Project description:Retinal function changes dramatically from day to night. Yet, clinical diagnosis, treatments, and experimental sampling occur during the day, leaving a significant gap in our understanding of the pathobiology occurring at night. While there is evidence that diabetes disrupts the circadian system that optimizes our physiology to the environmental light/dark cycle, the impact of such disruption is not well understood. This study investigates whether diabetes affects the retina's daily rhythm of gene expression to understand the pathobiology of diabetic retinopathy, a common complication of diabetes. Control and hyperglycemic littermate mice (Ins2Akita/J) were kept under a standard 12h:12h light/dark cycle until four months of age. Bulk mRNA sequencing was conducted in retinas collected every 4 hours throughout the 24 hr light/dark cycle. Computational approaches were used to detect rhythmicity, predict acrophase, identify differential rhythmic patterns, analyze phase set enrichment, and predict upstream regulators. The retinal transcriptome exhibited a tightly regulated rhythmic expression with a clear 12-hr axis of transcriptional rush, peaking at midday and midnight. The functions of day-peaking genes were enriched for DNA repair, RNA splicing, and ribosomal protein synthesis, whereas night-peaking genes were enriched for metabolic processes and growth factor signaling. Although the 12-hr transcriptional axis is retained in the diabetic retina, it was phase advanced by approximately 1-3 hours with a wider distribution. Upstream regulator analysis for the genes that showed phase shifts identified oxygen sensing mechanisms and HIF1alpha as regulators, but not the circadian clock, which remained in phase to the light/dark cycle. We propose a model in which early in diabetes, the diabetic retina experiences a ‘jet lag’ caused by the entrained circadian clock and its output being in one phase and metabolic pathways related to neuronal dysfunction and hypoxia driving advancement of gene expression to a different phase. Further studies are now required to evaluate the chronic implications of such internal jet lag for development of diabetic retinopathy.
Project description:The mammalian retina contains an endogenous circadian clock system, located in various cell types. This system enables timing of a broad range of essential retinal functions to anticipate daily changes in environmental lighting conditions. Furthermore, the circadian clocks appear to promote retinal health. A leading cause of blindness in developed countries is diabetic retinopathy. While it is clear that diabetes affects the master clock and its circadian output in the SCN, the effect of diabetic retinopathy on the retinal clock system is unknown. To investigate the influence of diabetic retinopathy on circadian regulation of the retina at a genome-wide level, microarray analysis was used to compare retinal transcriptomes between light- and dark-adapted non-diabetic and diabetic mice.
Project description:Diabetic retinopathy (DR) is one of the main causes of blindness in working age populations in industrialized countries. It is estimated that close to 100 million individuals worldwide suffer from DR. Regrettably, relatively little is known of the cellular processes at play during late stages of the disease, especially concerning diabetic macular edema (DME). Streptozotocin-induced diabetic retinopathy (STZ) allows to reproduce experimentally in the mouse retina the retina vascular leakage and neuroegeneration features observed in human pathological retina with non-proliferative DR. Using agnostic and orthogonal approaches, in our work we demonstrate that in contrast to healthy retina, the STZ diabetic retina engages pathways of cell cycle arrest, resulting in cellular senescence. These findings combined with further pharmacological approaches provide mechanistic evidence supporting that targeting selectively senescent vessels in DR represents a potential treatment for high vascular permeability in DME.
Project description:Virtually every mammalian tissue exhibits rhythmic expression in thousands of genes, which activate tissue-specific processes at appropriate times of the day. Much of this rhythmic expression is thought to be driven cell-autonomously by molecular circadian clocks present throughout the body. However, increasing evidence suggests that systemic signals, and more specifically rhythmic food intake (RFI), can regulate rhythmic gene expression independently of the circadian clock. To determine the relative contribution of cell autonomous clocks versus RFI in the regulation of rhythmic gene expression, we developed a system that allows long-term manipulation of the daily rhythm of food intake in the mouse, and analyzed liver gene expression by RNA-Seq in mice fed ad libitum, only at night, or arrhythmically (mouse eating 1/8th of their daily food intake every 3 hours). We show that 70% of the cycling mouse liver transcriptome loses rhythmicity under arrhythmic feeding. Remarkably, this loss of rhythmic gene expression under arrhythmic feeding is independent of the liver circadian clock, which continues to exhibit normal oscillations in core clock gene expression. Many genes that lose rhythmicity participate in the regulation of metabolic processes such as lipogenesis and glycogenesis, likely contributing to an increased sensitivity to insulin that was observed in arrhythmically-fed mice. We also show that night-restricted feeding significantly increases the number of rhythmically expressed genes as well as the amplitude of the rhythms. Together, these results indicate that metabolic transcription factors control a large fraction of the rhythmic mouse liver transcriptome, and demonstrate that systemic signals driven by rhythmic food intake play a more important role than the cell-autonomous circadian clock in driving rhythms in liver gene expression and metabolic functions.
Project description:We investigated Synechocystis high-density microarray data of three high-resolution time-series experiments with alternating light/dark rhythm, transition to continuous light, and transition to continuous darkness. Using ‘least oscillating set’ normalization and a clustering approach we found a daily temporal program for rhythmic expression of protein-coding and non-coding genes under light/dark conditions. All rhythms, however, damped out rapidly under continuous conditions.
Project description:Differences in regional protein expression within the human retina may explain molecular predisposition of specific regions to ophthalmic diseases like age-related macular degeneration, cystoid macular edema, retinitis pigmentosa, and diabetic retinopathy. To quantify protein levels in the human retina and identify patterns of differentially-expressed proteins, we collected foveal, macular, and peripheral retina punch biopsies from healthy donor eyes and analyzed protein content by liquid chromatography-tandem mass spectrometry (LC-MS/MS).
Project description:Diabetic retinopathy, a microvascular disease characterized by irreparable vascular damage, neurodegeneration and neuroinflammation, is a leading complication of diabetes mellitus. Medical interventions slow the progression of disease. However, current therapies do not specifically target microglia, a cell type implicated in mediating disease development. Microglia-mediated inflammation in the diabetic retina is regulated via CX3CR1-FKN signaling, where FKN serves as a dampening signal for microglial activation. Studying this signaling axis is important as polymorphic variants of CX3CR1 are found in 25% of the human population, hCX3CR1I249/M280, resulting in a receptor with lower binding affinity for FKN. Furthermore, disrupted CX3CR1-FKN signaling in CX3CR1-KO and FKN-KO mice leads to exacerbated microglial activation, robust neuronal cell loss and substantial vascular damage in the diabetic retina. Thus, studies to characterize the effects of hCX3CR1I249/M280-expression in microglia-mediated inflammation in the diseased retina are potentially clinically relevant to identify microglia-specific therapies. Our results show that hCX3CR1I249/M280 mice are significantly more susceptible to microgliosis and production of Cxcl10 and TNFα under acute inflammatory conditions. This pathology is exacerbated under diabetic conditions and coincides with robust neuronal loss in comparison to CX3CR1-WT mice. Therefore, to further investigate the role of hCX3CR1I249/M280-expression in microglial responses, we pharmacologically depleted microglia using PLX-5622, a CSF-1R antagonist. PLX-5622 treatment led to a robust (~70%) reduction in Iba1+ microglia in all non-diabetic and diabetic mice. CSF-1R antagonism in diabetic CX3CR1-WT prevented TUJ1+ axonal loss, angiogenesis and fibrinogen deposition. In contrast, PLX-5622 microglia depletion in CX3CR1-KO and hCX3CR1I249/M280 mice did not alleviate TUJ1+ axonal loss or angiogenesis. Interestingly, PLX-5622 treatment reduced fibrinogen deposition in CX3CR1-KO mice but not in hCX3CR1I249/M280 mice, revealing that hCX3CR1I249/M280 receptor variant mice behave differently in terms of vascular pathology compared to CX3CR1-KOs. mRNAseq gene expression analysis in CX3CR1-WT retinal isolates revealed that PLX-5622-induced microglia depletion and repopulation induced a downregulation in genes associated with microglial activation and phagocytosis, B2m, Cx3cr1, and Trem2, and complement-associated synaptic pruning, C1qa, C1qb, and C1qc. Furthermore, mRNAseq analysis of PLX-5622 treated CX3CR1-WT retinas showed lower fold changes in genes encoding proinflammatory mediators (Cxcl10, Ccl2, Il6, Cxcl1, Selp, Il12b, Tnf, Cxcl2, Icam1 and Vcam1) in comparison to diabetic + normal chow mice.
Project description:Endothelial cells (EC) play essential roles in retinal vascular homeostasis. This study aimed to characterize retinal EC heterogeneity and functional diversity using single-cell RNA sequencing (scRNA-seq). Systematic analysis of cellular compositions and cell-cell interaction networks identified a unique EC cluster with high inflammatory gene expression in the diabetic retina; sphingolipid metabolism in this cluster is a prominent aspect correlated with changes in retinal function. Among the sphingolipid-related genes, alkaline ceramidase 2 (ACER2) showed the most significant increase. We collected plasma and vitreous samples from patients with non-proliferative diabetic retinopathy (NPDR) and PDR for mass spectrometry analysis. Metabolomic profiling revealed that the ceramide levels were significantly elevated in NPDR and further increased in PDR compared with control patients. In vitro analyses showed that the ACER2 overexpression retarded endothelial barrier breakdown induced by ceramide, while silencing of ACER2 further disrupted the injury. Moreover, intravitreal injection of the recombinant ACER2 adeno-associated virus rescued diabetes-induced vessel leakiness, inflammatory response, and neurovascular disease in diabetic mouse models. Together, this study revealed a new diabetes-specific retinal EC population and a negative feedback regulation pathway that reduces ceramide content and endothelial dysfunction by upregulating ACER2 expression. These findings provide insights into cell-type targeted interventions for diabetic retinopathy.
Project description:Purpose. Patients with diabetic retinopathy may experience severe vision loss due to macular edema and neovascularization secondary to vascular abnormalities. However, before these abnormalities become apparent, there are functional deficits in contrast sensitivity, color perception, and dark adaptation. The goals of this study are to evaluate early changes (up to 3 months) in retinal gene expression, selected visual cycle proteins, and optokinetic tracking (OKT) in streptozotocin (STZ)-induced diabetic rats.Methods. Retinal gene expression in diabetic Long Evans rats was measured by whole genome microarray 7 days, 4 weeks, and three months after onset of hyperglycemia. Select gene and protein changes were probed by PCR and immunohistochemistry respectively, and OKT thresholds were measured using a virtual optokinetics system. Results. Microarray analysis showed that the most consistently affected molecular and cellular functions were cell-to-cell signaling and interaction, cell death, cellular growth and proliferation, molecular transport, and cellular movement. Further analysis revealed reduced expression of several genes encoding visual cycle proteins including lecithin:retinol acyltransferase (LRAT), retinal pigment epithelium (RPE)-specific protein 65kDa (RPE65) and RPE retinal G protein coupled receptor (RGR). Immunohistochemistry revealed a decrease in RPE65 in the RPE layer of diabetic rats. These molecular changes occurred simultaneously with a decrease in OKT thresholds by 4 weeks of diabetes. Conclusions. The data presented here are further evidence that inner retinal cells are affected by hyperglycemia prior to vasculopathy suggesting that glial and neuronal dysfunction may underlie some of the early visual deficits in diabetics. At each of the three timepoints (day 7, day 28, and day 84) one retina each from three diabetic rats were pooled for analysis on a single microarray chip. Three independent experiments were conducted for each group (n=9 animals/group). Each timepoint contained a hyperglycemic (STZ) and a control (buffer injection only) group. Additionally, on day 7 gene changes in the retina of rats which received a single injection of STZ, but did not develop hyperglycemia (STZ-non-c) were analyzed.
Project description:As a metabolic disease, diabetes often leads to health complications such as heart failure, nephropathy, neurological disorders, and vision loss. Diabetic retinopathy (DR) affects as many as 100 million people worldwide. The mechanism of DR is complex and known to impact both neural and vascular components in the retina. While recent advances in the field have identified major cellular signaling contributing to DR pathogenesis, little has been reported on the protein post-translational modifications (PTM) -known to define protein localization, function, and activity -in the diabetic retina overall. Protein glycosylation is the enzymatic addition of carbohydrates to proteins, which can influence many protein attributes including folding, stability, function, and subcellular localization. Olinked glycosylation is the addition of sugars to an oxygen atom in amino acids with a free oxygen atom in their side chain (i.e., threonine, serine). To date, more than 100 congenital disorders of glycosylation have been described. However, no studies have identified the retinal O-linked glycoproteome in health or disease. With a critical need to expedite the discovery of PTMomics in diabetic retinas, we identified both global changes in protein levels and the retinal O-glycoproteome of control and diabetic mice. Liquid chromatography/mass spectrometry-based glycoproteomics and high throughput screening identified proteins differentially glycosylated in the retinas of wildtype and diabetic mice. Here, we provide evidence that diabetes shifts O-glycosylation of metabolic and synaptic proteins in the retina.