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The crumbs (crb) apical polarity genes are essential for the development and functions of epithelia. Adult zebrafish retinal neuroepithelium expresses three crb genes {crbl, crb2a, and crb2b); however, it is unknown whether and how Crbl differs from other Crb proteins in expression, localization, and functions. Here, we show that, unlike zebrafish Crb2a and Crb2b as well as mammalian Crbl and Crb2, zebrafish Crbl does not localize to the subapical regions of photoreceptors and Muller glial cells; rather, it localizes to a small region of cone outer segments: the cell membranes surrounding the axonemes. Moreover, zebrafish Crbl is not required for retinal morphogenesis and photoreceptor patterning. Interestingly, Crbl promotes rod survival under strong white light irradiation in a previously unreported non-cell-autonomous fashion; in addition, Crbl delays UV and blue cones' chromatin condensation caused by UV light irradiation. Finally, Crbl plays a role in cones' responsiveness to light through an arrestin-translocation-independent mechanism. The localization of Crbl and its functions do not differ between male and female fish. We conclude that zebrafish Crbl has diverged from other vertebrate Crb proteins, representing a neofunctionalization in Crb biology during evolution. [ABSTRACT FROM AUTHOR]

Photoreceptor-specific transcription of individual genes collectively constitutes the transcriptional profile that orchestrates the structural and functional characteristics of each photoreceptor type. It is challenging, however, to study the transcriptional specificity of individual photoreceptor genes because each gene's distinct spatiotemporal transcription patterns are determined by the unique interactions between a specific set of transcription factors and the gene'sowncis-regulatory elements (CREs), which remainunknownfor most of the genes. For example, it is unknown what CREs underlie the zebrafish mpp5bponli (ponli) and crumbs2b (crb2b) apical polarity genes' restrictive transcription in the red, green, and blue (RGB) cones in the retina, but not in other retinal cell types. Here we show that the intronic enhancers of both the ponli and crb2b genes are conserved among teleost species and that they share sequence motifs that are critical for RGB cone-specific transcription. Given their similarities in sequences and functions, we name the ponli and crb2b enhancers collectively rainbow enhancers. Rainbow enhancers may represent a cis-regulatory mechanism to turn on a group of genes that are commonly and restrictively expressed in RGB cones, which largely define the beginning of the color vision pathway. [ABSTRACT FROM AUTHOR]

Neovascular age-related macular degeneration (nvAMD) is the leading cause of severe vision loss in the elderly in the developed world. While the introduction of therapies targeting vascular endothelial growth factor (VEGF) has provided the first opportunity to significantly improve vision in patients with nvAMD, many patients respond inadequately to current anti-VEGF therapies. It was recently demonstrated that expression of a second angiogenic mediator, angiopoietin-like 4 (ANGPTL4), synergizes with VEGF to promote choroidal neovascularization (CNV) in mice and correlates with reduced response to anti-VEGF therapy in patients with nvAMD. Here, we report that expression of ANGPTL4 in patients with nvAMD increases following treatment with anti-VEGF therapy and that this increase is dependent on accumulation of hypoxia-inducible factor (HIF)-1a in response to inhibition of VEGF/KDR signaling in the retinal pigment epithelium (RPE). We therefore explored HIF-1 inhibition with 32-134D, a recently developed pharmacologic HIF-inhibitor, for the treatment of nvAMD. 32-134D prevented the expression of both VEGF and ANGPTL4 and was at least as effective as aflibercept in treating CNV in mice. Moreover, by preventing the increase in HIF-1a accumulation in the RPE in response to anti-VEGF therapy, combining 32-134D with aflibercept was more effective than either drug alone for the treatment of CNV. Collectively, these results help explain why many patients with nvAMD respond inadequately to anti-VEGF therapy and suggest that the HIF inhibitor 32-134D will be an effective drug--alone or in combination with current anti-VEGF therapies--for the treatment of patients with this blinding disease. [ABSTRACT FROM AUTHOR]

It has previously been reported that antioxidant vitamins can help reduce the risk of vision loss associated with progression to advanced age-related macular degeneration (AMD), a leading cause of visual impairment among the elderly. Nonetheless, how oxidative stress contributes to the development of choroidal neovascularization (CNV) in some AMD patients and geographic atrophy (GA) in others is poorly understood. Here, we provide evidence demonstrating that oxidative stress cooperates with hypoxia to synergistically stimulate the accumulation of hypoxia-inducible factor (HIF)-1a in the retinal pigment epithelium (RPE), resulting in increased expression of the HIF-1-dependent angiogenic mediators that promote CNV. HIF-1 inhibition blocked the expression of these angiogenic mediators and prevented CNV development in an animal model of ocular oxidative stress, demonstrating the pathological role of HIF-1 in response to oxidative stress stimulation in neovascular AMD. While human-induced pluripotent stem cell (hiPSC)-derived RPE monolayers exposed to chemical oxidants resulted in disorganization and disruption of their normal architecture, RPE cells proved remarkably resistant to oxidative stress. Conversely, equivalent doses of chemical oxidants resulted in apoptosis of hiPSC-derived retinal photoreceptors. Pharmacologic inhibition of HIF-1 in the mouse retina enhanced--while HIF-1 augmentation reduced--photoreceptor apoptosis in two mouse models for oxidative stress, consistent with a protective role for HIF-1 in photoreceptors in patients with advanced dry AMD. Collectively, these results suggest that in patients with AMD, increased expression of HIF-1a in RPE exposed to oxidative stress promotes the development of CNV, but inadequate HIF-1a expression in photoreceptors contributes to the development of GA. [ABSTRACT FROM AUTHOR]

Many patients with diabetic eye disease respond inadequately to anti-VEGF therapies, implicating additional vasoactive mediators in its pathogenesis. We demonstrate that levels of angiogenic proteins regulated by HIF-1 and -2 remain elevated in the eyes of people with diabetes despite treatment with anti-VEGF therapy. Conversely, by inhibiting HIFs, we normalized the expression of multiple vasoactive mediators in mouse models of diabetic eye disease. Accumulation of HIFs and HIF-regulated vasoactive mediators in hyperglycemic animals was observed in the absence of tissue hypoxia, suggesting that targeting HIFs may be an effective early treatment for diabetic retinopathy. However, while the HIF inhibitor acriflavine prevented retinal vascular hyperpermeability in diabetic mice for several months following a single intraocular injection, accumulation of acriflavine in the retina resulted in retinal toxicity over time, raising concerns for its use in patients. Conversely, 32-134D, a recently developed HIF inhibitor structurally unrelated to acriflavine, was not toxic to the retina, yet effectively inhibited HIF accumulation and normalized HIF-regulated gene expression in mice and in human retinal organoids. Intraocular administration of 32-134D prevented retinal neovascularization and vascular hyperpermeability in mice. These results provide the foundation for clinical studies assessing 32-134D for the treatment of patients with diabetic eye disease. [ABSTRACT FROM AUTHOR]

Background: Studies assessing the efficacy of therapies for neovascular age-related macular degeneration (nvAMD) have demonstrated that aflibercept may have a longer treatment interval than its lesser-expensive alternative, bevacizumab. However, whether this benefit justifies the additional cost of aflibercept remains under debate. We have recently reported that a "treat-and-extend-pause/monitor" (TEP/M) approach can be used to successfully wean 31% of nvAMD patients off anti-VEGF therapy. Here we examine whether the choice of therapy influences the outcomes of this approach.Methods: In this retrospective analysis, 122 eyes of 106 patients with nvAMD underwent 3 consecutive monthly injections with either aflibercept (n=70) or bevacizumab (n=52) followed by a treat-and-extend protocol in which the decision to extend the interval between treatments was based on visual acuity, clinical exam, and the presence or absence of fluid on optical coherence tomography (OCT). Eyes that remained stable 12 weeks from their prior treatment were given a 6-week trial of holding further treatment, followed by quarterly monitoring. Treatment was resumed for worsening vision, clinical exam, or OCT findings.Results: At the end of one year, eyes receiving bevacizumab had similar vision but required more injections (8.7 ±0.3 vs. 7.2 ±0.3) compared to aflibercept. However, eyes treated with aflibercept were almost 3-times more likely to be weaned off treatment (43% vs. 15%) compared to eyes treated with bevacizumab at the end of one year.Conclusions: These observations expose a previously unappreciated advantage of aflibercept over bevacizumab and have important clinical implications for the selection of therapy for patients with nvAMD. [ABSTRACT FROM AUTHOR]

BackgroundTo reduce the treatment burden for patients with neovascular age-related macular degeneration (nvAMD), emerging therapies targeting vascular endothelial growth factor (VEGF) are being designed to extend the interval between treatments, thereby minimizing the number of intraocular injections. However, which patients will benefit from longer-acting agents is not clear.MethodsEyes with nvAMD (n = 122) underwent 3 consecutive monthly injections with currently available anti-VEGF therapies, followed by a treat-and-extend protocol. Patients who remained quiescent 12 weeks from their prior treatment entered a treatment pause and were switched to pro re nata (PRN) treatment (based on vision, clinical exam, and/or imaging studies). Proteomic analysis was performed on aqueous fluid to identify proteins that correlate with patients' response to treatment.ResultsAt the end of 1 year, 38 of 122 eyes (31%) entered a treatment pause (≥30 weeks). Conversely, 21 of 122 eyes (17%) failed extension and required monthly treatment at the end of year 1. Proteomic analysis of aqueous fluid identified proteins that correlated with patients' response to treatment, including proteins previously implicated in AMD pathogenesis. Interestingly, apolipoprotein-B100 (ApoB100), a principal component of drusen implicated in the progression of nonneovascular AMD, was increased in treated patients who required less frequent injections. ApoB100 expression was higher in AMD eyes compared with controls but was lower in eyes that develop choroidal neovascularization (CNV), consistent with a protective role. Accordingly, mice overexpressing ApoB100 were partially protected from laser-induced CNV.FundingThis work was supported by the National Eye Institute, National Institutes of Health grants R01EY029750, R01EY025705, and R01 EY27961; the Research to Prevent Blindness, Inc.; the Alcon Research Institute; and Johns Hopkins University through the Robert Bond Welch and Branna and Irving Sisenwein professorships in ophthalmology.ConclusionAqueous biomarkers could help identify patients with nvAMD who may not require or benefit from long-term treatment with anti-VEGF therapy. [ABSTRACT FROM AUTHOR]