-
[show abstract]
[hide abstract]
ABSTRACT: Although several genetic factors have been implicated as determinants of blood folate concentration in various populations, their effect on folate status in the Czech population has not yet been examined. We explored whether blood folate concentrations in healthy Czech population are associated with polymorphisms in 5,10-methylenetetrahydrofolate reductase (MTHFR), folate hydrolase 1 (FOLH1), reduced folate carrier (RFC), and folate receptor (FOLR1) genes. In a cross-sectional study of 591 control subjects we determined genotypes by PCR-RFLP or ARMS-PCR methods, and plasma and erythrocyte folates by MEIA. The effect of different genotypes on folate status was examined by non-parametric tests and by regression analysis. The prevalence of the MTHFR 677C>T, MTHFR 1298A>C, FOLH1 1561C>T, RFC 80G>A and FOLR1 480G>C variant alleles was 0.34, 0.33, 0.05, 0.44 and 0.00, respectively. Only the MTHFR 677C>T variant was significantly associated with plasma folate concentrations (median 14.7, 14.0 and 12.2 nmol/l for the CC, CT and TT genotypes, respectively). Our study showed that among the five studied allelic variants, only the 677C>T polymorphism in the MTHFR gene is a significant genetic determinant of plasma folate concentrations in Czech population.
Physiological research / Academia Scientiarum Bohemoslovaca 02/2005; 54(3):295-303. · 1.55 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: To explore the pathogenesis of cystathionine beta-synthase (CBS) deficiency and to test the efficacy of pharmacological therapy we examined a panel of metabolites in nine homocystinuric patients under treated and/or untreated conditions. Off pharmacological treatment, the biochemical phenotype was characterized by accumulation of plasma total homocysteine (median 135 micromol/L) and blood S -adenosylhomocysteine (median 246 nmol/L), and by normal levels of guanidinoacetate and creatine. In addition, enhanced remethylation was demonstrated by low serine level (median 81 micromol/L), and by increased concentration of methionine (median 76 micromol/L) and N -methylglycine (median 6.8 micromol/L). Despite the substantially blocked transsulphuration, which was evidenced by undetectable cystathionine and severely decreased total cysteine levels (median 102 micromol/L), blood glutathione was surprisingly not depleted (median 1155 micromol/L). In 5 patients in whom pharmacological treatment was withdrawn, the differences of median plasma total homocysteine levels (125 micromol/L after withdrawal versus 33 micromol/L under treatment conditions), total cysteine levels (139 versus 211 micromol/L) and plasma serine levels (53 versus 103 micromol/L) on and off treatment demonstrated the efficacy of long-term pyridoxine/betaine administration ( p <0.05). The treatment also decreased blood S -adenosylhomocysteine level (133 versus 59 nmol/L) with a borderline significance. In summary,our study shows that conventional treatment of CBS deficiency by diet and pyridoxine/betaine normalizes many but not all metabolic abnormalities associated with CBS deficiency. We propose that the finding of low plasma serine concentration in untreated CBS-deficient patients merits further exploration since supplementation with serine might be a novel and safe component of treatment of homocystinuria.
Journal of Inherited Metabolic Disease 02/2003; 26(8):761-73. · 3.58 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Patients with the cblE type of homocystinuria usually present with megaloblastic anaemia, feeding difficulties, developmental delay and cerebral atrophy. We present a 14-year-old Spanish girl (patient 1) and a 10-year-old Portuguese boy (patient 2) with cblE disease and mild clinical phenotype. The main clinical feature in both patients was persistent megaloblastic anaemia observed at 3 years and at 2 months of age, respectively. Diagnosis was made at the ages of 9 and 7 years, respectively, owing to persistent macrocytosis despite cobalamin treatment. Plasma total homocysteine values at diagnosis were 91 micromol/L and 44 micromol/L, respectively, in the absence of methylmalonic aciduria. Neurological and neurophysiological examinations were normal except for two small lesions on brain MRI suggestive of ischaemia and slight abnormalities in somatosensitive evoked potentials. Enzymatic analysis, complementation studies and clearly reduced production of methylcobalamin from 57Co-labelled cyanocobalamin indicated functional methionine synthase reductase deficiency due to the cblE defect. Genetic analysis confirmed that both patients are homozygous for a novel mutation c.1361C>T in the methionine synthase reductase gene leading to a replacement of serine by leucine (S454L) in a highly conserved FAD-binding domain. We propose that homozygosity for this novel mutation may be associated with a mild phenotype, although its long-term deleterious neurological consequences remain possible. Furthermore, we propose that even in the absence of apparent neurological involvement, total homocysteine should be investigated in patients with resistant megaloblastic anaemia to detect possible mild forms of the cblE type of homocystinuria.
Journal of Inherited Metabolic Disease 01/2003; 26(4):361-9. · 3.58 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The cblE type of homocystinuria is a rare autosomal recessive disorder, which manifests with megaloblastic anaemia and developmental delay in early childhood. This disease is caused by a defect in reductive activation of methionine synthase (MTR). Our study was directed at clinical, biochemical, enzymatic and molecular characterization of two Czech patients with the cblE type of homocystinuria. Case 1 involves a 20-year-old mentally retarded patient who presented with megaloblastic anaemia at 10 weeks of age. She was treated with folates and vitamin B12, and subsequent attempts to cease administration of folates led to recurrence of megaloblastic anaemia. Biochemical features included severe hyperhomocysteinaemia and hypomethioninaemia and in fibroblasts defective formation of methionine from formate, and no complementation with cblE cells. Subsequent molecular analysis of the methionine synthase reductase (MTRR) gene revealed compound heterozygosity for a transition c.1459G>A (G487R) and a 2bp insertion (c.1623-1624insTA). Case 2 involves an 8-year-old girl with nystagmus and developmental delay in whom megaloblastic anaemia was detected at 11 weeks of age. Severe hyperhomocysteinaemia with normal methionine levels was found and enzymatic and complementation studies confirmed the cblE defect. This patient is homozygous for a 140 bp insertion (c.903-904ins140). The insertion is caused by a T>C transition within intron 6 of the MTRR gene, which presumably leads to activation of an exon splicing enhancer. In the families of both patients, enzymatic and mutation analyses were successfully used for prenatal diagnosis. Our study expands the knowledge of the phenotypic and genotypic variability of the cblE type of homocystinuria and supports the concept that this disorder is caused by mutations in the MTRR gene.
Journal of Inherited Metabolic Disease 10/2002; 25(6):461-76. · 3.58 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Methionine loading test is commonly used to detect hyperhomocysteinemia in patients with arteriosclerosis and other conditions. As administration of methionine causes endothelial dysfunction in laboratory examinations, we explored whether loading with this compound leads to clinically relevant adverse effects, especially in vasculature.
When studying genetic factors in arteriosclerosis we recorded acute complications during a standard methionine loading test (with a dose of 100 mg/kg bw) and assessed a 30-day mortality in a group of 296 patients with coronary artery or peripheral arterial disease and in 591 controls. Acute complications were observed in 33% of the women and 16.5% of the men. For each sex, the patients and controls exhibited the same proportion of complications. The most common symptom, dizziness, was attributable to methionine loading. In addition, isolated sleepiness, nausea, polyuria and decreased or increased blood pressure were observed in part of the subjects. None of the 887 individuals died within the 30-day period following the test.
Our study suggests that although standard loading with L-methionine frequently causes transitory complications impairing perception and vigilance, the test does not have serious adverse effects on vasculature and may be considered a safe procedure.
Clinical Nutrition 05/2002; 21(2):151-6. · 3.73 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Recent reports suggested that homocystinuria due to cystathionine beta-synthase (CBS) deficiency is a more common inborn error of metabolism than originally thought. In this study we compared the prevalence of homocystinuric alleles ascertained by two different approaches. First, the incidence of homocystinuria estimated by selective biochemical screening in the Czech and Slovak Republics was 1:349,000 (95% CI 1:208,000-1:641,000). The two most common pathogenic mutant alleles found subsequently in these patients, IVS11-2A>C and c.833T>C, had a calculated population prevalence of 0.00042 (95% CI 0.00031-0.00055) and 0.00018 (95% CI 0.00013-0.00023), respectively. Second, to examine the possible negative detection bias of mildly affected patients we determined the prevalence of these two pathogenic mutations in a sample of 1284 unselected newborns. Indeed, the observed prevalence of the c.833T>C allele (0.00195, 95% CI 0.00063-0.00454) was 11x higher than in the previous group suggesting that many homozygotes for the c.833T>C had not been diagnosed by selective biochemical screening. The IVS11-2A>C allele was not detected among 2,568 newborn CBS alleles. The estimated incidence of homocystinuria of 1:83,000, calculated in a combined model, suggests that selective biochemical screening may ascertain only approximately 25% of all homocystinuric patients. In conclusion, homocystinuria in Central Europe may be sufficiently common to consider sensitive newborn screening programs for this disease.
Human Mutation 12/2001; 18(6):548-9. · 5.69 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Aminothiols have been implicated in the pathogenesis of arteriosclerosis, and reliable methods are needed to determine their concentrations in body fluids. We present a comparison of two analytical methods and focus on the reduction of low-molecular weight and protein-mixed disulfides of homocysteine, cysteine, cysteinyl-glycine, and glutathione.
The plasma total aminothiol profile was determined by HPLC with fluorescence detection after derivatization with ammonium 7-fluorobenzo-2-oxa-1,3-diazole-4-sulfonate. Disulfides and protein-bound aminothiols were reduced by either tri-n-butylphosphine (the TBP method) or tris(2-carboxyethyl)phosphine (the TCEP method); the effects of temperature, time of reduction, and concentration of reductants were evaluated.
The intraassay imprecision (CV) was <3% for all aminothiols using both methods. The interassay CVs for total cysteine (tCys), total cysteinyl-glycine (tCys-Gly), and total homocysteine (tHcy) were <4% and <8% for the TCEP and TBP methods, respectively, whereas for total glutathione (tGSH) the interassay CV was >12% for both methods. Deming regression and Bland-Altman difference plots showed positive biases for total aminothiol concentrations determined by the TCEP method relative to the TBP method. The mean proportional biases were 65%, 27%, 6%, and 60% for tCys, tCys-Gly, tHcy, and tGSH, respectively. The calculated concentrations of total aminothiols by the TCEP method were less influenced by changes in temperature and concentration of reducing agent or by calibrator matrix.
The agreement between the TCEP and TBP methods was considerably lower for the determination of tCys, tCys-Gly, and tGSH than for tHcy. For total-aminothiol determination, the TCEP method yields better reproducibility and is more robust than the TBP method.
Clinical Chemistry 10/2001; 47(10):1821-8. · 7.91 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Homocysteine is associated with an increased risk of atherosclerosis. The administration of fibrates has been reported to significantly increase plasma homocysteine levels, a potentially adverse effect of fibrates. We investigated the hypothesis that concomitant treatment with fenofibrate and folic acid leads to a smaller increase in plasma total homocysteine levels than treatment with fenofibrate alone.
A randomized, open-label study compared the effect of micronized fenofibrate (200 mg daily) alone versus fenofibrate plus folic acid (10 mg every other day) on plasma homocysteine levels. Twenty-two patients with mixed hyperlipidemia participated. The 9-wk treatment period was preceded by a 4-wk wash-out period without hypolipidemic drugs.
In patients treated with fenofibrate only, plasma homocysteine levels increased by 6.85 +/- 5.23 micromol/L (from 12.27 +/- 3.15 to 19.13 +/- 7.20 micromol/L); in patients treated with fenofibrate and folic acid, plasma homocysteine levels increased by 2.01 +/- 2.88 micromol/L (from 10.14 +/- 2.32 to 12.15 +/- 3.08 micromol/L). The difference in the homocysteine increase between the two groups was statistically significant at P = 0.014.
Folic acid supplementation in patients treated with fenofibrate significantly reduced the increase in plasma homocysteine levels. More studies are needed to clarify whether amelioration of this side effect increases the clinical benefit of fibrates.
Nutrition 10/2001; 17(9):721-3. · 3.03 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Endothelial nitric oxide synthase (eNOS) produces nitric oxide (NO) which, after diffusing into vascular smooth muscle cells, activates guanylate cyclase leading to vasodilatation. A polymorphism (894G to T) in exon 7 of the eNOS gene causes the conversion of Glu to Asp in position 298. The recently described crystal structure of the heme domain of eNOS protein shows that Glu298 is fully solvent accessible and distant from regions integral to enzyme function. Searching for phenotypic expression of eNOS gene variants, we genotyped a group of patients with essential hypertension (H, n = 119) for the Glu298Asp polymorphism and compared them with age- and sex-matched healthy normals (N, n = 85). To specify phenotypic expression further, the hypertensive patients were subdivided into one group that responded well to regular antihypertensive therapy (CH, n = 45) and one group that was resistant to the therapy (RH, n = 74). Patients with BP higher than 140/90 mmHg when on adequate lifestyle modification and triple-combination therapy (including diuretics) were considered resistant. In RH and H groups, a significantly higher frequency of T alleles (P = 0.022 and P = 0.046, respectively) was found compared to normotonics (N). In well-controlled hypertonics, the same tendency was found, but did not reach statistical significance. The Glu298Asp polymorphism may contribute to the complex pathogenesis of essential hypertension and may be a factor in the resistance of these patients to conventional antihypertensive therapy. The presence of this allele may thus be predictive of the patients' therapeutic response.
Biochemical and Biophysical Research Communications 07/2001; 284(2):426-30. · 2.48 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: During the past 20 years, cystathionine beta-synthase (CBS) deficiency has been detected in the former Czechoslovakia with a calculated frequency of 1:349,000. The clinical manifestation was typical of homocystinuria, and about half of the 21 patients were not responsive to pyridoxine. Twelve distinct mutations were detected in 30 independent homocystinuric alleles. One half of the alleles carried either the c.833 T-->C or the IVS11-2A-->C mutation; the remaining alleles contained private mutations. The abundance of five mutant mRNAs with premature stop codons was analyzed by PCR-RFLP. Two mRNAs, c.828_931ins104 (IVS7+1G-->A) and c.1226 G-->A, were severely reduced in the cytoplasm as a result of nonsense-mediated decay. In contrast, the other three mRNAs-c.19_20insC, c.28_29delG, and c.210_235del26 (IVS1-1G-->C)-were stable. Native western blot analysis of 14 mutant fibroblast lines showed a paucity of CBS antigen, which was detectable only in aggregates. Five mutations-A114V (c.341C-->T), A155T (c.463G-->A), E176K (c.526G-->A), I278T (c.833T-->C), and W409_G453del (IVS11-2A-->C)-were expressed in Escherichia coli. All five mutant proteins formed substantially more aggregates than did the wild-type CBS, and no aggregates contained heme. These data suggest that abnormal folding, impaired heme binding, and aggregation of mutant CBS polypeptides may be common pathogenic mechanisms in CBS deficiency.
The American Journal of Human Genetics 07/2001; 68(6):1506-13. · 10.60 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Homocystinuria is most frequently due to deficiency of cystathionine beta-synthase (CBS). We identified IVS12 as a polymorphism hot spot of the human CBS gene and report five novel single nucleotide polymorphisms (SNPs): g.13514G>A, g.13617A>G, g.13715C>T, g.13800G>A, and g.13904C>T. Analyzing 50 control DNA samples of unaffected and unrelated subjects of German origin the observed frequencies of heterozygosity were 0.02, 0.36, 0.18, 0.36, and 0.36, respectively. These polymorphic markers were combined into four distinct IVS12-haplotypes A1, A2, B1, and B2, revealing frequencies of 0.75, 0.01, 0.15, and 0.09, respectively, with an observed overall frequency of heterozygosity at 0.38. This haplotype system and the SNP c.699 were employed in the analysis of ten alleles affected by the most prevalent CBS mutation, c.833T>C (exon 8; I278T). We found that the I278T alleles segregate with at least two distinct haplotypes characterized by upstream and downstream polymorphic sites instead of sharing a common ancestral haplotype. This was a remarkable finding even in patients with very similar ethnic background. The novel haplotype system may facilitate future studies on the evolution of the CBS gene and might be suited for genotyping of families affected by homocystinuria.
Human Mutation 05/2001; 17(4):350-1. · 5.69 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Homocystinuria due to cystathionine beta-synthase deficiency is an autosomal recessive disorder of methionine metabolism. It manifests with vascular, central nervous system and connective tissue disturbances, and phenotypically resembles Marfan's syndrome. We analysed the clinical course of homocystinuria in Czech and Slovak patients.
The group of homocystinuric patients consisted of 19 individuals (12 males and 7 females) aged 5-32 years (average age 18 years), who were diagnosed between 1980 and 1999. The overall incidence of homocystinuria in the Czech and Slovak Republics was 1:287,000. The proportion of pyridoxine-responsive patients was 47%. The average follow-up period was 10 years (range 1 month to 19 years). The prevalence of the individual signs in the group was as follows: lens dislocation--95% of patients, progressive myopia--79%, marfanoid habitus--74%, kyfoscoliosis--68%, osteoporosis--63%, psychomotor retardation--58%, other neurologic symptomatology--58% and tromboembolism--21%. The average delay between the first sign of the disease and the time when the diagnosis was made was 4 years (range 1 to 14 years). At the time of diagnosis the average levels of metabolites in plasma were as follows: total homocysteine 348 mumol/l (range 211-536), free homocystine 70 mumol/l (range 0-203) and methionine 359 mumol/l (range 75-937).
Both the clinical course of homocystinuria due to the cystathionine beta-synthase deficiency and its incidence in the Czech and Slovak Republics are similar to those in other populations. Since homocystinuria is a treatable disease, it should be included in the differential diagnosis of Marfan's syndrome, tromboembolism and severe psychomotor retardation.
Casopís lékar̆ů c̆eských 09/2000; 139(16):500-7.
-
[show abstract]
[hide abstract]
ABSTRACT: Mevalonate kinase (MKase) deficiency (MKD) is a rare autosomal recessive disorder in the pathway of cholesterol and nonsterol isoprenoid biosynthesis. Thus far, two disease-causing missense alleles have been identified, N301T and A334T. We report four additional mutations associated with MKD: L264F, T243I, L265P, and I268T, the last found in a patient of Mennonite ancestry. Electrophoretic analysis of bacterially expressed wild-type and mutant MKase indicated that I268T and T243I mutants produced normal or somewhat reduced amounts of MKase protein; conversely, L264F and L265P mutations resulted in considerably decreased, or absent, MKase protein. Immunoblot analysis of MKase from all patients suggested that the MKase polypeptide was grossly intact and produced in amounts comparable to control levels. Three mutations resulted in significantly diminished MKase enzyme activity (<2%), whereas the I268T allele yielded approximately 20% residual enzyme activity. Our results should allow more-accurate identification of carriers and indicate a mutation "cluster" within amino acids 240-270 of the mature MKase polypeptide.
The American Journal of Human Genetics 08/1999; 65(2):327-35. · 10.60 Impact Factor
-
Journal of Inherited Metabolic Disease 07/1999; 22(5):674-5. · 3.58 Impact Factor
-
J Hyánek,
J Stríbrný,
P Sebesta,
M Klika,
J Kramár, V Kozich,
V Martiníková,
L Machácková,
M Orendác,
M Loucka,
L Dubská,
H Pejznochová,
L Táborský,
I Cabrnochová
[show abstract]
[hide abstract]
ABSTRACT: A rise of the homocysteine plasma level--mild hyperhomocysteinaemia--is considered an independent risk factor for the development of vascular damage. It is due to hereditary deficiency of 5,10-methylene-tetrahydrofolate reductase with accentuation of vitamin deficiency (folic acid, vitamin B6 and B12). In previous studies the authors confirmed this fact in the population of patients with aortocoronary or peripheral arterial bypasses. The assumed autosomal recessive transmission of this deficiency should make it possible to detect carriers of this metabolic deviation already in childhood. By selective screening of the child population at risk it would thus be possible to detect affected subjects in time and prevent the development of vascular disease by preventive folate administration.
In a group of 38 children and grandchildren from risk families where at least one of the parents or grandparents was operated on account of vascular obliterating disease the total homocysteine plasma level was examined by the chromatographic method. An increase of total homocystein (8.7 +/- 2.7 mumol/l) was found as compared with children from the non-risk population (5.4 +/- 1.8 mumol/l), (p < 0.001). The total homocysteine values however were dependent on the child's age and were more marked in children above 12 years of age. In the parental population mild hyperhomocysteinaemia was present in 38% of those with aortocoronary bypasses and in 43% of those with peripheral arterial bypasses.
The authors found significantly elevated total homocysteine levels in the child population from risk families with obliterating vascular disease. The total homocysteine level depends on the child's age and is more markedly expressed in children above 12 years of age.
Casopís lékar̆ů c̆eských 06/1999; 138(11):333-6.
-
[show abstract]
[hide abstract]
ABSTRACT: In the paper we show results of medical study from statistical point of view. The medical study was aimed to study genetic risk factors of peripheral arterial occlusive diseases in Czech population. Two genes, CBS and MTHFR were examined, as various genotypes of these genes are thought to have impact on amino thiols, who participate in variety of reactions in vasculature. Statistical part of the study was responsible for analysis and interpretation of collected data.
Studies in health technology and informatics 02/1999; 68:419-22.
-
J P Kraus,
M Janosík, V Kozich,
R Mandell,
V Shih,
M P Sperandeo,
G Sebastio,
R de Franchis,
G Andria,
L A Kluijtmans,
H Blom,
G H Boers,
R B Gordon,
P Kamoun,
M Y Tsai,
W D Kruger,
H G Koch,
T Ohura,
M Gaustadnes
[show abstract]
[hide abstract]
ABSTRACT: The major cause of homocystinuria is mutation of the gene encoding the enzyme cystathionine beta-synthase (CBS). Deficiency of CBS activity results in elevated levels of homocysteine as well as methionine in plasma and urine and decreased levels of cystathionine and cysteine. Ninety-two different disease-associated mutations have been identified in the CBS gene in 310 examined homocystinuric alleles in more than a dozen laboratories around the world. Most of these mutations are missense, and the vast majority of these are private mutations. The two most frequently encountered of these mutations are the pyridoxine-responsive I278T and the pyridoxine-nonresponsive G307S. Mutations due to deaminations of methylcytosines represent 53% of all point substitutions in the coding region of the CBS gene.
Human Mutation 02/1999; 13(5):362-75. · 5.69 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Homocystinuria due to cystathionine beta-synthase (CBS) deficiency is frequently caused by missense mutations. In this article, we report four novel missense mutations in the CBS gene: 172C-->T (R58W) linked in cis with A114V; 376A-->G (M126V); 904G-->A (E302K); and 1006C-->T (R336C). The CBS activity of the corresponding mutant enzymes expressed in Escherichia coli was greatly diminished, confirming the pathogenicity of these mutations. Western analysis showed that the R58W+A114V and M126V mutant enzymes were unstable in E. coli, while the E302K subunits were partially degraded to shorter products. Using site-directed mutagenesis we found that CBS containing either the R58W or A114V as the only mutations demonstrated 18% and 46% of normal activity, respectively. Both mutant forms of CBS were stable in E. coli. When these two mutations were expressed in cis, the resultant mutant protein exhibited activity 1.3% that of a control. All these in vitro results were in good agreement with the clinical manifestation in these patients. The Italian patient 2241, an A114V+R58W/M126V compound heterozygote, exhibited severe pyridoxine nonresponsive homocystinuria, while another Italian patient 2242, with an A114V/E302K genotype, responded to pyridoxine treatment and had a much milder phenotype. The third patient 3064, an English compound heterozygote for two severe mutations R336C and G307S, was B6 nonresponsive. This report of a ninth homocystinuric allele carrying two mutations in cis raises the possibility that double mutant alleles may be underestimated in homocystinuric patients. In this context, a search for additional mutations in cis may sometimes be necessary to establish a good genotype-phenotype relationship.
Human Mutation 01/1999; 13(6):453-7. · 5.69 Impact Factor
-
J P Kraus,
J Oliveriusová,
J Sokolová,
E Kraus,
C Vlcek,
R de Franchis,
K N Maclean,
L Bao,
Bukovsk,
D Patterson,
V Paces,
W Ansorge, V Kozich
[show abstract]
[hide abstract]
ABSTRACT: Cystathionine beta-synthase [CBS; l-serine hydro-lyase (adding homocysteine), EC 4.2.1.22] catalyzes the first committed step of transsulfuration and is the enzyme deficient in classical homocystinuria. In this report, we describe the molecular cloning and the complete nucleotide sequence of the human CBS gene. We report a total of 28,046 nucleotides of sequence, which, in addition to the CBS gene, contains approximately 5 kb of the 5' flanking region. The human CBS gene contains 23 exons ranging from 42 to 209 bp. The 5' UTR is formed by 1 of 5 alternatively used exons and 1 invariably present exon, while the 3' UTR is encoded by exons 16 and 17. We also describe the identification of two alternatively used promoter regions that are GC rich (approximately 80%) and contain numerous putative binding sites for Sp1, Ap1, Ap2, and c-myb, but lack the classical TATA box. The CBS locus contains an unusually high number of Alu repeats, which may predispose this gene to deleterious rearrangements. Additionally, we report on a number of DNA sequence repeats that are polymorphic in North American and European Caucasians.
Genomics 10/1998; 52(3):312-24. · 3.02 Impact Factor
-
Journal of Inherited Metabolic Disease 07/1998; 21(3):255-61. · 3.58 Impact Factor
