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Biomedical subjects

R Bonshek

Publications and source records attributed to R Bonshek.

At least 19 recordsLinked to original sources
PubMed2001

Missense mutations in COL8A2, the gene encoding the alpha2 chain of type VIII collagen, cause two forms of corneal endothelial dystrophy.

Corneal clarity is maintained by its endothelium, which functions abnormally in the endothelial dystrophies, leading to corneal opacification. This group of conditions includes Fuchs' endothelial dystrophy of the cornea (FECD), one of the commonest indications for corneal transplantation performed in developed countries, posterior polymorphous dystrophy (PPCD) and the congenital hereditary endothelial dystrophies (CHED). A genome-wide search of a three-generation family with early-onset FECD demonstrated significant linkage with D1S2830 (Z(max) = 3.72, theta = 0.0). Refinement of the critical region defined a 6-7 cM interval of chromosome 1p34.3-p32 within which lies the COL8A2 gene. This encodes the 703 amino acid alpha2 chain of type VIII collagen, a short-chain collagen which is a component of endothelial basement membranes and which represented a strong candidate gene. Analysis of its coding sequence defined a missense mutation (gln455lys) within the triple helical domain of the protein in this family. Mutation analysis in patients with FECD and PPCD demonstrated further missense substitutions in familial and sporadic cases of FECD as well as in a single family with PPCD. This is the first description of the molecular basis of any of the corneal endothelial dystrophies or of mutations in type VIII collagen in association with human disease. This suggests that the underlying pathogenesis of FECD and PPCD may be related to disturbance of the role of type VIII collagen in influencing the terminal differentiation of the neural crest derived corneal endothelial cell.

Amino Acid Sequence↗
PubMed2000

Ultrastructural localization of sulfated and unsulfated keratan sulfate in normal and macular corneal dystrophy type I.

Keratan sulfate (KS) proteoglycans are of importance for the maintenance of corneal transparency as evidenced in the condition macular corneal dystrophy type I (MCD I), a disorder involving the absence of KS sulfation, in which the cornea becomes opaque. In this transmission electron microscope study quantitative immuno- and histochemical methods have been used to examine a normal and MCD I cornea. The monoclonal antibody, 5-D-4, has been used to localize sulfated KS and the lectin Erythrina cristagalli agglutinin (ECA) to localize poly N -acetyllactosamine (unsulfated KS). In normal cornea high levels of sulfated KS were detected in the stroma, Bowman's layer, and Descemet's membrane and low levels in the keratocytes, epithelium and endothelium. Furthermore, in normal cornea, negligible levels of labeling were found for N -acetyllactosamine (unsulfated KS). In the MCD I cornea sulfated KS was not detected anywhere, but a specific distribution of N -acetyllactosamine (unsulfated KS) was evident: deposits found in the stroma, keratocytes, and endothelium labeled heavily as did the disrupted posterior region of Descemet's membrane. However, the actual cytoplasm of cells and the undisrupted regions of stroma revealed low levels of labeling. In conclusion, little or no unsulfated KS is present in normal cornea, but in MCD I cornea the abnormal unsulfated KS was localized in deposits and did not associate with the collagen fibrils of the corneal stroma. This study has also shown that ECA is an effective probe for unsulfated KS.

Adult↗
PubMed2000

Late onset lattice corneal dystrophy with systemic familial amyloidosis, amyloidosis V, in an English family.

AIMS: To establish a clinical and molecular diagnosis in a family with late onset lattice corneal dystrophy. METHODS: Linkage analysis, single strand conformation polymorphism (SSCP) analysis, and direct sequencing of genomic DNA were performed. A review of the patients' clinical symptoms and signs was undertaken. RESULTS: Linkage to chromosome 9q34 was established and a mutation in the gelsolin gene was found in affected individuals. Numerous symptoms experienced by the patients were attributable to this mutation. CONCLUSION: A diagnosis of amyloidosis type V (familial amyloidosis, Finnish type, FAF/Meretoja syndrome/gelsolin related amyloidosis) was made. This is the first case of amyloidosis type V described in the UK. This emphasises the importance of recognition of the extraocular manifestations of eye disease both in the diagnosis and management of the patient. In addition, these findings can help molecular geneticists in their search for disease-causing mutations.

Age of Onset↗
PubMed2000

Human herpesviruses in the cornea.

AIMS: To determine the sensitivity and specificity of culture, immunohistochemistry (IHC), the polymerase chain reaction (PCR), and in situ hybridisation (ISH) for detecting herpes simplex virus (HSV-1) in the cornea of patients undergoing penetrating keratoplasty. To compare the incidence of HSV-1 in the cornea with that of varicella zoster virus (VZV), cytomegalovirus (CMV), and Epstein-Barr virus (EBV). METHODS: The corneas of 110 patients, 52 with a documented history of herpes keratitis (HSK) and 58 with non-herpetic corneal disease, were investigated using IHC, PCR, ISH, and culture. RESULTS: HSV-1 DNA and antigen were detected in 82% and 74% respectively, of corneas of patients with HSK and in 22% and 15% of corneas of patients with no history of HSK. The sensitivity of PCR and IHC was 82% and 74% with a specificity of 78% and 85%, respectively. HSV-1 DNA and antigen were found more frequently and in increased amounts in corneas of patients with a short interval between their last attack of HSK and surgery. There was a good correlation between PCR and IHC in 71%. HSV-1 was isolated by culture in 2%. Latency associated transcripts were not detected using ISH. Evidence of VZV DNA or antigen was found significantly more frequently in the corneas of patients with a history of HSK (p<0.001). No evidence of EBV or CMV was found in any cornea. CONCLUSIONS: PCR and IHC are both sensitive for the detection of HSV-1 in the cornea. A combination of PCR and IHC increases the specificity for the diagnosis of HSK to 97%. HSV-1 appears to be slowly removed from the cornea. VZV and HSV-1 may co-infect the cornea.

Carrier State↗
PubMed2000

Developmental changes in patterns of expression of tenascin-C variants in the human cornea.

PURPOSE: To study patterns of expression of alternatively spliced tenascin-C (TN-C) variants believed to mediate cellular activities in human corneal development. METHODS: Serial sections of preterm, neonatal, child, and adult globes with normal anterior segments were labeled with monoclonal antibodies to TN-C. The antibodies included BC-4 and BC-8, which recognize epitopes in conserved domains of TN-C and can thus detect all TN-C variants, and BC-2, alpha-A2, alpha-A3, alpha-IIIB, TN11, and alpha-D, which bind to epitopes in alternatively spliced fibronectin type III repeats of TN-C. Bound antibodies were localized and visualized using an avidin-biotin complex-alkaline phosphatase technique. RESULTS: BC-4 and BC-8 showed similar patterns of staining, widely observed in preterm corneas, less so in neonatal corneas, and restricted to the limbus in the child and adult. BC-2, alpha-A2, alpha-A3, alpha-IIIB, TN11, and alpha-D staining was largely localized in corneal epithelium (preterm and neonatal), limbal epithelium, mast cells, and matrix surrounding limbal vessels (preterm, neonatal, child, and adult). CONCLUSIONS: TN-C may play a role in corneal development and in growth and differentiation of stem cells because it is widely expressed in the preterm cornea, less so in the neonate, and is restricted to the limbus in the child and adult. The differential patterns of expression of TN-C variants in normal corneas (preterm and neonatal), and in the limbus (preterm, neonatal, child, and adult), suggest specific roles played by each variant, and cell type-specific expression of the different variants.

Adult↗
PubMed1999

Heterogeneity in granular corneal dystrophy: identification of three causative mutations in the TGFBI (BIGH3) gene-lessons for corneal amyloidogenesis.

Six autosomal dominant corneal dystrophies are caused by mutations in the TGFBI (BIGH3) gene on chromosome 5q31: three types of lattice corneal dystrophy (LCD), including type I and type IIIA, granular, Avellino (ACD), and Reis-Bucklers. Initially an exact genotype-phenotype correlation was reported. We report three families, with differing clinical features, all presenting with "granular" corneal dystrophy. We analysed the TGFBI gene by SSCP analysis and direct sequencing in order to further assess the genotype-phenotype correlation. We describe three separate mutations in TGFBI: one novel, one initially described as causing ACD, and one previously described. The novel mutation, R124S, is at the identical position to the mutation causing LCD type I (CDL1). We review the clinical and histological phenotypes of the corneal dystrophies and hypothesize that the ability of a mutation to cause amyloid deposition depends on the location and nature of the mutation. In addition, we suggest that the classification of the granular corneal dystrophies be revised according to mutation type and that ACD should not be classified as a distinct morphological entity.

Amyloid↗
PubMed1999

Coats' disease of the retina (unilateral retinal telangiectasis) caused by somatic mutation in the NDP gene: a role for norrin in retinal angiogenesis.

Coats' disease is characterized by abnormal retinal vascular development (so-called 'retinal telangiectasis') which results in massive intraretinal and subretinal lipid accumulation (exudative retinal detachment). The classical form of Coats' disease is almost invariably isolated, unilateral and seen in males. A female with a unilateral variant of Coats' disease gave birth to a son affected by Norrie disease. Both carried a missense mutation within the NDP gene on chromosome Xp11.2. Subsequently analysis of the retinas of nine enucleated eyes from males with Coats' disease demonstrated in one a somatic mutation in the NDP gene which was not present within non-retinal tissue. We suggest that Coats' telangiectasis is secondary to somatic mutation in the NDP gene which results in a deficiency of norrin (the protein product of the NDP gene) within the developing retina. This supports recent observations that the protein is critical for normal retinal vasculogenesis.

Amino Acid Substitution↗
PubMed1997

Keratan sulphate in the trabecular meshwork and cornea.

PURPOSE: A study was made of the distribution of keratan sulphate in the human anterior chamber. METHODS: The monoclonal antibody, 5-D-4, was used in immuno-electron microscopy to visualise keratan sulphate distribution in the anterior chamber of 16 normal eyes, 7 Fuchs' dystrophy corneas, and a macular dystrophy cornea. RESULTS: Keratan sulphate was detected in normal human aqueous humour and also on the surface of trabecular cells in the uveal meshwork. Normal corneal stroma showed an increase in keratan sulphate labelling from anterior to posterior, with marked labelling in the posterior region of Descemet's membrane. The apical surface of the corneal endothelium labelled positively, but showed considerable variation in the level of labelling from cell to cell. The macular dystrophy cornea had the classic histopathological features of a type I case, including a highly abnormal Descemet's membrane. No keratan sulphate was detected in the macular dystrophy patient's corneal stroma or serum. The Fuchs' endothelial dystrophy corneas showed a normal distribution of keratan sulphate labelling in the stroma. The Fuchs' endothelial cells labelled for keratan sulphate but were highly abnormal in appearance, often exhibiting long filopodia and appearing to be actively migrating. CONCLUSIONS: This work has shown that keratan sulphate has a much wider distribution than was previously believed. The detection of keratan sulphate on the trabecular and endothelial cell surfaces also suggests a possible role for this molecule in cell adhesion and/or migration.

Antibodies, Monoclonal↗
PubMed1995

Florid xanthelasmata (yellow lids) in orbital Wegener's granulomatosis.

AIMS: A new sign of florid xanthelasmata is described in four male patients with orbital manifestations of Wegener's granulomatosis. METHODS: The case notes of four patients with Wegener's granulomatosis, with orbital involvement accompanied by yellow lid lesions, are reviewed. RESULTS: All the patients had active Wegener's granulomatosis at the time the lid lesions were most florid. The lesions gradually resolved as the inflammatory disease was controlled with immunosuppressive agents. The lesions displayed marked asymmetry and predominantly involved the side with the most severe inflammation. Abnormalities of lipid metabolism were not identified and it is believed that the lesions developed in a susceptible anatomical region affected by a vasculitic process. CONCLUSION: A 'yellow lid' associated with orbital inflammation and is a strong pointer to the clinical diagnosis of Wegener's granulomatosis.

Adult↗
PubMed1993

Foreign body giant cell reactions and ossification associated with benign melanocytic naevi.

AIMS: To assess the incidence of foreign body giant cell reactions and ossification in benign/melanocytic naevi; and to examine their pathological features to gain an insight into their pathogenesis. METHODS: Intradermal (n = 185) and compound naevi (n = 110) from a routine histology service, together with 60 naevi submitted to an ophthalmic pathologist, were examined for foreign body reactions and ossification. Additional cases were identified prospectively in the course of routine reporting. The clinical and pathological features of positive cases were assessed. RESULTS: Foreign body reactions were identified in nine (4.9%) intradermal and four (3.6%) compound naevi, but in none of the naevi from around the eye. One intradermal naevus showed ossification. A further 11 naevi showing foreign body reaction and five showing ossification alone were identified prospectively. The 24 naevi showing a foreign body reaction had a similar age and sex distribution to controls but were more likely to occur on the head and neck. The reaction usually occurred deep to the naevus, sometimes in relation to a hair follicle, and fragments of hair or keratin were identified in most. Osteoid or bone was present within the reaction in five. In six other naevi, all from the head and neck of women, osteoid or mature bone was present deep to the naevus in the absence of a giant cell reaction. CONCLUSIONS: Foreign body giant cell reactions occur not uncommonly in relation to benign naevi, as a result of follicular damage, possibly due to trauma. The similar siting of foci of bone suggests that ossification occurs as a secondary phenomenon in these cases.

Adult↗