Showing papers by "Anand Swaroop published in 2020"

Deep-learning-based prediction of late age-related macular degeneration progression

Abstract: Both genetic and environmental factors influence the etiology of age-related macular degeneration (AMD), a leading cause of blindness. AMD severity is primarily measured by fundus images and recently developed machine learning methods can successfully predict AMD progression using image data. However, none of these methods have utilized both genetic and image data for predicting AMD progression. Here we jointly used genotypes and fundus images to predict an eye as having progressed to late AMD with a modified deep convolutional neural network (CNN). In total, we used 31,262 fundus images and 52 AMD-associated genetic variants from 1,351 subjects from the Age-Related Eye Disease Study (AREDS) with disease severity phenotypes and fundus images available at baseline and follow-up visits over a period of 12 years. Our results showed that fundus images coupled with genotypes could predict late AMD progression with an averaged area under the curve (AUC) value of 0.85 (95%CI: 0.83-0.86). The results using fundus images alone showed an averaged AUC of 0.81 (95%CI: 0.80-0.83). We implemented our model in a cloud-based application for individual risk assessment.

Pluripotent stem cell-derived retinal organoids for disease modeling and development of therapies.

Abstract: Retinal diseases constitute a genetically and phenotypically diverse group of clinical conditions leading to vision impairment or blindness with limited treatment options. Advances in reprogramming of somatic cells to induced pluripotent stem cells and generation of three-dimensional organoids resembling the native retina offer promising tools to interrogate disease mechanisms and evaluate potential therapies for currently incurable retinal neurodegeneration. Next-generation sequencing, single-cell analysis, advanced electrophysiology, and high-throughput screening approaches are expected to greatly expand the utility of stem cell-derived retinal cells and organoids for developing personalized treatments. In this review, we discuss the current status and future potential of combining retinal organoids as human models with recent technologies to advance the development of gene, cell, and drug therapies for retinopathies.

Pharmacologic fibroblast reprogramming into photoreceptors restores vision.

Abstract: Photoreceptor loss is the final common endpoint in most retinopathies that lead to irreversible blindness, and there are no effective treatments to restore vision1,2. Chemical reprogramming of fibroblasts offers an opportunity to reverse vision loss; however, the generation of sensory neuronal subtypes such as photoreceptors remains a challenge. Here we report that the administration of a set of five small molecules can chemically induce the transformation of fibroblasts into rod photoreceptor-like cells. The transplantation of these chemically induced photoreceptor-like cells (CiPCs) into the subretinal space of rod degeneration mice (homozygous for rd1, also known as Pde6b) leads to partial restoration of the pupil reflex and visual function. We show that mitonuclear communication is a key determining factor for the reprogramming of fibroblasts into CiPCs. Specifically, treatment with these five compounds leads to the translocation of AXIN2 to the mitochondria, which results in the production of reactive oxygen species, the activation of NF-κB and the upregulation of Ascl1. We anticipate that CiPCs could have therapeutic potential for restoring vision. A set of five small molecules can induce the transformation of fibroblasts into rod photoreceptor-like cells, which can partially restore pupil reflex and visual function when transplanted into a rod degeneration mouse model.

A simple and efficient method for generating human retinal organoids

Abstract: Purpose Retinal organoids (ROs) derived from human pluripotent stem cells largely recapitulate key features of in vivo retinal development, thus permitting the study of retinogenesis, disease modeling, and therapeutic development. However, the complexities of current protocols limit the use of this in vitro system in applications requiring large-scale production of organoids. Currently, widely used methods require the isolation of presumed optic vesicle-like structures from adherent cultures by dissection, a labor-intensive and time-consuming step that involves extensive practice and training. Method We report a simple and efficient method for generating ROs by scraping the entire adherent culture and growing the resulting cell aggregates in a free-floating condition. Results Within 1 to 7 days following the procedure, emerging morphologically well-defined optic vesicles can be identified and harvested with ease. The transition from two-dimensional (2D) to 3D culture condition favored the formation of ROs from areas devoid of typical optic vesicle-like structures, thus increasing the RO yield. Moreover, ROs generated by this approach were more often associated with the pigment epithelium. Conclusions This improved, robust, and efficient protocol should facilitate large-scale differentiation of pluripotent stem cells into retinal organoids in support of human disease modeling and therapy development.

Retinal Organoids derived from hiPSCs of an AIPL1-LCA Patient Maintain Cytoarchitecture despite Reduced levels of Mutant AIPL1.

Abstract: Aryl hydrocarbon receptor-interacting protein-like 1 (AIPL1) is a photoreceptor-specific chaperone that stabilizes the effector enzyme of phototransduction, cGMP phosphodiesterase 6 (PDE6). Mutations in the AIPL1 gene cause a severe inherited retinal dystrophy, Leber congenital amaurosis type 4 (LCA4), that manifests as the loss of vision during the first year of life. In this study, we generated three-dimensional (3D) retinal organoids (ROs) from human induced pluripotent stem cells (hiPSCs) derived from an LCA4 patient carrying a Cys89Arg mutation in AIPL1. This study aimed to (i) explore whether the patient hiPSC-derived ROs recapitulate LCA4 disease phenotype, and (ii) generate a clinically relevant resource to investigate the molecular mechanism of disease and safely test novel therapies for LCA4 in vitro. We demonstrate reduced levels of the mutant AIPL1 and PDE6 proteins in patient organoids, corroborating the findings in animal models; however, patient-derived organoids maintained retinal cell cytoarchitecture despite significantly reduced levels of AIPL1.

Adherence to a Mediterranean diet and cognitive function in the Age-Related Eye Disease Studies 1 & 2

Abstract: Introduction The objective was to determine whether closer adherence to the alternative Mediterranean Diet (aMED) was associated with altered cognitive function. Methods Observational analyses of participants (n = 7,756) enrolled in two randomized trials of nutritional supplements for age-related macular degeneration: Age-Related Eye Disease Study (AREDS) and AREDS2. Results Odds ratios for cognitive impairment, in aMED tertile 3 (vs 1), were 0.36 (P = .0001) for Modified Mini-Mental State ( Discussion Closer Mediterranean diet adherence was associated with lower risk of cognitive impairment but not slower decline in cognitive function. Apolipoprotein E (APOE) haplotype did not influence these relationships.

An optimized protocol for retina single-cell RNA sequencing.

Abstract: Purpose Single-cell RNA sequencing (scRNA-seq) is a powerful technique used to explore gene expression at the single cell level. However, appropriate preparation of samples is essential to obtain the most information out of this transformative technology. Generating high-quality single-cell suspensions from the retina is critical to preserve the native expression profile that will ensure meaningful transcriptome data analysis. Methods We modified the conditions for rapid and optimal dissociation of retina sample preparation. We also included additional filtering steps in data analysis for retinal scRNA-seq. Results We report a gentle method for dissociation of the mouse retina that minimizes cell death and preserves cell morphology. This protocol also results in detection of higher transcriptional complexity. In addition, the modified computational pipeline leads to better-quality single-cell RNA-sequencing data in retina samples. We also demonstrate the advantages and limitations of using fresh versus frozen retinas to prepare cell or nuclei suspensions for scRNA-seq. Conclusions We provide a simple yet robust and reproducible protocol for retinal scRNA-seq analysis, especially for comparative studies.

A mega-analysis of expression quantitative trait loci in retinal tissue

Abstract: Significant association signals from genome-wide association studies (GWAS) point to genomic regions of interest. However, for most loci the causative genetic variant remains undefined. Determining expression quantitative trait loci (eQTL) in a disease relevant tissue is an excellent approach to zoom in on disease- or trait-associated association signals and hitherto on relevant disease mechanisms. To this end, we explored regulation of gene expression in healthy retina (n = 311) and generated the largest cis-eQTL data set available to date. Genotype- and RNA-Seq data underwent rigorous quality control protocols before FastQTL was applied to assess the influence of genetic markers on local (cis) gene expression. Our analysis identified 403,151 significant eQTL variants (eVariants) that regulate 3,007 genes (eGenes) (Q-Value < 0.05). A conditional analysis revealed 744 independent secondary eQTL signals for 598 of the 3,007 eGenes. Interestingly, 99,165 (24.71%) of all unique eVariants regulate the expression of more than one eGene. Filtering the dataset for eVariants regulating three or more eGenes revealed 96 potential regulatory clusters. Of these, 31 harbour 130 genes which are partially regulated by the same genetic signal. To correlate eQTL and association signals, GWAS data from twelve complex eye diseases or traits were included and resulted in identification of 80 eGenes with potential association. Remarkably, expression of 10 genes is regulated by eVariants associated with multiple eye diseases or traits. In conclusion, we generated a unique catalogue of gene expression regulation in healthy retinal tissue and applied this resource to identify potentially pleiotropic effects in highly prevalent human eye diseases. Our study provides an excellent basis to further explore mechanisms of various retinal disease etiologies.

Family-based exome sequencing identifies rare coding variants in age-related macular degeneration.

Abstract: Genome-wide association studies (GWAS) have identified 52 independent variants at 34 genetic loci that are associated with age-related macular degeneration (AMD), the most common cause of incurable vision loss in the elderly worldwide. However, causal genes at the majority of these loci remain unknown. In this study, we performed whole exome sequencing of 264 individuals from 63 multiplex families with AMD and analyzed the data for rare protein-altering variants in candidate target genes at AMD-associated loci. Rare coding variants were identified in the CFH, PUS7, RXFP2, PHF12 and TACC2 genes in three or more families. In addition, we detected rare coding variants in the C9, SPEF2 and BCAR1 genes, which were previously suggested as likely causative genes at respective AMD susceptibility loci. Identification of rare variants in the CFH and C9 genes in our study validated previous reports of rare variants in complement pathway genes in AMD. We then extended our exome-wide analysis and identified rare protein-altering variants in 13 genes outside the AMD-GWAS loci in three or more families. Two of these genes, SCN10A and KIR2DL4, are of interest because variants in these genes also showed association with AMD in case-control cohorts, albeit not at the level of genome-wide significance. Our study presents the first large-scale, exome-wide analysis of rare variants in AMD. Further independent replications and molecular investigation of candidate target genes, reported here, would assist in gaining novel insights into mechanisms underlying AMD pathogenesis.

Tbx2a Modulates Switching of RH2 and LWS Opsin Gene Expression.

Abstract: Sensory systems are tuned by selection to maximize organismal fitness in particular environments. This tuning has implications for intraspecies communication, the maintenance of species boundaries, and speciation. Tuning of color vision largely depends on the sequence of the expressed opsin proteins. To improve tuning of visual sensitivities to shifts in habitat or foraging ecology over the course of development, many organisms change which opsins are expressed. Changes in this developmental sequence (heterochronic shifts) can create differences in visual sensitivity among closely related species. The genetic mechanisms by which these developmental shifts occur are poorly understood. Here, we use quantitative trait locus analyses, genome sequencing, and gene expression studies in African cichlid fishes to identify a role for the transcription factor Tbx2a in driving a switch between long wavelength sensitive (LWS) and Rhodopsin-like (RH2) opsin expression. We identify binding sites for Tbx2a in the LWS promoter and the highly conserved locus control region of RH2 which concurrently promote LWS expression while repressing RH2 expression. We also present evidence that a single change in Tbx2a regulatory sequence has led to a species difference in visual tuning, providing the first mechanistic model for the evolution of rapid switches in sensory tuning. This difference in visual tuning likely has important roles in evolution as it corresponds to differences in diet, microhabitat choice, and male nuptial coloration.

Integration of genomics and transcriptomics predicts diabetic retinopathy susceptibility genes

Abstract: One of the side effects of diabetes is loss of vision from diabetic retinopathy, which is caused by injury to the light sensing tissue in the eye, the retina. Almost all individuals with diabetes develop diabetic retinopathy to some extent, and it is the leading cause of irreversible vision loss in working-age adults in the United States. How long a person has been living with diabetes, the extent of increased blood sugars and genetics all contribute to the risk and severity of diabetic retinopathy. Unfortunately, virtually no genes associated with diabetic retinopathy have yet been identified. When a gene is activated, it produces messenger molecules known as mRNA that are used by cells as instructions to produce proteins. The analysis of mRNA molecules, as well as genes themselves, can reveal the role of certain genes in disease. The studies of all genes and their associated mRNAs are respectively called genomics and transcriptomics. Genomics reveals what genes are present, while transcriptomics shows how active genes are in different cells. Skol et al. developed methods to study genomics and transcriptomics together to help discover genes that cause diabetic retinopathy. Genes involved in how cells respond to high blood sugar were first identified using cells grown in the lab. By comparing the activity of these genes in people with and without retinopathy the study identified genes associated with an increased risk of retinopathy in diabetes. In people with retinopathy, the activity of the folliculin gene (FLCN) increased more in response to high blood sugar. This was further verified with independent groups of people and using computer models to estimate the effect of different versions of the folliculin gene. The methods used here could be applied to understand complex genetics in other diseases. The results provide new understanding of the effects of diabetes. They may also help in the development of new treatments for diabetic retinopathy, which are likely to improve on the current approach of using laser surgery or injections into the eye.

Soy Protein Nanofiber Scaffolds for Uniform Maturation of Human Induced Pluripotent Stem Cell-Derived Retinal Pigment Epithelium.

Abstract: Retinal pigment epithelium (RPE) differentiated from human induced pluripotent stem cells, called induced retinal pigment epithelium (iRPE), is being explored as a cell-based therapy for the treatment of retinal degenerative diseases, especially age-related macular degeneration. The success of RPE implantation is linked to the use of biomimetic scaffolds that simulate Bruch's membrane and promote RPE maturation and integration as a functional tissue. Due to difficulties associated with animal protein-derived scaffolds, including sterility and pro-inflammatory responses, current practices favor the use of synthetic polymers, such as polycaprolactone (PCL), for generating nanofibrous scaffolds. In this study, we tested the hypothesis that plant protein-derived fibrous scaffolds can provide favorable conditions permissive for the maturation of RPE tissue sheets in vitro. Our natural, soy protein-derived nanofibrous scaffolds exhibited a J-shaped stress-strain curve that more closely resembled the mechanical properties of native tissues than PCL with significantly higher hydrophilicity of the natural scaffolds, favoring in vivo implantation. We then demonstrate that iRPE sheets growing on these soy protein scaffolds are equivalent to iRPE monolayers cultured on synthetic PCL nanofibrous scaffolds. Immunohistochemistry demonstrated RPE-like morphology and functionality with appropriate localization of RPE markers RPE65, PMEL17, Ezrin, and ZO1 and with anticipated histotypic polarization of vascular endothelial growth factor and pigment epithelium-derived growth factor as indicated by enzyme-linked immunosorbent assay. Scanning electron microscopy revealed dense microvilli on the cell surface and homogeneous tight junctional contacts between the cells. Finally, comparative transcriptome analysis in conjunction with principal component analysis demonstrated that iRPE on nanofibrous scaffolds, either natural or synthetic, matured more consistently than on nonfibrous substrates. Taken together, our studies suggest that the maturation of cultured iRPE sheets for subsequent clinical applications might benefit from the use of nanofibrous scaffolds generated from natural proteins. Impact statement Induced retinal pigment epithelium (iRPE) from patient-derived induced pluripotent stem cells (iPSCs) may yield powerful treatments of retinal diseases, including age-related macular degeneration. Recent studies, including early human clinical trials, demonstrate the importance of selecting appropriate biomaterial scaffolds to support tissue-engineered iRPE sheets during implantation. Electrospun scaffolds show particular promise due to their similarity to the structure of the native Bruch's membrane. In this study, we describe the use of electroprocessed nanofibrous soy protein scaffolds to generate polarized sheets of human iPSC-derived iRPE sheets. Our evaluation, including RNA-seq transcriptomics, indicates that these scaffolds are viable alternatives to scaffolds electrospun from synthetic polymers.

A unique PRDM13-associated variant in a Georgian Jewish family with probable North Carolina macular dystrophy and the possible contribution of a unique CFH variant.

Abstract: Purpose North Carolina macular dystrophy (NCMD) is an autosomal dominant maculopathy that is considered a non-progressive developmental disorder with variable expressivity. Our study aimed to clinically and genetically characterize macular dystrophy in a family (MOL1154) consisting of six affected subjects with a highly variable maculopathy phenotype in which no correlation between age and severity exists. Methods Clinical characterization included visual acuity testing and electroretinography. Genetic analysis included Sanger sequencing and whole exome sequencing (WES). Results WES analysis performed on DNA samples from two individuals revealed a heterozygous deletion of six nucleotides [c.2247_2252del; p.(Leu750_Lys751del)] in the CFH gene. Co-segregation analysis revealed that five of the six NCMD affected subjects carried this deletion, while one individual who had a relatively mild phenotype compatible with dry age-related macular degeneration (AMD) did not carry it. We subsequently analyzed the upstream region of PRDM13 that has previously been reported to be associated with NCMD and identified a unique heterozygous transversion (chr6:100040974A>C) located within the previously described suspected control region in all six affected individuals. This transversion is likely to cause NCMD. Conclusions NCMD has a wide spectrum of clinical phenotypes that can overlap with AMD, making it challenging to correctly diagnose affected individuals and family members. The DNA sequence variant we found in the CFH gene of some of the affected family members may suggest some role as a modifier gene. However, this variant still does not explain the huge phenotypic variability of NCMD and needs to be studied in other and larger populations.

Accelerated Development of Rod Photoreceptors in Retinal Organoids Derived from Human Pluripotent Stem Cells by Supplementation with 9-cis Retinal.

Abstract: Human pluripotent stem cells (PSCs) can be differentiated into retinal organoids with proper neural layer organization, yet the protocols are technically challenging and time consuming. We have modified a widely used differentiation protocol by switching all-trans retinoic acid with 9-cis retinal to accelerate photoreceptor differentiation and improve morphogenesis. In this report, we provide a detailed and improved protocol to generate retinal organoids from human pluripotent stem cells. For complete details on the use and execution of this protocol, please refer to Kaya et al. (2019).

Methylation of two-component response regulator MtrA in mycobacteria negatively modulates its DNA binding and transcriptional activation

Abstract: Post-translational modifications such as phosphorylation, nitrosylation, and pupylation modulate multiple cellular processes in Mycobacterium tuberculosis. While protein methylation at lysine and arginine residues is widespread in eukaryotes, to date only two methylated proteins in Mtb have been identified. Here, we report the identification of methylation at lysine and/or arginine residues in nine mycobacterial proteins. Among the proteins identified, we chose MtrA, an essential response regulator of a two-component signaling system, which gets methylated on multiple lysine and arginine residues to examine the functional consequences of methylation. While methylation of K207 confers a marginal decrease in the DNA-binding ability of MtrA, methylation of R122 or K204 significantly reduces the interaction with the DNA. Overexpression of S-adenosyl homocysteine hydrolase (SahH), an enzyme that modulates the levels of S-adenosyl methionine in mycobacteria decreases the extent of MtrA methylation. Most importantly, we show that decreased MtrA methylation results in transcriptional activation of mtrA and sahH promoters. Collectively, we identify novel methylated proteins, expand the list of modifications in mycobacteria by adding arginine methylation, and show that methylation regulates MtrA activity. We propose that protein methylation could be a more prevalent modification in mycobacterial proteins.

Divergent Effects of HSP70 Overexpression in Photoreceptors During Inherited Retinal Degeneration.

Abstract: Purpose Disruption of proteostasis is a key event in many neurodegenerative diseases. Heat shock proteins (HSPs) participate in multiple functions associated with intracellular transport and proteostasis. We evaluated the effect of augmented HSP70 expression in mutant photoreceptors of mouse retinal degeneration models to test the hypothesis that failure to sustain HSP70 expression contributes to photoreceptor cell death. Methods We examined HSP70 expression in retinas of wild-type and mutant mice by RNA and protein analysis. A transgenic mouse line, TgCrx-Hspa1a-Flag, was generated to express FLAG-tagged full-length HSP70 protein under control of a 2.3 kb mouse Crx promoter. This line was crossed to three distinct retinal degeneration mouse models. Retinal structure and function were evaluated by histology, immunohistochemistry, and electroretinography. Results In seven different mouse models of retinal degeneration, we detected transient elevation of endogenous HSP70 expression at early stages, followed by a dramatic reduction as cell death ensues, suggesting an initial adaptive response to cellular stress. Augmented expression of HSP70 in RHOT17M mice, in which mutant rhodopsin is misfolded, marginally improved photoreceptor survival, whereas elevated HSP70 led to more severe retinal degeneration in rd10 mutants that produce a partially functional PDE6B. In Rpgrip1-/- mice that display a ciliary defect, higher HSP70 had no impact on photoreceptor survival or function. Conclusions HSP70 overexpression has divergent effects in photoreceptors determined, at least in part, by the nature of the mutant protein each model carries. Additional investigations on HSP pathways and associated chaperone networks in photoreceptors are needed before designing therapeutic strategies targeting proteostasis.

Loss of endocytosis-associated RabGEF1 causes aberrant morphogenesis and altered autophagy in photoreceptors leading to retinal degeneration.

Abstract: Rab-GTPases and associated effectors mediate cargo transport through the endomembrane system of eukaryotic cells, regulating key processes such as membrane turnover, signal transduction, protein recycling and degradation. Using developmental transcriptome data, we identified Rabgef1 (encoding the protein RabGEF1 or Rabex-5) as the only gene associated with Rab GTPases that exhibited strong concordance with retinal photoreceptor differentiation. Loss of Rabgef1 in mice (Rabgef1-/-) resulted in defects specifically of photoreceptor morphology and almost complete loss of both rod and cone function as early as eye opening; however, aberrant outer segment formation could only partly account for visual function deficits. RabGEF1 protein in retinal photoreceptors interacts with Rabaptin-5, and RabGEF1 absence leads to reduction of early endosomes consistent with studies in other mammalian cells and tissues. Electron microscopy analyses reveal abnormal accumulation of macromolecular aggregates in autophagosome-like vacuoles and enhanced immunostaining for LC3A/B and p62 in Rabgef1-/- photoreceptors, consistent with compromised autophagy. Transcriptome analysis of the developing Rabgef1-/- retina reveals altered expression of 2469 genes related to multiple pathways including phototransduction, mitochondria, oxidative stress and endocytosis, suggesting an early trajectory of photoreceptor cell death. Our results implicate an essential role of the RabGEF1-modulated endocytic and autophagic pathways in photoreceptor differentiation and homeostasis. We propose that RabGEF1 and associated components are potential candidates for syndromic traits that include a retinopathy phenotype.

Proneural genes define ground state rules to regulate neurogenic patterning and cortical folding

Abstract: Transition from smooth, lissencephalic brains to highly-folded, gyrencephalic structures is associated with neuronal expansion and breaks in neurogenic symmetry. Here we show that Neurog2 and Ascl1 proneural genes regulate cortical progenitor cell differentiation through cross-repressive interactions to sustain neurogenic continuity in a lissencephalic rodent brain. Using in vivo lineage tracing, we found that Neurog2 and Ascl1 expression defines a lineage continuum of four progenitor pools, with double+ progenitors displaying several unique features (least lineage-restricted, complex gene regulatory network, G2 pausing). Strikingly, selective killing of double+ progenitors using split-Cre;Rosa-DTA transgenics breaks neurogenic symmetry by locally disrupting Notch signaling, leading to cortical folding. Finally, consistent with NEUROG2 and ASCL1 driving discontinuous neurogenesis and folding in gyrencephalic species, their transcripts are modular in folded macaque cortices and pseudo-folded human cerebral organoids. Neurog2/Ascl1 double+ progenitors are thus Notch-ligand expressing niche cells that control neurogenic periodicity to determine cortical gyrification. HIGHLIGHTSO_LINeurog2 and Ascl1 expression defines four distinct transitional progenitor states C_LIO_LIDouble+ NPCs are transcriptionally complex and mark a lineage branch point C_LIO_LIDouble+ NPCs control neurogenic patterning and cortical folding via Notch signaling C_LIO_LINeurog2 and Ascl1 expression is modular in folded and not lissencephalic cortices C_LI eTOC BLURBEmergence of a gyrencephalic cortex is associated with a break in neurogenic continuity across the cortical germinal zone. Han et al. identify a pool of unbiased neural progenitors at a lineage bifurcation point that co-express Neurog2 and Ascl1 and produce Notch ligands to control neurogenic periodicity and cortical folding.

HIPRO: A High-Efficiency, Hypoxia-Induced Protocol for Generation of Photoreceptors in Retinal Organoids from Mouse Pluripotent Stem Cells

Abstract: Mouse pluripotent stem cells can be efficiently differentiated into retinal organoids with polarized, laminated neural retina harboring all retinal cell types by the Hypoxia-Induced Generation of Photoreceptor in Retinal Organoids (HIPRO) protocol. In our recent publication, we modified the HIPRO protocol on the basis of comparative transcriptome analyses to facilitate photoreceptor biogenesis and maturation. Here, we provide a detailed protocol for efficient generation of retinal organoids from mouse pluripotent stem cells. For complete details on the use and execution of this protocol, please refer to (Chen et al., 2016, DiStefano et al., 2018, Brooks et al., 2019).

Deep-learning-based Prediction of Late Age-Related Macular Degeneration Progression

Abstract: Both genetic and environmental factors influence the etiology of age-related macular degeneration (AMD), a leading cause of blindness. AMD severity is primarily measured by fundus images and recently developed machine learning methods can successfully predict AMD progression using image data. However, none of these methods have utilized both genetic and image data for predicting AMD progression. Here we jointly used genotypes and fundus images to predict an eye as having progressed to late AMD with a modified deep convolutional neural network (CNN). In total, we used 31,262 fundus images and 52 AMD-associated genetic variants from 1,351 subjects from the Age-Related Eye Disease Study (AREDS) with disease severity phenotypes and fundus images available at baseline and follow-up visits over a period of 12 years. Our results showed that fundus images coupled with genotypes could predict late AMD progression with an averaged area under the curve (AUC) value of 0.85 (95%CI: 0.83-0.86). The results using fundus images alone showed an averaged AUC of 0.81 (95%CI: 0.80-0.83). We implemented our model in a cloud-based application for individual risk assessment.

HiCRes: a computational method to estimate and predict the resolution of HiC libraries

Abstract: Three-dimensional (3D) conformation of the chromatin is crucial to stringently regulate gene expression patterns and DNA replication in a cell-type specific manner. HiC is a key technique for measuring 3D chromatin interactions genome wide. Estimating and predicting the resolution of a library is an essential step in any HiC experimental design. Here, we present the mathematical concepts to estimate the resolution of a library and predict whether deeper sequencing would enhance the resolution. We have developed HiCRes, a docker pipeline, by applying these concepts to human and mouse HiC libraries.

AMP-activated-kinase (AMPK) is essential sensor and metabolic regulator of retinal neurons and their integrated metabolism with RPE.

Abstract: The retina has one of the highest energy demands in the human body, and proper regulation of metabolism among the cell types of the retina is required for functional vision. Recent studies have reported that retinal metabolism is disrupted during retinal degeneration and aging, while therapies designed to enhance metabolism can slow or prevent degeneration. Here, we show that multiple metabolic pathways, including those regulated by a key ATP sensor and regulator of metabolism, AMP-activated-kinase (AMPK), were dysregulated in a model of inherited retinal degeneration. In order to assess the direct role of AMPK in regulating retinal metabolism, we used mice with retina-specific knockout of AMPK activity. Conditional loss of AMPK resulted in impaired visual function at an early age, with slow photoreceptor loss observed in older mice. Moreover, we found that loss of AMPK resulted in decreased metabolic flux from glucose, decreased mitochondrial DNA copy number, decreased mitochondrial-related gene expression, and alterations in mitochondrial morphology in the photoreceptors, all of which preceded degeneration. Surprisingly, metabolic changes from the loss of AMPK in retinal neurons also resulted in secondary degeneration of retinal pigment epithelial (RPE) cells. Together, these data show that AMPK signaling is important for maintaining metabolic homeostasis of the retina and support the hypothesis that photoreceptors and RPE have a shared metabolic ecosystem that is controlled, in part, by AMPK.

Mendelian randomization identifies folliculin expression as a mediator of diabetic retinopathy.

Abstract: The goal of the study was to identify genes whose aberrant expression can contribute to diabetic retinopathy. We determined differential response in gene expression to high glucose in lymphoblastoid cell lines derived from matched individuals with type 1 diabetes (T1D) with and without retinopathy. Those genes exhibiting the largest difference in glucose response between individuals with diabetes with and without retinopathy were assessed for association to diabetic retinopathy utilizing genotype data from a meta-genome-wide association study. All genetic variants associated with gene expression (expression quantitative trait loci, eQTLs) of the glucose response genes were tested for association with diabetic retinopathy. We detected an enrichment of the eQTLs from the glucose response genes among small association p-values and identified folliculin (FLCN) as a susceptibility gene for diabetic retinopathy. We show that expression of FLCN in response to glucose was greater in individuals with diabetic retinopathy compared to individuals with diabetes without retinopathy. Three large, independent cohorts of individuals with diabetes revealed an association of FLCN eQTL to diabetic retinopathy. Mendelian randomization further confirmed a direct positive effect of increased FLCN expression on retinopathy in individuals with diabetes. Together, our studies integrating genetic association and gene expression implicate FLCN as a disease gene for diabetic retinopathy.

Rpgr vectors for treating x-linked retinitis pigmentosa

Abstract: Disclosed are adeno-associated virus (AAV) vectors comprising a nucleotide sequence encoding RP2 or RPGR-ORF15 and related pharmaceutical compositions. Also disclosed are methods of treating or preventing X-linked retinitis pigmentosa, increasing photoreceptor number in a retina of a mammal, and increasing visual acuity of a mammal using the vectors and pharmaceutical compositions.