Sorsby Fundus Dystrophy Research Articles

A novel splice site mutation in the tissue inhibitor of the metalloproteinases-3 gene in Sorsby's fundus dystrophy with unusual clinical features.

Sorsby's fundus dystrophy (SFD) is an autosomal dominant macular dystrophy which is developed usually in the third or fourth decade of life, and is characterized by central visual loss and nyctalopia due to fundus changes of exudative or atrophic macular lesions. Its functional prognosis is usually poor because of disciform macular scars and peripheral chorioretinal atrophies. To date, five different mutations in the tissue inhibitor of the metalloproteinases-3 (TIMP3) gene have been identified in families of a wide geographic origin, all of which are missense mutations that cause replacement by cysteine of conserved amino acids in the C-terminus of exon 5 of TIMP3. We have studied two Japanese families with SFD, the first report from the Eastern world, and identified a novel 3' splice site mutation in the TIMP3 gene, namely a single base insertion at the intron 4/exon 5 junction which converts the consensus sequence CAG to CAAG in the splice acceptor site. In addition, our patients displayed a distinctive clinical expression in that they developed macular dystrophies at an approximately 30-year later age of onset and preserved functional vision until later life with essentially uninvolved peripheral retina. The present findings may provide some insight into the genotype-phenotype relationship in SFD.

Localization of the Functional Domains of Human Tissue Inhibitor of Metalloproteinases-3 and the Effects of a Sorsby's Fundus Dystrophy Mutation

A transient COS-7 cell expression system was used to investigate the functional domain arrangement of tissue inhibitor of metalloproteinases-3 (TIMP-3), specifically to assess the contribution of the amino- and carboxyl-terminal domains of the molecule to its matrix metalloproteinase (MMP) inhibitory and extracellular matrix (ECM) binding properties. Wild type TIMP-3 was entirely localized to the ECM in both its glycosylated (27 kDa) and unglycosylated (24 kDa) forms. A COOH-terminally truncated TIMP-3 molecule was found to be a non-ECM bound MMP inhibitor, whereas a chimeric TIMP molecule, consisting of the NH2-terminal domain of TIMP-2 fused to the COOH-terminal domain of TIMP-3, displayed ECM binding, albeit with a lower affinity than the wild type TIMP-3 molecule. Thus the functional domain arrangement of TIMP-3 is analogous to that seen in TIMP-1 and -2, namely that the NH2-terminal domain is responsible for MMP inhibition whereas the COOH-terminal domain is most important in mediating the specific functions of the molecule. A mutant TIMP-3 in which serine 181 was changed to a cysteine, found in Sorsby's fundus dystrophy, a hereditary macular degenerative disease, was also expressed in COS-7 cells. This gave rise to an additional 48-kDa species (possibly a TIMP-3 dimer) that retained its ability to inhibit MMPs and localize to the ECM. These data favor the hypothesis that the TIMP-3 mutations seen in Sorsby's fundus dystrophy contribute to disease progression by accumulation of mutant protein rather than by the loss of functional TIMP-3.

Exclusion of TIMP3 as a Candidate Locus in Age-related Macular Degeneration

Purpose. Age-related macular degeneration (AMD) is a genetically complex disorder. Tissue inhibitor of metalloproteinases-3 (TIMP3) on chromosome 22 has been identified as a gene that is mutated in Sorsby's fundus dystrophy, an autosomal-dominant macular dystrophy that phenotypically resembles AMD. The purpose of this study was to determine whether TIMP3 is a major susceptibility gene for the AMD phenotype. Methods. Thirty-eight multiplex families with AMD were identified in Massachusetts and North Carolina. The macular findings were graded according to a modification of the grading system used in the Age-Related Eye Disease Study, and persons with extensive intermediate drusen, any large drusen, geographic atrophy, or evidence of exudative maculopathy were coded as affected for the purpose of the analysis. Linkage analysis was performed using both model-dependent (lod score) and model-independent (sibpair) methods. For the lod score analysis, both autosomaldominant as well as recessive low penetrance affecteds only analyses were examined. Three markers, D22S280, D22S529, and D225268, linked tightly and flanking die TIMP3 locus, were chosen for die analysis. Association studies were performed by examining one randomly chosen affected person per family and comparing the patients with AMD widi a series of age, gender, and ethnically matched control subjects widi no known history of AMD. Results. Lod score analysis excluded linkage in these data for an approximately 10-cm interval surrounding the TIMP3 gene for all models tested. In addition, no significant findings were observed with either die sibpair or the association study. Conclusiom. No evidence of linkage or association or both was found between AMD and TIMP3 in these 38 families. These data suggest that although clinically similar, the genetic defect in Sorsby's fundus dystrophy is of a different cause than die majority of the genetic causes of AMD. Invest Ophthalmol Vis Sci. 1997; 38:1060-1065.

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.

Discrete expression and distribution pattern of TIMP-3 in the human retina and choroid

PURPOSE. Extracellular matrix homeostasis is dependent in part upon a family of matrix metalloproteinases and their specific inhibitors, the tissue inhibitors of metalloproteinases (TIMPs). Recently, gene defects in TIMP-3 have been identified in the affected individuals of several families with Sorsby's fundus dystrophy (SFD). Very little information is available regarding TIMP-3 function or even its existence in the retina or choroid. METHODS. We used reverse transcription-polymerase chain reaction and Northern analysis to evaluate the expression of TIMP mRNA and Western immunoblots to evaluate TIMP protein produced by select cells of the human retina and choroid. We also used these methods and immunohistochemistry to localize the TIMPs in the retina and choroid. RESULTS. TIMP-3 transcripts are found in cultured human retinal pigment epithelium (RPE), choroidal microcapillary endothelium and pericytes. RPE cells also express and secrete TIMP-3 protein, which is localized to the extracellular matrix and is not found in culture medium; TIMP-1 and -2 are found almost exclusively in the medium. Immunohistochemistry of human retina/ choroid sections shows pronounced TIMP-3 immunostaining in Bruch's membrane, particularly near the surface of the RPE and endothelial cells, presumably in their basement membranes, with minimal staining in other portions of the retina. Immunostaining for TIMP-1 is absent and for TIMP-2 is much less prevalent, but detectable in Bruch's membrane. CONCLUSIONS. TIMP-1, -2 and -3 exhibit distinctive expression patterns in the retina and choroid. This distribution and expression pattern partially explains why TIMP-3 mutations result in SFD, rather than other retinal pathologies, such as those associated with proliferative diabetic retinopathy.

Electroretinographic findings in macular dystrophy.

The flash and pattern electroretinogram were investigated in a group of families with rare forms of inherited macular dystrophy, which included Sorsby's fundus dystrophy, X-linked retinoschisis and macular dystrophy of uncertain classification and variable expression. Flash electroretinograms, under both photopic and scotopic conditions, were attenuated in both Sorsby's fundus dystrophy and X-linked retinoschisis--with some effect on implicit time being noted in the latter condition--but in the unknown group the effect was less demonstrable, only 50% having attenuated flash electroretinograms. Pattern electroretinograms were reduced in all three conditions and in almost all cases. The study demonstrates that some so-called macular dystrophies also have widespread abnormalities affecting the peripheral retina. These findings may contribute to a better understanding of the underlying pathophysiologic mechanisms in these rare forms of retinal dysfunction.

A review of tissue inhibitor of metalloproteinases-3 (TIMP-3) and experimental analysis of its effect on primary tumor growth.

The family of tissue inhibitors of metalloproteinases (TIMPs) presently numbers four distinct gene products that are specific inhibitors of the matrix metalloproteinases (MMPs). The local balance between MMPs and TIMPs is believed to play a major role in extracellular matrix (ECM) remodeling during development and in diseases such as cancer and arthritis. Unlike the other TIMPs, which are soluble. TIMP-3 is unique in being a component of ECM. Mutations in the human TIMP-3 gene cause a dominantly inherited, adult-onset blindness (Sorsby's fundus dystrophy or SFD). In this article, we summarize what is currently known about TIMP-3, discuss possible mechanisms leading up to SFD, and investigate the effect of TIMP-3 on tumor growth. Breast carcinoma and malignant melanoma cell lines were transfected with TIMP-3 expression plasmids and injected subcutaneously into nude mice. Growth curves of the resulting tumors over a period of 6 to 8 weeks demonstrated that increased expression of TIMP-3 resulted in a statistically significant suppression of tumor growth. Deposition of TIMP-3 in the surrounding ECM by tumor cells may inhibit tumor growth by preventing local expansion of tumor, retarding the release of growth factors sequestered in ECM, or inhibiting angiogenesis. TIMP-3 over-expression had no effect on the growth of the two tumor cell lines in vitro. Because recombinant TIMP-3 inhibits endothelial cell migration and tube formation in response to angiogenic factors, we believe that the effect of TIMP-3 on tumor growth seen in this study may be a consequence of its angiostatic action.

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.

Sorsby's fundus dystrophy in the British Isles: demonstration of a striking founder effect by microsatellite-generated haplotypes.

Sorsby's fundus dystrophy (SFD) has been mapped to a genetic interval of 8 cM between loci D22S275 and D22S278. A total of 15 families, unrelated on the basis of genealogy and expressing the SFD phenotype were identified from a large data base of genetic eye disease families originating from diverse parts of the British Isles. The identification of the same Ser181Cys mutation cosegregating with disease in each family led us to consider the hypothesis of a founder effect being present. In all families studied, the same relatively infrequent allele (occurring in just 11% of the control group) was associated with disease at marker locus D22S280. A highly significant disease-associated haplotype, spanning across 3 cM of the SFD locus, was conserved in 11 of the 15 families (68% of all affected chromosomes); a further extended haplotype spanning up to 7 cM, was identified in 5 families (27% of SFD-associated chromosomes) and possibly represents the ancestral haplotype. This haplotype analysis has refined the TIMP3 gene localization to a 1- to 3-cM interval between marker loci D22S273 and D22S281 and provides strong evidence for a single mutational event being responsible for the majority of SFD identified in the British Isles.

Night blindness in Sorsby's fundus dystrophy reversed by vitamin A

Sorsby's fundus dystrophy (SFD) is an autosomal dominant retinal degeneration caused by mutations in the tissue inhibitor of metalloproteinases-3 (TIMP3) gene. Mechanisms of the visual loss in SFD, however, remain unknown. In a SFD family with a novel TIMP3 point mutation, we tested a hypothesis that their night blindness is due to a chronic deprivation of vitamin A at the level of the photoreceptors caused by a thickened membrane barrier between the photoreceptor layer and its blood supply. Vitamin A at 50,000 IU/d was administered orally. Within a week, the night blindness disappeared in patients at early stages of disease. Nutritional night blindness is thus part of the pathophysiology of this genetic disease and vitamin A supplementation can lead to dramatic restoration of photoreceptor function.

The Gene Structure of Tissue Inhibitor of Metalloproteinases (TIMP)-3 and Its Inhibitory Activities Define the Distinct TIMP Gene Family

Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) play a critical role in extracellular matrix homeostasis. We have previously cloned human and mouse TIMP-3 cDNAs and mapped their chromosomal loci (Apte, S. S., Mattei, M-G., and Olsen, B. R. (1994) Genomics 19, 86-90; Apte, S. S., Hayashi, K., Seldin, M. F., Mattei, M-G., Hayashi, M., and Olsen, B. R. (1994) Dev. Dynam. 200, 177-197); the identification of TIMP3 mutations in Sorsby's fundus dystrophy has underscored the functional importance of TIMP-3. We now report that TIMP-3 is encoded by five exons spanning over 30 kilobase pairs of mouse genomic DNA. In the attribution of protein domains to specific exons, as well as exon structures, the Timp-3 and Timp-1 genes are similar, confirming the common evolutionary origin of the TIMPs and defining a distinct gene family. We have expressed human and mouse TIMP-3 in mouse NSO myeloma cells. In each case, an N-glycosylated 27-kDa protein was generated, that, like TIMP-1 and TIMP-2, inhibited collagenase-1, stromelysin-1, and gelatinases A and B. TIMP-3 and TIMP-1 inhibition were quantitatively similar, implying that all TIMPs are equally efficient in MMP inhibition. Instead, differential regulation of the TIMP genes or divergent C-terminal protein sequences may underlie distinct biological functions for each TIMP.

Linkage refinement localises Sorsby fundus dystrophy between markers D22S275 and D22S278.

Sorsby fundus dystrophy is an autosomal dominant disorder which both clinically and histopathologically bears striking similarities to age related macular degeneration, one of the leading causes of blindness in the developed world. Recent studies have suggested a genetic localisation of the disease to chromosome 22q in a large genetic interval of approximately 25 cM. Independent genetic linkage analysis in a six generation British pedigree confirms linkage to the chromosome 22q region. A maximum two point lod score of 7.09 with no recombination was obtained with marker D22S280. Haplotype data positioned the disease between loci D22S275 and D22S278, thus significantly reducing the region on chromosome 22q where the gene is located.

SORSBY??S FUNDUS DYSTROPHY

The authors studied the variable expressivity of the phenotype and molecular genetics of a South African family with the fundus appearance of Sorsby's fundus dystrophy. Seventeen members of a single family underwent examination. Five of these were affected. Clinical details of five other affected family members were obtained from their ophthalmologists. Patients were questioned about age of onset, history of night blindness, and color defects. Examination included fundoscopy, color testing, color photographs, and fluorescein angiography. Blood for molecular genetic analysis was taken from 23 family members. The age of onset of symptoms was 29 to 56 years, and the rate of progression was variable. Sudden decreased vision was associated with subretinal choroidal neovascularization. Slower visual decline was associated with central chorioretinal atrophy. Progressive retinal pigment epithelial atrophy and peripheral pigment clumping occurred in elderly relatives who lost ambulatory vision. DNA studies show linkage to the long arm of chromosome 22 and a point mutation in the tissue inhibitor of metalloproteinases-3 gene. This South African family presents with a dominantly inherited fundus dystrophy with clinical and molecular features compatible with Sorsby's fundus dystrophy.

A novel Ser156Cys mutation in the tissue inhibitor of metalloproteinases-3 (TIMP3) in Sorsby's fundus dystrophy with unusual clinical features.

Journal Article A novel Ser156Cys mutation in the tissue inhibitor of metalloproteinases-3 (TIMP3) in Sorsby's fundus dystrophy with unusual clinical features Get access Ute Felbor, Ute Felbor Institut für Humangenetik, Universität WürzburgD-97074 Wurzburg Search for other works by this author on: Oxford Academic PubMed Google Scholar Heidl Stöhr, Heidl Stöhr Institut für Humangenetik, Universität WürzburgD-97074 Wurzburg Search for other works by this author on: Oxford Academic PubMed Google Scholar Thomas Amann, Thomas Amann 1Augenklinik mit Poliklinik, Universität Erlangen-NürnbergD-91054 Erlangen, Germany Search for other works by this author on: Oxford Academic PubMed Google Scholar Ulrich Schönherr, Ulrich Schönherr 1Augenklinik mit Poliklinik, Universität Erlangen-NürnbergD-91054 Erlangen, Germany Search for other works by this author on: Oxford Academic PubMed Google Scholar Bernhard H.F. Weber Bernhard H.F. Weber * *To whom correspondence should be addressed Search for other works by this author on: Oxford Academic PubMed Google Scholar Human Molecular Genetics, Volume 4, Issue 12, December 1995, Pages 2415–2416, https://doi.org/10.1093/hmg/4.12.2415 Published: 01 December 1995 Article history Received: 08 August 1995 Revision received: 13 September 1995 Accepted: 13 September 1995 Published: 01 December 1995

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.

Sorsby's fundus dystrophy is genetically linked to chromosome 22q13-qter.

Sorsby's fundus dystrophy (SFD) is an autosomal dominant macular degeneration developing in the third or fourth decade. Patients lose central vision from subretinal neovascularization and atrophy of the choriocapillaris, pigment epithelium and retina. SFD shares some striking clinical features with age-related macular degeneration (AMD), the most common cause of blindness in western countries thereby providing a valuable genetic model for AMD. To map the SFD locus, we performed linkage analysis in a single large SFD family. After exclusion of approximately 65% of the autosomal genome, we found significant linkage to several markers from chromosome 22. Recombinant chromosomes sublocalize the SFD gene to 22q13-qter between D22S275 and D22S274.

RECURRENT CHOROIDAL NEOVASCULARIZATION AFTER LASER PHOTOCOAGULATION IN SORSBYʼS FUNDUS DYSTROPHY

Patients with autosomal dominant Sorsby's fundus dystrophy are at high risk of severe visual loss due to choroidal neovascularization (CNV) during the fourth or fifth decade of life. To assess the efficacy of argon laser photocoagulation for extrafoveal well-defined CNV, we analyzed retrospectively the clinical course in 10 eyes of 7 patients who had Sorsby's fundus dystrophy with CNV 200 microns to 2,500 microns from the center of the foveal avascular zone, and who subsequently underwent laser photocoagulation. All treated eyes developed severe visual loss as a consequence of recurrent or persistent CNV occurring on the foveal side of the treatment scar, which extended under the fovea. The average time until occurrence of angiographically documented CNV after initial treatment was 8.1 +/- 8.9 weeks, but ranged from 2 weeks to 32 weeks. Retreatment for persistent or recurrent extrafoveal CNV was performed in 5 eyes, but CNV recurred in all 5. Results of this study suggest that the risk of persistence or recurrence of CNV after laser photocoagulation for extrafoveal CNV is unusually high in patients with Sorsby's fundus dystrophy, and that this treatment is ineffective in preventing severe visual loss in such patients.

Choroidal Perfusion Abnormality With Age-Related Bruch's Membrane Change

Observation of patients with Sorsby's fundus dystrophy has shown that a prolonged choroidal filling phase on fluorescein angiography may indicate the presence of diffuse thickening of Bruch's membrane. We analyzed fluorescein angiography transit photographs in 100 eyes of 100 consecutive patients with age-related changes at the level of Bruch's membrane. Of these, 26 eyes had evidence of a prolonged choroidal filling phase during the initial dye transit. We suggest that this may represent a clinical correlate of diffuse thickening of Bruch's membrane, and that the two features are causally related.

Sorsby's Fundus Dystrophy: A Light and Electron Microscopic Study

The light and electron microscopic changes in both eyes of a patient with Sorsby's fundus dystrophy are reported. The most striking finding was a 30-µm thick deposit present within Bruch's membrane that stained positive for lipids. The deposit has several unique features when compared with those found in other retinal dystrophies and in aged eyes. In addition, there was gross loss of the outer retina, the retinal pigment epithelium was discontinuous, and there was atrophy of the choriocapillaris. These findings are discussed in relation to the published clinical observations of other members of this pedigree.

Sorsby's Fundus Dystrophy

Ever since Sorsby described his pseudoinflammatory dystrophy in five families, its characteristics have been unclear. The findings in ten affected members of a seven-generation pedigree are discussed and the literature is reviewed. Patients with this dominantly inherited fundus dystrophy lose central vision between the second and fourth decade of life. Three variations in the fundus appearances were distinguished: in the first and most common, white to yellow fundus spots (which are not drusen) accompany a disciform macular degeneration; in the second, the fundus spots are absent; in the third, the yellow deposits are associated with atrophic macular degeneration. Atrophy of the retina, pigment epithelium, and choroid then slowly progresses toward the periphery. Treatment does not halt the progress of the disease. Although variations in this dystrophy may be examples of genetic heterogeneity, Sorsby's fundus dystrophy is a distinct clinical disorder.