Biomedical subjects

J S Beckmann

Publications and source records attributed to J S Beckmann.

At least 55 records · Page 3Linked to original sources

PubMed1999

Calpainopathy-a survey of mutations and polymorphisms.

Limb-girdle muscular dystrophy type 2A (LGMD2A) is an autosomal recessive disorder characterized mainly by symmetrical and selective atrophy of the proximal limb muscles. It derives from defects in the human CAPN3 gene, which encodes the skeletal muscle-specific member of the calpain family. This report represents a compilation of the mutations and variants identified so far in this gene. To date, 97 distinct pathogenic calpain 3 mutations have been identified (4 nonsense mutations, 32 deletions/insertions, 8 splice-site mutations, and 53 missense mutations), 56 of which have not been described previously, together with 12 polymorphisms and 5 nonclassified variants. The mutations are distributed along the entire length of the CAPN3 gene. Thus far, most mutations identified represent private variants, although particular mutations have been found more frequently. Knowledge of the mutation spectrum occurring in the CAPN3 gene may contribute significantly to structure/function and pathogenesis studies. It may also help in the design of efficient mutation-screening strategies for calpainopathies.

Amino Acid Sequence↗

PubMed1999

Genetic linkage of the Muckle-Wells syndrome to chromosome 1q44.

The Muckle-Wells syndrome (MWS) is a hereditary inflammatory disorder characterized by acute febrile inflammatory episodes comprising abdominal pain, arthritis, and urticaria. Progressive nerve deafness develops subsequently, and, after several years, the disease is complicated by multiorgan AA-type amyloidosis (i.e., amyloidosis derived from the inflammatory serum amyloid-associated protein) (MIM 191900) with renal involvement and end-stage renal failure. The mode of inheritance is autosomal dominant, but some sporadic cases have also been described. No specific laboratory findings have been reported. The genetic basis of MWS is unknown. Using a genomewide search strategy in three families, we identified the locus responsible for MWS, at chromosome 1q44. Our results indicate that the gene is located within a 13.9-cM region between markers D1S2811 and D1S2882, with a maximum two-point LOD score of 4. 66 (recombination fraction.00) at D1S2836 when full penetrance is assumed. Further identification of the specific gene that is responsible for MWS will therefore provide the first biological element for characterizing MWS, other than doing so on the basis of its variable clinical expression.

Abdominal Pain↗

PubMed1999

An alpha-tectorin gene defect causes a newly identified autosomal recessive form of sensorineural pre-lingual non-syndromic deafness, DFNB21.

In our efforts to identify new loci responsible for non-syndromic autosomal recessive forms of deafness, DFNB loci, we have pursued the analysis of large consanguineous affected families living in geographically isolated areas. Here, we report on the study of a Lebanese family comprising nine members presenting with a pre-lingual severe to profound sensorineural isolated form of deafness. Linkage analysis led to the characterization of a new locus, DFNB21, which was assigned to chromosome 11q23-25. Already mapped to this chromosomal region was TECTA. This gene encodes alpha-tectorin, a 2155 amino acid protein which is a component of the tectorial membrane. This gene recently has been shown to be responsible for a dominant form of deafness, DFNA8/12. Sequence analysis of the TECTA gene in the DFNB21-affected family revealed a G to A transition in the donor splice site (GT) of intron 9, predicted to lead to a truncated protein of 971 amino acids. This establishes that alpha-tectorin mutations can be responsible for both dominant and recessive forms of deafness. Comparison of the phenotype of the DFNB21 heterozygous carriers with that of DFNA8/12-affected individuals supports the hypothesis that the TECTA mutations which cause the dominant form of deafness have a dominant-negative effect. The present results provide genetic evidence for alpha-tectorin forming homo- or heteromeric structures.

Base Sequence↗

PubMed1999

Dysferlin is a plasma membrane protein and is expressed early in human development.

Recently, a single gene, DYSF, has been identified which is mutated in patients with limb-girdle muscular dystrophy type 2B (LGMD2B) and with Miyoshi myopathy (MM). This is of interest because these diseases have been considered as two distinct clinical conditions since different muscle groups are the initial targets. Dysferlin, the protein product of the gene, is a novel molecule without homology to any known mammalian protein. We have now raised a monoclonal antibody to dysferlin and report on the expression of this new protein: immunolabelling with the antibody (designated NCL-hamlet) demonstrated a polypeptide of approximately 230 kDa on western blots of skeletal muscle, with localization to the muscle fibre membrane by microscopy at both the light and electron microscopic level. A specific loss of dysferlin labelling was observed in patients with mutations in the LGMD2B/MM gene. Furthermore, patients with two different frameshifting mutations demonstrated very low levels of immunoreactive protein in a manner reminiscent of the dystrophin expressed in many Duchenne patients. Analysis of human fetal tissue showed that dysferlin was expressed at the earliest stages of development examined, at Carnegie stage 15 or 16 (embryonic age 5-6 weeks). Dysferlin is present, therefore, at a time when the limbs start to show regional differentiation. Lack of dysferlin at this critical time may contribute to the pattern of muscle involvement that develops later, with the onset of a muscular dystrophy primarily affecting proximal or distal muscles.

Amino Acid Sequence↗

PubMed1999

Expression and functional characteristics of calpain 3 isoforms generated through tissue-specific transcriptional and posttranscriptional events.

Calpain 3 is a nonlysosomal cysteine protease whose biological functions remain unknown. We previously demonstrated that this protease is altered in limb girdle muscular dystrophy type 2A patients. Preliminary observations suggested that its gene is subjected to alternative splicing. In this paper, we characterize transcriptional and posttranscriptional events leading to alterations involving the NS, IS1, and IS2 regions and/or the calcium binding domains of the mouse calpain 3 gene (capn3). These events can be divided into three groups: (i) splicing of exons that preserve the translation frame, (ii) inclusion of two distinct intronic sequences between exons 16 and 17 that disrupt the frame and would lead, if translated, to a truncated protein lacking domain IV, and (iii) use of an alternative first exon specific to lens tissue. In addition, expression of these isoforms seems to be regulated. Investigation of the proteolytic activities and titin binding abilities of the translation products of some of these isoforms clearly indicated that removal of these different protein segments affects differentially the biochemical properties examined. In particular, removal of exon 6 impaired the autolytic but not fodrinolytic activity and loss of exon 16 led to an increased titin binding and a loss of fodrinolytic activity. These results are likely to impact our understanding of the pathophysiology of calpainopathies and the development of therapeutic strategies.

Alternative Splicing↗

PubMed1999

Disease taxonomy--monogenic muscular dystrophy.

The field of the autosomal recessive progressive muscular dystrophies has clarified significantly following the recent elucidation of the genetic and molecular etiology of a number of these entities. These studies illustrate how genetics provides a rationale and objective basis for a new, refined nosology. Furthermore, whereas most of these studies point towards the pivotal role played by a number of structural proteins--all directly or indirectly associated with dystrophin--a calpain protease was shown to be involved in the Réunion-type limb girdle muscular dystrophy. This discovery raises the issue of whether these mechanisms are all part of one and the same pathway or of distinct pathophysiological pathways (structuropathy versus enzymopathy) leading to similar phenotypes. Finally, all of these diseases are considered as classical monogenic traits. Some findings suggest, however, that epistatic interactions have been overlooked and that the inheritance models could be slightly more complex. These results are discussed in light of the coming challenges of the identification of genes underlying complex multifactorial traits.

Humans↗

PubMed1998

A physical map of 30,000 human genes.

A map of 30,181 human gene-based markers was assembled and integrated with the current genetic map by radiation hybrid mapping. The new gene map contains nearly twice as many genes as the previous release, includes most genes that encode proteins of known function, and is twofold to threefold more accurate than the previous version. A redesigned, more informative and functional World Wide Web site (www.ncbi.nlm.nih.gov/genemap) provides the mapping information and associated data and annotations. This resource constitutes an important infrastructure and tool for the study of complex genetic traits, the positional cloning of disease genes, the cross-referencing of mammalian genomes, and validated human transcribed sequences for large-scale studies of gene expression.

Animals↗

PubMed1998

Functional defects of a muscle-specific calpain, p94, caused by mutations associated with limb-girdle muscular dystrophy type 2A.

p94 (calpain3), a muscle-specific member of the calpain family, has been shown to be responsible for limb-girdle muscular dystrophy type 2A (LGMD2A), a form of autosomal recessive and progressive neuromuscular disorder. To elucidate the molecular mechanism of LGMD2A, we constructed nine p94 missense point mutants found in LGMD2A and analyzed their p94 unique properties. All mutants completely or almost completely lose the proteolytic activity against a potential substrate, fodrin. However, some of the mutants still possess autolytic activity and/or connectin/titin binding ability, indicating these properties are not necessary for the LGMD2A phenotypes. These results provide strong evidence that LGMD2A results from the loss of proteolysis of substrates by p94, suggesting a novel molecular mechanism leading to muscular dystrophies.

Animals↗

PubMed1998

Expression of genes (CAPN3, SGCA, SGCB, and TTN) involved in progressive muscular dystrophies during early human development.

The developmental expression pattern of four human genes, three of which are involved in progressive muscular dystrophies, was investigated. The rationale for these experiments is that these patterns might provide useful information on the pathophysiology underlying these myopathies. Despite the presence of overlapping clinical signs, the spatiotemporal expression profiles of the corresponding genes differed widely. Transcripts of alpha-sarcoglycan (SGCA) were visible as soon as myotomes were formed, and constitute, together with titin transcripts, precocious muscular system landmarks. beta-sarcoglycan (SGCB) was initially transcribed in a ubiquitous manner, and, toward the second part of the embryonic period, became specific to striated muscle, heart, and the central nervous system. Whereas titin (TTN) transcription and translation seem to be coupled, for the sarcoglycans, translation seemed restricted to skeletal muscle. Calpain3 (CAPN3) RNA was found in only skeletal muscles during the fetal period. It was, however, present earlier in the whole heart, where it selectively disappeared. Finally, evidence for differentially spliced calpain3 variants in smooth muscles was also seen. The expression profiles of these genes is suggestive of their having a role during myogenesis, knowledge of which could be pertinent to the understanding of the pathophysiology of the associated diseases.

Adult↗

PubMed1998

Pseudometabolic expression and phenotypic variability of calpain deficiency in two siblings.

Two siblings originating from Reunion Island were affected by a limb-girdle muscular dystrophy (LGMD) type 2A and carried the same two mutations in the calpain gene: 946-1 AG-->AA, affecting a splice site, and S744G. They demonstrated the clinical variability possible with calpain-3 mutations. Onset was around 20 years of age in each of them. The girl's symptoms mimicked a metabolic myopathy, while her brother, at the same age, presented a classical phenotype of LGMD in an advanced functional stage.

Adult↗

PubMed1998

Clinical, pathological, and genetic features of limb-girdle muscular dystrophy type 2A with new calpain 3 gene mutations in seven patients from three Japanese families.

We report on the clinical, pathological, and genetic features of 7 patients with limb-girdle muscular dystrophy type 2A (LGMD2A) from three Japanese families. The mean age of onset was 9.7+/-3.1 years (mean+/-SD), and loss of ambulance occurred at 38.5+/-2.1 years. Muscle atrophy was predominant in the pelvic and shoulder girdles, and proximal limb muscles. Muscle pathology revealed dystrophic changes. In two families, an identical G to C mutation at position 1080 the in calpain 3 gene was identified, and a frameshift mutation (1796insA) was found in the third family. The former mutation results in a W360R substitution in the proteolytic site of calpain 3, and the latter in a deletion of the Ca2+-binding domain.

Age of Onset↗

PubMed1998

Characterization of monoclonal antibodies to calpain 3 and protein expression in muscle from patients with limb-girdle muscular dystrophy type 2A.

Monoclonal antibodies were raised to two regions of calpain 3 (muscle-specific calcium-activated neutral protease), which is the product of the gene that is defective in limb-girdle muscular dystrophy type 2A. The antibodies produced characteristic patterns of bands on Western blots: normal calpain 3 protein was represented by bands at 94 kd, plus additional fragments at approximately 60 or 30 kd, according to the antibody used. Specificity was confirmed by the loss of all bands in patients with null gene mutations. The "normal" profile of bands was observed in muscle from 33 control subjects and 70 disease-control patients. Calpain 3 protein was found to be extremely stable in fresh human muscle, with full-size protein being detected 8 hours after the muscle had been removed. Blots of muscle from nine limb-girdle muscular dystrophy type 2A patients with defined mutations showed variation in protein expression, with seven showing a clear reduction in the abundance of protein detected. No simple relationship was found between the abundance and clinical severity. Two patients showed normal expression of the full-size 94 kd band accompanied by a clear reduction in the smaller fragments. This pattern was also observed in one patient with an undefined form of limb-girdle dystrophy. These results indicate that immunodiagnosis is feasible, but caution will need to be exercised with the interpretation of near-normal protein profiles.

Adult↗

PubMed1998

Beta-sarcoglycan: genomic analysis and identification of a novel missense mutation in the LGMD2E Amish isolate.

The sarcoglycan complex is involved in the etiology of four autosomal recessive limb-girdle muscular dystrophies (LGMD2C-F). A missense mutation (T151R) in the beta-sarcoglycan gene on chromosome 4q12 has been shown to cause a mild form of LGMD2E in 11 families from a Southern Indiana Amish community sharing a common haplotype. We now report that two sibs from another Amish family with mild LGMD2E are compound heterozygotes for chromosome 4q12 markers. In order to characterize the genetic defect in this new family, we determined the genomic organization of the beta-sarcoglycan gene. A second missense mutation (R91C) has now been identified in this LGMD2E Amish family. This mutation is also present in the homozygous state in another family of probable Amish ancestry. Finally, analysis of all the components of the dystrophin-glycoprotein complex was performed for the first time on a biopsy from a patient homozygous for the beta-sarcoglycan mutation (T151R). Interestingly, in addition to the loss of the entire sarcoglycan complex, we detected a reduction of alpha-dystroglycan which suggests a role for the sarcoglycan complex in stabilizing alpha-dystroglycan at the sarcolemma.

Adolescent↗

PubMed1998

Targeted disruption of the mouse Caspase 8 gene ablates cell death induction by the TNF receptors, Fas/Apo1, and DR3 and is lethal prenatally.

Homozygous targeted disruption of the mouse Caspase 8 (Casp8) gene was found to be lethal in utero. The Caspase 8 null embryos exhibited impaired heart muscle development and congested accumulation of erythrocytes. Recovery of hematopoietic colony-forming cells from the embryos was very low. In fibroblast strains derived from these embryos, the TNF receptors, Fas/Apo1, and DR3 were able to activate the Jun N-terminal kinase and to trigger IkappaB alpha phosphorylation and degradation. They failed, however, to induce cell death, while doing so effectively in wild-type fibroblasts. These findings indicate that Caspase 8 plays a necessary and nonredundant role in death induction by several receptors of the TNF/NGF family and serves a vital role in embryonal development.

Animals↗

PubMed1998

A gene related to Caenorhabditis elegans spermatogenesis factor fer-1 is mutated in limb-girdle muscular dystrophy type 2B.

The limb-girdle muscular dystrophies are a genetically heterogeneous group of inherited progressive muscle disorders that affect mainly the proximal musculature, with evidence for at least three autosomal dominant and eight autosomal recessive loci. The latter mostly involve mutations in genes encoding components of the dystrophin-associated complex; another form is caused by mutations in the gene for the muscle-specific protease calpain 3. Using a positional cloning approach, we have identified the gene for a form of limb-girdle muscular dystrophy that we previously mapped to chromosome 2p13 (LGMD2B). This gene shows no homology to any known mammalian gene, but its predicted product is related to the C. elegans spermatogenesis factor fer-1. We have identified two homozygous frameshift mutations in this gene, resulting in muscular dystrophy of either proximal or distal onset in nine families. The proposed name 'dysferlin' combines the role of the gene in producing muscular dystrophy with its C. elegans homology.

Adolescent↗

PubMed1998

Vocal cord and pharyngeal weakness with autosomal dominant distal myopathy: clinical description and gene localization to 5q31.

Distal myopathy refers to a heterogeneous group of disorders in which the initial manifestations are weakness and atrophy of the hands and feet. We report a family segregating an autosomal dominant distal myopathy, with multiple affected individuals in whom vocal cord and pharyngeal weakness may accompany the distal myopathy, without involvement of the ocular muscles. To our knowledge, this pedigree displays a distinct distal myopathy with the added features of pharyngeal and vocal cord dysfunction (VCPDM) that has not been previously reported. We mapped the MPD2 gene for VCPDM to chromosome 5q within a 12-cM linkage interval between markers D5S458 and D5S1972 in a large pedigree (a maximum LOD score of 12.94 at a recombination fraction of 0 for D5S393) and combined genome screening and DNA pooling successfully adapted to fluorescent markers. This technique provides for the possibility of fully automated genome scans.

Adult↗

PubMed1998

Limb-girdle muscular dystrophy in Guipúzcoa (Basque Country, Spain).

The concept of limb-girdle muscular dystrophy (LGMD) is changing rapidly due to the advances in molecular genetics. Recently, seven different gene loci have been described, demonstrating that limb-girdle muscular dystrophy is a heterogeneous syndrome, which includes different diseases with a similar phenotype. In isolated populations which have little genetic exchange with neighbouring populations, an accumulation of cases may be found. We carried out an epidemiological study in Guipúzcoa, a small mountainous Basque province in northern Spain, and found the highest prevalence rate of LGMD described so far: 69 per million. Genetic studies demonstrated that 38 cases corresponded to the LGMD2A type, due to calpain-3 gene mutations. Only one patient with alpha-sarcoglycanopathy was found, and in 12 patients the genetic defect was not identified. Moreover, the particular calpain-3 mutation predominant in Basque chromosomes (exon 22, 2362AG-->TCATCT), has only been rarely found in the rest of the world. This observation strongly suggests a founder effect in the indigenous population of Guipúzcoa. The clinical characteristics of the patients with calpain-3 gene mutations were quite homogeneous and different from the other groups (sarcoglycanopathy and unknown gene defect), allowing for a precise clinical diagnostic. The disease onset was between the ages of 8 and 15 years, in most cases in the pelvic girdle, and the patients became wheelchair-bound between 11 and 28 years after onset. No pseudohypertrophy of calves or contractures were observed. No clear correlations were found between the nature and site of the mutation and the resulting phenotype.

Adult↗

PubMed1997

Dynamic molecular combing: stretching the whole human genome for high-resolution studies.

DNA in amounts representative of hundreds of eukaryotic genomes was extended on silanized surfaces by dynamic molecular combing. The precise measurement of hybridized DNA probes was achieved directly without requiring normalization. This approach was validated with the high-resolution mapping of cosmid contigs on a yeast artificial chromosome (YAC) within yeast genomic DNA. It was extended to human genomic DNA for precise measurements ranging from 7 to 150 kilobases, of gaps within a contig, and of microdeletions in the tuberous sclerosis 2 gene on patients' DNA. The simplicity, reproducibility, and precision of this approach makes it a powerful tool for a variety of genomic studies.

Calpain↗