Publications by authors named "Simon J Clark"

53 Publications

Tumor cell IDO enhances immune suppression and decreases survival independent of tryptophan metabolism in glioblastoma.

Clin Cancer Res 2021 Sep 3. Epub 2021 Sep 3.

Neurological Surgery, Northwestern University Feinberg School of Medicine

Purpose: Glioblastoma (GBM) is an incurable primary brain tumor that has not benefited from immunotherapy to-date. Greater than 90% of GBM expresses the tryptophan (Trp) metabolic enzyme, indoleamine 2,3-dioxygenase 1 (IDO). This observation supported the historical hypothesis that IDO suppresses the antitumor immune response solely through a mechanism that requires intratumoral Trp depletion. However, recent findings led us to investigate the alternative hypothesis that IDO suppresses the anti-GBM immune response independent of its association with Trp metabolism.

Experimental Design: IDO-deficient GBM cell lines reconstituted with IDO wild-type or IDO enzyme-null cDNA were created and validated and Microarray analysis was conducted to search for genes that IDO regulates, followed by the analysis of human GBM cell lines, patient GBM and plasma, and the TCGA database. cell co-culture assays, syngeneic and humanized mouse GBM models were used to test the alternative hypothesis.

Results: Non-enzymic tumor cell IDO activity decreased the survival of experimental animals and increased the expression of complement factor H (CFH) and its isoform, factor H like protein 1 (FHL-1) in human GBM. Tumor cell IDO increased CFH and FHL-1 expression independent of tryptophan metabolism. Increased intratumoral CFH and FHL-1 levels were associated with poorer survival among glioma patients. Similar to IDO effects, GBM cell FHL-1 expression increased intratumoral Tregs and MDSCs while it decreased overall survival in mice with GBM.

Conclusions: Our study reveals a newly non-metabolic IDO-mediated enhancement of CFH expression and provides a new therapeutic target in patients with GBM.
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http://dx.doi.org/10.1158/1078-0432.CCR-21-1392DOI Listing
September 2021

CFH Loss in Human RPE Cells Leads to Inflammation and Complement System Dysregulation via the NF-κB Pathway.

Int J Mol Sci 2021 Aug 13;22(16). Epub 2021 Aug 13.

Institute for Ophthalmic Research, Department for Ophthalmology, Eberhard Karls University of Tübingen, 72076 Tübingen, Germany.

Age-related macular degeneration (AMD), the leading cause of vision loss in the elderly, is a degenerative disease of the macula, where retinal pigment epithelium (RPE) cells are damaged in the early stages of the disease, and chronic inflammatory processes may be involved. Besides aging and lifestyle factors as drivers of AMD, a strong genetic association to AMD is found in genes of the complement system, with a single polymorphism in the complement factor H gene (), accounting for the majority of AMD risk. However, the exact mechanism of dysregulation confers such a great risk for AMD and its role in RPE cell homeostasis is unclear. To explore the role of endogenous locally in RPE cells, we silenced in human hTERT-RPE1 cells. We demonstrate that endogenously expressed in RPE cells modulates inflammatory cytokine production and complement regulation, independent of external complement sources, or stressors. We show that loss of the factor H protein (FH) results in increased levels of inflammatory mediators (e.g., IL-6, IL-8, GM-CSF) and altered levels of complement proteins (e.g., upregulation, and downregulation) that are known to play a role in AMD. Moreover, our results identify the NF-κB pathway as the major pathway involved in regulating these inflammatory and complement factors. Our findings suggest that in RPE cells, FH and the NF-κB pathway work in synergy to maintain inflammatory and complement balance, and in case either one of them is dysregulated, the RPE microenvironment changes towards a proinflammatory AMD-like phenotype.
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http://dx.doi.org/10.3390/ijms22168727DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8396051PMC
August 2021

Beyond factor H: The impact of genetic-risk variants for age-related macular degeneration on circulating factor-H-like 1 and factor-H-related protein concentrations.

Am J Hum Genet 2021 08 13;108(8):1385-1400. Epub 2021 Jul 13.

Stoller Biomarker Discovery Centre and Division of Cancer Sciences, School of Medical Sciences, Faculty of Biology, Medicine, and Health, The University of Manchester, Manchester, M13 9NQ, United Kingdom. Electronic address:

Age-related macular degeneration (AMD) is a leading cause of vision loss; there is strong genetic susceptibility at the complement factor H (CFH) locus. This locus encodes a series of complement regulators: factor H (FH), a splice variant factor-H-like 1 (FHL-1), and five factor-H-related proteins (FHR-1 to FHR-5), all involved in the regulation of complement factor C3b turnover. Little is known about how AMD-associated variants at this locus might influence FHL-1 and FHR protein concentrations. We have used a bespoke targeted mass-spectrometry assay to measure the circulating concentrations of all seven complement regulators and demonstrated elevated concentrations in 352 advanced AMD-affected individuals for all FHR proteins (FHR-1, p = 2.4 × 10; FHR-2, p = 6.0 × 10; FHR-3, p = 1.5 × 10; FHR-4, p = 1.3 × 10; FHR-5, p = 1.9 × 10) and FHL-1 (p = 4.9 × 10) when these individuals were compared to 252 controls, whereas no difference was seen for FH (p = 0.94). Genome-wide association analyses in controls revealed genome-wide-significant signals at the CFH locus for all five FHR proteins, and univariate Mendelian-randomization analyses strongly supported the association of FHR-1, FHR-2, FHR-4, and FHR-5 with AMD susceptibility. These findings provide a strong biochemical explanation for how genetically driven alterations in circulating FHR proteins could be major drivers of AMD and highlight the need for research into FHR protein modulation as a viable therapeutic avenue for AMD.
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http://dx.doi.org/10.1016/j.ajhg.2021.05.015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8387294PMC
August 2021

Common haplotypes at the CFH locus and low-frequency variants in CFHR2 and CFHR5 associate with systemic FHR concentrations and age-related macular degeneration.

Am J Hum Genet 2021 08 13;108(8):1367-1384. Epub 2021 Jul 13.

Department of Ophthalmology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, 6525EX, the Netherlands; Department of Human Genetics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Centre, 6525GA, the Netherlands. Electronic address:

Age-related macular degeneration (AMD) is the principal cause of blindness in the elderly population. A strong effect on AMD risk has been reported for genetic variants at the CFH locus, encompassing complement factor H (CFH) and the complement-factor-H-related (CFHR) genes, but the underlying mechanisms are not fully understood. We aimed to dissect the role of factor H (FH) and FH-related (FHR) proteins in AMD in a cohort of 202 controls and 216 individuals with AMD. We detected elevated systemic levels of FHR-1 (p = 1.84 × 10), FHR-2 (p = 1.47 × 10), FHR-3 (p = 1.05 × 10) and FHR-4A (p = 1.22 × 10) in AMD, whereas FH concentrations remained unchanged. Common AMD genetic variants and haplotypes at the CFH locus strongly associated with FHR protein concentrations (e.g., FH p.Tyr402His and FHR-2 concentrations, p = 3.68 × 10), whereas the association with FH concentrations was limited. Furthermore, in an International AMD Genomics Consortium cohort of 17,596 controls and 15,894 individuals with AMD, we found that low-frequency and rare protein-altering CFHR2 and CFHR5 variants associated with AMD independently of all previously reported genome-wide association study (GWAS) signals (p = 5.03 × 10 and p = 2.81 × 10, respectively). Low-frequency variants in CFHR2 and CFHR5 led to reduced or absent FHR-2 and FHR-5 concentrations (e.g., p.Cys72Tyr in CFHR2 and FHR-2, p = 2.46 × 10). Finally, we showed localization of FHR-2 and FHR-5 in the choriocapillaris and in drusen. Our study identifies FHR proteins as key proteins in the AMD disease mechanism. Consequently, therapies that modulate FHR proteins might be effective for treating or preventing progression of AMD. Such therapies could target specific individuals with AMD on the basis of their genotypes at the CFH locus.
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http://dx.doi.org/10.1016/j.ajhg.2021.06.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8387287PMC
August 2021

FHL-1 interacts with human RPE cells through the α5β1 integrin and confers protection against oxidative stress.

Sci Rep 2021 Jul 8;11(1):14175. Epub 2021 Jul 8.

Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Oxford, UK.

Retinal pigment epithelial (RPE) cells that underlie the neurosensory retina are essential for the maintenance of photoreceptor cells and hence vision. Interactions between the RPE and their basement membrane, i.e. the inner layer of Bruch's membrane, are essential for RPE cell health and function, but the signals induced by Bruch's membrane engagement, and their contributions to RPE cell fate determination remain poorly defined. Here, we studied the functional role of the soluble complement regulator and component of Bruch's membrane, Factor H-like protein 1 (FHL-1). Human primary RPE cells adhered to FHL-1 in a manner that was eliminated by either mutagenesis of the integrin-binding RGD motif in FHL-1 or by using competing antibodies directed against the α5 and β1 integrin subunits. These short-term experiments reveal an immediate protein-integrin interaction that were obtained from primary RPE cells and replicated using the hTERT-RPE1 cell line. Separate, longer term experiments utilising RNAseq analysis of hTERT-RPE1 cells bound to FHL-1, showed an increased expression of the heat-shock protein genes HSPA6, CRYAB, HSPA1A and HSPA1B when compared to cells bound to fibronectin (FN) or laminin (LA). Pathway analysis implicated changes in EIF2 signalling, the unfolded protein response, and mineralocorticoid receptor signalling as putative pathways. Subsequent cell survival assays using HO to induce oxidative stress-induced cell death suggest hTERT-RPE1 cells had significantly greater protection when bound to FHL-1 or LA compared to plastic or FN. These data show a non-canonical role of FHL-1 in protecting RPE cells against oxidative stress and identifies a novel interaction that has implications for ocular diseases such as age-related macular degeneration.
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http://dx.doi.org/10.1038/s41598-021-93708-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8266909PMC
July 2021

The complement system in age-related macular degeneration.

Cell Mol Life Sci 2021 May 9;78(10):4487-4505. Epub 2021 Mar 9.

Department for Ophthalmology, Institute for Ophthalmic Research, Eberhard Karls University of Tübingen, Tübingen, Germany.

Age-related macular degeneration (AMD) is a chronic and progressive degenerative disease of the retina, which culminates in blindness and affects mainly the elderly population. AMD pathogenesis and pathophysiology are incredibly complex due to the structural and cellular complexity of the retina, and the variety of risk factors and molecular mechanisms that contribute to disease onset and progression. AMD is driven by a combination of genetic predisposition, natural ageing changes and lifestyle factors, such as smoking or nutritional intake. The mechanism by which these risk factors interact and converge towards AMD are not fully understood and therefore drug discovery is challenging, where no therapeutic attempt has been fully effective thus far. Genetic and molecular studies have identified the complement system as an important player in AMD. Indeed, many of the genetic risk variants cluster in genes of the alternative pathway of the complement system and complement activation products are elevated in AMD patients. Nevertheless, attempts in treating AMD via complement regulators have not yet been successful, suggesting a level of complexity that could not be predicted only from a genetic point of view. In this review, we will explore the role of complement system in AMD development and in the main molecular and cellular features of AMD, including complement activation itself, inflammation, ECM stability, energy metabolism and oxidative stress.
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http://dx.doi.org/10.1007/s00018-021-03796-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8195907PMC
May 2021

Searching for the true attrition rate of UK paediatric trainees.

Arch Dis Child 2021 09 12;106(9):903-905. Epub 2021 Feb 12.

Royal College of Paediatrics and Child Health, London, UK.

Objective: To quantitatively analyse the number of doctors leaving the paediatric specialty training (ST) programme in the UK, to assist with evidence-based workforce planning.

Design: Data were sought on those leaving the UK paediatrics training programme between 2014 and 2019 from Heads of Schools of Paediatrics and Freedom of Information Act requests.

Setting: Retrospective data analysis.

Outcome Measures: Overall attrition rate, attrition rate across level of training, attrition rate across geographical area, recorded reason for leaving.

Results: All results must be interpreted with caution due to limitations in record keeping and analysis. The annual attrition rate across all ST levels between 2014 and 2019 is estimated at 3.7%-4.2% (ie, 749-845 trainees may have left the paediatric training programme over 2014-2019). No reason for leaving was recorded for three-quarters of individuals, around 630 doctors. Of those leaving paediatrics, significantly more (χ², p=0.015) did so at ST3 (20.3%) versus the next highest training year, ST2 (13.6%).

Conclusions: This project seems to demonstrate worryingly poor record-keeping of the true attrition rate of paediatric trainees by organisations responsible for workforce planning, including Health Education England, the Royal College of Paediatrics and Child Health and individual paediatric schools across the UK. To allow evidence-based workforce planning for the benefit of UK children, it is vital that accurate records on trainees who leave the training programme are kept and shared across the UK.
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http://dx.doi.org/10.1136/archdischild-2020-321415DOI Listing
September 2021

Case for change: a standardised inpatient paediatric early warning system in England.

Arch Dis Child 2021 07 8;106(7):648-651. Epub 2021 Jan 8.

Department of Paediatric Surgery, Alderhey Children's NHS Foundation Trust, Liverpool, UK.

Most children in hospital who are clinically deteriorating are monitored regularly, and their treatment is escalated effectively. However a small, but significant, number of deteriorating children experience suboptimal outcomes because of a failure to recognise and respond to acute deterioration early enough leading to unintended harm. Tragically this occasionally can have fatal consequences. Investigations into these rare events highlight common themes of missed early signs of deterioration in children, prompting regulatory agencies to suggest paediatric early warning systems (PEWS) to aid clinical practice. In England, track and trigger tools (TTT), which are one facet of PEWS have been widely rolled out but in a heterogeneous fashion. The evidence for TTT is mixed but they are complex interventions and current outcomes do not fully define the entirety of their potential impact. This article explains the rationale behind the decision of the NHS England and NHS Improvement, Royal College of Paediatrics and Child Health and Royal College of Nursing to implement a standardised inpatient PEWS as part of a system-wide paediatric observations tracking system in England and how this fits into a wider programme of activity.
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http://dx.doi.org/10.1136/archdischild-2020-320466DOI Listing
July 2021

Control of Complement Activation by the Long Pentraxin PTX3: Implications in Age-Related Macular Degeneration.

Front Pharmacol 2020 26;11:591908. Epub 2020 Nov 26.

Department of Biomedical Sciences, Humanitas University, Milan, Italy.

Dysregulation of the complement system is central to age-related macular degeneration (AMD), the leading cause of blindness in the developed world. Most of the genetic variation associated with AMD resides in complement genes, with the greatest risk associated with polymorphisms in the () gene; factor H (FH) is the major inhibitor of the alternative pathway (AP) of complement that specifically targets C3b and the AP C3 convertase. Long pentraxin 3 (PTX3) is a soluble pattern recognition molecule that has been proposed to inhibit AP activation via recruitment of FH. Although present in the human retina, if and how PTX3 plays a role in AMD is still unclear. In this work we demonstrated the presence of PTX3 in the human vitreous and studied the PTX3-FH-C3b crosstalk and its effects on complement activation in a model of retinal pigment epithelium (RPE). RPE cells cultured in inflammatory AMD-like conditions overexpressed the PTX3 protein, and up-regulated AP activating genes. PTX3 bound RPE cells in a physiological setting, however this interaction was reduced in inflammatory conditions, whereby PTX3 had no complement-inhibiting activity on inflamed RPE. However, on non-cellular surfaces, PTX3 formed a stable ternary complex with FH and C3b that acted as a "hot spot" for complement inhibition. Our findings suggest a protective role for PTX3 in response to complement dysregulation in AMD and point to a novel mechanism of complement regulation by this pentraxin with potential implications in pathology and pharmacology of AMD.
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http://dx.doi.org/10.3389/fphar.2020.591908DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7725797PMC
November 2020

Physician associates: a potential solution to our workforce crisis.

Arch Dis Child 2021 07 30;106(7):727. Epub 2020 Oct 30.

Paediatric Allergy, Sheffield Children's NHS Foundation Trust, Sheffield, UK.

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http://dx.doi.org/10.1136/archdischild-2020-320618DOI Listing
July 2021

Association of plasma trace element levels with neovascular age-related macular degeneration.

Exp Eye Res 2020 12 21;201:108324. Epub 2020 Oct 21.

Wellcome Trust Centre for Cell-Matrix Research, Division of Cell-Matrix Biology & Regenerative Medicine, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Oxford Road, Manchester, M13 9PT, UK; Lydia Becker Institute of Immunology and Inflammation, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Oxford Road, Manchester, M13 9PT, UK. Electronic address:

Although the triggers causing angiogenesis in the context of neovascular age-related macular degeneration (nAMD) are not fully understood, oxidative stress is likely involved. Oxidative stress in the eye can occur through exposure of macular tissues to sunlight and local or systemic exposure to oxidative stressors associated with environmental or lifestyle factors. Because trace elements have been implicated as regulators of oxidative stress and cellular antioxidant defense mechanisms, we hypothesized that they may play a role as a risk factor, modifying the progression toward nAMD. Herein, we determined whether levels of human plasma trace elements are different in 236 individuals with nAMD compared to 236 age-matched controls without AMD. Plasma levels of 16 trace elements including arsenic, barium, calcium, cadmium, cobalt, chromium, copper, iron, magnesium, manganese, molybdenum, lead, antimony, selenium, vanadium and zinc were measured using inductively coupled plasma mass spectrometry. Associations of trace elements with demographic, environmental and lifestyle factors and AMD-associated genetic variants were assessed. Elevated levels of barium and cadmium and reduced levels of chromium were observed in nAMD patients compared to controls. Mean plasma concentrations of barium were 1.35 μg/L (standard deviation [SD] 0.71) in nAMD and 1.15 μg/L (SD 0.63) in controls (P = 0.001). Mean levels of chromium were 0.37 μg/L (SD 0.22) in nAMD and 0.46 μg/L (SD 0.34) in controls (P = 0.001). Median levels for cadmium, which were not normally distributed, were 0.016 μg/L (interquartile range [IQR] 0.001-0.026) in nAMD and 0.012 μg/L (IQR 0.001-0.022) in controls (P = 0.002). Comparison of the Spearman's correlation coefficients between nAMD patients and controls identified a difference in correlations for 8 trace elements. Cadmium levels were associated with the smoking status (P < 0.001), while barium levels showed a trend of association with the usage of antihypertensive drugs. None of the AMD-associated genetic variants were associated with any trace element levels. In conclusion, in this case-control study we detected elevated plasma levels of barium and cadmium and reduced plasma levels of chromium in nAMD patients. An imbalance in plasma trace elements, which is most likely driven by environmental and lifestyle factors, might have a role in the pathogenesis of AMD. These trace elements may be incorporated as biomarkers into models for prediction of disease risk and progression. Additionally, population-based preventive strategies to decrease Cd exposure, especially by the cessation of smoking, could potentially reduce the burden of nAMD. Future studies are warranted to investigate whether supplementation of Cr would have a beneficial effect on nAMD.
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http://dx.doi.org/10.1016/j.exer.2020.108324DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7773981PMC
December 2020

Completion of paediatric training: trends across 2011-2017 cohorts.

Arch Dis Child 2021 04 24;106(4):367-371. Epub 2020 Sep 24.

Royal College of Paediatrics and Child Health, London, UK.

Objective: To determine trends in the demographics and destinations of doctors who have recently completed paediatric training in the UK.

Design: A survey was sent to all new paediatric certificate holders 1 year on from completing specialty training every year from 2011 to 2017.

Setting: Retrospective survey.

Outcome Measures: Demographics, career destinations, time to complete training, working patterns, subspecialty registration, numbers of job applications, and use of the period of grace are reported.

Results: 1262 people who gained their paediatric certificate in the UK between 2011 and 2017 completed the survey (60.6% response rate). 58.5% (n=738) of respondents were female, and 32.4% (n=224) of women work less than full time, compared with 4.6% (n=23) of men. 85.9% (n=1056) of respondents were in a UK consultant post. 7.6% (n=94) were working overseas. 65.1% (n=722) remained in the region they trained in. 64.8% (n=1348) were registered for general paediatrics, whereas 35.2% (n=733) had subspecialised.Respondents who held a non-UK medical degree (47.5%, n=501) made more job applications on average (mean=2.2; 95% CI 2.0 to 2.5) than those with a UK degree (52.5%, n=554) (mean=1.1; 95% CI 1.0 to 1.2) (p<0.001). Average training time increased from 9.8 years (95% CI 9.4 to 10.2) to 11.3 years (95% CI 11.1 to 11.6) (p<0.001). Respondents' use of their grace period reduced from 42.7% (n=47) to 20.6% (n=29) (p<0.001).

Conclusions: The data reflect the diverse paediatric workforce and doctors' working patterns following the completion of paediatric training in the UK. The trends demonstrated are vital to consider for evidence-based workforce planning.
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http://dx.doi.org/10.1136/archdischild-2020-320163DOI Listing
April 2021

Basement membrane ligands initiate distinct signalling networks to direct cell shape.

Matrix Biol 2020 08 6;90:61-78. Epub 2020 Mar 6.

Wellcome Centre for Cell-Matrix Research, Division of Cell-Matrix Biology and Regenerative Medicine, School of Biological Sciences, Faculty of Biology Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, Manchester, UK; Department of Paediatric Nephrology, Royal Manchester Children's Hospital, Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, UK. Electronic address:

Cells have evolved mechanisms to sense the composition of their adhesive microenvironment. Although much is known about general mechanisms employed by adhesion receptors to relay signals between the extracellular environment and the cytoskeleton, the nuances of ligand-specific signalling remain undefined. Here, we investigated how glomerular podocytes, and four other basement membrane-associated cell types, respond morphologically to different basement membrane ligands. We defined the composition of the respective adhesion complexes using mass spectrometry-based proteomics. On type IV collagen, all epithelial cell types adopted a round morphology, with a single lamellipodium and large adhesion complexes rich in actin-binding proteins. On laminin (511 or 521), all cell types attached to a similar degree but were polygonal in shape with small adhesion complexes enriched in endocytic and microtubule-binding proteins. Consistent with their distinctive morphologies, cells on type IV collagen exhibited high Rac1 activity, while those on laminin had elevated PKCα. Perturbation of PKCα was able to interchange morphology consistent with a key role for this pathway in matrix ligand-specific signalling. Therefore, this study defines the switchable basement membrane adhesome and highlights two key signalling pathways within the systems that determine distinct cell morphologies. Proteomic data are availableviaProteomeXchange with identifier PXD017913.
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http://dx.doi.org/10.1016/j.matbio.2020.02.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7327512PMC
August 2020

Increased circulating levels of Factor H-Related Protein 4 are strongly associated with age-related macular degeneration.

Nat Commun 2020 02 7;11(1):778. Epub 2020 Feb 7.

Division of Evolution and Genomic Sciences, Faculty of Biology Medicine and Health, School of Biological Sciences, University of Manchester, Oxford Road, Manchester, M13 9PT, UK.

Age-related macular degeneration (AMD) is a leading cause of blindness. Genetic variants at the chromosome 1q31.3 encompassing the complement factor H (CFH, FH) and CFH related genes (CFHR1-5) are major determinants of AMD susceptibility, but their molecular consequences remain unclear. Here we demonstrate that FHR-4 plays a prominent role in AMD pathogenesis. We show that systemic FHR-4 levels are elevated in AMD (P-value = 7.1 × 10), whereas no difference is seen for FH. Furthermore, FHR-4 accumulates in the choriocapillaris, Bruch's membrane and drusen, and can compete with FH/FHL-1 for C3b binding, preventing FI-mediated C3b cleavage. Critically, the protective allele of the strongest AMD-associated CFH locus variant rs10922109 has the highest association with reduced FHR-4 levels (P-value = 2.2 × 10), independently of the AMD-protective CFHR1-3 deletion, and even in those individuals that carry the high-risk allele of rs1061170 (Y402H). Our findings identify FHR-4 as a key molecular player contributing to complement dysregulation in AMD.
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http://dx.doi.org/10.1038/s41467-020-14499-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7005798PMC
February 2020

Loss-of-Function Mutations in the CFH Gene Affecting Alternatively Encoded Factor H-like 1 Protein Cause Dominant Early-Onset Macular Drusen.

Ophthalmology 2019 10 21;126(10):1410-1421. Epub 2019 Mar 21.

Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom; Manchester Centre for Genomic Medicine, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, St. Mary's Hospital, Manchester, United Kingdom. Electronic address:

Purpose: To characterize the molecular mechanism underpinning early-onset macular drusen (EOMD), a phenotypically severe subtype of age-related macular degeneration (AMD), in a subgroup of patients.

Design: Multicenter case series, in vitro experimentation, and retrospective analysis of previously reported variants.

Participants: Seven families with apparently autosomal dominant EOMD.

Methods: Patients underwent a comprehensive ophthalmic assessment. Affected individuals from families A, B, and E underwent whole exome sequencing. The probands from families C, D, F, and G underwent Sanger sequencing analysis of the complement factor H (CFH) gene. Mutant recombinant factor H like-1 (FHL-1) proteins were expressed in HEK293 cells to assess the impact on FHL-1 expression and function. Previously reported EOMD-causing variants in CFH were reviewed.

Main Outcome Measures: Detailed clinical phenotypes, genomic findings, in vitro characterization of mutation effect on protein function, and postulation of the pathomechanism underpinning EOMD.

Results: All affected participants demonstrated bilateral drusen. The earliest reported age of onset was 16 years (median, 46 years). Ultra-rare (minor allele frequency [MAF], ≤0.0001) CFH variants were identified as the cause of disease in each family: CFH c.1243del, p.(Ala415ProfsTer39) het; c.350+1G→T het; c.619+1G→A het, c.380G→A, p.(Arg127His) het; c.694C→T p.(Arg232Ter) het (identified in 2 unrelated families in this cohort); and c.1291T→A, p.(Cys431Ser). All mutations affect complement control protein domains 2 through 7, and thus are predicted to impact both FHL-1, the predominant isoform in Bruch's membrane (BrM) of the macula, and factor H (FH). In vitro analysis of recombinant proteins FHL-1, FHL-1, and FHL-1 demonstrated that they are not secreted, and thus are loss-of-function proteins. Review of 29 previously reported EOMD-causing mutations found that 75.8% (22/29) impact FHL-1 and FH. In total, 86.2% (25/29) of EOMD-associated variants cause haploinsufficiency of FH or FHL-1.

Conclusions: Early-onset macular drusen is an underrecognized, phenotypically severe subtype of AMD. We propose that haploinsufficiency of FHL-1, the main regulator of the complement pathway in BrM, where drusen develop, is an important mechanism underpinning the development of EOMD in a number of cases. Understanding the molecular basis of EOMD will shed light on AMD pathogenesis given their pathologic similarities.
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http://dx.doi.org/10.1016/j.ophtha.2019.03.013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6856713PMC
October 2019

Whole-genome methylation profiling of the retinal pigment epithelium of individuals with age-related macular degeneration reveals differential methylation of the SKI, GTF2H4, and TNXB genes.

Clin Epigenetics 2019 01 14;11(1). Epub 2019 Jan 14.

Department of Eye and Vision Science, William Duncan Building, University of Liverpool, Liverpool, UK.

Background: Age-related macular degeneration (AMD) is a degenerative disorder of the central retina and the foremost cause of blindness. The retinal pigment epithelium (RPE) is a primary site of disease pathogenesis. The genetic basis of AMD is relatively well understood; however, this knowledge is yet to yield a treatment for the most prevalent non-neovascular disease forms. Therefore, tissue-specific epigenetic mechanisms of gene regulation are of considerable interest in AMD. We aimed to identify differentially methylated genes associated with AMD in the RPE and differentiate local DNA methylation aberrations from global DNA methylation changes, as local DNA methylation changes may be more amenable to therapeutic manipulation.

Methods: Epigenome-wide association study and targeted gene expression profiling were carried out in RPE cells from eyes of human donors. We performed genome-wide DNA methylation profiling (Illumina 450k BeadChip array) on RPE cells from 44 human donor eyes (25 AMD and 19 normal controls). We validated the findings using bisulfite pyrosequencing in 55 RPE samples (30 AMD and 25 normal controls) including technical (n = 38) and independent replicate samples (n = 17). Long interspersed nucleotide element 1 (LINE-1) analysis was then applied to assess global DNA methylation changes in the RPE. RT-qPCR on independent donor RPE samples was performed to assess gene expression changes.

Results: Genome-wide DNA methylation profiling identified differential methylation of multiple loci including the SKI proto-oncogene (SKI) (p = 1.18 × 10), general transcription factor IIH subunit H4 (GTF2H4) (p = 7.03 × 10), and Tenascin X (TNXB) (p = 6.30 × 10) genes in AMD. Bisulfite pyrosequencing validated the differentially methylated locus cg18934822 in SKI, and cg22508626 within GTF2H4, and excluded global DNA methylation changes in the RPE in AMD. We further demonstrated the differential expression of SKI, GTF2H4, and TNXB in the RPE of independent AMD donors.

Conclusions: We report the largest genome-wide methylation analysis of RPE in AMD along with associated gene expression changes to date, for the first-time reaching genome-wide significance, and identified novel targets for functional and future therapeutic intervention studies. The novel differentially methylated genes SKI and GTF2H4 have not been previously associated with AMD, and regulate disease pathways implicated in AMD, including TGF beta signaling (SKI) and transcription-dependent DNA repair mechanisms (GTF2H4).
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http://dx.doi.org/10.1186/s13148-019-0608-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6332695PMC
January 2019

Paediatric outcomes and timing of admission.

Arch Dis Child 2018 06 15;103(6):611-617. Epub 2018 Mar 15.

Neonatal Unit, Sheffield Teaching Foundation Hospitals Trust, Sheffield, UK.

Studies of adult patients have demonstrated that weekend admissions compared with weekday admissions had a significantly higher hospital mortality rate. We have reviewed the literature to determine if the timing of admission, for example, weekend or weekday, influenced mortality and morbidity in children. Seventeen studies reported the effect of timing of admission on mortality, and only four studies demonstrated an increase in those admitted at the weekend. Meta-analysis of the results of 15 of the studies demonstrated there was no significant weekend effect. There was, however, considerable heterogeneity in the studies. There were two large UK studies: one reported an increased mortality only for planned weekend admissions likely explained by planned admissions for complex conditions and the other showed no significant weekend effect. Two studies, one of which was large (n=2913), reported more surgical complications in infants undergoing weekend oesophageal atresia and trachea-oesophageal repair. Medication errors have also been reported to be more common at weekends. Five studies reported the effect of length of stay, meta-analysis demonstrated a significantly increased length of stay following a weekend admission, the mean difference was approximately 1 day. Those data, however, should be interpreted with the caveat that there was no adjustment in all of the studies for differences in disease severity. We conclude that weekend admission overall does not increase mortality but may be associated with a longer length of stay and, in certain conditions, with greater morbidity.
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http://dx.doi.org/10.1136/archdischild-2017-314559DOI Listing
June 2018

C-reactive protein and pentraxin-3 binding of factor H-like protein 1 differs from complement factor H: implications for retinal inflammation.

Sci Rep 2018 01 26;8(1):1643. Epub 2018 Jan 26.

Division of Evolution and Genomic Science, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Oxford Road, Manchester, M13 9PT, UK.

Retinal inflammation plays a key role in the progression of age-related macular degeneration (AMD), a condition that leads to loss of central vision. The deposition of the acute phase pentraxin C-reactive protein (CRP) in the macula activates the complement system, thereby contributing to dysregulated inflammation. The complement protein factor H (FH) can bind CRP and down-regulate an inflammatory response. However, it is not known whether a truncated form of FH, called factor H-like protein 1 (FHL-1), which plays a significant regulatory role in the eye, also interacts with CRP. Here, we compare the binding properties of FHL-1 and FH to both CRP and the related protein pentraxin-3 (PTX3). We find that, unlike FH, FHL-1 can bind pro-inflammatory monomeric CRP (mCRP) as well as the circulating pentameric form. Furthermore, the four-amino acid C-terminal tail of FHL-1 (not present in FH) plays a role in mediating its binding to mCRP. PTX3 was found to be present in the macula of donor eyes and the AMD-associated Y402H polymorphism altered the binding of FHL-1 to PTX3. Our findings reveal that the binding characteristics of FHL-1 differ from those of FH, likely underpinning independent immune regulatory functions in the context of the human retina.
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http://dx.doi.org/10.1038/s41598-017-18395-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5786067PMC
January 2018

Bruch's Membrane Compartmentalizes Complement Regulation in the Eye with Implications for Therapeutic Design in Age-Related Macular Degeneration.

Front Immunol 2017 19;8:1778. Epub 2017 Dec 19.

Division of Evolution and Genomic Medicine, Faculty of Biology Medicine and Health, School of Biological Sciences, University of Manchester, Manchester, United Kingdom.

Age-related macular degeneration (AMD) is the leading cause of blindness in the western world and affects nearly 200 million people globally. Local inflammation driven by complement system dysregulation is currently a therapeutic target. Bruch's membrane (BrM) is a sheet of extracellular matrix that separates the retina from the underlying choroid, a highly vascularized layer that supplies oxygen and nutrition to the outer retina. Here, we show that most complement proteins are unable to diffuse through BrM, although FHL-1, factor D and C5a can. AMD-associated lipid deposition in BrM decreases FHL-1 diffusion. We show that this impermeability of BrM creates two separate semi-independent compartments with respect to complement activation and regulation. Complement proteins synthesized locally on either side of BrM, or on the choroidal side if derived from the circulation, predominantly remain on their side of origin. As previous studies suggest that complement activation in AMD is confined to the choroidal side of BrM, we propose a model whereby complement activation in the choriocapillaris layer of the choroid generates C5a, which crosses BrM to interact with its specific receptor on RPE cells to initiate an inflammatory response in the retina. Understanding mechanisms underpinning AMD is essential for developing therapeutics that target the right molecule in the right anatomical compartment.
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http://dx.doi.org/10.3389/fimmu.2017.01778DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5742201PMC
December 2017

The eye as a complement dysregulation hotspot.

Semin Immunopathol 2018 01 25;40(1):65-74. Epub 2017 Sep 25.

Division of Evolution and Genomic Medicine, School of Biological Sciences, Faculty of Biology Medicine and Health, University of Manchester, Oxford Road, Manchester, M13 9PT, UK.

Complement turnover is tightly regulated throughout the human body in order to prevent over-activation and subsequent damage from inflammation. In the eye, low-level complement activation is maintained to provide immune tolerance in this immune privileged organ. Conversely, the complement system is suppressed in the cornea to protect it from continuous immunological insult. Over-activation of the complement cascade has been implicated in the disease progression of glaucoma and diabetic retinopathy and is now known to be a central driver in the pathogenesis of age-related macular degeneration (AMD). Indeed, it is with AMD where the most recent and exciting work has been carried out with complement-based therapies entering into clinical trials. However, the success of these trials will depend upon delivering the therapeutics to the correct anatomical sites within the eye, so a full understanding of how complement regulation is compartmentalized in the eye is required, a topic that will be highlighted in this review.
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http://dx.doi.org/10.1007/s00281-017-0649-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5794836PMC
January 2018

Complement factor H in host defense and immune evasion.

Cell Mol Life Sci 2017 05 10;74(9):1605-1624. Epub 2016 Dec 10.

Wellcome Trust Centre for Cell-Matrix Research, Division of Cell-Matrix Biology and Regenerative Medicine, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Oxford Road, Manchester, M13 9PT, UK.

Complement is the major humoral component of the innate immune system. It recognizes pathogen- and damage-associated molecular patterns, and initiates the immune response in coordination with innate and adaptive immunity. When activated, the complement system unleashes powerful cytotoxic and inflammatory mechanisms, and thus its tight control is crucial to prevent damage to host tissues and allow restoration of immune homeostasis. Factor H is the major soluble inhibitor of complement, where its binding to self markers (i.e., particular glycan structures) prevents complement activation and amplification on host surfaces. Not surprisingly, mutations and polymorphisms that affect recognition of self by factor H are associated with diseases of complement dysregulation, such as age-related macular degeneration and atypical haemolytic uremic syndrome. In addition, pathogens (i.e., non-self) and cancer cells (i.e., altered-self) can hijack factor H to evade the immune response. Here we review recent (and not so recent) literature on the structure and function of factor H, including the emerging roles of this protein in the pathophysiology of infectious diseases and cancer.
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http://dx.doi.org/10.1007/s00018-016-2418-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5378756PMC
May 2017

Induction of Chemokine Secretion and Monocyte Migration by Human Choroidal Melanocytes in Response to Proinflammatory Cytokines.

Invest Ophthalmol Vis Sci 2016 12;57(15):6568-6579

University of Copenhagen, Department of Immunology and Microbiology, Eye Research Unit, Copenhagen, Denmark.

Purpose: To determine to which extent inflammatory cytokines affect chemokine secretion by primary human choroidal melanocytes (HCMs), their capacity to attract monocytes, and whether HCMs are able to influence the proliferation of activated T cells.

Methods: Primary cultures of HCMs were established from eyes of 13 donors. Human choroidal melanocytes were stimulated with IFN-γ and TNF-α or with supernatant from activated T cells (T-cell-conditioned media [TCM]). Gene expression analysis was performed by using microarrays. Protein levels were quantified with ELISA or cytometric bead array. Supernatants of HCMs were assessed for the capability to attract monocytes in a transwell plate. Proliferation of activated T cells was assessed in a direct coculture with HCMs by a [3H]-thymidine incorporation assay.

Results: Stimulation of HCMs with TCM or IFN-γ and TNF-α resulted in increased expression and secretion of CXCL8, CXCL9, CXCL10, CXCL11, CCL2, CCL5 and intercellular adhesion molecule 1. Vascular endothelial growth factor and monocyte migration inhibitory factor were constitutively expressed without changes in response to proinflammatory cytokines. Supernatants derived from unstimulated cultures of 10 HCM donors induced a high initial level of monocyte migration, which decreased upon stimulation with either TCM or IFN-γ and TNF-α. The supernatants from three HCM donors initially showed a low level of monocyte attraction, which increased after exposure to proinflammatory cytokines. Direct coculture of HCMs with T cells resulted in inhibition of T-cell proliferation.

Conclusions: These results showed that normal and activated HCMs are immunologically active by secreting chemokines, and that HCMs are able to attract monocytes in addition to inhibiting T-cell proliferation.
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http://dx.doi.org/10.1167/iovs.15-18524DOI Listing
December 2016

The changing UK paediatric consultant workforce: report from the Royal College of Paediatrics and Child Health.

Arch Dis Child 2017 Feb 27;102(2):170-173. Epub 2016 Oct 27.

Royal College of Paediatrics and Child Health, London, UK.

Objectives: To determine if there had been changes in the size of the UK paediatric workforce and working patterns between 1999 and 2013.

Design: Analysis of prospectively collected datasets.

Setting: UK consultant paediatricians.

Interventions: Data from the Royal College of Paediatrics and Child Health's workforce census from 1999 to 2013 and the annual surveys of new paediatric Certificate of Completion of Training (CCT) and Certificate of Equivalence of Specialist Registration (CESR) holders between 2010 and 2013.

Main Outcome Measures: Paediatric consultant numbers, programmed activities (PAs) and resident shift working.

Results: The UK paediatric consultant workforce grew from 1933 in 1999 to 3718 in 2013. Over the same time period, there was a decline in the number of consultants with a primary academic contract from 210 to 143. There was an increase in the proportion of consultants who were female (40% in 1999 to 50% in 2013, p<0.01). The median number of PAs declined from 11 in 2009 to 10 in 2013 (p<0.001) as did the median number of PAs for supporting professional activities (2.5-2.3, p<0.001). In 2013, 38% of new consultants in general paediatrics or neonatology were working resident shifts. Between 2009 and 2013, the proportion of less than full-time working consultants rose from 18% to 22%, which was more common among female consultants (35% vs 9%).

Conclusion: The paediatric consultant workforce has doubled since 1999, but more are working less than full time. The decline in those with a primary academic contract is of concern.
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http://dx.doi.org/10.1136/archdischild-2016-312055DOI Listing
February 2017

Age and Smoking Related Changes in Metal Ion Levels in Human Lens: Implications for Cataract Formation.

PLoS One 2016 21;11(1):e0147576. Epub 2016 Jan 21.

Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom.

Age-related cataract formation is the primary cause of blindness worldwide and although treatable by surgical removal of the lens the majority of sufferers have neither the finances nor access to the medical facilities required. Therefore, a better understanding of the pathogenesis of cataract may identify new therapeutic targets to prevent or slow its progression. Cataract incidence is strongly correlated with age and cigarette smoking, factors that are often associated with accumulation of metal ions in other tissues. Therefore this study evaluated the age-related changes in 14 metal ions in 32 post mortem human lenses without known cataract from donors of 11 to 82 years of age by inductively coupled plasma mass spectrometry; smoking-related changes in 10 smokers verses 14 non-smokers were also analysed. A significant age-related increase in selenium and decrease in copper ions was observed for the first time in the lens tissue, where cadmium ion levels were also increased as has been seen previously. Aluminium and vanadium ions were found to be increased in smokers compared to non-smokers (an analysis that has only been carried out before in lenses with cataract). These changes in metal ions, i.e. that occur as a consequence of normal ageing and of smoking, could contribute to cataract formation via induction of oxidative stress pathways, modulation of extracellular matrix structure/function and cellular toxicity. Thus, this study has identified novel changes in metal ions in human lens that could potentially drive the pathology of cataract formation.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0147576PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4721641PMC
August 2016

Enrichment of Bruch's Membrane from Human Donor Eyes.

J Vis Exp 2015 Nov 15(105). Epub 2015 Nov 15.

Centre for Ophthalmology & Vision Sciences, Institute of Human Development, University of Manchester; Centre for Advanced Discovery and Experimental Therapeutics, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre;

Age-related macular degeneration (AMD) is a leading cause of visual impairment in the developed world. The disease manifests itself by the destruction of the center of the retina, called the macula, resulting in the loss of central vision. Early AMD is characterised by the presence of small, yellowish lesions called soft drusen that can progress onto late AMD such as geographic atrophy (dry AMD) or neovascularisation (wet AMD). Although the clinical changes are well described, and the understanding of genetic influences on conferring AMD risk are getting ever more detailed, one area lacking major progress is an understanding of the biochemical consequences of genetic risk. This is partly due to difficulties in understanding the biochemistry of Bruch's membrane, a very thin extracellular matrix that acts as a biological filter of material from the blood supply and a scaffold on which the retinal pigment epithelial (RPE) cell monolayer resides. Drusen form within Bruch's membrane and their presence disrupts nutrient flow to the RPE cells. Only by investigating the protein composition of Bruch's membrane, and indeed how other proteins interact with it, can researchers hope to unravel the biochemical mechanisms underpinning drusen formation, development of AMD and subsequent vision loss. This paper details methodologies for enriching either whole Bruch's membrane, or just from the macula region, so that it can be used for downstream biochemical analysis, and provide examples of how this is already changing the understanding of Bruch's membrane biochemistry.
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http://dx.doi.org/10.3791/53382DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4692728PMC
November 2015

Lithium toxicity in a neonate owing to false elevation of blood lithium levels caused by contamination in a lithium heparin container: case report and review of the literature.

Paediatr Int Child Health 2016 Aug 16;36(3):240-2. Epub 2016 May 16.

c Sheffield Teaching Hospitals NHS Fountation Trust , UK.

Lithium toxicity in a neonate can occur owing to antenatal exposure as a result of maternal treatment for psychiatric illnesses. False elevation of lithium levels has been reported in the paediatric population when the sample was mistakenly collected in a lithium heparin container. A term, male infant was born to a mother who was on lithium treatment for a psychiatric illness. On day 1, the infant was jittery, had a poor suck with difficulties in establishing feeds. Blood taken from the infant approximately 8 hours after birth demonstrated a lithium level of 4.9 mmol/L (adult toxic level w1.5 mmol/L). However, the sample for lithium levels was sent in a lithium heparin container and the probability of false elevation was considered. He was closely monitored in the neonatal intensive care unit and his hydration was optimised with intravenous fluids. Clinically, he remained well and commenced feeding, and his jitteriness had decreased the following day. A repeat blood lithium level, collected in a gel container, was only 0.4 mmol/L. The initially raised lithium level was owing to contamination from the lithium heparin container.
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http://dx.doi.org/10.1179/2046905515Y.0000000050DOI Listing
August 2016

Age-related macular degeneration: genome-wide association studies to translation.

Genet Med 2016 Apr 28;18(4):283-9. Epub 2015 May 28.

Centre for Ophthalmology and Vision Sciences, Institute of Human Development, University of Manchester, Manchester, UK.

In recent years, genome-wide association studies (GWAS), which are able to analyze the contribution to disease of genetic variations that are common within a population, have attracted considerable investment. Despite identifying genetic variants for many conditions, they have been criticized for yielding data with minimal clinical utility. However, in this regard, age-related macular degeneration (AMD), the most common form of blindness in the Western world, is a striking exception. Through GWAS, common genetic variants at a number of loci have been discovered. Two loci in particular, including genes of the complement cascade on chromosome 1 and the ARMS2/HTRA1 genes on chromosome 10, have been shown to convey significantly increased susceptibility to developing AMD. Today, although it is possible to screen individuals for a genetic predisposition to the disease, effective interventional strategies for those at risk of developing AMD are scarce. Ongoing research in this area is nonetheless promising. After providing brief overviews of AMD and common disease genetics, we outline the main recent advances in the understanding of AMD, particularly those made through GWAS. Finally, the true merit of these findings and their current and potential translational value is examined.Genet Med 18 4, 283-289.
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http://dx.doi.org/10.1038/gim.2015.70DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4823638PMC
April 2016

Age-related macular degeneration and the role of the complement system.

Mol Immunol 2015 Sep 21;67(1):43-50. Epub 2015 Mar 21.

Centre for Ophthalmology & Vision Sciences, Institute of Human Development, University of Manchester, Manchester, UK; Centre for Advanced Discovery & Experimental Therapeutics, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, UK; Manchester Royal Eye Hospital, Central Manchester University Hospitals NHS Foundation Trust, Manchester, UK. Electronic address:

Age-related macular degeneration (AMD) is a leading cause of visual impairment. It is characterised by damage to a tissue complex composed of the retinal pigment epithelium, Bruch's membrane and choriocapillaris. In early AMD extracellular debris including drusen accumulates in Bruch's membrane and then in late AMD geographic atrophy and/or neovascularisation develop. Variants in genes encoding components of the alternative pathway of the complement cascade have a major influence on AMD risk, especially at the RCA locus on chromosome 1, which contains CFH and the CFHR genes. Immunohistochemical studies have demonstrated complement components in unaffected and AMD macular tissue. Whilst other factors, including oxidative stress, play important roles in AMD pathogenesis, evidence for the central role played by complement dysregulation is discussed in this review.
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http://dx.doi.org/10.1016/j.molimm.2015.02.032DOI Listing
September 2015

Role of Factor H and Related Proteins in Regulating Complement Activation in the Macula, and Relevance to Age-Related Macular Degeneration.

J Clin Med 2015 Jan;4(1):18-31

Centre for Hearing & Vision Research, Institute of Human Development, AV Hill Building, University of Manchester, Oxford Road, Manchester M13 9PL, UK ; Centre for Advanced Discovery and Experimental Therapeutics, University of Manchester and Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester M13 9WL, UK ; Manchester Royal Eye Hospital, Central Manchester University Hospitals NHS Foundation Trust, Manchester M13 9WH, UK.

The recent revolution in age-related macular degeneration (AMD) genetics has demonstrated that genetic alterations affecting the alternative pathway of the complement cascade have a major influence on AMD risk. One of the two most important genetic loci is on chromosome 1 and contains genes encoding complement factor H (FH) and the factor H related proteins (FHR proteins). In macular tissue, especially Bruch's membrane, relatively high levels of a truncated splice variant of FH called factor H-like protein 1 (FHL-1) are present. Here we discuss how genetic variations may alter the amounts, or by altering their protein sequences, the functions of these proteins. In particular, the common Y402H polymorphism affects the ability of FHL-1 and FH to localize to Bruch's membrane and the inner choroid because it alters the ability of these complement regulators to bind heparan sulphate (HS) in these structures. In addition, there is an age-related loss of HS from Bruch's membrane. We hypothesize that a combination of poor binding of the 402H variants of FHL-1 and FH to Bruch's membrane, combined with a decrease in binding due to age-related HS loss, eventually results in insufficient FHL-1 and FH binding to Bruch's membrane. This could result in complement activation, inflammation and thereby predispose to AMD.
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http://dx.doi.org/10.3390/jcm4010018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4340553PMC
January 2015

Complementing the Sugar Code: Role of GAGs and Sialic Acid in Complement Regulation.

Front Immunol 2015 2;6:25. Epub 2015 Feb 2.

Centre for Hearing and Vision Research, Institute of Human Development, University of Manchester , Manchester , UK ; Centre for Advanced Discovery and Experimental Therapeutics, University of Manchester and Central Manchester University Hospitals NHS Foundation Trust , Manchester , UK.

Sugar molecules play a vital role on both microbial and mammalian cells, where they are involved in cellular communication, govern microbial virulence, and modulate host immunity and inflammatory responses. The complement cascade, as part of a host's innate immune system, is a potent weapon against invading bacteria but has to be tightly regulated to prevent inappropriate attack and damage to host tissues. A number of complement regulators, such as factor H and properdin, interact with sugar molecules, such as glycosaminoglycans (GAGs) and sialic acid, on host and pathogen membranes and direct the appropriate complement response by either promoting the binding of complement activators or inhibitors. The binding of these complement regulators to sugar molecules can vary from location to location, due to their different specificities and because distinct structural and functional subpopulations of sugars are found in different human organs, such as the brain, kidney, and eye. This review will cover recent studies that have provided important new insights into the role of GAGs and sialic acid in complement regulation and how sugar recognition may be compromised in disease.
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http://dx.doi.org/10.3389/fimmu.2015.00025DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4313701PMC
February 2015
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