Project description:Rhodopsin (RHO) mutations such as Pro23His, are the leading cause of dominantly inherited retinitis pigmentosa in North America. As with other dominant retinal dystrophies, these mutations lead to production of a toxic protein product, and treatment will require knockdown of the mutant allele. The purpose of this study was to develop a CRISPR-Cas9-mediated transcriptional repression strategy using catalytically inactive S. aureus Cas9 (dCas9) fused to the Krüppel-associated box (KRAB) transcriptional repressor domain. Using a reporter construct carrying GFP cloned downstream of the RHO promoter fragment (nucleotides -1403 to +73), we demonstrate a ~74%-84% reduction in RHO promoter activity in RHOpCRISPRi treated vs plasmid only controls. Following subretinal transduction of human retinal explants and transgenic Pro23His mutant pigs, significant knockdown of rhodopsin protein was achieved. Suppression of mutant transgene in vivo was associated with a reduction in ER-stress and apoptosis markers and preservation of photoreceptor cell layer thickness.
Project description:The goal of the study was to identify transcriptional modifications in retinal tissues from mouse model of rhodopsin mutation-associated retinitis pigmentosa (RP), Q344X compared to wild-type (WT). We implemented RNA-sequencing (RNA-seq) at poly(A) selected RNA for transcriptomic profiling. Differentially expressed genes were determined by DESeq2 using the Benjamini & Hochberg p-value adjustment and an absolute log2 fold change cutoff. The results indicate that there is specificity in transcriptional patterns in the retina from Q344x mice relative to WT, including differential expression in the potassium channel gene, Kcnv2, and differential expression in histone genes including the H1 family histone member, H1foo, the H3 histone family 3B, H3f3b, and the histone deacetylase 9, Hdac9.
Project description:Inherited retinal degenerations (IRDs) constitute a group of clinically and genetically diverse vision-impairing disorders. Retinitis pigmentosa (RP), the most common form of IRD, is characterized by gradual dysfunction and degeneration of rod photoreceptors, followed by the loss of cone photoreceptors. Recently, we identified reserpine as a lead molecule for maintaining rod survival in mouse and human retinal organoids as well as in the rd16 mouse, which phenocopy Leber congenital amaurosis caused by mutations in the cilia-centrosomal gene CEP290 (Chen et al. eLife 2023;12:e83205. DOI: https://doi.org/10.7554/eLife.83205). Here, we show the therapeutic potential of reserpine in a rhodopsin P23H rat model of autosomal dominant RP. At postnatal day (P) 68, when males and females are analyzed together, the reserpine-treated rats exhibit higher rod-derived scotopic b-wave amplitudes compared to the controls with little or no change in scotopic a-wave or cone-derived photopic b-wave. Interestingly, the reserpine-treated female rats display enhanced scotopic a- and b-waves and photopic b-wave responses at P68, along with a better contrast threshold and increased outer nuclear layer thickness. The female rats demonstrate better preservation of both rod and cone photoreceptors following reserpine treatment. Retinal transcriptome analysis reveals sex-specific responses to reserpine, with significant upregulation of phototransduction genes and proteostasis-related pathways, and notably, genes associated with stress response. This study builds upon our previously reported results reaffirming the potential of reserpine for gene-agnostic treatment of IRDs and emphasizes the importance of biological sex in retinal disease research and therapy development.
Project description:Sex-specific attenuation of photoreceptor degeneration by reserpine in a rhodopsin P23H rat model of autosomal dominant retinitis pigmentosa
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:Retinitis pigmentosa (RP) is an inherited eye disease that causes progressive vision loss.To investigate the biological processes and molecular changes that occur in different cell types in the retinas in rd1 mice, a mouse model of retinitis pigmentosa, we performed single-cell RNA-seq to examine the transcriptomes of various retinal cells.
Project description:Recessive retinitis pigmentosa (RP) is often caused by nonsense mutations that lead to low mRNA levels as a result of nonsense-mediated decay. Some RP genes are expressed at detectable levels in leukocytes as well as in the retina. We designed a microarray-based method to find recessive RP genes based on low lymphoblast mRNA expression levels Keywords: Recessive mutations; mRNA expression; nonsense mediated-decay; retinitis pigmentosa; lymphocyte; Affymetrix genechip Human Genome U133Plus2.0.
Project description:Neuronal plasticity of the inner retina has been observed in response to photoreceptor degeneration. Typically, this phenomenon has been considered maladaptive and may preclude vision restoration in the blind. However, several recent studies utilizing triggered photoreceptor ablation have shown adaptive responses in bipolar cell dendrites expected to support normal vision. Whether such homeostatic plasticity occurs during progressive photoreceptor degenerative disease to help maintain normal visual behavior is unknown. We addressed these issues in an established mouse model of Retinitis Pigmentosa caused by the P23H mutation in rhodopsin. We show robust modulation of the retinal transcriptomic network reminiscent of the neurodevelopmental state as well as potentiation of rod – rod bipolar cell signaling following rod photoreceptor degeneration. Additionally, we found highly sensitive night vision in P23H mice even when more than half of the rod photoreceptors were lost. The results implicate retinal adaptation leading to persistent visual function during photoreceptor degenerative disease.
Project description:Neuronal plasticity of the inner retina has been observed in response to photoreceptor degeneration. Typically, this phenomenon has been considered maladaptive and may preclude vision restoration in the blind. However, several recent studies utilizing triggered photoreceptor ablation have shown adaptive responses in bipolar cell dendrites expected to support normal vision. Whether such homeostatic plasticity occurs during progressive photoreceptor degenerative disease to help maintain normal visual behavior is unknown. We addressed these issues in an established mouse model of Retinitis Pigmentosa caused by the P23H mutation in rhodopsin. We show robust modulation of the retinal transcriptomic network reminiscent of the neurodevelopmental state as well as potentiation of rod – rod bipolar cell signaling following rod photoreceptor degeneration. Additionally, we found highly sensitive night vision in P23H mice even when more than half of the rod photoreceptors were lost. The results implicate retinal adaptation leading to persistent visual function during photoreceptor degenerative disease.
Project description: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.