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Biomedical subjects

F M Pope

Publications and source records attributed to F M Pope.

At least 91 records · Page 5Linked to original sources

Type III collagen deficient EDS IV producing muscular hypotonia with abnormal muscle fibroblasts.

Muscle biopsy and fibroblast culture of a floppy child with Ehlers-Danlos syndrome type IV were studied. Biochemical analysis of the tissue showed drastically reduced amount of collagen type III. Electron microscopic examination of muscle as well as of cultured fibroblasts showed grossly dilated and dominated the cytoplasm endoplasmic reticulum. Dilatation may result from storage of an abnormal collagen type III molecule. Our observations indicate that type III collagen deficiency may be present clinically as a congenital muscle hypotonia. Specific ultrastructural abnormalities of fibroblasts found in muscle biopsy can enable the proper diagnosis.

Child↗

Platelet and coagulation studies in Ehlers-Danlos syndrome.

Fifty-one patients with Ehlers-Danlos syndrome were investigated for abnormalities of platelets and coagulation. Thirty-eight were examined prospectively and 13 retrospectively. A bleeding history was taken from all patients; only four (8%) gave no history of a bruising or bleeding tendency. Nine patients (18%) had significant haemostatic abnormalities of whom four (8%) had a platelet release defect, three (6%) had a factor XI deficiency and two (4%) had a factor XIII deficiency. Additionally 16 patients (31%) had mild abnormalities of uncertain significance of whom four (8%) had prolonged bleeding times (three in association with platelet aggregation abnormalities), 13 (26%) had platelet aggregation abnormalities and two had a positive Hess test. Twenty-four patients (47%) had normal tests for haemostasis of whom 20 (39%) had a bleeding diathesis and four (8%) had no such tendency. Results were analysed according to the type of Ehlers-Danlos syndrome, but there was no pattern to the abnormalities. The high frequency of a bleeding tendency in Ehlers-Danlos patients with normal tests for haemostasis (83%) supports the conventional explanation for this clinical feature, that defects in the structural integrity of skin and blood vessels lead to easy bruising.

Adolescent↗

Lipoid proteinosis--new immunopathological observations.

Lipoid proteinosis is described in a family of Scottish descent. Chromosome studies performed on five members were normal. Direct immunofluorescence studies performed on skin with anti-collagen antibodies showed an abnormal distribution of collagen within the skin. No abnormality was detected in DNA extracted from lymphocytes taken from five family members, when probed with gene probes to collagen types alpha 1 (I), alpha 2 (I), alpha 1 (III) and alpha 2 (V).

Adult↗

Substitution of cysteine for glycine at residue 415 of one allele of the alpha 1(I) chain of type I procollagen in type III/IV osteogenesis imperfecta.

We have examined the type I collagen in a patient with type III/IV osteogenesis imperfecta. Two forms of alpha 1(I) chain were produced, one normal and the other containing a cysteine residue within the triple helical domain of the molecule. Cysteine is not normally present in this domain of type I collagen. Peptide mapping experiments localised the mutation to peptide alpha 1(I)CB3 which spans residues 403 to 551 of the triple helix. Subsequent PCR amplification of cDNA covering this region followed by sequencing showed a G to T single base change in the GGC codon for glycine 415 generating TGC, the codon for cysteine. The effect of the mutation on the protein is to delay secretion from the cell, reduce the thermal stability of the molecule by 2 degrees C, and cause excessive post-translational modification of all chains in molecules containing one or more mutant alpha 1(I) chains. The clinical phenotype observed in this patient and the position of the mutation conform to the recent prediction of Starman et al that Gly----Cys mutations in the alpha 1(I) chain have a gradient of severity decreasing from the C-terminus to the N-terminus.

Alleles↗

Characterisation of a glycine to valine substitution at amino acid position 910 of the triple helical region of type III collagen in a patient with Ehlers-Danlos syndrome type IV.

We have studied a patient with Ehlers-Danlos syndrome type IV. Protein mapping studies of her type III collagen had indicated that cyanogen bromide fragment 9 contained the site of the mutation. Here we describe the mapping of this region for a single base mutation using a chemical modification and cleavage technique. Sequence analysis of cDNA showed a G to T mutation resulting in the substitution of glycine 910 by valine. This was confirmed by allele specific oligonucleotide hybridisation to the proband's genomic DNA.

Alleles↗

Type III collagen mutations cause fragile cerebral arteries.

Premature vascular aneurysms and fragility of cerebral arteries are commonly associated with type III collagen mutations and physical signs suggesting a generalized abnormality of connective tissue. Sometimes these traits are clearly genetically transmitted. Here we present seven examples of early cerebrovascular aneurysms or fragility including five examples of carotid cavernous sinus aneurysms. With one exception in which we suspect the mutation is too small to be detected, all of them had easily visible abnormalities of their type III collagen proteins. Further work in progress will eventually allow the characterization of their mutations at gene sequence level and will be followed by the ability to prevent transmission of the mutant genes in these families.

Adult↗

An exclusion map of Marfan syndrome.

The combined genetic data between the Marfan syndrome and 75 informative loci on 18 autosomes were used to construct an exclusion map for this disorder. Data are also presented for a further two unmapped markers. The most likely location of the Marfan syndrome gene is highlighted and all the unexcluded areas of the genome are displayed in a graphical form. This exclusion map shows that almost 75% of the genome has been excluded as a likely location for the Marfan syndrome gene in the majority of the families studied. Apart from chromosomes 8, 13, 21, and 22, for which no data were available, other regions not excluded yet include 5p, 6p, 9p, 10p, 12p, 15, 17p, 18, and 20p. Future linkage analysis using markers located in the highlighted regions should facilitate the identification of the site of the Marfan syndrome gene.

Chromosome Mapping↗

Linkage data for Marfan syndrome and markers on chromosomes 1 and 11.

Six large families with classical Marfan syndrome were studied using markers on chromosomes 1 and 11. Two of three families tested showed negative scores using D1S7 but a third family gave a positive score (0.92) at theta = 0.1. The other chromosome 1 markers typed (MUCI, NGFB, D1S8) excluded close linkage. Negative lod scores with two chromosome 11q22 markers (D11S84, D11S148) excluded at least 20 cM in this area (Z = less than -2), which was chosen for study as two enzymes responsible for collagen degradation (collagenase and stromelysin) are localised to this region.

Chromosomes, Human, Pair 1↗

Cerebrovascular disease in Ehlers-Danlos syndrome type IV.

We describe two patients with cerebrovascular complications of Ehlers-Danlos syndrome type IV. A 16-year-old girl with spontaneous internal carotid artery dissection and a 46-year-old woman with aneurysmal subarachnoid hemorrhage and multiple aortic dissections were both deficient in collagen type III, analyzed in cultured skin fibroblasts. To our knowledge, spontaneous carotid artery dissection associated with collagen type III deficiency has not been reported previously. Early clinical recognition of this syndrome is of great importance in view of the hazards of angiography and surgery. Collagen type III deficiency plays a role in the pathogenesis of intracranial saccular aneurysms and may also be involved in the pathogenesis of carotid cavernous fistulas and dissections of the cervical arteries.

Adolescent↗

Consistent linkage of dominantly inherited osteogenesis imperfecta to the type I collagen loci: COL1A1 and COL1A2.

The segregation of COL1A1 and COL1A2, the two genes which encode the chains of type I collagen, was analyzed in 38 dominant osteogenesis imperfecta (OI) pedigrees by using polymorphic markers within or close to the genes. This was done in order to estimate the consistency of linkage of OI genes to these two loci. None of the 38 pedigrees showed evidence of recombination between the OI gene and both collagen loci, suggesting that the frequency of unlinked loci in the population must be low. From these results, approximate 95% confidence limits for the proportion of families linked to the type I collagen genes can be set between .91 and 1.00. This is high enough to base prenatal diagnosis of dominantly inherited OI on linkage to these genes even in families which are too small for the linkage to be independently confirmed to high levels of significance. When phenotypic features were compared with the concordant collagen locus, all eight pedigrees with Sillence OI type IV segregated with COL1A2. On the other hand, Sillence OI type I segregated with both COL1A1 (17 pedigrees) and COL1A2 (7 pedigrees). The concordant locus was uncertain in the remaining six OI type I pedigrees. Of several other features, the presence or absence of presenile hearing loss was the best predictor of the mutant locus in OI type I families, with 13 of the 17 COL1A1 segregants and none of the 7 COL1A2 segregants showing this feature.

Chromosomes, Human, Pair 17↗

Single base mutation in the type III procollagen gene that converts the codon for glycine 883 to aspartate in a mild variant of Ehlers-Danlos syndrome IV.

Experiments were carried out to test the hypothesis that a 19-year-old proband with a mild variant of Ehlers-Danlos syndrome type IV had a mutation in the gene for type III procollagen. cDNA and genomic DNA were analyzed by using the polymerase chain reaction and cloning of the products into M13 filamentous phage. A mutation was found that converted the codon for glycine 883 of the triple-helical domain in one allele for type III procollagen to a codon for aspartate. The polymerase chain reaction introduced a few artifactual single base substitutions. Also, it was difficult to distinguish copies from the two alleles in many of the M13 clones. Therefore, several different strategies and analyses of about 50,000 nucleotide sequences in a series of clones were used to demonstrate that the mutation in the codon for glycine 883 was the only mutation in coding sequences for the triple-helical domain of type III procollagen that could have contributed to the phenotype. The same mutation in the codon for glycine 883 in one allele for type III procollagen was found in the proband's 52-year-old father who also had a mild variant of Ehlers-Danlos syndrome type IV. The type III procollagen synthesized by the proband's fibroblasts was analyzed by polyacrylamide gel electrophoresis. Less type III procollagen was secreted by the proband's fibroblasts than by control fibroblasts. Also, the thermal stability of the type III procollagen synthesized by the proband's fibroblasts was lower than the thermal stability of normal type III procollagen as assayed by brief protease digestion. The results, therefore, demonstrated that the single base mutation that converted the codon of glycine 883 to a codon for aspartate destabilized the entire triple helix of type III procollagen and probably accounted for the mild phenotype of Ehlers-Danlos syndrome type IV seen in the proband and her father.

Adult↗

A type VI collagen-related glycopolypeptide is the major concanavalin A-binding component in pig skin.

The major concanavalin A-binding component in urea/deoxycholate/mercaptoethanol extracts of pig skin was a collagenous disulphide-cross-linked glycopolypeptide with an apparent molecular mass of 150 kDa and a pI of 5.5. Antiserum against the electrophoretically purified glycopolypeptide gave strong dermal staining similar to that seen with fluorescent concanavalin A. Immunocytochemical labelling showed prominent labelling of 3-4 nm dermal microfilaments, particularly those associated with dermal blood vessels and mast cells. Immunoblotting with authentic antiserum indicated that the major skin glycopolypeptide was probably identical with collagen-like glycoprotein, the tissue form of the alpha 1/alpha 2 subunits of type VI collagen. This was confirmed by immunoblotting of authentic type VI collagen from pepsin-treated pig skin. Immunoblotting, metabolic labelling with [3H]glucosamine and immune precipitation showed that an immunoreactive collagenous glycopolypeptide was synthesized and secreted by cultured pig skin fibroblasts. The results suggest that type VI collagen is the major concanavalin A-binding component in pig skin.

Animals↗

Prenatal diagnosis and prevention of inherited abnormalities of collagen.

There is now strong evidence for the implication of collagen alpha 1(I), alpha 2(I) and alpha 1(III) mutations in many forms of osteogenesis imperfecta and inherited arterial aneurysms (Ehlers Danlos syndrome type IV). A sizeable proportion of these disorders have detectable abnormalities by conventional protein chemistry, immunofluorescence, or more sophisticated DNA analysis. Everyone of them with specific defects or with linkage to appropriate gene markers is therefore amenable to prevention using conventional prenatal diagnosis by chorionic villus biopsy (with fibroblast culture), fetoscopic biopsy (with fibroblast culture), ultrasound diagnosis of the severely deformed fetus, or gene linkage studies by chorionic villus biopsy or amniocentesis. Already many collagen alpha 1(I), alpha 2(I) and alpha 1(III) mutations have been characterized including point mutations, small and large deletions and regulatory mutations. Many others are likely to be rapidly studied by exploiting recent advances in DNA technology, and other strong candidate genes include collagen II (some chondrodystrophies), collagen VI (certain arterial and cardiovascular diseases) and collagen VII (dystrophic epidermolysis bullosa). Other important common diseases are likely to include osteoporosis, osteoarthritis and cerebral aneurysms. A detailed review is provided of collagen interstitial genes and proteins, together with a description of the various forms of osteogenesis imperfecta and Ehlers Danlos syndrome in which either collagen alpha 1(I), alpha 2(I) or alpha 1(III) mutations have been identified. Appropriate restriction length polymorphisms (RFLPs) useful in identifying carriers of these mutant genes are also described.

Collagen↗