detects hypermethioninemia.
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Affiliation(s)
- Isao Ishii
- Department of Biochemistry and Integrative Medical Biology, Keio University School of Medicine, Shinjuku, Tokyo 160-8582, Japan.
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Kraus JP, Hašek J, Kožich V, Collard R, Venezia S, Janošíková B, Wang J, Stabler SP, Allen RH, Jakobs C, Finn CT, Chien YH, Hwu WL, Hegele RA, Mudd SH. Cystathionine gamma-lyase: Clinical, metabolic, genetic, and structural studies. Mol Genet Metab 2009; 97:250-9. [PMID: 19428278 PMCID: PMC2752209 DOI: 10.1016/j.ymgme.2009.04.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2009] [Revised: 04/01/2009] [Accepted: 04/02/2009] [Indexed: 11/28/2022]
Abstract
We report studies of six individuals with marked elevations of cystathionine in plasma and/or urine. Studies of CTH, the gene that encodes cystathionine gamma-lyase, revealed the presence among these individuals of either homozygous or compound heterozygous forms of a novel large deletion, p.Gly57_Gln196del, two novel missense mutations, c.589C>T (p.Arg197Cys) and c.932C>T (p.Thr311Ile), and one previously reported alteration, c.200C>T (p.Thr67Ile). Another novel missense mutation, c.185G>T (p.Arg62His), was found in heterozygous form in three mildly hypercystathioninemic members of a Taiwanese family. In one severely hypercystathioninemic individual no CTH mutation was found. Brief clinical histories of the cystathioninemic/cystathioninuric patients are presented. Most of the novel mutations were expressed and the CTH activities of the mutant proteins determined. The crystal structure of the human enzyme, hCTH, and the evidence available as to the effects of the mutations in question, as well as those of the previously reported p.Gln240Glu, on protein structure, enzymatic activity, and responsiveness to vitamin B(6) administration are discussed. Among healthy Czech controls, 9.3% were homozygous for CTH c.1208G>T (p.Ser403Ile), previously found homozygously in 7.5% of Canadians for whom plasma total homocysteine (tHcy) had been measured. Compared to wild-type homozygotes, among the 55 Czech c.1208G>T (p.Ser403Ile) homozygotes a greater level of plasma cystathionine was found only after methionine loading. Three of the four individuals homozygous or compound heterozygous for inactivating CTH mutations had mild plasma tHcy elevations, perhaps indicating a cause-and-effect relationship. The experience with the present patients provides no evidence that severe loss of CTH activity is accompanied by adverse clinical effects.
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Affiliation(s)
- Jan P. Kraus
- Department of Pediatrics, University of Colorado School of Medicine
| | - Jindrich Hašek
- Department of Structure Analysis, Institute of Macromolecular Chemistry AS CR, Prague, Czech Republic
| | - Viktor Kožich
- Institute of Inherited Metabolic Diseases, Charles University in Prague-First Faculty of Medicine, Prague, Czech Republic
| | - Renata Collard
- Department of Pediatrics, University of Colorado School of Medicine
| | - Sarah Venezia
- Department of Pediatrics, University of Colorado School of Medicine
| | - Bohumila Janošíková
- Institute of Inherited Metabolic Diseases, Charles University in Prague-First Faculty of Medicine, Prague, Czech Republic
| | - Jian Wang
- Robarts Research Institute, London, Ontario, Canada
| | - Sally P. Stabler
- Division of Hematology, University of Colorado Health Sciences Center, Denver, CO
| | - Robert H. Allen
- Division of Hematology, University of Colorado Health Sciences Center, Denver, CO
| | - Cornelis Jakobs
- Department of Clinical Chemistry, VU University Medical Center, Amsterdam, The Netherlands
| | - Christine T. Finn
- Massachusetts General Hospital, Department of Psychiatry, Harvard-Partners Center for Genetics and Genomics, Boston, MA
| | - Yin-Hsiu Chien
- Departments of Medical Genetics and Pediatrics, National Taiwan University Hospital and College of Medicine, Taipei, Taiwan
| | - Wuh-Liang Hwu
- Departments of Medical Genetics and Pediatrics, National Taiwan University Hospital and College of Medicine, Taipei, Taiwan
| | | | - S. Harvey Mudd
- Laboratory of Molecular Biology, National Institute of Mental Health, Bethesda, MD
- Corresponding author: S.H. Mudd (Telephone: 301-496-0681; Fax: 301-402-0245, )
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Fiorucci S, Distrutti E, Cirino G, Wallace JL. The emerging roles of hydrogen sulfide in the gastrointestinal tract and liver. Gastroenterology 2006; 131:259-71. [PMID: 16831608 DOI: 10.1053/j.gastro.2006.02.033] [Citation(s) in RCA: 280] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2005] [Accepted: 02/15/2006] [Indexed: 02/07/2023]
Abstract
Hydrogen sulfide, like nitric oxide, was best known as a toxic pollutant before becoming recognized as a key regulator of several physiologic processes. In recent years, evidence has accumulated to suggest important roles for hydrogen sulfide as a mediator of several aspects of gastrointestinal and liver function. Moreover, alterations in hydrogen sulfide production could contribute to disorders of the gastrointestinal tract and liver. For example, nonsteroidal anti-inflammatory drugs can reduce production of hydrogen sulfide in the stomach, and this has been shown to contribute to the generation of mucosal injury. Hydrogen sulfide has also been shown to play a key role in modulation of visceral hyperalgesia. Inhibitors of hydrogen sulfide synthesis and drugs that can generate safe levels of hydrogen sulfide in vivo have been developed and are permitting interventional studies in experimental models and, in the near future, humans.
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Affiliation(s)
- Stefano Fiorucci
- Dipartimenti di Medicina Clinica and Patologia, University of Perugia, Perugia, Italy
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Tadiboyina VT, Rupar A, Atkison P, Feigenbaum A, Kronick J, Wang J, Hegele RA. Novel mutation in DGUOK in hepatocerebral mitochondrial DNA depletion syndrome associated with cystathioninuria. Am J Med Genet A 2005; 135:289-91. [PMID: 15887277 DOI: 10.1002/ajmg.a.30748] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Mitochondrial depletion syndrome (MDS) refers to a heterogeneous group of mitochondrial disorders characterized by a reduction of the mtDNA copy number in affected tissues. Mutations in DGUOK encoding deoxyguanosine kinase (MIM 601465) cause the hepatocerebral form of MDS (MIM 251880). Cystathioninuria (MIM 219500) can result from mutations in CTH encoding cystathionine gamma lyase (MIM 607657) or can be a secondary finding in several diverse clinical conditions. We present three patients from two apparently unrelated old colony Mennonite families, each of whom had the hepatocerebral form of MDS together with cystathioninuria. Each affected child was homozygous for the novel DGUOK p.D255Y mutation, but had no CTH mutation, indicating that the hepatocerebral form of MDS might be associated with secondary cystathioninuria.
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Affiliation(s)
- Venu T Tadiboyina
- Robarts Research Institute and University of Western Ontario, London, Ontario, Canada
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Ishii I, Akahoshi N, Yu XN, Kobayashi Y, Namekata K, Komaki G, Kimura H. Murine cystathionine gamma-lyase: complete cDNA and genomic sequences, promoter activity, tissue distribution and developmental expression. Biochem J 2004; 381:113-23. [PMID: 15038791 PMCID: PMC1133768 DOI: 10.1042/bj20040243] [Citation(s) in RCA: 227] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2004] [Revised: 03/22/2004] [Accepted: 03/23/2004] [Indexed: 01/06/2023]
Abstract
Cystathionine gamma-lyase (CSE) is the last key enzyme in the trans-sulphuration pathway for biosynthesis of cysteine from methionine. Cysteine could be provided through diet; however, CSE has been shown to be important for the adequate supply of cysteine to synthesize glutathione, a major intracellular antioxidant. With a view to determining physiological roles of CSE in mice, we report the sequence of a complete mouse CSE cDNA along with its associated genomic structure, generation of specific polyclonal antibodies, and the tissue distribution and developmental expression patterns of CSE in mice. A 1.8 kb full-length cDNA containing an open reading frame of 1197 bp, which encodes a 43.6 kDa protein, was isolated from adult mouse kidney. A 35 kb mouse genomic fragment was obtained by lambda genomic library screening. It contained promoter regions, 12 exons, ranging in size from 53 to 579 bp, spanning over 30 kb, and exon/intron boundaries that were conserved with rat and human CSE. The GC-rich core promoter contained canonical TATA and CAAT motifs, and several transcription factor-binding consensus sequences. The CSE transcript, protein and enzymic activity were detected in liver, kidney, and, at much lower levels, in small intestine and stomach of both rats and mice. In developing mouse liver and kidney, the expression levels of CSE protein and activity gradually increased with age until reaching their peak value at 3 weeks of age, following which the expression levels in liver remained constant, whereas those in kidney decreased significantly. Immunohistochemical analyses revealed predominant CSE expression in hepatocytes and kidney cortical tubuli. These results suggest important physiological roles for CSE in mice.
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Affiliation(s)
- Isao Ishii
- Department of Molecular Genetics, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Ogawahigashi 4-1-1, Kodaira, Tokyo 187-8502, Japan.
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Wang J, Hegele RA. Genomic basis of cystathioninuria (MIM 219500) revealed by multiple mutations in cystathionine gamma-lyase (CTH). Hum Genet 2003; 112:404-8. [PMID: 12574942 DOI: 10.1007/s00439-003-0906-8] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2002] [Accepted: 12/13/2002] [Indexed: 11/24/2022]
Abstract
Hereditary cystathioninuria (MIM 219500) is presumed to be caused by deficiency of the activity of cystathionine gamma-lyase (cystathionase; CTH EC 4.4.1.1), which is normally required for the conversion of methionine into cysteine. To date, no mutations have been described among patients with cystathioninuria. From genomic DNA, we sequenced CTH in four unrelated probands with cystathioninuria. We found two nonsense mutations, namely exon 8 c.940-941delCT and exon 11 c.1220delC, and two missense mutations, namely exon 2 c.356C>T (T67I) and exon 7 c.874C>G (Q240E). All affected subjects were either simple homozygotes or compound heterozygotes. A common non-synonymous single nucleotide polymorphism in exon 12, namely c.1364G>T (S403I), was also identified and characterized in four ethnic groups. The reagents described in this report make the molecular diagnosis of cystathioninuria possible, allowing for studies of phenotype-genotype correlation. Also, the availability of a common non-synonymous SNP can allow for testing of association of the CTH gene with biochemical traits affected by trans-sulfuration, such as plasma concentrations of homocysteine or even cystathionine itself, in addition to more downstream clinical phenotypes, such as vascular disease.
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Affiliation(s)
- Jian Wang
- Blackburn Cardiovascular Genetics Laboratory, Robarts Research Institute, 406-100 Perth Drive, London, Ontario, N6A 5K8, Canada
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Mudd SH, Tangerman A, Stabler SP, Allen RH, Wagner C, Zeisel SH, Levy HL. Maternal methionine adenosyltransferase I/III deficiency: reproductive outcomes in a woman with four pregnancies. J Inherit Metab Dis 2003; 26:443-58. [PMID: 14518826 DOI: 10.1023/a:1025121326959] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Four pregnancies in a women with moderately severe deficiency of methionine adenosyltransferase I/III (MAT I/III) activity are reported. She is an apparent homozygote for a point mutation in MAT1A, the gene that encodes the catalytically active subunit of MAT I/III. This mutation reduces the activity of her expressed enzyme to some 11% of wild-type. She was the first such individual identified in the United States, and these are the first pregnancies known in anyone with this extent of MAT I/III deficiency. No adverse effects were noted in the mother. Three normal babies resulted, but fetal arrest was detected in one embryo at 10-11 weeks gestation. Plasma methionine concentrations remained virtually constant at their elevated levels of 300-350 micromol/L throughout the pregnancies. Plasma free choline was below the reference range. In view of the evidence that maternal choline delivery to the fetus is important for brain development, it was suggested the patient ingest two eggs daily from gestation week 17. Plasma choline and phosphatidylcholine tended to rise during such supplementation. Plasma cystathionine concentrations rose progressively to far above normal during these pregnancies, but not during pregnancies in control women. This may be explained by delivery of excessive methionine to the fetus, with consequent increased cystathionine synthesis by fetal tissues. Because fetal tissues lack gamma-cystathionase, presumably cystathionine accumulated abnormally in the fetus and was transferred in abnormal amounts back to the mother. Plasma and urinary concentrations of methionine transamination metabolites rose during pregnancy for reasons that remain obscure.
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Affiliation(s)
- S H Mudd
- Laboratory of Molecular Biology, National Institute of Mental Health, DIRP, Bethesda, Maryland 20892-4034, USA.
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