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Lopez MJ, Seyed-Razavi Y, Jamali A, Harris DL, Hamrah P. The Chemokine Receptor CXCR4 Mediates Recruitment of CD11c+ Conventional Dendritic Cells Into the Inflamed Murine Cornea. Invest Ophthalmol Vis Sci 2018;59(13):5671-5681.Abstract
Purpose: The cornea contains distinct populations of antigen-presenting cells (APCs), including conventional dendritic cells (cDCs). Little is known about the molecular mechanisms involved in cDCs homing and recruitment into the naïve and inflamed cornea. The purpose of this study was to investigate the presence of CXCR4 and its ligand CXCL12 in the murine cornea and its role in cDC migration during corneal inflammation. Methods: The expression of CXCR4 and CXCL12 in naïve and suture-inflamed murine corneas was assessed by whole-mount staining, flow cytometry, and quantitative PCR. The role of CXCR4 in recruitment into inflamed corneas was investigated using adoptive transfer of cDCs blocked with neutralizing antibody against CXCR4. Results: We show the chemokine receptor CXCR4 to be expressed on 51.7% and 64.8% of total corneal CD11c+ cDCs, equating to 98.6 ± 12.5 cells/mm2 in the peripheral and 64.7 ± 10.6 cells/mm2 in the central naïve cornea, respectively. Along with a 4.5-fold increase in CXCL12 expression during inflammation (P < 0.05), infiltrating cDCs also expressed CXCR4 in both the peripheral (222.6 ± 33.3 cells/mm2; P < 0.001) and central cornea (161.9 ± 23.8 cells/mm2; P = 0.001), representing a decrease to 31.0% and 37.3% in the cornea, respectively. Further, ex vivo blockade (390.1 ± 40.1 vs. 612.1 ± 78.3; P = 0.008) and local blockade (263.5 ± 27.1 vs. 807.5 ± 179.5, P < 0.001) with anti-CXCR4 neutralizing antibody resulted in a decrease in cDCs homing into the cornea compared with cells pretreated with isotype controls. Conclusions: Our results demonstrate that corneal CXCL12 plays a direct role in CXCR4+ cDC recruitment into the cornea. The CXCR4/CXCL12 axis is therefore a potential target to modulate corneal inflammatory responses.
Ibrahim AS, Elmasry K, Wan M, Abdulmoneim S, Still A, Khan F, Khalil A, Saul A, Hoda MN, Al-Shabrawey M. A Controlled Impact of Optic Nerve as a New Model of Traumatic Optic Neuropathy in Mouse. Invest Ophthalmol Vis Sci 2018;59(13):5548-5557.Abstract
Purpose: Traumatic optic neuropathy (TON) is the most feared visual consequence of head and ocular trauma in both military and civilian communities, for which standard treatment does not exist. Animal models are critical for the development of novel TON therapies as well as the understanding of TON pathophysiology. However, the models currently used for TON have some limitations regarding consistency and mirroring the exact pathological progression of TON in closed ocular trauma. In this study, we modified the model of controlled cortical impact and adapted it for studying TON. Methods: We defined new standardized procedures to induce TON in mice, wherein the optic nerve is reproducibly exposed to a graded controlled impact of known velocity to produce a graded deficit in retinal ganglion cell (RGC) electrophysiological functions. Results: The key results of validating this newly modified model, "controlled orbital impact (COI)," included (1) the injury parameters (velocity as well as contusion depth and time), which were quantifiable and manageable to generate a wide range of TON severities; (2) a reproducible endpoint of diminished positive scotopic threshold response (pSTR) has been achieved without the interference of surgical variability and destruction of surrounding tissues; (3) the contralateral eyes showed no significant difference to the eyes of naïve mice, allowing them to be used as an internal control to minimize interindividual variability among mice; and (4) the occurrence of injury-associated mortality and/or ocular comorbidity was rare. Conclusions: Taken together, this model overcomes some limitations of prior TON mouse models and provides an innovative platform to identify therapeutic targets for neuroprotection and/or neurorestoration following traumatic ocular injury.
Fortin E, Cestari DM, Weinberg DH. Ocular myasthenia gravis: an update on diagnosis and treatment. Curr Opin Ophthalmol 2018;29(6):477-484.Abstract
PURPOSE OF REVIEW: Myasthenia gravis is an autoimmune disease that commonly affects the palpebral and extraocular muscles. Ocular myasthenia gravis (OMG) is a variant of the disease that is confined to the ocular muscles but frequently becomes generalized over time. The diagnosis of OMG is often challenging but both clinical and laboratory findings are helpful in confirming the clinical suspicion. This review provides an update on the diagnostic approach and therapeutic options for OMG. RECENT FINDINGS: Antimuscle-specific tyrosine kinase and LDL-related receptor-related protein 4 are newly available serologic testing for myasthenia gravis that can help in increasing the diagnostic sensitivity of OMG. They should be included to the diagnostic algorithm of OMG in appropriate clinical situations. SUMMARY: OMG remains a primarily clinical diagnosis, but recent advances in laboratory testing can improve the diagnostic accuracy and should be used in appropriate clinical settings. The mainstay of treatment for OMG has not significantly changed over the past years, but the increasing availability of steroid-sparing agents improved the disease control while minimizing steroid-induced complications.
Chwalisz BK, Stone JH. Neuro-ophthalmic complications of IgG4-related disease. Curr Opin Ophthalmol 2018;29(6):485-494.Abstract
PURPOSE OF REVIEW: IgG4-related disease (IgG4-RD) is increasingly recognized as a fibroinflammatory disease with a plethora of organ-specific manifestations but a particular predilection for head and neck tissues, including the nervous system. This review discusses general features and organ-specific presentations of IgG4-RD as well as treatment considerations, particularly emphasizing features of neuro-ophthalmic interest. RECENT FINDINGS: IgG4-RD is emerging as a common cause of several fibroinflammatory disorders in the head and neck that were previously considered idiopathic, such as sclerosing orbital pseudotumor, orbital myositis, hypophysitis, and hypertrophic pachymeningitis. New and unusual presentations continue to be described, including a number of vascular manifestations. Substantial progress has been made in elucidating the cell types involved in IgG4-RD, and new pathogenic models are being proposed. Although clinicopathologic correlation remains the cornerstone of diagnosis, ancillary tests such as flow cytometry for circulating plasmablasts and PET-computed tomography have high sensitivity, and certain radiologic features are recognized to be particularly suggestive, such as infraorbital nerve enlargement in IgG4-RD orbitopathy. IgG4-RD often responds to steroids but incomplete responses and relapses are common. Rituximab is emerging as a promising new therapy. SUMMARY: The current review summarizes manifestations of IgG4RD that are of particular relevance to neuro-ophthalmic practice.
Koo EB, VanderVeen DK, Lambert SR. Global Practice Patterns in the Management of Infantile Cataracts. Eye Contact Lens 2018;44 Suppl 2:S292-S296.Abstract
OBJECTIVES: Surveys are an important tool to assess the impact of research on physicians' approach to patient care. This survey was conducted to assess current practice patterns in the management of infantile cataracts in light of the findings of the Infant Aphakia Treatment Study. METHODS: Pediatric ophthalmologists were emailed a link to the survey using newsletters from American Association of Pediatric Ophthalmology and Strabismus, World Society of Pediatric Ophthalmology and Strabismus, and the Pediatric Listserv. The 17-question survey was anonymous and active during July to August 2016. RESULTS: One hundred twenty-five respondents (North America, 65%; Asia, 12%; Europe, 9%; and other, 14%) reported operating on pediatric cataracts. Most practice in a university setting (55%). There was a strong consensus that unilateral cataract surgery should be performed between ages 4 to 6 weeks and aphakic contact lenses should be used to optically correct their eyes, particularly in children ≤6 months of age. For bilateral cataracts, there was a trend for surgeons to perform cataract surgery at an older age than unilateral cataract surgery. Surgeons who performed less than 5 versus greater than 20 pediatric cataract surgeries/year were more likely to use aphakic contact lenses in children undergoing cataract surgery more than 6 months of age (62% vs. 35%, P=0.04). Most respondents (73%) indicated that the Infant Aphakia Treatment Study had changed how they manage unilateral congenital cataracts. CONCLUSION: Most pediatric cataract surgeons perform congenital cataract surgery between ages 4 to 6 weeks and use aphakic contact lenses for initial optical correction in infants less than 6 months. Surgeons have equal preference for intraocular lenses and contact lenses in infants more than 6 months of age.
Aiello LP, Odia I, Glassman AR, Melia M, Jampol LM, Bressler NM, Kiss S, Silva PS, Wykoff CC, Sun JK, Sun JK. Comparison of Early Treatment Diabetic Retinopathy Study Standard 7-Field Imaging With Ultrawide-Field Imaging for Determining Severity of Diabetic Retinopathy. JAMA Ophthalmol 2018;Abstract
Importance: Moderate to substantial agreement between Early Treatment Diabetic Retinopathy Study (ETDRS) 7-field imaging and ultrawide-field (UWF) imaging has been suggested in single-center studies. Comparing images obtained by multiple centers could increase confidence that UWF images can be used reliably in place of ETDRS imaging in future clinical trials. Objective: To compare diabetic retinopathy (DR) severity from modified ETDRS 7-field imaging and UWF imaging. Design, Setting, and Participants: This preplanned, cross-sectional analysis included modified ETDRS 7-field images obtained using the Diabetic Retinopathy Clinical Research Network acquisition protocol and UWF images obtained captured with the Optos 200Tx system (Optos, PLC) from adult participants (≥18 years old) with type 1 or type 2 diabetes. Both image types were evaluated by trained graders masked to clinical data. Data collection occurred from February 2015 to December 2015, and data analysis from June 2016 to December 2017. Main Outcomes and Measures: Agreement between UWF images, UWF imagesmasked to include only the ETDRS 7-field area, and ETDRS 7-field images were calculated using κ statistics. Results: A total of 764 eyes from 385 participants were included; participants had a median (IQR) age of 62.2 (53.6-69.2) years, 194 (50.4%) were women, and 256 (66.5%) were white. Of 742 eyes with both ETDRS 7-field images and UWF masked images graded, 359 (48.4% [95% CI, 44.4%-52.4%]) eyes had exact agreement, and 653 eyes (88.0% [95% CI, 85.2%-90.3%]) agreed within 1 step (weighted κ, 0.51 [95% CI, 0.44-0.58]). After open adjudication by an independent senior grader of all images with more than a 2-step discrepancy, perfect agreement was found in 435 eyes (59.0% [95% CI, 55.1%-62.8%]) and agreement within 1 step in 714 eyes (96.9% [95% CI, 95.1%-98.0%]; κ, 0.77 [95% CI, 0.73-0.82]). Ability of the imaging modalities to detect retinopathy severity in an individual eye was considered similar in 59 eyes (50.9% [95% CI, 41.3%-60.4%]), better for ETDRS 7-field imaging in 22 eyes (19.0% [95% CI, 12.5%-27.7%]), and better for UWF-masked images in 31 eyes (26.7% [95% CI 18.8%-36.5%]). Comparing UWF masked and unmasked images, 94 of 751 eyes (12.5%) had DR graded as at least 1 step more severe on UWF unmasked images vs UWF masked images. Predominantly peripheral DR lesions were present in 308 of 751 eyes (41.0%); this suggested increased DR severity by 2 or more steps in 34 eyes (11.0%). Conclusions and Relevance: Imaging by the ETDRS 7-field and UWF imaging systems have moderate to substantial agreement when determining the severity of DR within the 7 standard fields. Disparities in an individual eye are equivalently distributed between imaging modalities and can be better or worse on 1 or the other. Longitudinal follow-up will evaluate the primary outcome of this study to determine if peripheral retinal findings are associated with future retinopathy outcomes.
Yu G, Sun P, van Zyl T, Tandias R, Arroyo JG. BILATERAL CENTRAL RETINAL VEIN OCCLUSIONS IN A YOUNG PATIENT WITH A HISTORY OF EOSINOPHILIC PNEUMONIA AND THALAMIC STROKE. Retin Cases Brief Rep 2018;12(4):300-304.Abstract
PURPOSE: To describe a case of a central retinal vein occlusion in a young patient with a history of eosinophilic pneumonia. METHODS: A retrospective case report of a 45-year-old woman with acute painless vision loss for 9 days after multiple episodes of eosinophilic pneumonia and thalamic stroke. Fluorescein angiography, spectral domain optical coherence tomography, and clinical examination were performed. She was then treated with intravitreal bevacizumab and pan-retinal photocoagulations. RESULTS: Retinal examination revealed tortuosity and dilatation of all branches of the central retinal vein and flame-shaped hemorrhages in all four quadrants of the right eye associated with cystoid macular edema, optic disc edema, and cotton wool spots. The left eye had mild venous dilatation and tortuosity with a few dot retinal hemorrhages in the far temporal periphery. The cystoid macular edema resolved after one intravitreal injection of bevacizumab and remained resolved at the most recent follow-up. Fluorescein angiography at the most recent follow-up revealed vasculitis in the far periphery of the nontreated eye. CONCLUSION: Central retinal vein occlusion in young patients is a rare condition often presenting as a manifestation of an underlying inflammatory or hematological disorder. Combined anti-vascular endothelial growth factor treatment and pan-retinal photocoagulation may have resolved the associated cystoid macular edema in this case, although continued observation is necessary.
Shen J, Xiao R, Bair J, Wang F, Vandenberghe LH, Dartt D, Baranov P, Ng YSE. Novel engineered, membrane-localized variants of vascular endothelial growth factor (VEGF) protect retinal ganglion cells: a proof-of-concept study. Cell Death Dis 2018;9(10):1018.Abstract
Endogenous vascular endothelial growth factor (VEGF-A) can protect retinal ganglion cells (RGC) from stress-induced cell death in ocular hypertensive glaucoma. To exploit the neuroprotective function of VEGF-A for therapeutic application in ocular disorders such as glaucoma while minimizing unwanted vascular side effects, we engineered two novel VEGF variants, eVEGF-38 and eVEGF-53. These variants of the diffusible VEGF-A isoform VEGF121 are expressed as dimeric concatamers and remain tethered to the cell membrane, thus restricting the effects of the engineered VEGF to the cells expressing the protein. For comparison, we tested a Myc-tagged version of VEGF189, an isoform that binds tightly to the extracellular matrix and heparan sulfate proteoglycans at the cell surface, supporting only autocrine and localized juxtacrine signaling. In human retinal endothelial cells (hREC), expression of eVEGF-38, eVEGF-53, or VEGF189 increased VEGFR2 phosphorylation without increasing expression of pro-inflammatory markers, relative to VEGF165 protein and vector controls. AAV2-mediated transduction of eVEGF-38, eVEGF-53, or VEGF189 into primary mouse RGC promoted synaptogenesis and increased the average total length of neurites and axons per RGC by ~ 12-fold, an increase that was mediated by VEGFR2 and PI3K/AKT signaling. Expression of eVEGF-38 in primary RGC enhanced expression of genes associated with neuritogenesis, axon outgrowth, axon guidance, and cell survival. Transduction of primary RGC with any of the membrane-associated VEGF constructs increased survival both under normal culture conditions and in the presence of the cytotoxic chemicals HO (via VEGFR2/PI3K/AKT signaling) and N-methyl-D-aspartate (via reduced Ca influx). Moreover, RGC number was increased in mouse embryonic stem cell-derived retinal organoid cultures transduced with the eVEGF-53 construct. The novel, engineered VEGF variants eVEGF-38 and eVEGF-53 show promise as potential therapeutics for retinal RGC neuroprotection when delivered using a gene therapy approach.
Mauschitz MM, Bonnemaijer PWM, Diers K, Rauscher FG, Elze T, Engel C, Loeffler M, Colijn JM, Ikram AM, Vingerling JR, Williams KM, Hammond CJ, Creuzot-Garcher C, Bron AM, Silva R, Nunes S, Delcourt C, Cougnard-Grégoire A, Holz FG, Klaver CCW, Breteler MMB, Finger RP, Finger RP. Systemic and Ocular Determinants of Peripapillary Retinal Nerve Fiber Layer Thickness Measurements in the European Eye Epidemiology (E3) Population. Ophthalmology 2018;125(10):1526-1536.Abstract
PURPOSE: To investigate systemic and ocular determinants of peripapillary retinal nerve fiber layer thickness (pRNFLT) in the European population. DESIGN: Cross-sectional meta-analysis. PARTICIPANTS: A total of 16 084 European adults from 8 cohort studies (mean age range, 56.9±12.3-82.1±4.2 years) of the European Eye Epidemiology (E3) consortium. METHODS: We examined associations with pRNFLT measured by spectral-domain OCT in each study using multivariable linear regression and pooled results using random effects meta-analysis. MAIN OUTCOME MEASURES: Determinants of pRNFLT. RESULTS: Mean pRNFLT ranged from 86.8±21.4 μm in the Rotterdam Study I to 104.7±12.5 μm in the Rotterdam Study III. We found the following factors to be associated with reduced pRNFLT: Older age (β = -0.38 μm/year; 95% confidence interval [CI], -0.57 to -0.18), higher intraocular pressure (IOP) (β = -0.36 μm/mmHg; 95% CI, -0.56 to -0.15), visual impairment (β = -5.50 μm; 95% CI, -9.37 to -1.64), and history of systemic hypertension (β = -0.54 μm; 95% CI, -1.01 to -0.07) and stroke (β = -1.94 μm; 95% CI, -3.17 to -0.72). A suggestive, albeit nonsignificant, association was observed for dementia (β = -3.11 μm; 95% CI, -6.22 to 0.01). Higher pRNFLT was associated with more hyperopic spherical equivalent (β = 1.39 μm/diopter; 95% CI, 1.19-1.59) and smoking (β = 1.53 μm; 95% CI, 1.00-2.06 for current smokers compared with never-smokers). CONCLUSIONS: In addition to previously described determinants such as age and refraction, we found that systemic vascular and neurovascular diseases were associated with reduced pRNFLT. These may be of clinical relevance, especially in glaucoma monitoring of patients with newly occurring vascular comorbidities.
Gao Z, Hwang A, Zhai G, Peli E. Correcting geometric distortions in stereoscopic 3D imaging. PLoS One 2018;13(10):e0205032.Abstract
Motion in a distorted virtual 3D space may cause visually induced motion sickness. Geometric distortions in stereoscopic 3D can result from mismatches among image capture, display, and viewing parameters. Three pairs of potential mismatches are considered, including 1) camera separation vs. eye separation, 2) camera field of view (FOV) vs. screen FOV, and 3) camera convergence distance (i.e., distance from the cameras to the point where the convergence axes intersect) vs. screen distance from the observer. The effect of the viewer's head positions (i.e., head lateral offset from the screen center) is also considered. The geometric model is expressed as a function of camera convergence distance, the ratios of the three parameter-pairs, and the offset of the head position. We analyze the impacts of these five variables separately and their interactions on geometric distortions. This model facilitates insights into the various distortions and leads to methods whereby the user can minimize geometric distortions caused by some parameter-pair mismatches through adjusting of other parameter pairs. For example, in postproduction, viewers can correct for a mismatch between camera separation and eye separation by adjusting their distance from the real screen and changing the effective camera convergence distance.
Cakir B, Liegl R, Hellgren G, Lundgren P, Sun Y, Klevebro S, Löfqvist C, Mannheimer C, Cho S, Poblete A, Duran R, Hallberg B, Canas J, Lorenz V, Liu Z-J, Sola-Visner MC, Smith LEH, Hellström A. Thrombocytopenia is associated with severe retinopathy of prematurity. JCI Insight 2018;3(19)Abstract
Retinopathy of prematurity (ROP) is characterized by abnormal retinal neovascularization in response to vessel loss. Platelets regulate angiogenesis and may influence ROP progression. In preterm infants, we assessed ROP and correlated with longitudinal postnatal platelet counts (n = 202). Any episode of thrombocytopenia (<100 × 109/l) at ≥30 weeks postmenstrual age (at onset of ROP) was independently associated with severe ROP, requiring treatment. Infants with severe ROP also had a lower weekly median platelet count compared with infants with less severe ROP. In a mouse oxygen-induced retinopathy model of ROP, platelet counts were lower at P17 (peak neovascularization) versus controls. Platelet transfusions at P15 and P16 suppressed neovascularization, and platelet depletion increased neovascularization. Platelet transfusion decreased retinal of vascular endothelial growth factor A (VEGFA) mRNA and protein expression; platelet depletion increased retinal VEGFA mRNA and protein expression. Resting platelets with intact granules reduced neovascularization, while thrombin-activated degranulated platelets did not. These data suggest that platelet releasate has a local antiangiogenic effect on endothelial cells to exert a downstream suppression of VEGFA in neural retina. Low platelet counts during the neovascularization phase in ROP is significantly associated with the development of severe ROP in preterm infants. In a murine model of retinopathy, platelet transfusion during the period of neovascularization suppressed retinopathy.
Verticchio Vercellin AC, Jassim F, Poon LY-C, Tsikata E, Braaf B, Shah S, Ben-David G, Shieh E, Lee R, Simavli H, Que CJ, Papadogeorgou G, Guo R, Vakoc BJ, Bouma BE, de Boer JF, Chen TC. Diagnostic Capability of Three-Dimensional Macular Parameters for Glaucoma Using Optical Coherence Tomography Volume Scans. Invest Ophthalmol Vis Sci 2018;59(12):4998-5010.Abstract
Purpose: To compare the diagnostic capability of three-dimensional (3D) macular parameters against traditional two-dimensional (2D) retinal nerve fiber layer (RNFL) thickness using spectral domain optical coherence tomography. To determine if manual correction and interpolation of B-scans improve the ability of 3D macular parameters to diagnose glaucoma. Methods: A total of 101 open angle glaucoma patients (29 with early glaucoma) and 57 healthy subjects had peripapillary 2D RNFL thickness and 3D macular volume scans. Four parameters were calculated for six different-sized annuli: total macular thickness (M-thickness), total macular volume (M-volume), ganglion cell complex (GCC) thickness, and GCC volume of the innermost 3 macular layers (retinal nerve fiber layer + ganglion cell layer + inner plexiform layer). All macular parameters were calculated with and without correction and interpolation of frames with artifacts. The areas under the receiver operating characteristic curves (AUROC) were calculated for all the parameters. Results: The 3D macular parameter with the best diagnostic performance was GCC-volume-34, with an inner diameter of 3 mm and an outer of 4 mm. The AUROC for RNFL thickness and GCC-volume-34 were statistically similar for all regions (global: RNFL thickness 0.956, GCC-volume-34 0.939, P value = 0.3827), except for the temporal GCC-volume-34, which was significantly better than temporal RNFL thickness (P value = 0.0067). Correction of artifacts did not significantly change the AUROC of macular parameters (P values between 0.8452 and 1.0000). Conclusions: The diagnostic performance of best macular parameters (GCC-volume-34 and GCC-thickness-34) were similar to or better than 2D RNFL thickness. Manual correction of artifacts with data interpolation is unnecessary in the clinical setting.
Pan H, Yan Y, Zhang J, Zhao S, Feng L, Ou J, Cao N, Li M, Zhao W, Wan C, Ismail AM, Rajaiya J, Chodosh J, Zhang Q. Rapid Construction of a Replication-Competent Infectious Clone of Human Adenovirus Type 14 by Gibson Assembly. Viruses 2018;10(10)Abstract
In 1955, Human adenovirus type 14 (HAdV-B14p) was firstly identified in a military trainee diagnosed as acute respiratory disease (ARD) in the Netherlands. Fifty years later, a genomic variant, HAdV-B14p1, re-emerged in the U.S. and caused large and fatal ARD outbreaks. Subsequently, more and more ARD outbreaks occurred in Canada, the UK, Ireland, and China, in both military and civil settings. To generate a tool for the efficient characterization of this new genomic variant, a full-length infectious genomic clone of HAdV-B14 was successfully constructed using one-step Gibson Assembly method in this study. Firstly, the full genome of HAdV-B14p1 strain GZ01, the first HAdV-B14 isolate in China, was assembled into pBR322 plasmid by Gibson Assembly. The pBRAdV14 plasmid, generated by Gibson Assembly, was analyzed and verified by PCR, restriction enzymes digestion and the sequencing. Secondly, viruses were rescued from pBRAdV14-transfected A549 cells. The integrity of the rescued viruses was identified by restriction enzyme analysis. The complete sequence of the infectious clone was further sequenced. No mutation was found in the infectious clone during the construction when compared with the parental virus and pBR322 sequences. The direct immunofluorescence assay indicated the expression of the hexon protein. Finally, typical virions were observed; the one-step growth curves further showed that the DNA replication and viral reproduction efficiency of pBRAd14 derived viruses was similar with that of wild-type HAdV-B14 strain. The successful construction of the replication-competent infectious clone of pBRAdV14 facilitates the development of vaccine and antiviral drugs against HAdV-B14, as well as provides a novel strategy for rapid construction of infectious viral clones for other large-genome DNA viruses.
Bonnemaijer PWM, Iglesias AI, Nadkarni GN, Sanyiwa AJ, Hassan HG, Cook C, Cook C, Simcoe M, Taylor KD, Schurmann C, Belbin GM, Kenny EE, Bottinger EP, van de Laar S, Wiliams SEI, Akafo SK, Ashaye AO, Zangwill LM, Girkin CA, Ng MCY, Rotter JI, Weinreb RN, Li Z, Allingham RR, of Consortium EAG, Nag A, Hysi PG, Meester-Smoor MA, Wiggs JL, Wiggs JL, Hauser MA, Hammond CJ, Lemij HG, Loos RJF, van Duijn CM, Thiadens AAHJ, Klaver CCW. Genome-wide association study of primary open-angle glaucoma in continental and admixed African populations. Hum Genet 2018;137(10):847-862.Abstract
Primary open angle glaucoma (POAG) is a complex disease with a major genetic contribution. Its prevalence varies greatly among ethnic groups, and is up to five times more frequent in black African populations compared to Europeans. So far, worldwide efforts to elucidate the genetic complexity of POAG in African populations has been limited. We conducted a genome-wide association study in 1113 POAG cases and 1826 controls from Tanzanian, South African and African American study samples. Apart from confirming evidence of association at TXNRD2 (rs16984299; OR 1.20; P = 0.003), we found that a genetic risk score combining the effects of the 15 previously reported POAG loci was significantly associated with POAG in our samples (OR 1.56; 95% CI 1.26-1.93; P = 4.79 × 10). By genome-wide association testing we identified a novel candidate locus, rs141186647, harboring EXOC4 (OR 0.48; P = 3.75 × 10), a gene transcribing a component of the exocyst complex involved in vesicle transport. The low frequency and high degree of genetic heterogeneity at this region hampered validation of this finding in predominantly West-African replication sets. Our results suggest that established genetic risk factors play a role in African POAG, however, they do not explain the higher disease load. The high heterogeneity within Africans remains a challenge to identify the genetic commonalities for POAG in this ethnicity, and demands studies of extremely large size.

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