1,721,023 research outputs found
Determination of a gene and environment risk model for age-related macular degeneration
Full text linkBackground/aims: We have recently identified an association between age-related macular degeneration (AMD) and genetic variants in the serpin peptidase inhibitor, clade G, member 1 (SERPING1) gene. In the current study we interrogated the genomic region in linkage disequilibrium (LD) with the SERPING1 gene, and modelled the contribution to disease of known genetic and environmental AMD risk factors. Methods: We analysed genes neighbouring SERPING1 and examined haplotype association with AMD. A stepwise logistic regression model was developed including known genetic and environmental risk factors (age, sex and smoking). Individual risk scores were assessed between groups of cases and controls. Results: In SERPING1 region rs2511989 remains most significantly associated (p=1.77×10?5, OR 0.67). One haplotype, containing the rs2511989 variant and the majority of SERPING1, exhibits marginally stronger association (p=5.13×10?6, OR 0.66). Our risk model includes six SNPs in CFH, C3, HTRA1 and SERPING1, showing independent effects, which together account for 45% of risk of developing AMD (p=1.65×10?50) with a combined population attributable risk of 87%. Conclusion-Results: implicate SERPING1, with no convincing evidence for involvement of other genes in the region. We demonstrate a multifactorial model with significant differences in risk scores for cases versus controls (p=9.81×10?71) and across Age-Related Eye Disease Study (AREDS) score-stratified cases (p=1.88×10?11). <br/
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Dementia of the Eye- Alzheimer’s-linked Amyloid beta proteins provide new insights into retinal degeneration
No full textPurpose: age-related Macular Degeneration (AMD) is the most common cause of irreversible blindness in the developed world for which there is no effective treatment. Advanced stages of the disease manifests as two broadly-defined phenotypes; geographic atrophy or neovascular AMD. The disease has a complex aetiology underlying a mixture of genetic and non-genetic/environmental risk factors that are still incompletely understood. Adding to this complexity is the Alzheimer’s-associated Amyloid beta (A) family of misfolding proteins which accumulate in aged and AMD retinas. The deposition of A within pathogenic deposits under the retina and its dysregulation in plasma of AMD patients offers the possibility of studying degenerative changes in the retina from a new perspective. Methods: we developed a mouse model of A-induced retinal degeneration in order to study its effects in the living retina. We then exploited a cell culture model to determine its effects at single-cell resolution.Results: sub-retinally injected human oligomeric A aggregated in murine eyes in a manner consistent with amyloid deposition in donor tissues, and caused progressive retinal degeneration. Two weeks after treatment, A injected eyes showed features similar to neovascular AMD. However, overall retinal function remained unaffected as non-invasive OCT and ERG scans revealed this damage to be highly localised. Studies at single-cell resolution revealed that A was internalised by RPE cells to accumulate within late endosomes and lysosomes. The activity of the lysosomal proteolytic enzyme cathepsin B was upregulated in response to lysosomal A cargos. However, A persisted after cathepsin B activity had returned to baseline levels suggesting a potential new mechanism through which A can accumulate within RPE lysosomes over time. The ability to degrade POS cargos were also diminished in RPE with lysosomal A, revealing an altogether novel cellular mechanism through which A can contribute to AMD.Conclusions: our findings reveal a novel disease-causing pathway in the senescent retina. They also shed light on how impaired cargo-handling processes including poor responses to the accumulation of aggregate-prone/high-molecular-weight molecules within lysosomes underpin related pathophysiologies such as Alzheimer’s disease. As an unhealthy diet and metabolic disorders are associated with increased A pathology in the eye and brain, our results provide further evidence of shared pathophysiology in these tissues.Disclosures: none<br/
Chlamydia infection status, genotype, and age-related macular degeneration
No full textPURPOSE: To evaluate whether Chlamydia (C.) infections are associated with age-related macular degeneration (AMD) and to assess if this association is influenced by the complement factor H (CFH) Y402H or the high temperature requirement A serine peptidase 1 (HTRA1) rs11200638 risk genotypes.METHODS: One hundred ninety-nine AMD patients with early and late forms of the disease and 100 unaffected controls, at least 50 years old were included in the study. Patients in the AMD and control groups were selected based on known CFH Y402H variant genotype status (one third homozygous CC, one third heterozygous CT, and one third wild-type TT). Plasma from all patients and controls was tested for C. pneumoniae, C. trachomatis, and C. psittaci IgG seropositivity using a micro-immunofluorescent assay to establish previous infection status. Assays were conducted blind to risk genotypes and the results analyzed using univariate and multivariate (logistic regression) analysis.RESULTS:IgG seropositivity to C. pneumoniae was most prevalent (69.2%, n=207), followed by C. trachomatis (7.4%, n=22) and C. psittaci (3.3%, n=10). No association was found between each of the three Chlamydia species IgG seropositivity and AMD status or severity (early/late). There was also no significant association between Chlamydia species IgG seropositivity and AMD status or severity, in patients carrying at least one CFH Y402H risk allele (C) or HTRA1 rs11200638 risk allele (A), with univariate or logistic regression analysis. CONCLUSIONS:Chlamydia infection status does not appear to be associated with AMD status or severity. The presence of CFH Y402H and HTRA1 rs11200638 risk genotypes does not alter this negative association
In vitro stem cell modelling demonstrates a proof-of-concept for excess functional mutant TIMP3 as the cause of Sorsby Fundus Dystrophy
No full textSorsby Fundus Dystrophy (SFD) is a rare autosomal dominant disease of the macula that leads to bilateral loss of central vision and is caused by mutations in the TIMP3 gene. However, the mechanisms by which TIMP3 mutations cause SFD are poorly understood. Here, we generated human induced pluripotent stem cell-derived retinal pigmented epithelial (hiPSC-RPE) cells from three SFD patients carrying TIMP3 p.(Ser204Cys) and three non-affected controls to study disease related structural and functional differences in the RPE. SFD-hiPSC-RPE exhibited characteristic RPE structure and physiology but showed significantly reduced transepithelial electrical resistance associated with enriched expression of cytoskeletal remodelling proteins. SFD-hiPSC-RPE exhibited basolateral accumulation of TIMP3 monomers, despite no change in TIMP3 gene expression. TIMP3 dimers were observed in both SFD and control hiPSC-RPE, suggesting mutant TIMP3 dimerization does not drive SFD pathology. Furthermore, mutant TIMP3 retained matrix metalloproteinase activity. Proteomic profiling showed increased expression of extracellular matrix proteins, endothelial cell interactions and angiogenesis-related pathways in SFD-hiPSC-RPE. By contrast, there were no changes in VEGF secretion. However, SFD-iPSC-RPE secreted higher levels of monocyte chemoattractant protein 1, platelet-derived growth factor, and angiogenin. Our findings provide a proof-of-concept that SFD patient-derived hiPSC-RPE mimic mature RPE cells and support the hypothesis that excess accumulation of mutant TIMP3, rather than an absence or deficiency of functional TIMP3, drives ECM and angiogenesis related changes in SFD
An ex-vivo platform for manipulation and study of Retinal Pigment Epithelial (RPE) cells in long-term culture
No full textPurpose: Impairment of the Retinal Pigment Epithelium (RPE) is strongly correlated with degenerative retinas including Age-related Macular Degeneration (AMD). Studies to elucidate dynamic intracellular processes underlying chronic degeneration of the RPE are limited by poor access of microscopes in the retinal space. Here we combine the use of an ex-vivo platform with live-confocal and ultrastructural imaging to study these events in individual RPE cells of mouse and human origin over long time periods. Our experimental model system provides a powerful tool to recapitulate chronic degenerative mechanisms in early AMD.Methods: Confluent monolayers of RPE cells were grown on a synthetic porous support which mimics the Bruch’s membrane. Cultures were maintained overs several months. We analysed morphology and barrier properties of the RPE monolayer, including expression of junctional complexes, trans-epithelial resistance (TER) as well as directional secretion of key RPE proteins. We used a combination of live-confocal microscopy, immunofluorescence, transmission electron microscopy (TEM), ELISA and biochemical approaches.Results: Ultrastructural studies show formation of a monolayer with features typical of RPE cells, including melanin pigmentation, apical microvilli and basal infoldings. Ultrastructural mapping of lysosomes and mitochondria provided convenient readouts of key organelles linked with RPE dysfunction at nanoscale resolution. A mobile custom-designed chamber allowed longitudinal analysis of live-cellular physiology using organelle-specific probes LysoSensor blue/yellow and MitoTracker in long-term cultures. For the first time we show that primary mouse RPE cells can be cultured for several weeks with an average TER measurement of 55 ±0.69 Ω/cm2. Directionally secreted proteins VEGF (Vascular Endothelial Growth Factor) and Aβ (Amyloid beta) were quantified using ELISA.Conclusions: Our ex-vivo model system which mimics the RPE/Bruch’s complex can be subject to a high degree of experimental manipulation, and is a powerful tool to investigate dynamic intracellular events as well as ultrastructural changes associated with chronic RPE degeneration in the ageing retina. This tool may be utilized to study RPE physiology at single-molecule resolution, providing mechanistic insights into early AMD
Complement factor I and age-related macular degeneration
No full textOur results identified a much higher frequency of heterozygosity for p.Gly119Arg in both cases and controls than in previous studies. Of note is that our sub-cohort from Guernsey had a particularly high frequency of p.Gly119Arg heterozygosity in affected individuals (4%) compared to our sub-cohort from the mainland (0.71%). Although these data support the conclusions of van de Ven et al. that the p.Gly119Arg substitution confers a high risk of AMD, our data suggest that this missense mutation is not as rare or as highly penetrant as previously reported. There was no difference in frequency for a second CFI variant, p.Gly188Ala, between the cases and the controls
Fine-scale linkage disequilibrium mapping of age-related macular degeneration in the complement factor H gene region
No full textAim: To present results from a nested association study of the complement factor H (CFH) gene region using a novel methodology that uses a high-resolution genetic linkage disequilibrium map to estimate a point location for a causal mutation. Method: Age-related macular degeneration (AMD) case–control data from a genomewide single-nucleotide polymorphism (SNP) panel were used to identify the target interval to be genotyped at higher density in a second independent panel. The pattern of linkage disequilibrium (LD) and segmental duplications across this region are described in detail. Result: Data were consistent with other studies in that strong association between the Y402H variant and AMD is observed. However, composite likelihood analysis, which combines association data from all SNPs in the region, and uses genetic locations on a high-resolution LD map, gave a point location for a causal variant between exons 1 and 2 of the CFH gene. Conclusion: The findings are consistent with evidence that, in addition to the widely described Y402H variant, there is at least one and, most probably, several other mutations in the CFH gene which determine disease manifestation in AMD. A genetic model in which multiple mutations contribute to a varying degree to disease aetiology has been previously well described in ophthalmic genetics, and is typified by the COL2A1 and ABCA4 genes
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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