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U Felbor

Publications and source records attributed to U Felbor.

18 recordsLinked to original sources
PubMed2001

A nonsense mutation in MSX1 causes Witkop syndrome.

Witkop syndrome, also known as tooth and nail syndrome (TNS), is a rare autosomal dominant disorder. Affected individuals have nail dysplasia and several congenitally missing teeth. To identify the gene responsible for TNS, we used candidate-gene linkage analysis in a three-generation family affected by the disorder. We found linkage between TNS and polymorphic markers surrounding the MSX1 locus. Direct sequencing and restriction-enzyme analysis revealed that a heterozygous stop mutation in the homeodomain of MSX1 cosegregated with the phenotype. In addition, histological analysis of Msx1-knockout mice, combined with a finding of Msx1 expression in mesenchyme of developing nail beds, revealed that not only was tooth development disrupted in these mice, but nail development was affected as well. Nail plates in Msx1-null mice were defective and were thinner than those of their wild-type littermates. The resemblance between the tooth and nail phenotype in the human family and that of Msx1-knockout mice strongly supports the conclusions that a nonsense mutation in MSX1 causes TNS and that Msx1 is critical for both tooth and nail development.

Adult↗
PubMed2000

Generation and degradation of human endostatin proteins by various proteinases.

The angiogenesis inhibitor endostatin is a fragment of the NC1 domain of collagen XVIII. The generation of endostatin has been investigated only in murine hemangioendothelioma cell cultures and was ascribed to cathepsin L. Distinct endostatin-like fragments were detected in human tissues and serum. To identify proteinases able to generate such fragments, we incubated human NC1 with proteinases of all classes, including cathepsin L. Eleven out of 12 generate fragments with an N-terminus within the same 15 residue stretch as those occurring physiologically, indicating that this region is sensitive to many proteinases. None correspond to mouse endostatin. However, the efficiencies of these proteinases differed markedly. Some proteinases also proved to degrade endostatin, pointing to another regulatory loop of angiogenesis.

Angiogenesis Inhibitors↗
PubMed2000

Secreted cathepsin L generates endostatin from collagen XVIII.

Endostatin, an inhibitor of angiogenesis and tumor growth, was identified originally in conditioned media of murine hemangioendothelioma (EOMA) cells. N-terminal amino acid sequencing demonstrated that it corresponds to a fragment of basement membrane collagen XVIII. Here we report that cathepsin L is secreted by EOMA cells and is responsible for the generation of endostatin with the predicted N-terminus, while metalloproteases produce larger fragments in a parallel processing pathway. Efficient endostatin generation requires a moderately acidic pH similar to the pericellular milieu of tumors. The secretion of cathepsin L by a tumor cell line of endothelial origin suggests that this cathepsin may play a role in angiogenesis. We propose that cleavage within collagen XVIII's protease-sensitive region evolved to regulate excessive proteolysis in conditions of induced angiogenesis.

Animals↗
PubMed2000

Collagen XVIII/endostatin structure and functional role in angiogenesis.

The angiogenesis inhibitor endostatin is a 20 kDA C-terminal fragment of collagen XVIII, a proteoglycan/collagen found in vessel walls and basement membranes. The endostatin fragment was originally identified in conditioned media from a murine endothelial tumor cell line. Endostatin inhibits endothelial cell migration in vitro and appears to be highly effective in murine in vivo studies. The molecular mechanisms behind the inhibition of angiogenesis have not yet been elucidated. Studies of the crystal structure of endostatin have shown a compact globular fold, with one face particularly rich in arginine residues acting as a heparin-binding epitope. It was initially suggested that zinc binding was essential for the antiangiogenic mechanism but later studies indicate that zinc has a structural rather than a functional role in endostatin. The generation of endostatin or endostatin-like collagen XVIII fragments is catalyzed by proteolytic enzymes, including cathepsin L and matrix metalloproteases, that cleave peptide bonds within the protease-sensitive hinge region of the C-terminal domain. The processing of collagen XVIII to endostatin may represent a local control mechanism for the regulation of angiogenesis.

Angiogenesis Inhibitors↗
PubMed1999

Allelic heterogeneity of alkaptonuria in Central Europe.

Defects of the homogentisate 1,2 dioxygenase (HGO; E.C. No. 1.13.11.5) have been identified as the molecular cause of alkaptonuria in humans (AKU) and the aku mouse. Here, we report on the genetic basis of 30 AKU patients from Central Europe. In addition to five mutations described previously, we have detected five novel HGO mutations. Recombinant expression of mutated HGO enzymes in E. coli demonstrates the inactivating effect of three of these mutations. A genetic epidemiologic study in Slovakia, the country with the highest incidence of alkaptonuria, demonstrates that two recurrent mutations (c.183-1G > A and Glyl61Arg) are found on more than 50% of AKU chromosomes. An analysis of the allelic association with intragenic DNA markers and of the geographic origins of the AKU chromosomes suggests that several independent founders have contributed to the gene pool, and that subsequent genetic isolation is likely to be responsible for the high prevalence of alkaptonuria in Slovakia.

Alkaptonuria↗
PubMed1999

Ocular ochronosis in alkaptonuria patients carrying mutations in the homogentisate 1,2-dioxygenase gene.

AIMS: To assess the involvement of the recently identified human homogentisate 1,2-dioxygenase gene (HGO) in alkaptonuria (AKU) in two unrelated patients with ochronosis of the conjunctiva, sclera, and cornea. METHODS: A mutation screen of the entire coding region of the HGO gene was performed using single stranded conformational analysis after polymerase chain reaction with oligonucleotide primers flanking all 14 exons of the HGO gene. Fragments showing aberrant mobility were directly sequenced. RESULTS: Two homozygous missense mutations, L25P and M368V, were identified, each of which leads to the replacement of a highly conserved amino acid in the HGO protein. CONCLUSIONS: The authors describe a novel mutation, L25P, in the German population and bring to 18 the total number of known HGO mutations.

Aged↗
PubMed1998

[Sorsby's fundus dystrophy. A genetically homogeneous disease].

BACKGROUND: The recent identification of the tissue inhibitor of metalloproteinases-3 (TIMP3) as the gene underlying SFD pathology has made it possible to address the question of genetic heterogeneity in this disorder. In addition, it now has become feasible to clarify whether SFD is directly involved in other maculopathies and, in particular, may represent a genetic model for age-related macular degeneration. PATIENTS: Genetic analysis were performed in five unrelated and 18 related British SFD pedigrees as well as in 143 patients affected with age-related macular degeneration, 28 patients with adult vitelliform macular dystrophy, 21 patients with central areolar choroidal dystrophy and 25 individuals with other forms of macular dystrophies. RESULTS: Molecular genetic analyses confirmed the autosomal dominant mode of inheritance in SFD. In all five unrelated SFD pedigrees individual TIMP3 mutations were identified introducing an additional cysteine residue into the C-terminal region of the mature protein. Affected individuals from 18 SFD families residing in Great Britain, Canada, Oregon and South Africa were found to carry a common ancestral Ser181Cys mutation. The clinical variability of this Ser181Cys mutation was reevaluated. A mutational screen in 217 patients with various maculopathies revealed no disease-causing mutations in the TIMP3 gene. CONCLUSION: So far, TIMP3 mutations have exclusively been associated with SFD. Therefore, this disorder appears to be genetically homogeneous with complete penetrance but variable expressivity.

Adult↗
PubMed1998

Assessment of the interphotoreceptor matrix proteoglycan-1 (IMPG1) gene localised to 6q13-q15 in autosomal dominant Stargardt-like disease (ADSTGD), progressive bifocal chorioretinal atrophy (PBCRA), and North Carolina macular dystrophy (MCDR1).

We have recently characterised the genomic organisation of a novel interphotoreceptor matrix proteoglycan, IMPG1, and have mapped the gene locus to chromosome 6q13-q15 by fluorescence in situ hybridisation. As the interphotoreceptor matrix (IPM) is thought to play a critical role in retinal adhesion and the maintenance of photoreceptor cells, it is conceivable that a defect in one of the IPM components may cause degenerative lesions in retinal structures and thus may be associated with human retinopathies. By genetic linkage analysis, several retinal dystrophies including one form of autosomal dominant Stargardt-like macular dystrophy (STGD3), progressive bifocal chorioretinal atrophy (PBCRA), and North Carolina macular dystrophy (MCDR1) have previously been localised to a region on proximal 6q that overlaps the IMPG1 locus. We have therefore assessed the entire coding region of IMPG1 by exon amplification and subsequent single stranded conformational analysis in patients from 6q linked multigeneration families diagnosed with PBCRA and MCDR1, as well as a single patient from an autosomal dominant STGD pedigree unlinked to either of the two known STGD2 and STGD3 loci on chromosomes 13q and 6q, respectively. No disease associated mutations were identified. In addition, using an intragenic polymorphism, IMPG1 was excluded by genetic recombination from both the PBCRA and the MCDR1 loci. However, as the autosomal dominant Stargardt-like macular dystrophies are genetically heterogeneous, other forms of this disorder, in particular STGD3 previously linked to 6q, may be caused by mutations in IMPG1.

Adult↗
PubMed1998

Genomic organization and chromosomal localization of the interphotoreceptor matrix proteoglycan-1 (IMPG1) gene: a candidate for 6q-linked retinopathies.

The interphotoreceptor matrix is a unique extracellular matrix occupying the space between the photoreceptors and the retinal pigment epithelium. Due to its putative function in the maintenance and integrity of the photoreceptor cells, it is conceivable that it is involved in retinal degeneration processes. More recently, a novel gene encoding a 150-kDa interphotoreceptor matrix proteoglycan, designated IMPG1, was cloned and shown to be expressed in both rod and cone photoreceptor cells. To assess this gene in human retinal dystrophies, we have now determined the genomic organization and chromosome location of IMPG1. It is composed of 17 exons ranging from 21 to 533 bp, including an alternatively spliced exon 2. Using somatic cell hybrid mapping and FISH analysis, we have assigned the IMPG1 locus to 6q13-->q15. As this interval overlaps with the chromosomal loci of several human retinopathies, including autosomal dominant Stargardt-like macular dystrophy (STGD3), progressive bifocal chorioretinal atrophy (PBCRA), and North Carolina macular dystrophy (MCDR1), IMPG1 represents an attractive candidate for these 6q-linked disorders.

Alternative Splicing↗
PubMed1997

Sorsby fundus dystrophy: reevaluation of variable expressivity in patients carrying a TIMP3 founder mutation.

Interfamilial phenotypic variations in Sorsby fundus dystrophy (SFD) have given rise to controversy as to whether SFD constitutes more than 1 nosologic entity. The recent identification of the tissue inhibitor of metalloproteinases-3 (TIMP3) as the gene causing SFD has made it possible to readdress the question of genetic and clinical heterogeneity. In this study, we have extended previous findings on a Ser181Cys founder mutation in SFD families from the British Isles and show that carriers of this mutation residing in Canada, the United States, and South Africa likewise are descendants of the British ancestor. In addition, we have reevaluated the question of variable SFD phenotypes by analyzing the available clinical data on carriers of the Ser181Cys mutation.

Adolescent↗
PubMed1997

Adult vitelliform macular dystrophy is frequently associated with mutations in the peripherin/RDS gene.

Mutations in the peripherin/RDS gene, which encodes a photoreceptor-specific membrane glycoprotein, have been identified in a variety of retinal phenotypes. However, the mechanisms by which specific mutations in this gene can cause typical features of retinal dystrophies clinically as distinct as retinitis pigmentosa or macular degeneration are still unknown. Recently, a single case of adult vitelliform macular dystrophy (AVMD) has been associated with a Y258Stop mutation. To assess the frequency of peripherin/RDS mutations in the clinically heterogeneous group of AVMD, we analyzed the entire coding region of the gene in 28 unrelated patients. We identified five novel mutations including two presumed null allele mutations. Thus, our results demonstrate that a significant portion of AVMD patients (18%) carry point mutations in peripherin/RDS, suggesting that this gene is frequently involved in the pathogenesis of this macular disorder. In addition, this study shows that the variable phenotypes in AVMD are due, at least in part, to genetic heterogeneity and are likely to be caused by mutations in disease genes thus far unknown.

Aged↗
PubMed1997

Autosomal recessive Sorsby fundus dystrophy revisited: molecular evidence for dominant inheritance.

Sorsby fundus dystrophy (SFD) originally was characterized as an autosomal dominant disorder in which patients lose central vision during the 4th or 5th decade of life. Since Sorsby's initial description, interfamilial phenotypic variations have been noted and have given rise to controversy as to whether SFD constitutes more than one nosologic entity. In addition, several reports have proposed the existence of a recessively inherited form of SFD. The recent identification of the tissue inhibitor of metalloproteinases-3 (TIMP3) as the disease-causing gene in SFD has made it possible to address the questions of clinical and genetic heterogeneity. In this study, we reinvestigated a large, highly consanguineous Finnish family previously diagnosed as having early-onset autosomal recessive SFD. We identified a novel heterozygous Gly166Cys mutation in TIMP3 in all affected individuals and provide strong evidence for an autosomal dominant inheritance of the SFD phenotype in this family. Our results, in conjunction with a critical review of the reported cases, render the existence of a recessive mode of inheritance in SFD questionable. Considering all available data, we suggest that SFD is a genetically homogeneous, autosomal dominant condition.

Adult↗
PubMed1997

Evaluation of the gene encoding the tissue inhibitor of metalloproteinases-3 in various maculopathies.

PURPOSE: Mutations in the gene encoding the tissue inhibitor of metalloproteinases-3 (TIMP3) have been shown previously to cause Sorsby's fundus dystrophy, an autosomal-dominant disorder characterized by extracellular matrix irregularities in Bruch's membrane. To assess the involvement of TIMP3 in a variety of other macular dystrophies, the authors have screened this gene for disease-causing mutations in age-related macular degeneration (AMD), adult vitelliform macular dystrophy (AVMD), central areolar choroidal dystrophy (CACD), syndrome-associated macular dystrophies, cone-rod dystrophy, and a group with unspecified macular degeneration. METHODS: Single-stranded conformational analysis of the entire coding region was performed using the polymerase chain reaction and oligonucleotide primers flanking the five exons of the TIMP3 gene as well as the putative promotor region and a highly conserved fragment of the 3'-untranslated region. The authors analyzed a total of 217 patients, including 143 patients with AMD, 28 patients with AVMD, 21 patients with CACD, and 25 patients with other forms of macular dystrophy. RESULTS: In the 217 patients analyzed, the authors have identified one sequence alteration (a G-to-C base change) in the 5'-untranslated region in a patient with AMD. However, the functional consequences of this mutation are not clear. No other disease-causing mutations were found. The authors have characterized a frequent intragenic polymorphism in exon 3 of the TIMP3 gene (heterozygosity = 0.57) that will be useful for genetic linkage or allele sharing analyses or both. CONCLUSIONS: The authors' results suggest that TIMP3 is not a major factor in the cause of AMD, AVMD, and CACD. Thus far, Sorsby's fundus dystrophy appears to be the only phenotype known to be associated with mutations in TIMP3.

Aged↗
PubMed1996

A second independent Tyr168Cys mutation in the tissue inhibitor of metalloproteinases-3 (TIMP3) in Sorsby's fundus dystrophy.

Sorsby's fundus dystrophy (SFD) is a rare autosomal dominant macular disorder with age of onset usually in the fourth decade. It is characterised by loss of central vision owing to subretinal neovascularisation and disciform macular degeneration. In an effort to identify the SFD gene, the disease locus was first mapped to chromosome 22q13-qter by genetic linkage analysis, the same chromosomal region as the gene encoding the tissue inhibitor of metalloproteinases-3 (TIMP3). Subsequently, two separate mutations in TIMP3 were found in affected members of two unrelated SFD pedigrees (Tyr168Cys and Ser181Cys). More recently, two additional SFD related mutations, Ser156Cys and Gly167Cys, have provided further confirmation that heterozygous mutations in TIMP3 are causally responsible for the SFD phenotype. We now report the occurrence of the Tyr168Cys mutation in an SFD patient of Austrian descent and show that this mutation found earlier in an American SFD family arose independently. The new findings add to an emerging pattern of SFD mutations which all seem to affect the C-terminal region of the mature TIMP3 protein. In addition, all known mutations cause a change of an amino acid to a cysteine residue. This suggests a critical role for the additional C-terminal free thiol group in SFD pathogenesis.

Adult↗
PubMed1995

Genomic organization of the human tissue inhibitor of metalloproteinases-3 (TIMP3)

The tissue inhibitors of metalloproteinases (TIMPs) play a crucial role in the physiological turnover of the extracellular matrix (ECM) by tightly regulating matrix metalloproteinase (MMP) activities. Disturbances in the TIMP/MMP system have been implicated in many disease processes where loss of ECM integrity is a principal feature. More recently, we have shown that mutations in TIMP3 cause the autosomal dominant disorder Sorsby's fundus dystrophy (SFD). This is a macular degeneration disorder with characteristic ECM irregularities in Bruch's membrane. To further facilitate mutational analysis and to provide a basis for functional studies, we now report the genomic organization of the human TIMP3 gene.

Animals↗
PubMed1994

Mutations in the tissue inhibitor of metalloproteinases-3 (TIMP3) in patients with Sorsby's fundus dystrophy.

The hereditary macular dystrophies are progressive degenerations of the central retina and contribute significantly to irreversible visual loss in developed countries. Among these disorders, Sorsby's fundus dystrophy (SFD), an autosomal dominant condition, provides an excellent mendelian model for the study of the genetically complex age-related macular degeneration (AMD), the most common maculopathy in the elderly. Recently, we mapped the SFD locus to 22q13-qter. This same region contains the gene for tissue inhibitor of metalloproteinases-3 (TIMP3), which is known to play a pivotal role in extracellular matrix remodeling. We have now identified point mutations in the TIMP3 gene in affected members of two SFD pedigrees. These mutations are predicted to disrupt the tertiary structure and thus the functional properties of the mature protein.

Amino Acid Sequence↗
PubMed1993

[Not Available].

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Germany↗