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Biomedical subjects

L Tranebjaerg

Publications and source records attributed to L Tranebjaerg.

At least 73 records · Page 4Linked to original sources
PubMed1997

IsK and KvLQT1: mutation in either of the two subunits of the slow component of the delayed rectifier potassium channel can cause Jervell and Lange-Nielsen syndrome.

The Jervell and Lange-Nielsen syndrome (JLNS) comprises profound congenital sensorineural deafness associated with syncopal episodes. These are caused by ventricular arrhythmias secondary to abnormal repolarisation, manifested by a prolonged QT interval on the electrocardiogram. Recently, in families with JLNS, Neyroud et al. reported homozygosity for a single mutation in KVLQT1 , a gene which has previously been shown to be mutated in families with dominantly inherited isolated long QT syndrome [Neyroud et al . (1997) Nature Genet ., 15, 186-189]. We have analysed a group of families with JLNS and shown that the majority are consistent with mutation at this locus: five families of differing ethnic backgrounds were homozygous by descent for markers close to the KVLQT1 gene and a further three families from the same geographical region were shown to be homozygous for a common haplotype and to have the same homozygous mutation of the KVLQT1 gene. However, analysis of a single small consanguineous family excluded linkage to the KVLQT1 gene, establishing genetic heterogeneity in JLNS. The affected children in this family were homozygous by descent for markers on chromosome 21, in a region containing the gene IsK . This codes for a transmembrane protein known to associate with KVLQT1 to form the slow component of the delayed rectifier potassium channel. Sequencing of the affected boys showed a homozygous mutation, demonstrating that mutation in the IsK gene may be a rare cause of JLNS and that an indistinguishable phenotype can arise from mutations in either of the two interacting molecules.

Chromosomes, Human, Pair 21↗
PubMed1997

alpha-Mannosidosis: functional cloning of the lysosomal alpha-mannosidase cDNA and identification of a mutation in two affected siblings.

a-Mannosidosis (MIM 248500) is an autosomal recessive lysosomal storage disorder resulting from deficient activity of lysosomal alpha-mannosidase (LAMAN) (EC 3.2.1.24). The disease is characterized by massive intracellular accumulation of mannose-rich oligosaccharides with resulting mental retardation, hearing loss, immune deficiency and skeletal changes. We report here the purification and characterization of human placenta LAMAN. The enzyme is synthesized as a single-chain precursor which is processed into three glycopeptides of 70, 42 and 15 kDa. The 70 kDa peptide is further partially proteolysed into three more peptides that are joined by disulfide bridges. The laman cDNA sequence was assembled from overlapping fragments obtained by PCR on human fibroblast and human lung cDNA. The deduced amino acid sequence contains a putative signal peptide of 48 amino acids followed by a polypeptide sequence of 962 amino acids. Northern blot analyses revealed a single transcript of approximately 3.5 kb present in all tissues examined but at varying levels. Two affected siblings of Palestinian origin were homozygous for a mutation that causes a His-->Leu replacement at a position which is conserved among class 2 alpha-mannosidases from several species.

Amino Acid Sequence↗
PubMed1997

Macrocephaly with cutis marmorata, haemangioma and syndactyly--a distinctive overgrowth syndrome.

We describe nine children with a similar pattern of features including macrocephaly and cutis marmorata telangiectatica congenita. All were large at birth and had a distinctive capillary haemangioma involving the philtrum and upper lip. The seven who survived all developed hydrocephalus and had developmental delay. Six developed body asymmetry and three had internal arteriovenous malformations. Syndactyly of the second and third toes and/or the third and fourth fingers or toes was commonly seen. All of the cases were sporadic. This condition is easily recognizable and should be considered in the differential diagnosis of patients presenting with overgrowth and macrocephaly.

Abnormalities, Multiple↗
PubMed1996

XLMR genes: update 1996.

A current list of all known forms of X-linked mental retardation (XLMR) and a slightly revised classification are presented. The number of known disorders has not increased because 6 disorders have been combined based on new molecular data or on clinical grounds and only 6 newly described XLMR disorders have been reported. Of the current 105 XLMR disorders, 34 have been mapped, and 18 disorders and 1 nonspecific XLMR (FRAXE) have been cloned. The number of families with nonspecific XLMR with a LOD score of > or = 2.0 has more than doubled, with 42 (including FRAXE) now being known. a summary of the localization of presumed nonspecific mental retardation (MR) genes from well-studied X-chromosomal translocations and deletions is also included. Only 10-12 nonoverlapping loci are required to explain all localizations of nonspecific MR from both approaches. These new trends mark the beginning of a significantly improved understanding of the role of genes on the X chromosome in producing MR. Continued close collaboration between clinical and molecular investigators will be required to complete the process.

Chromosome Mapping↗
PubMed1996

Inheritance of skewed X chromosome inactivation in a large family with an X-linked recessive deafness syndrome.

A new X-linked recessive deafness syndrome was recently reported and mapped to Xq22 (Mohr-Tranebjaerg syndrome). In addition to deafness, the patients had visual impairment, dystonia, fractures, and mental deterioration. The female carriers did not have any significant manifestations of the syndrome. We examined X chromosome inactivation in 8 obligate and 12 possible carriers by using a polymerase chain reaction analysis of the methylation-dependent amplification of the polymorphic triplet repeat at the androgen receptor locus. Seven of 8 obligate carriers and 1 of 5 carriers by linkage analysis had an extremely skewed pattern in blood DNA not found in 30 normal females. The X inactivation pattern in fibroblast DNA from 2 of the carriers with the extremely skewed pattern was also skewed but to a lesser degree than in blood DNA. One obligate carrier had a random X inactivation pattern in both blood and fibroblast DNA. A selection mechanism for the skewed pattern is therefore not likely. The extremely skewed X inactivation in 8 females of 3 generations in this family may be caused by a single gene that influences skewing of X chromosome inactivation.

Deafness↗
PubMed1996

A novel X-linked gene, DDP, shows mutations in families with deafness (DFN-1), dystonia, mental deficiency and blindness.

In 1960, progressive sensorineural deafness (McKusick 304,700, DFN-1) was shown to be X-linked based on a description of a large Norwegian pedigree. More recently, it was shown that this original DFN-1 family represented a new type of recessive neurodegenerative syndrome characterized by postlingual progressive sensorineural deafness as the first presenting symptom in early childhood, followed by progressive dystonia, spasticity, dysphagia, mental deterioration, paranoia and cortical blindness. This new disorder, termed Mohr-Tranebjaerg syndrome (referred to here as DFN-1/MTS) was mapped to the Xq21.3-Xq22 region2. Using positional information from a patient with a 21-kb deletion in chromosome Xq22 and sensorineural deafness along with dystonia, we characterized a novel transcript lying within the deletion as a candidate for this complex syndrome. We now report small deletions in this candidate gene in the original DFN-1/MTS family, and in a family with deafness, dystonia and mental deficiency but not blindness. This gene, named DDP (deafness/ dystonia peptide), shows high levels of expression in fetal and adult brain. The DDP protein demonstrates striking similarity to a predicted Schizosaccharomyces pombe protein of no known function. Thus, is it likely that the DDP gene encodes an evolutionarily conserved novel polypeptide necessary for normal human neurological development.

Abnormalities, Multiple↗
PubMed1996

Identification of a new locus for autosomal dominant non-syndromic hearing impairment (DFNA7) in a large Norwegian family.

Hereditary hearing impairment affects about 1 in 1000 newborns. In most cases hearing loss is non-syndromic with no other clinical features, while in other families deafness is associated with specific clinical abnormalities. Analysis of large families with non-syndromic and syndromic deafness have been used to identify genes or gene locations that cause hearing impairment. The present report describes a large Norwegian family with autosomal dominant non-syndromic, progressive high tone hearing loss with linkage to 1q21-q23. A maximum LOD score of 7.65 (theta = 0.00) was obtained with the microsatellite marker D1S196. Analysis of recombinant individuals maps the deafness gene (DFNA7) to a 22 cM region between D1S104 and D1S466. The region contains several attractive candidate genes. This report supports the idea of extensive genetic heterogeneity in hereditary hearing impairment and represents the first localization of a deafness gene in a Norwegian family.

Adolescent↗
PubMed1996

Full-field electroretinograms in a family with Mohr-Tranebjaerg syndrome.

A family with a newly detected X-linked syndrome including sensorineural deafness, mental retardation, dystonia and blindness was examined with full-field electroretinography in order to order to find out if the blindness was caused by a retinal degeneration. Six affected males and 2 obligate carriers showed no signs of retinal degeneration. One of 7 affected males had central areolar choroidal dystrophy confirmed by central scotomas in visual fields and an electroretinographic pattern consisting of an attenuated amplitude as well as a prolonged implicit time of the cone b-wave on stimulation with 30 Hz flickering white light.

Adult↗
PubMed1996

Mutation spectrum in patients with Wiskott-Aldrich syndrome and X-linked thrombocytopenia: identification of twelve different mutations in the WASP gene.

Twelve different mutations in the WASP gene were found in twelve unrelated families with Wiskott-Aldrich syndrome (WAS) or X-linked thrombocytopenia (XLT). Four frameshift, one splice, one nonsense mutation, and one 18-base-pair deletion were detected in seven patients with WAS. Only missense mutations were found in five patients diagnosed as having XLT. One of the nucleotide substitutions in exon 2 (codon 86) results in an Arg to Cys replacement. Two other nucleotide substitutions in this codon, R86L and R86H, have been reported previously, both giving rise to typical WAS symptoms, indicating a mutational hot spot in this codon. The finding of mutations in the WASP gene in both WAS and XLT gives further evidence of these syndromes being allelic. The relatively small size of the WASP gene facilitates the detection of mutations and a reliable diagnosis of both carriers and affected fetuses in families with WAS or XLT.

Base Sequence↗
PubMed1995

[Alpha-mannosidosis].

Alpha-mannosidosis is a rare autosomal recessively inherited lysosomal storage disorder. We describe three patients with alpha-mannosidosis who were born in Tromsø between 1983 and 1987, in order to increase awareness of the disease. It is characterized by a typical facial look, with a prominent forehead, hypertelorism, small nose, flat nasal bridge and hypoplastic teeth. The patients are mentally retarded, often have dysostosis multiplex, recurrent infections and typically severe loss of hearing and delayed speech development. The disease is slowly progressive in the first decade, but shows considerable clinical variability. In most cases, the lymphocytes are vacuolized, but diagnosis depends on measurement of alpha-mannosidase activity in the lymphocytes. Prenatal diagnosis is available, based on chorionic villi sampling in the 9th to 11th week of pregnancy. No causal therapy is known, but establishment of the diagnosis is important to avoid complications, recognize hearing loss and provide speech therapy and special education. The specific diagnosis is critical for genetic counselling and prenatal diagnosis. The authors therefore outline the diagnostic strategy.

Abnormalities, Multiple↗
PubMed1995

Genes and languages in Europe: an analysis of mitochondrial lineages.

When mitochondrial DNA sequence variation is analyzed from a sample of 637 individuals in 14 European populations, most populations show little differentiation with respect to each other. However, the Saami distinguish themselves by a comparatively large amount of sequence difference when compared with the other populations, by a different distribution of sequence diversity within the population, and by the occurrence of particular sequence motifs. Thus, the Saami seem to have a long history distinct from other European populations. Linguistic affiliations are not reflected in the patterns of relationships of mitochondrial lineages in European populations, whereas prior studies of nuclear gene frequencies have shown a correlation between genetic and linguistic evolution. It is argued that this apparent contradiction is attributable to the fact that genetic lineages and gene frequencies reflect different time perspectives on population history, the latter being more in concordance with linguistic evolution.

Base Sequence↗
PubMed1995

A new X linked recessive deafness syndrome with blindness, dystonia, fractures, and mental deficiency is linked to Xq22.

X linked recessive deafness accounts for only 1.7% of all childhood deafness. Only a few of the at least 28 different X linked syndromes associated with hearing impairment have been characterised at the molecular level. In 1960, a large Norwegian family was reported with early onset progressive sensorineural deafness, which was indexed in McKusick as DFN-1, McKusick 304700. No associated symptoms were described at that time. This family has been restudied clinically. Extensive neurological, neurophysiological, neuroradiological, and biochemical, as well as molecular techniques, have been applied to characterise the X linked recessive syndrome. The family history and extensive characterisation of 16 affected males in five generations confirmed the X linked recessive inheritance and the postlingual progressive nature of the sensorineural deafness. Some obligate carrier females showed signs of minor neuropathy and mild hearing impairment. Restudy of the original DFN-1 family showed that the deafness is part of a progressive X linked recessive syndrome, which includes visual disability leading to cortical blindness, dystonia, fractures, and mental deficiency. Linkage analysis indicated that the gene was linked to locus DXS101 in Xq22 with a lod score of 5.37 (zero recombination). Based on lod-1 support interval of the multipoint analysis, the gene is located in a region spanning from 5 cM proximal to 3 cM distal to this locus. As the proteolipid protein gene (PLP) is within this region and mutations have been shown to be associated with non-classical PMD (Pelizaeus-Merzbacher disease), such as complex X linked hereditary spastic paraplegia, PLP may represent a candidate gene for this disorder. This family represents a new syndrome (Mohr-Tranebjaerg syndrome, MTS) and provides significant new information about a new X linked recessive sydromic type of deafness which was previously thought to be isolated deafness.

Adolescent↗
PubMed1995

Prenatal diagnosis of osteogenesis imperfecta.

The lethal perinatal types (II A-C) of osteogenesis imperfecta are reported to occur in approximately 1:55000 births. We here present three cases in three unrelated families, diagnosed by antenatal ultrasound within one year. A reliable diagnosis of the lethal perinatal type of osteogenesis imperfecta can be made by ultrasound examination during the second trimester, by identification of fractures of the long bones. The compression of the fetal head by the ultrasound probe and the low echogeneity of the cranium, should raise the suspicion of skeletal dysplasia, but is not diagnostic for osteogenesis imperfecta. The diagnosis is confirmed by postmortem examination including radiography and biochemical studies of cultivated fibroblasts from the fetus. Although rare, this lethal condition should be recognized when an ultrasound examination is performed, to prevent unnecessary obstetric intervention. In families with a previously affected fetus, prenatal diagnosis by first trimester transvaginal ultrasound investigation or chorionic villus sampling should be discussed.

Adult↗
PubMed1995

Fluorescent detection of microsatellite polymorphisms: properdin deficiency linked to PFC microsatellite.

Microsatellite polymorphisms are widely used to map the genes responsible for inherited disorders. The most commonly used detection is based on radioactive labelling and autoradiography. We now present the successful detection of fluorescence-labelled allelic fragments on an automated DNA sequencer. This allows for safer and quicker detection as well as a potential for more efficient processing of the data, e.g. for linkage analysis. The system was tested in the mapping of properdin deficiency, an X-linked condition with increased risk for a severe infection in the affected.

DNA, Satellite↗
PubMed1994

Prevalence of fra(X) in the county of Funen in Denmark is lower than expected.

Population based cytogenetic fra(X) surveys have not previously been reported from Denmark. In the present study we present an estimate of fra(X) based on 1) information from the Danish Central Cytogenetic Registry of diagnosed fra(X) males of all age groups in all Denmark in the period 1980-1992 and 2) a systematic cytogenetic fra(X) survey of 175 of 8-10-year-old children with special educational needs resident in a defined, demographically representative area of Denmark (the county of Funen). The study was performed in 1988-90 before the cloning of the FMR-1 gene. In the county of Funen there were 7,837 male children in the age group of 8-10 years. In the cytogenetic survey of learning disabled children, no fra(X) positive was diagnosed. There were 99 registered males with fra(X) in all Denmark, equivalent to a prevalence of 0.04 per 1,000 males (confidence interval 0.032:1,000-0.048:1,000). Molecular fra(X) surveys of different, large populations are needed in order to estimate the frequency of fra(X) and clarify whether significant differences in prevalence exist in different populations.

Child↗
PubMed1994

Clinical diagnosis of the Usher syndromes. Usher Syndrome Consortium.

The Usher syndromes are genetically distinct disorders which share specific phenotypic characteristics. This paper describes a set of clinical criteria recommended for the diagnosis of Usher syndrome type I and Usher syndrome type II. These criteria have been adopted by the Usher Syndrome Consortium and are used in studies reported by members of this Consortium.

Diagnosis, Differential↗