Molecular basis of retinal remodeling in a Zebrafish model of Retinitis Pigmentosa
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ABSTRACT: A hallmark of inherited retinal degenerative diseases such as Retinitis Pigmentosa (RP) is progressive structural and functional remodeling of the remaining retinal cells as photoreceptors degenerate. Extensive remodeling of the retina stands as a barrier for the successful implementation of strategies to restore vision. To understand the molecular basis of remodeling, we performed analyses of single-cell transcriptome data from adult Zebrafish retina of wild-type and a P23H mutant rhodopsin transgenic model of RP with continuous degeneration and regeneration. We provide a benchmark atlas of retinal cell type transcriptomes in Zebrafish and find changes in all retinal cell types in the P23H model. These include widespread oxidative stress, changes in reliance on oxidative metabolism and glycolysis, widespread synaptic remodeling, and changes in circadian rhythm regulation. This comprehensive transcriptomic analysis provides a molecular road map to understand how the retina remodels in the context of chronic retinal degeneration with ongoing regeneration.
Project description:In inherited retinal disorders such as retinitis pigmentosa (RP), rod photoreceptor-specific mutations cause primary rod degeneration that is followed by secondary cone death and loss of high-acuity vision. Mechanistic studies of retinal degeneration are challenging because of retinal heterogeneity. Moreover, the detection of early cone responses to rod death is especially difficult due to the paucity of cones in the retina. To resolve heterogeneity in the degenerating retina and investigate events in both types of photoreceptors during primary rod degeneration, we utilized droplet-based single-cell RNA sequencing in an RP mouse model, rd10.
Project description:Zebrafish possess the innate ability to regenerate any lost or damaged retinal cell type with Müller glia serving as resident stem cells. Recently, we discovered that this process is aided by a population of damage-induced senescent immune cells. As part of the Senescence Associated Secretory Phenotype (SASP), senescent cells secrete numerous factors that can play a role in the modulation of inflammation and remodeling of the retinal microenvironment during regeneration. However, the identity of specific SASP factors that drive initiation and progression of retina regeneration remain unclear. Here, we mined the SASP Atlas and RNAseq datasets to identify differentially expressed SASP factors after retina injury, including two distinct acute damage regimens, as well as a chronic, genetic model of retina degeneration. We discovered a 31 factor “Regeneration-associated Senescence Signature” (RASS) that represents SASP factors and senescence markers that are conserved across all data sets and are upregulated after damage. Among these, we show that depletion of npm1a inhibits retina regeneration. Our data support the model that differential expression of SASP factors promotes regeneration after both acute and chronic retinal damage.
Project description:Retinitis pigmentosa (RP) is a photoreceptor disease that affects approximately 100,000 people in the United States. There are currently very limited treatment options and the prognosis for most patients is progressive vision loss. Unfortunately, the understanding of the molecular underpinnings of RP initiation and progression is still poorly understood. However, the development of animal models of RP, coupled with high-throughput sequencing, has provided an opportunity to study the underlying cellular and molecular changes of this disease. Using RNA-Seq, we present the first retinal transcriptome analysis of the rd10 murine model of retinal degeneration. RNA-Seq on whole-retina samples from rd10, wild-type and GFP-expressing mouse retina. Three biological replicates of each.
Project description:Purpose: Investigate the molecular determinants of retinal regeneration in adult vertebrates by analyzing the gene expression profiles of control and post-lesion retina of adult zebrafish, a system that regenerates following injury. Methods: Gene expression profiles of zebrafish retina and brain were determined with DNA microarray, RT-PCR, and real-time quantitative PCR analyses. Damaged retinas and their corresponding controls were analyzed 2-5 days post-lesion (acute injury condition) or 14 d post-lesion (cell regeneration condition). Results: Expected similarities and differences in the gene expression profile of zebrafish retina and brain were observed, confirming the applicability of the gene expression techniques. Mechanical lesion of retina triggered significant, time-dependent changes in retinal gene expression. The induced transcriptional changes were consistent with cellular phenomena known to occur, in a time-dependent manner, subsequent to retinal lesion, including cell cycle progression, axonal regeneration, and regenerative cytogenesis. Conclusions: The results indicate that retinal regeneration in adult zebrafish involves a complex set of induced, targeted changes in gene transcription, and suggest that these molecular changes underlie the ability of the adult vertebrate retina to regenerate. Keywords: time course; injury response; cellular correlation Control brain and retina (unlesioned); Control and lesioned retina (matched animals, at least n = 8 for each condition).
Project description:P23H is the most common mutation in the RHODOPSIN (RHO) gene leading to a dominant form of retinitis pigmentosa (RP), a rod photoreceptor degeneration that invariably causes vision loss. Specific disruption of the disease P23H RHO mutant while preserving the wild-type (WT) functional allele would be an invaluable therapy for this disease. However, various technologies tested in the past failed to achieve effective changes and consequently therapeutic benefits. We validated a CRISPR/Cas9 strategy to specifically inactivate the P23H RHO mutant, while preserving the WT allele in vitro. We, then, translated this approach in vivo by delivering the CRISPR/Cas9 components in murine Rho+/P23H mutant retinae. Targeted retinae presented a high rate of cleavage in the P23H but not WT Rho allele. This gene manipulation was sufficient to slow photoreceptor degeneration and improve retinal functions. To improve the translational potential of our approach, we tested intravitreal delivery of this system by means of adeno-associated viruses (AAVs). To this purpose, the employment of the AAV9-PHP.B resulted the most effective in disrupting the P23H Rho mutant. Finally, this approach was translated successfully in human cells engineered with the homozygous P23H RHO gene mutation. Overall, this is a significant proof-of-concept that gene allele specific targeting by CRISPR/Cas9 technology is specific and efficient and represents an unprecedented tool for treating RP and more broadly dominant genetic human disorders affecting the eye, as well as other tissues.
Project description:Background: Adult zebrafish spontaneously regenerate their retinas after damage. Although a number of genes and signaling pathways involved in regeneration have been identified, the extent of mechanisms regulating regeneration is unclear. Small non-coding RNAs, microRNAs (miRNAs), that regulate regeneration of various tissues in lower vertebrates were examined for their potential roles in regulating zebrafish retinal regeneration. Results: To investigate the requirement of miRNAs during zebrafish retinal regeneration, we knocked down the expression of the miRNA-processing enzyme Dicer in retinas prior to light-induced damage. Dicer loss significantly reduced proliferation of Müller glia-derived neuronal progenitor cells during regeneration. To identify individual miRNAs with roles in retina regeneration, we collected retinas at different stages of light damage and performed small RNA high-throughput sequencing. We identified subsets of miRNAs that were differentially expressed during active regeneration but returned to basal levels once regeneration was completed. To validate the roles of differentially expressed miRNAs, we knocked down 6 different miRNAs that were upregulated in expression during regeneration and demonstrated that they have distinct effects on neuronal progenitor cell proliferation and migration during retina regeneration. Conclusions: miRNAs are necessary for retinal regeneration. miRNA expression is dynamic during regeneration. miRNAs function during initiation and progression of retinal regeneration. Identification of miRNAs before, during and after completion of zebrafish retinal regeneration
Project description:Zebrafish spontaneously regenerate the retina after injury. Currently, studies have observed gene expression profiles in this species however this may be a poor reflection of protein function. To further address this and expand our understanding of the regenerative process in the zebrafish, we compared the proteomic profile of the retina during injury and upon regeneration. Ouabain was injected intravitreously to create a model of degeneration and regeneration of the retina which was extracted at 0, 3 and 18 days after injection. Differences in protein expression indicates reduced metabolic processing, and increase in fibrin clot formation, with significant upregulation of fibrinogen gamma polypeptide, apolipoproteins A-Ib and A-II, galectin-1, and vitellogenin-6 during degeneration when compared to normal retina. In addition, cytoskeleton and membrane transport proteins were considerably altered during regeneration, with the highest fold upregulation observed for tubulin beta 2A, histone H2B and brain type fatty acid binding protein. Key proteins identified in this study may play an important role in the regeneration of the zebrafish retina and investigations on the potential regulation of these proteins may support future investigations in this field.
Project description:In the retina of adult teleosts, stem cells are sustained in two specialized niches: the ciliary marginal zone (CMZ) and the microenvironment surrounding adult Müller glia. Recently, Müller glia were identified as the regenerative stem cells in the teleost retina. Secreted signaling molecules that regulate neuronal regeneration in the retina are largely unknown. In a microarray screen to discover such factors, we identified midkine-b (mdkb). Midkine is a highly conserved heparin-binding growth factor with numerous biological functions. The zebrafish genome encodes two distinct midkine genes: mdka and mdkb. Here, we describe the cellular expression of mdka and mdkb during retinal development and the initial, proliferative phase of photoreceptor regeneration. The results show that in the embryonic and larval retina mdka and mdkb are expressed in stem cells, retinal progenitors and neurons in distinct patterns that suggest different functions for the two molecules. Following the selective death of photoreceptors in the adult, mdka and mdkb are co-expressed in horizontal cells and proliferating Müller glia and their neurogenic progeny. These data reveal that Mdka and Mdkb are signaling factors present in the retinal stem cell niches in both embryonic and mature retinas, and that their cellular expression is actively modulated during retinal development and regeneration. Experiment Overall Design: As a means to identify genes necessary for photoreceptor regeneration, we evaluated transcriptional in the retina of the zebrafish as photoreceptors are regenerated. Albino zebrafish were dark adapted, then half were exposed to bright constant light and half were returned to normal lighting. After 72hrs of light exposure, retinal RNA was isolated and analysis of gene expression was performed using Affymetriz zebrafish gene arrays.
Project description:Neuroprotective therapies for retinal degeneration may be used to rescue retinal cells and preserve vision. Hypoxic preconditioning stabilizes the transcription factor HIF-1α in the retina and strongly protects photoreceptors in an animal model of light-induced retinal degeneration. Our data suggest that neuroprotection after hypoxic preconditioning of the retina is the result of the differential expression of a multitude of genes which may act in concert to protect visual cells against a toxic insult. Experiment Overall Design: In total 24 samples were analyzed on Affymetrix mouse 430.2 arrays, the samples represent different durations of regeneration (none = 0 h, 2 h, 4 h and 16 h) from hypoxic or normoxic treatments, that were tested in triplicates.
Project description:Retinitis Pigmentosa (RP) is a progressive retinal degeneration in which the retina loses nearly all of its photoreceptor cells and undergoes major structural changes. Little is known regarding the role the resident glia, the MM-CM-<ller glia, play in the progression of the disease. Here we define gene expression changes in MM-CM-<ller glial cells (MGCs) from two different mouse models of RP, the retinal degeneration 1 (rd1) and rhodopsin knock-out (Rhod-ko) models. The RNA repertoire of 28 single MGCs was comprehensively profiled, and a comparison was made between MGC from wild type (WT) and mutant retinas. Two time points were chosen for analysis, one at the peak of rod photoreceptor death and one during the period of cone photoreceptor death. MGCs have been shown to respond to retinal degeneration by undergoing gliosis, a process marked by the upregulation of GFAP. In this data, many additional transcripts were found to change. These can be placed into functional clusters, such as retinal remodeling, stress response, and immune related response. It is noteworthy that a high degree of heterogeneity among the individual cells was observed, possibly due to their different spatial proximities to dying cells, and/or inherent heterogeneity among MGCs. Retinas were dissociated and single Muller Glial Cells were picked under a dissecting microscope using a micropipette based on their distinct morphological shape. Single cell cDNAs were generated and genome wide profiles were obtained by hybridization to Affymetrix 430 2.0 microarrays. Data was normalized using MAS5.0 software. A total of 28 Muller Glial Cells were analyzed and confirmed post hoc by expression of known marker genes.