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Biomedical subjects

Beat Steinmann

Publications and source records attributed to Beat Steinmann.

At least 19 recordsLinked to original sources
PubMed2006

Mutation and biochemical analysis of 19 probands with mut0 and 13 with mut- methylmalonic aciduria: identification of seven novel mutations.

Isolated methylmalonic acidurias (MMA-urias) comprise a group of rare autosomal recessively inherited disorders characterised by accumulation of MMA in urine and other body fluids, resulting from deficient activity of the mitochondrial enzyme methylmalonyl-CoA mutase (MCM). Isolated MMA-uria results from either MCM apoenzyme defects (mut(0) and mut(-)) or defects in synthesis of its cofactor 5-deoxyadenosylcobalamin, i.e. cblA, cblB and cblD-variant 2. To date various studies have identified 171 disease-causing mutations in the MCM gene (MUT). We report mutation analysis in 32 probands with mut MMA-uria including 13 probands with a mut(-) defect. Sixty two of 64 possible mutant alleles were identified, seven of which were novel missense alleles. We found three novel mutations (c.427C>T/p.H143Y; c.862T>C/p.S288P; c.1361G>A/p.G454E) among 19 probands with a mut(0) defect and four novel mutations (c.299A>G/p.Y100C; c.1031C>T/p.S344F; c.1097A>G/p.N366S; c.2081G>T/p.R694L) among 13 probands with a mut(-) defect. Our study provides evidence that the p.Y100C, p.R108H, p.N366S, p.V633G, p.R694W, p.R694L and p.M700K mutations are associated with a mut(-) phenotype.

Adolescent↗
PubMed2006

Xanthinuria type I: a rare cause of urolithiasis.

Xanthinuria type I is a rare disorder of purine metabolism caused by xanthine oxidoreductase or dehydrogenase (XDH) deficiency. We report a family with two affected children out of 335 pediatric stone patients studied since 1991 in Armenia. The propositus, a 13-month-old boy, presented with abdominal pain and urinary retention followed by stone passage (0.9x0.6 cm). Infrared spectroscopy in Yerevan revealed a pure xanthine stone. Family examination in the parents and brother was normal, but the propositus and his 8-year-old asymptomatic sister had hypouricemia, hypouricosuria, and high urinary excretion of hypoxanthine and xanthine. Ultrasonography in the index patient showed bilateral stones requiring pyelolithotomy. High fluid intake and purine restriction did not prevent further stone passages. The affected asymptomatic sister had a small pelvic stone (4 mm). Mutation analysis revealed a heterozygous novel base pair substitution in exon 25 of the XDH gene (c.2810C>T), resulting in an amino acid substitution (p.Thr910Met). The second mutation could not be detected. Despite this, the heterozygous mutation, the chemical findings, and the positive allopurinol test altogether prove xanthinuria type I, which may present wide clinical intrafamilial variation. Diagnosis is suspected usually from low serum uric acid. No specific therapy is available.

Armenia↗
PubMed2006

Cardiac and vascular hypertrophy in Fabry disease: evidence for a new mechanism independent of blood pressure and glycosphingolipid deposition.

OBJECTIVE: Fabry disease is an X-linked disorder resulting from alpha-galactosidase A deficiency. The cardiovascular findings include left ventricular hypertrophy (LVH) and increased intima-media thickness of the common carotid artery (CCA IMT). The current study examined the possible correlation between these parameters. To corroborate these clinical findings in vitro, plasma from Fabry patients was tested for possible proliferative effect on rat vascular smooth muscle cells (vascular smooth muscle cell [VSMC]) and mouse neonatal cardiomyocytes. METHODS AND RESULTS: Thirty male and 38 female patients were enrolled. LVH was found in 60% of men and 39% of women. Increased CCA IMT was equally present in males and females. There was a strong positive correlation between LV mass and CCA IMT (r2=0.27; P<0.0001). VSMC and neonatal cardiomyocyte proliferative response in vitro correlated with CCA IMT (r2=0.39; P<0.0004) and LV mass index (r2=0.19; P=0.028), respectively. CONCLUSIONS: LVH and CCA IMT occur concomitantly in Fabry suggesting common pathogenesis. The underlying cause may be a circulating growth-promoting factor whose presence has been confirmed in vitro.

Adolescent↗
PubMed2006

Identification and in silico analyses of novel TGFBR1 and TGFBR2 mutations in Marfan syndrome-related disorders.

Very recently, heterozygous mutations in the genes encoding transforming growth factor beta receptors I (TGFBR1) and II (TGFBR2) have been reported in Loeys-Dietz aortic aneurysm syndrome (LDS). In addition, dominant TGFBR2 mutations have been identified in Marfan syndrome type 2 (MFS2) and familial thoracic aortic aneurysms and dissections (TAAD). In the past, mutations of these genes were associated with atherosclerosis and several human cancers. Here, we report a total of nine novel and one known heterozygous sequence variants in the TGFBR1 and TGFBR2 genes in nine of 70 unrelated individuals with MFS-like phenotypes who previously tested negative for mutations in the gene encoding the extracellular matrix protein fibrillin-1 (FBN1). To assess the pathogenic impact of these sequence variants, in silico analyses were performed by the PolyPhen, SIFT, and Fold-X algorithms and by means of a 3D homology model of the TGFBR2 kinase domain. Our results showed that in all but one of the patients the pathogenic effect of at least one sequence variant is highly probable (c.722C > T, c.799A > C, and c.1460G > A in TGFBR1 and c.773T > G, c.1106G > T, c.1159G > A, c.1181G > A, and c.1561T > C in TGFBR2). These deleterious alleles occurred de novo or segregated with the disease in the families, indicating a causative association between the sequence variants and clinical phenotypes. Since TGFBR2 mutations found in patients with MFS-related disorders cannot be distinguished from heterozygous TGFBR2 mutations reported in tumor samples, we emphasize the importance of segregation analysis in affected families. In order to be able to find the mutation that is indeed responsible for a MFS-related phenotype, we also propose that genetic testing for sequence alterations in TGFBR1 and TGFBR2 should be complemented by mutation screening of the FBN1 gene.

Activin Receptors, Type I↗
PubMed2006

Different patterns of aortic wall elasticity in patients with Marfan syndrome: a noninvasive follow-up study.

OBJECTIVE: Aortic complications determine the life expectancy of most patients with Marfan syndrome. To find out whether there is heterogenous aortic involvement among patients and, if there is, to characterize aortic patterns and response to long-term beta-blocker therapy, we investigated aortic elastic properties before and during beta-blocker treatment. METHODS: In 46 patients with Marfan syndrome (age, 17.4 +/- 11.1 years) and 46 healthy control subjects, ascending and descending aortic elastic parameters were determined noninvasively before and after 39 +/- 16 months of beta-blocker treatment with atenolol. RESULTS: Aortic diameters and distensibility distinguished Marfan patients and controls with a sensitivity of 85% and a specificity of 87%. Cluster analysis revealed 4 patterns of aortic phenotypic expression: (1) reduced ascending aortic elasticity (46% of patients), (2) diminished ascending and descending aortic elasticity (17%), (3) minimal alterations of ascending and descending aortic elasticity (20%), and (4) reduced descending aortic elasticity (17%). During follow-up, aortic elastic properties improved in 21 (70%) of 30 patients and deteriorated in 9 (30%) irrespective of beta-blocker dosage. Improvement was observed in 100% of patients (n = 7; age, 5.3 +/- 4.2 years) with end-diastolic aortic root diameters between 20 and 30 mm and in 61% of patients (14/23; age, 20.5 +/- 10.0 years) with root diameters between 30 and 52 mm. CONCLUSIONS: Aortic elastic parameters distinguish between patients with Marfan syndrome and healthy controls and show the pattern of regional aortic involvement. Improvement or deterioration during follow-up can influence therapeutic decisions to prevent aortic dissection and rupture. Young age, small root diameter, and high distensibility are favorable prognostic factors.

Adolescent↗
PubMed2006

Pharmacological chaperone corrects lysosomal storage in Fabry disease caused by trafficking-incompetent variants.

Fabry disease is a lysosomal storage disorder caused by deficiency of alpha-galactosidase A (alpha-Gal A) resulting in lysosomal accumulation of glycosphingolipid globotriosylceramide Gb3. Misfolded alpha-Gal A variants can have residual enzyme activity but are unstable. Their lysosomal trafficking is impaired because they are retained in the endoplasmic reticulum (ER) by quality control. Subinhibitory doses of the competitive inhibitor of alpha-Gal A, 1-deoxygalactonojirimycin (DGJ), stabilize mutant alpha-Gal A in vitro and correct the trafficking defect. We showed by immunolabeling that the chaperone-like action of DGJ significantly reduces the lysosomal Gb3 storage in human Fabry fibroblasts harboring the novel mutations T194I and V390fsX8. The specificity of the DGJ effect was proven by RNA interference. Electron microscopic morphometry demonstrated a reduction of large-size, disease-associated lysosomes and loss of characteristic multilamellar lysosomal inclusions on DGJ treatment. In addition, the pre-Golgi intermediates were decreased. However, the rough ER was not different between DGJ-treated and untreated cells. Pulse-chase experiments revealed that DGJ treatment resulted in maturation and stabilization of mutant alpha-Gal A. Genes involved in cell stress signaling, heat shock response, unfolded protein response, and ER-associated degradation show no apparent difference in expression between untreated and DGJ-treated fibroblasts. The DGJ treatment has no apparent cytotoxic effects. Thus our data show the usefulness of a pharmacological chaperone for correction of the lysosomal storage in Fabry fibroblasts harboring different mutations with residual enzyme activity. Pharmacological chaperones acting on misfolded, unstable mutant proteins that exhibit residual biological activity offer a convenient and cost-efficient therapeutic strategy.

1-Deoxynojirimycin↗
PubMed2005

A bioinformatics framework for genotype-phenotype correlation in humans with Marfan syndrome caused by FBN1 gene mutations.

Mutations in the human FBN1 gene are known to be associated with the Marfan syndrome, an autosomal dominant inherited multi-systemic connective tissue disorder. However, in the absence of solid genotype-phenotype correlations, the identification of an FBN1 mutation has only little prognostic value. We propose a bioinformatics framework for the mutated FBN1 gene which comprises the collection, management, and analysis of mutation data identified by molecular genetic analysis (DHPLC) and data of the clinical phenotype. To query our database at different levels of information, a relational data model, describing mutational events at the cDNA and protein levels, and the disease's phenotypic expression from two alternative views, was implemented. For database similarity requests, a query model which uses a distance measure based on log-likelihood weights for each clinical manifestation, was introduced. A data mining strategy for discovering diagnostic markers, classification and clustering of phenotypic expressions was provided which enabled us to confirm some known and to identify some new genotype-phenotype correlations.

Computational Biology↗
PubMed2005

Mutation analysis of the PLOD1 gene: an efficient multistep approach to the molecular diagnosis of the kyphoscoliotic type of Ehlers-Danlos syndrome (EDS VIA).

The kyphoscoliotic type of Ehlers-Danlos syndrome (EDS VIA) is an inheritable connective tissue disorder characterized by a deficiency of lysyl hydroxylase due to mutations in PLOD1. We describe a mutation analysis strategy for the PLOD1 gene using either cDNA or gDNA or a combination thereof, which allows for reliable, time-effective and efficient mutation detection in patients with EDS VIA. We report the results obtained in 9 index patients from 12 unrelated families: three patients were homozygous for three novel mutations (p.Ile454IlefsX2, p.Ala667Thr, and p.His706Arg), four patients were homozygous for the common duplication of exons 10-16, one patient was compound heterozygous for the common duplication and p.Ile454IlefsX2, and one patient was homozygous for p.Arg319X.

Adolescent↗
PubMed2005

Familial X-linked cardiomyopathy (Danon disease): diagnostic confirmation by mutation analysis of the LAMP2gene.

UNLABELLED: A boy presented at age 2.5 years with mild left ventricular hypertrophy and mild myopathy. Hypertrophic cardiomyopathy progressed relentlessly, leading to death at age 16 years shortly before planned heart transplantation. During the course of the disease, his mother developed severe dilated cardiomyopathy and died of its complications at 46 years of age. The combination of myopathy and cardiomyopathy, the biochemical and electron microscopy findings in a muscle biopsy, and the pedigree suggested Danon disease (MIM 300257), an X-linked lysosomal storage disorder caused by deficiency of lysosome-associated membrane protein-2 (LAMP2). The diagnosis was confirmed by the identification of a novel mutation, G138A, in the LAMP2gene, leading to the premature stop codon W46X. CONCLUSION: Early diagnosis of Danon disease is important for genetic counselling and timely cardiac transplantation, the only effective therapeutic option.

Adolescent↗
PubMed2005

Nevo syndrome is allelic to the kyphoscoliotic type of the Ehlers-Danlos syndrome (EDS VIA).

We report on seven patients affected with Nevo syndrome, a rare, autosomal recessive disorder characterized by increased perinatal length, kyphosis, muscular hypotonia, and joint laxity. Since its first description by Nevo et al. [1974], only a few cases have been reported. Because some of these patients present clinical features similar to those of the kyphoscoliotic type of Ehlers-Danlos syndrome (EDS VIA), an inherited connective tissue disorder characterized by a deficiency of lysyl hydroxylase due to mutations in PLOD1, we studied seven patients with Nevo syndrome, three of whom have previously been reported, and four of whom are new. In the five patients from whom urine was available, the ratio of total urinary lysyl pyridinoline (LP) to hydroxylysyl pyridinoline (HP) was elevated (8.2, 7.8, 8.6, 3.5, and 4.8, respectively) compared with that in controls (0.20 +/- 0.05, range 0.10-0.38), and similar to that observed in patients with EDS VIA (5.97 +/- 0.99, range 4.3-8.1). Six patients were homozygous for a point mutation in exon 9 of PLOD1 causing a p.R319X nonsense mutation, while one patient was homozygous for a large deletion comprising exon 17 of PLOD1. We conclude that the Nevo syndrome is allelic to and clinically indistinguishable from EDS VIA, and present evidence that increased length at birth and wristdrop, in addition to muscular hypotonia and kyphoscoliosis, should prompt the physician to consider EDS VIA earlier than heretofore.

Abnormalities, Multiple↗
PubMed2005

A splicing mutation in the alpha/beta GlcNAc-1-phosphotransferase gene results in an adult onset form of mucolipidosis III associated with sensory neuropathy and cardiomyopathy.

A 47-year-old female who presented with a dilated cardiomyopathy and mild neuropathy was found to have pseudoHurler polydystrophy (mucolipidosis III). The serum lysosomal enzymes were strikingly elevated and GlcNAc-1-phosphotransferase activity in the patient's fibroblasts was 3% of normal. Sequence analysis of the patient's genomic DNA revealed a homozygous mutation of the last nucleotide of the 135-bp exon 7 of the phosphotransferase gene encoding the alpha/beta subunits, resulting in aberrant splicing and skipping of this exon. Remarkably, none of the skeletal and connective tissue anomalies characteristic of the disease were present. This case is the first example of mucolipidosis III presenting in an adult patient and further broadens the clinical spectrum of the disease.

Age of Onset↗
PubMed2005

The spectrum of aldolase B (ALDOB) mutations and the prevalence of hereditary fructose intolerance in Central Europe.

We investigated the molecular basis of hereditary fructose intolerance (HFI) in 80 patients from 72 families by means of a PCR-based mutation screening strategy, consisting of heteroduplex analysis, restriction enzyme digest, DNA single strand electrophoresis, and direct sequencing. For a subset of patients mutation screening with DHPLC was established which turned out to be as fast and as sensitive as the more conventional methods. Fifteen different mutations of the aldolase B (ALDOB) gene were identified in HFI patients. As in smaller previous studies, p.A150P (65%), p.A175D (11%) and p.N335K (8%) were the most common mutated alleles, followed by c.360_363delCAAA, p.R60X, p.Y204X, and c.865delC. Eight novel mutations were identified in eight families with HFI: a small indel mutation (c.1044_1049delTTCTGGinsACACT), two small deletions (c.345_372del28; c.841_842delAC), two splice site mutations (c.113-1G>A, c.799+2T>A), one nonsense mutation (c.612T>G (p.Y204X)), and two missense mutations (c.532T>C (p.C178R), c.851T>C (p.L284P)). By mutation screening for the three most common ALDOB mutations by DHPLC in 2,000 randomly selected newborns we detected 21 heterozygotes. Based on these data and after correction for less common and private ALDOB mutations, HFI prevalence in central Europe is estimated to be 1:26,100 (95% confidence interval 1: 12,600-79,000).

Chromatography, High Pressure Liquid↗
PubMed2005

Diagnostic power of aortic elastic properties in young patients with Marfan syndrome.

BACKGROUND: In patients with Marfan syndrome, progressive aortic dilation implicates a still-unpredictable risk of life-threatening aortic dissection and rupture. We sought to quantify aortic wall dysfunction noninvasively, determine the diagnostic power of various aortic parameters, and establish a diagnostic model for the early detection of aortic abnormalities associated with Marfan syndrome. METHODS: In 19 patients with Marfan syndrome (age, 17.7 +/- 9.5 years) and 19 age- and sex-matched healthy control subjects, computerized ascending and abdominal aortic wall contour analysis with continuous determination of aortic diameters was performed out of transthoracic M-mode echocardiographic tracings. After simultaneous oscillometric blood pressure measurement, aortic elastic properties were determined automatically. RESULTS: The following ascending aortic elastic parameters showed statistically significant differences between the Marfan group and the control group: (1) decreased aortic distensibility ( P < .001), (2) increased wall stiffness index ( P < .01), (3) decreased systolic diameter increase ( P < .01), and (4) decreased maximum systolic area increase ( P < .001). The diagnostic power of all investigated parameters was tested by single logistic regression models. A multiple logistic regression model including solely aortic parameters yielded a sensitivity of 95% and a specificity of 100%. CONCLUSIONS: In young patients with Marfan syndrome, a computerized image-analyzing technique revealed decreased aortic elastic properties expressed by parameters showing high diagnostic power. A multiple logistic regression model including merely aortic parameters can serve as useful predictor for Marfan syndrome.

Adolescent↗
PubMed2004

Brittle cornea syndrome and its delineation from the kyphoscoliotic type of Ehlers-Danlos syndrome (EDS VI): report on 23 patients and review of the literature.

The brittle cornea syndrome (BCS) is a generalized connective tissue disorder characterized by corneal rupture following only minor trauma, keratoconus or keratoglobus, blue sclerae, hyperelasticity of the skin without excessive fragility, and hypermobility of the joints. It is inherited as an autosomal recessive trait but the underlying genetic defect remains undetermined. We present 23 patients (11 male) from 13 nuclear families followed at the King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia, aged 3-28 years at last follow-up. A total of 28 events of corneal rupture were noted in 17 patients (eight male), among whom nine had had bilateral ruptures, and eight had had unilateral ruptures (four of the right cornea), while two had experienced re-rupture 2 and 4 years, respectively, after surgery; six patients (aged 3-21 years) had had no ruptures. We describe the natural history of our cases and discuss them together with those others reported in the literature. Because of similarities between the BCS and the kyphoscoliotic type of the Ehlers-Danlos syndrome (EDS VI), both disorders tend to have been confounded. Here, we show that all of our BCS patients tested in this regard had biochemical findings reflective of normal activity of lysyl hydroxylase, characteristically deficient in EDS VI, such as normal urinary total pyridinoline ratios and/or normal electrophoretic migration of collagen chains produced by dermal fibroblasts. The BCS is, therefore, an entity distinct from the kyphoscoliotic type of EDS, which has a much poorer prognosis.

Adolescent↗
PubMed2004

Progeria: a new kind of Laminopathy-- report of the First European Symposium on Progeria and creation of EURO-Progeria, a European Consortium on Progeria and related disorders.

Progeria is a rare, genetically determined condition characterized by accelerated aging in children. Its name is derived from Greek (Geron) and means "prematurely old". The classic type is the Hutchinson-Gilford Progeria Syndrome (HGPS), which was first described in England in 1886 by Dr. Jonathan Hutchinson (1) and again in 1904 by Dr. Hastings Gilford (2). Since then and up to now, very little advancement toward the understanding of this devastating disorder has been accomplished. In early 2003 a French group succeeded in identifying point mutations in the LMNA gene, encoding A-type lamins, as the main cause of this disorder. These results were concomitantly confirmed by an American group, who identified mutations in LMNA, working on a large cohort of patients (3,4). HGPS is thus the most severe disorder added to the expanding list of "laminopathies", diseases caused by mutations in the LMNA gene encoding A-type lamins. To date, up to ten disorders are associated with mutations in LMNA. These disorders are diverse, both in their symptomatology and pattern of inheritance (see below and table 1). Due to the extremely low prevalence of progeria and the putative functional links between progeria and other premature aging disorders, setting-up a network about these disorders has become an absolute necessity. A reunion of families with a child affected with progeria, gathered within the European Progeria Family Circle, was held from September 25th to 29th 2003 in Magdeburg, Germany. In parallel to this event, a scientific symposium centered on clinical and molecular update of HGPS and related syndromes was organised. Several international experts, including clinical and molecular geneticists, cell biologists involved in the field of laminopathies, as well as paediatricians and other physicians with clinical experience in diagnosis, treatment and research on progeria and progeria-like syndromes presented their experience as well as their research projects and yet unpublished results. The main discussed topics as well as the developing research fields on progeria and related premature ageing disorders will be presented here.

Adult↗
PubMed2003

Leigh syndrome due to compound heterozygosity of dihydrolipoamide dehydrogenase gene mutations. Description of the first E3 splice site mutation.

UNLABELLED: A boy with recurrent episodes of hypoglycaemia and ataxia, microcephaly, mental retardation, permanent lactic acidaemia, intermittent 2-oxoglutaric aciduria as well as elevation of serum branched chain amino acids was diagnosed with dihydrolipoamide dehydrogenase (E3) deficiency. Analysis of genomic DNA revealed compound heterozygosity for two novel mutations: I393T in exon 11, located at the interface domain of the protein and possibly interfering with its dimerisation, and IVS9+1G>A located at a consensus splice site. A heterozygous polymorphism was also detected. In the patient's cDNA the I393T mutation and the polymorphism appeared to be homozygous, indicating that the mRNA coming from the IVS9+1G>A mutant allele is not stable. CONCLUSION: as opposed to the non-neurological phenotype of patients with a homozygous G229C mutation, this patient developed Leigh syndrome. Dihydrolipoamide dehydrogenase and pyruvate dehydrogenase complex activities in muscle were 29% and 14% of the lowest control values, respectively. Pyruvate dehydrogenase complex activity in fibroblasts was normal, however, indicating that the biochemical examination of defects in energy metabolism should be performed in a more energy demanding tissue.

Child, Preschool↗
PubMed2003

Update of the UMD-FBN1 mutation database and creation of an FBN1 polymorphism database.

Fibrillin is the major component of extracellular microfibrils. Mutations in the fibrillin gene on chromosome 15 (FBN1) were first described in the heritable connective disorder, Marfan syndrome (MFS). FBN1 has also been shown to harbor mutations related to a spectrum of conditions phenotypically related to MFS, called "type-1 fibrillinopathies." In 1995, in an effort to standardize the information regarding these mutations and to facilitate their mutational analysis and identification of structure/function and phenotype/genotype relationships, we created a human FBN1 mutation database, UMD-FBN1. This database gives access to a software package that provides specific routines and optimized multicriteria research and sorting tools. For each mutation, information is provided at the gene, protein, and clinical levels. This tool is now a worldwide reference and is frequently used by teams working in the field; more than 220,000 interrogations have been made to it since January 1998. The database has recently been modified to follow the guidelines on mutation databases of the HUGO Mutation Database Initiative (MDI) and the Human Genome Variation Society (HGVS), including their approved mutation nomenclature. The current update shows 559 entries, of which 421 are novel. UMD-FBN1 is accessible at www.umd.be/. We have also recently developed a FBN1 polymorphism database in order to facilitate diagnostics.

Animals↗