Ophthalmologies
Abstract
An arginine to cysteine substitution at amino acid position 203 (C203R) is the most common missense mutation in human cone opsin. Linked to color blindness and blue cone monochromacy (BCM), C203 is involved in a crucial disulfide bond required for proper folding. It has previously been postulated that expression of mutant C203R cone opsin exerts a toxic effect on cone photoreceptors, similar to some well-characterized missense mutations in rhodopsin that lead to protein misfolding. In this study, we generated and characterized a BCM mouse model carrying the equivalent C203R mutation (Opn1mwC198ROpn1sw–/–) to investigate the disease mechanism and develop a gene therapy approach for this disorder. Untreated Opn1mwC198ROpn1sw–/– cones phenocopied affected cones in human patients with the equivalent mutation, exhibiting shortened or absent cone outer segments and loss of function. We determined that gene augmentation targeting cones specifically yielded robust rescue of cone function and structure when Opn1mwC198ROpn1sw–/– mice were treated at early ages. Importantly, treated cones displayed elaborated outer segments and replenished expression of crucial cone phototransduction proteins. Interestingly, we were unable to detect OPN1MWC198R mutant opsin at any age. This is the first proof-of-concept study exploring the efficacy of gene therapy in BCM associated with a C203R mutation.
Authors
Emily R. Sechrest, Xiaojie Ma, Marion E. Cahill, Robert J. Barbera, Yixiao Wang, Wen-Tao Deng
Abstract
Syndromic ciliopathies and retinal degenerations are large heterogeneous groups of genetic diseases. Pathogenic variants in the CFAP418 gene may cause both disorders, and its protein sequence is evolutionarily conserved. However, the disease mechanism underlying CFAP418 mutations has not been explored. Here, we apply quantitative lipidomic, proteomic, and phosphoproteomic profiling and affinity purification coupled with mass spectrometry to address the molecular function of CFAP418 in retinas. We show that CFAP418 protein binds to lipid metabolism precursor phosphatidic acid (PA) and mitochondrion-specific lipid cardiolipin but does not form a tight and static complex with proteins. Loss of Cfap418 in mice disturbs membrane lipid homeostasis and membrane-protein association, which subsequently causes mitochondrial defects and membrane remodeling abnormalities across multiple vesicular trafficking pathways in photoreceptors, especially the endosomal sorting complexes required for transport (ESCRT) pathway. Ablation of Cfap418 also increases the activity of PA-binding protein kinase Cα in the retina. Overall, our results indicate that membrane lipid imbalance is a pathological mechanism underlying syndromic ciliopathies and retinal degenerations, which is associated with other known causative genes of these diseases.
Authors
Anna M. Clark, Dongmei Yu, Grace Neiswanger, Daniel Zhu, Junhuang Zou, J. Alan Maschek, Thomas Burgoyne, Jun Yang
Abstract
The management of preretinal fibrovascular membranes, a devastating complication of advanced diabetic retinopathy (DR), remains challenging. We characterized the molecular profile of cell populations in these fibrovascular membranes to identify new therapeutic targets. Preretinal fibrovascular membranes were surgically removed from patients and submitted for single cell RNA (scRNA) sequencing. Differential gene expression was implemented to define the transcriptomic profile of these cells and revealed the presence of endothelial, inflammatory, and stromal cells. Endothelial cell re-clustering identified subclusters characterized by non-canonical trascriptomic profile, and active angiogenesis. Deeper investigation of the inflammatory cells showed a subcluster of macrophages expressing pro-angiogenic cytokines, presumably contributing to angiogenesis. The stromal cell cluster included a pericyte-myofibroblast transdifferentiating subcluster, indicating the involvement of pericytes in fibrogenesis. Differentially expressed gene analysis showed that Adipocyte Enhancer-binding Protein 1, AEBP1, was significantly upregulated in myofibroblast clusters, suggesting that this molecule may have a potential role in transformation. Cell culture experiments with human retinal pericytes (HRP) in high glucose condition confirmed the molecular transformation of pericytes towards myofibroblastic lineage. siAEBP1 transfection in HRP reduced the expression of profibrotic markers in high glucose. In conclusion, AEBP1 signaling modulates pericyte-myofibroblast transformation, suggesting that targeting AEBP1 could prevent scar tissue formation in advanced DR.
Authors
Katia Corano-Scheri, Jeremy A. Lavine, Thomas R. Tedeschi, Benjamin R. Thomson, Amani A. Fawzi
Abstract
The penetration of allergens through the epithelial layer is the initial step in the development of allergic conjunctivitis. Although the pollinosis patients manifest symptoms in minutes after pollen exposure, the mechanisms of the rapid allergen transport remain unclear. In the present study, we found that the instillation of pollen shells rapidly induces a large number of goblet cell-associated antigen passages (GAPs) in the conjunctiva. Antigen acquisition by the stromal cells including macrophages and CD11b+ dendritic cells correlated with the surface GAP formation. Furthermore, a substantial amount of antigen was transported to the stroma during the first 10 minutes of the pollen exposure, which was sufficient for the full induction of an allergic conjunctivitis mouse model. This inducible rapid GAP formation and antigen acquisition was suppressed by topical lidocaine or trigeminal ablation, indicating that the sensory nervous system plays an essential role. Interestingly, pollen shell-stimulated GAP formation was not suppressed by topical atropine, suggesting that the conjunctival GAPs and intestinal GAPs are differentially regulated. These results identify pollen shell-induced GAP as a novel therapeutic target for allergic conjunctivitis.
Authors
Meiko Kimura, Tomoaki Ando, Yasuharu Kume, Saaya Fukase, Moe Matsuzawa, Kosuke Kashiwagi, Kumi Izawa, Ayako Kaitani, Nobuhiro Nakano, Keiko Maeda, Hideoki Ogawa, Ko Okumura, Shintaro Nakao, Akira Murakami, Nobuyuki Ebihara, Jiro Kitaura
Abstract
Retinitis pigmentosa (RP) is the most common inherited retinal disease (IRD) and is characterized by photoreceptor degeneration and progressive loss of vision. We report here four patients who presented with RP from three unrelated families with variants in TBC1D32, which to date has never been associated with an IRD. To validate TBC1D32 as a putative RP causative gene, we combined Xenopus in vivo approaches and human iPSC-derived retinal models. Our data showed that TBC1D32 was expressed during retinal development and that it played an important role in retinal pigment epithelium (RPE) differentiation. Furthermore, we identified a role for TBC1D32 in ciliogenesis of the RPE. We demonstrated elongated ciliary defects that resulted in disrupted apical tight junctions, loss of functionality (delayed retinoid cycling and altered secretion balance), and the onset of an epithelial-mesenchymal transition-like phenotype. Lastly, our results also suggested photoreceptor differentiation defects, including connecting cilium anomalies, that resulted in impaired trafficking to the outer segment in both cones and rods in TBC1D32 iPSC-derived retinal organoids. Overall, our data not only highlight a critical role for TBC1D32 in the retina but demonstrate that TBC1D32 mutations lead to RP. We thus identify TBC1D32 as an IRD causative gene.
Authors
Béatrice Bocquet, Caroline Borday, Nejla Erkilic, Daria Mamaeva, Alicia Donval, Christel Masson-Garcia, Karine Parain, Karolina Kaminska, Mathieu Quinodoz, Irene Perea-Romero, Gema Garcia-Garcia, Carla Jimenez-Medina, Hassan Boukhaddaoui, Arthur Coget, Nicolas Leboucq, Giacomo Calzetti, Stefano A. Gandolfi, Antonio Percesepe, Valeria Barili, Vera Uliana, Marco Delsante, Francesca Bozzetti, Hendrik P.N. Scholl, Marta Corton, Carmen Ayuso, Jose M. Millan, Carlo Rivolta, Isabelle Meunier, Muriel Perron, Vasiliki Kalatzis
Abstract
Diabetic retinopathy (DR) is a leading cause of blindness in working-age adults and remains an important public health issue worldwide. Here we demonstrate that the expression of stimulator of interferon genes (STING) is increased in patients with DR and animal models of diabetic eye disease. STING has been previously shown to regulate cell senescence and inflammation, key contributors to the development and progression of DR. To investigate the mechanism whereby STING contributes to the pathogenesis of DR, diabetes was induced in STING-KO mice and STINGGT (loss-of-function mutation) mice, and molecular alterations and pathological changes in the retina were characterized. We report that retinal endothelial cell senescence, inflammation, and capillary degeneration were all inhibited in STING-KO diabetic mice; these observations were independently corroborated in STINGGT mice. These protective effects resulted from the reduction in TBK1, IRF3, and NF-κB phosphorylation in the absence of STING. Collectively, our results suggest that targeting STING may be an effective therapy for the early prevention and treatment of DR.
Authors
Haitao Liu, Sayan Ghosh, Tanuja Vaidya, Sridhar Bammidi, Chao Huang, Peng Shang, Archana Padmanabhan Nair, Olivia Chowdhury, Nadezda A. Stepicheva, Anastasia Strizhakova, Stacey Hose, Nikolaos Mitrousis, Santosh Gopikrishna Gadde, Thirumalesh MB, Pamela Strassburger, Gabriella Widmer, Eleonora M. Lad, Patrice E. Fort, José-Alain Sahel, J. Samuel Zigler Jr., Swaminathan Sethu, Peter D. Westenskow, Alan D. Proia, Akrit Sodhi, Arkasubhra Ghosh, Derrick Feenstra, Debasish Sinha
Abstract
Over 30 million people worldwide suffer from untreatable vision loss and blindness associated with childhood-onset and age-related eye diseases caused by photoreceptor (PR), retinal pigment epithelium (RPE), and choriocapillaris (CC) degeneration. Recent work suggests that RPE-based cell therapy may slow down vision loss in late stages of age-related macular degeneration (AMD), a polygenic disease induced by RPE atrophy. However, accelerated development of effective cell therapies is hampered by the lack of large-animal models that allow testing safety and efficacy of clinical doses covering the human macula (20 mm2). We developed a versatile pig model to mimic different types and stages of retinal degeneration. Using an adjustable power micropulse laser, we generated varying degrees of RPE, PR, and CC damage and confirmed the damage by longitudinal analysis of clinically relevant outcomes, including analyses by adaptive optics and optical coherence tomography/angiography, along with automated image analysis. By imparting a tunable yet targeted damage to the porcine CC and visual streak — with a structure similar to the human macula — this model is optimal for testing cell and gene therapies for outer retinal diseases including AMD, retinitis pigmentosa, Stargardt, and choroideremia. The amenability of this model to clinically relevant imaging outcomes will facilitate faster translation to patients.
Authors
Francesca Barone, Juan Amaral, Irina Bunea, Mitra Farnoodian, Rohan Gupta, Rishabh Gupta, Dara Baker, M. Joseph Phillips, Richard J. Blanch, Arvydas Maminishkis, David M. Gamm, Kapil Bharti
Abstract
Variants within the high copy number mitochondrial genome (mtDNA) can disrupt organelle function and lead to severe multi-system disease. The wide range of manifestations observed in mitochondrial disease patients results from varying fractions of abnormal mtDNA molecules in different cells and tissues, a phenomenon termed heteroplasmy. However, the landscape of heteroplasmy across cell types within tissues and its influence on phenotype expression in affected patients remains largely unexplored. Here, we identify non-random distribution of a pathogenic mtDNA variant across a complex tissue using single-cell RNA sequencing, mitochondrial single-cell ATAC sequencing, and multimodal single-cell sequencing. We profile the transcriptome, chromatin accessibility state, and heteroplasmy in cells from the eyes of a patient with mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) and healthy control donors. Utilizing the retina as a model for complex multi-lineage tissues, we found that the proportion of the pathogenic m.3243A>G allele was neither evenly nor randomly distributed across diverse cell types. All neuroectoderm-derived neural cells exhibited a high percentage of the mutant variant. However, a subset of mesoderm-derived lineage, namely the vasculature of the choroid, was near homoplasmic for the wildtype allele. Gene expression and chromatin accessibility profiles of cell types with high and low proportions of m.3243A>G implicate mTOR signaling in the cellular response to heteroplasmy. We further found by multimodal single-cell sequencing of retinal pigment epithelial cells that a high proportion of the pathogenic mtDNA variant was associated with transcriptionally and morphologically abnormal cells. Together, these findings show the non-random nature of mitochondrial variant partitioning in human mitochondrial disease and underscore its implications for mitochondrial disease pathogenesis and treatment.
Authors
Nathaniel K. Mullin, Andrew P. Voigt, Miles J. Flamme-Wiese, Xiuying Liu, Megan J. Riker, Katayoun Varzavand, Edwin M. Stone, Budd A. Tucker, Robert F. Mullins
Abstract
BACKGROUND. A randomized clinical trial from 1984-1992 indicated that vitamin A supplementation had a beneficial effect on the progression of retinitis pigmentosa (RP), while vitamin E had an adverse effect. METHODS. Sequencing of banked DNA samples from that trial provided the opportunity to determine if certain genotypes responded preferentially to vitamin supplementation. RESULTS. The genetic solution rate was 587/765 (77%) of sequenced samples. Combining genetic solutions with electroretinogram outcomes showed that there were systematic differences in severity and progression seen among different genetic subtypes of RP, extending findings made for USH2A, RHO, RPGR, PRPF31, and EYS. Baseline electroretinogram 30Hz flicker implicit time was an independent strong predictor of progression rate. Using additional data and baseline implicit time as a predictor, the deleterious effect of vitamin E was still present. Surprisingly, the effect of vitamin A progression in the cohort as a whole was not detectable, with or without data from subsequent trials. Subgroup analyses are also discussed. CONCLUSION. Overall, genetic subtype and implicit time have significant predictive power for a patient’s rate of progression, which is useful prognostically. While vitamin E supplementation should still be avoided, these data do not support a generalized neuroprotective effect of vitamin A for all types of RP. TRAIL REGISTRATION. ClinicalTrials.gov NCT00000114, NCT00000116, NCT00346333 FUNDING. the Foundation Fighting Blindness and the National Eye Institute: RO1 EY012910 (EAP), R01 EY031036 (JC), R01EY026904 (KMB/EAP), and P30EY014104.
Authors
Jason Comander, Carol Weigel DiFranco, Kit Green Sanderson, Emily M. Place, Matthew Maher, Erin Zampaglione, Yan Zhao, Rachel M. Huckfeldt, Kinga M. Bujakowska, Eric A. Pierce
Abstract
Familial exudative vitreoretinopathy (FEVR) is a complex hereditary eye disorder characterized by incomplete development of the retinal vasculature, thereby affecting retinal angiogenesis. But the genetic factors contributing to its development or pathogenesis remain elusive. In a Chinese FEVR family with 19 members, by utilizing whole exome sequencing, we identified a candidate disease-causing DNA variant in sorting nexin 31 (SNX31) (c.963delG; p. Trp321Cys), which results in a frameshift mutation. Herein we studied the biochemical mechanism of this mutation and uncovered that it is deficient in β1-integrin binding and integrin stability. The SNX31 c.963delG point mutation mouse model (SNX31m/m) was constructed using CRISPR/Cas9 technology. At 2-4 months of age, SNX31m/m mice showed fundus phenotypes similar to FEVR-like changes, including vascular leakage and retinal atrophy. Moreover, we found that VEGF and apoptotic pathways were involved in these ocular phenotypes. At present, the FEVR-like mouse model is mainly constructed by intravitreal injection, and we are the first to construct it by gene knockout. Hence our study extended FEVR mutation spectrum to include SNX31. Meanwhile, these findings expanded our understanding of the molecular pathogenesis of FEVR and may facilitate the development of methods for the diagnosis and prevention of FEVR patients.
Authors
Ningda Xu, Yi Cai, Jiarui Li, Tianchang Tao, Caifei Liu, Yan Shen, Xiaoxin Li, Leiliang Zhang, Mingwei Zhao, Xuan Shi, Jing Li, Lvzhen Huang
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