Project description:Primary and secondary cone photoreceptor cell death in retinal degenerative diseases, including age-related macular degeneration and retinitis pigmentosa, leads to severe vision impairment and blindness. Regardless of the fact that protection of cone photoreceptor cells under stress conditions, such as retinal degenerative diseases, is crucial for maintaining vision, the underlying molecular mechanisms are unclear. Here, we investigated the function of the deubiquitinase Otud7b/Cezanne in the retina. We identified that Otud7b is predominantly expressed in photoreceptor cells in the mouse retina. While the ablation of Otud7b did not cause a significant defect in development and maturation of the mouse retina, Otud7b‒/‒ mice subjected to light-induced damage, which is one of the dry age-related macular degeneration models, exhibited increased cone photoreceptor degeneration. In addition, Otud7b deficiency in Mak‒/‒ mice, a retinitis pigmentosa mouse model, resulted in further cone photoreceptor degeneration. Moreover, neuronal cells deficient in Otud7b were susceptible to serum starvation, resulting in cell death. We found that NF-κB activity is increased in the Otud7b‒/‒ retinas exposed to light by RNA-sequencing analysis. Luciferase reporter assay also demonstrated increased NF-κB activation in Otud7b-deficient neuronal cells under stress. The neuronal cell death resulting from Otud7b deficiency was suppressed through the inhibition of NF-κB. Furthermore, we observed that inhibition of NF-κB attenuated cone photoreceptor degeneration in the light-exposed Otud7b‒/‒ retina. Together, the current study suggests that Otud7b deubiquitinase protects cone photoreceptor cells under stress conditions by modulating the NF-κB activity.
Project description:Cone photoreceptors are specialised sensory retinal neurons responsible for photopic vision, colour perception and visual acuity. Retinal degenerative diseases are a heterogeneous group of eye diseases in which the most severe vision loss typically arises from cone photoreceptor dysfunction or degeneration. Establishing a method to purify cone photoreceptors from retinal tissue can accelerate the identification of key molecular determinants that underlie cone photoreceptor development, survival and function. The work herein describes a new method to purify enhanced green fluorescent protein (EGFP)-labelled cone photoreceptors from adult retina of Tg(3.2TαCP:EGFP) zebrafish. Electropherograms confirmed downstream isolation of high-quality RNA with RNA integrity number (RIN) >7.6 and RNA concentration >5.7 ng/µl obtained from both populations. Reverse Transcriptase-PCR (RT-PCR) confirmed that the EGFP-positive cell populations express known genetic markers of cone photoreceptors that were not expressed in the EGFP-negative cell population. This work is an important step towards the identification of cone photoreceptor-enriched genes, protein and signalling networks responsible for their development, survival and function. In addition, this advancement facilitates the identification of novel candidate genes for inherited human blindness. In order to analyse and sort samples by flow cytometry, values for FSC and SSC were displayed in a logarithmic scale, as this is normally the default starting display. This allowed for the identification of different sub-populations of cells present in the retina, which were mixed with unwanted cell debris and cell fragments. Since there were multiple cell populations, different levels of auto-fluorescence were thus successfully detected. It was therefore important to change the strategy and display side scatter and fluorescence characteristics of control and EGFP samples, which ultimately allowed the identification of the extremely well-defined population of EGFP-cone photoreceptors. This improved sorting process minimised RNA degradation. The purified EGFP+ cone photoreceptors represent ~5% of the original dissociated population, which is consistent with humans, wherein the total number of cones (6 million) in the retina is approximately 20 times the one of rods (120 million) (Williamson and Cummins 1983). This work allows high-quality RNA to be obtained from sorted-adult cone photoreceptors. RNA integrity is assessed via 28S and 18S rRNA (Imbeaud et al 2005), and our electropherogram results demonstrate production of high-quality RNA with two clearly visible ribosomal peaks (28S and 18S) from EGFP-sorted cones. In addition, the RNA Integrity Number (RIN), an algorithm for assigning integrity values to RNA based on 28S to 18S rRNA ratios (Sambrook et al 1989; Imbeaud et al 2005; Schroeder et al 2006), had a value of 7.6, higher than the minimum-required 7.0. RNA yields of 5.7 ng/µl were relatively high and sufficient for downstream profiling. RT-PCR confirmed expression of the cone specific gene gnat2, and promoter fragment TαC, but not the retinal pigment epithelium specific gene rpe65 in flow cytometry-sorted GFP-positive photoreceptors (GFP+ cells). rpe65 was neither present in flow cytometry-sorted GFP-negative cones (GFP- cells) as this gene is only expressed in the retinal pigment epithelium (RPE). This study therefore permits the identification of cone photoreceptor-enriched genes, protein and signalling networks responsible for their development, survival and function. In addition, this advancement facilitates the identification of novel candidate genes for inherited human blindness.
Project description:Bardet-Biedl syndrome (BBS) is a syndromic ciliopathy leading to progressive blindness starting in childhood, but the mechanism leading to photoreceptor degeneration in BBS is unknown. The basal body of the photoreceptor primary cilium originates from the centrosome’s mother centriole, and the BBS-related proteins form a complex present at basal body. Centrosomes organize microtubules of the mitotic spindle and are required for proper cell division. We show here that immature cones, but not rods, from bbs10-/- mouse pups present an early-onset DNA damage response (DDR) that becomes persistent and localizes to the basal body. Using patient-derived induced pluripotent stem cells (iPSCs), we found that BBS10 retinal progenitor cells (RPCs) also present a DDR that correlates with activation of the mitotic spindle checkpoint. Pharmaceutical inhibition of the cell cycle checkpoint kinase 2 (Chk2) in BBS10 RPCs mitigates cell death and genomic instability and largely restores the perturbed phospho-proteome. Drug treatment of BBS10 retinal organoids improves tissue organization, cone photoreceptor survival, and outer segment maturation. These findings reveal an important function for BBS10 in the maintenance of RPCs and cone photoreceptors genomic stability during development and may open new therapeutic avenues to delay photoreceptor degeneration in BBS.
Project description:Photoreceptor loss is a leading cause of blindness, but mechanisms underlying photoreceptor degeneration are not well understood. Treatment strategies would benefit from an improved understanding of gene-expression patterns directing photoreceptor development, as many genes are implicated in both development and degeneration. Neural retina leucine zipper (NRL) is critical for rod photoreceptor genesis and degeneration, with NRL mutations known to cause enhanced S-cone syndrome and retinitis pigmentosa. While murine Nrl loss has been characterized, studies of human NRL can identify important insights for human retinal disease. Here we utilized human organoid models of retinal development to molecularly define developmental alterations in a human model of NRL loss. Consistent with the function of NRL in rod fate specification, human retinal organoids lacking NRL develop S-opsin dominant photoreceptor populations. We report generation of two distinct S-opsin expressing populations in NRL null retinal organoids and identify MEF2C as a candidate regulator of cone development.
Project description:We performed RNA sequencing on melanopsin deleted retinas (Opn4-DTA/DTA) to determine potential cues involved in instructing cone photoreceptor positioning
Project description:Cone photoreceptors are the primary initiator of visual transduction in the human retina. Dysfunction or death of rod photoreceptors precedes cone loss in many retinal and macular degenerative diseases, suggesting a rod-dependent trophic support for cone survival. Rod differentiation and homeostasis are dependent on the basic motif leucine zipper transcription factor NRL. The loss of Nrl in mice (Nrl-/-) results in a retina with predominantly S-opsin containing cones that exhibit molecular and functional characteristics of WT cones. Here we report that Nrl-/- retina undergoes a rapid but transient period of degeneration in early adulthood, with cone apoptosis, retinal detachment, alterations in retinal vessel structure, and activation and translocation of retinal microglia. However, cone degeneration stabilizes by four months of age, resulting in a thinned but intact outer nuclear layer with residual cones expressing S- and M-opsins and a preserved photopic ERG. At this stage, microglia translocate back to the inner retina and reacquire a quiescent morphology. Gene profiling analysis during the period of transient degeneration reveals misregulation of stress response and inflammation genes, implying their involvement in cone death. The Nrl-/- retina illustrates the long-term viability of cones in the absence of rods and may serve as a model for elucidating mechanisms of cone homeostasis and degeneration that would be relevant to understanding diseases of the cone-dominant human macula. Targets were generated from a pair of retinas (one Nrl-/- mouse) per biological replicate. Four biological replicates were generated for each of the five aging timepoints (1, 2, 4, 6, and 10 months post natal).
Project description:Purpose: To define the cone photoreceptor diversity and underlying transcriptional controls in mouse retina Methods: Individual retinal cone cells were isolated by micro-manipulator from dissociated pieces of superior/inferior retina from heterozygous (or homozygous) Thrb-b2Cre:Ai6 mice. Single cell libraries were constructed for RNA-seq analysis. Thrb-b2Cre;Rosa26-Sun1Gfp mice were used to isolate cone nuclei for ATAC-seq analysis. Thrb-HAB mice were used to identify TRb2 genomic binding sites using ChAP-seq analysis. Results: Developmental analyses of individual cones revealed a network of gradient genes. Many of these gradient genes are regulated by TRb2, a thyroid hormone receptor that has been associated with color visual impairment. Conclusions: The results suggest that TRb2 controls chromatin remodeling and transcriptional plasticity in the cone lineage to promote diversity.
Project description:For isolation of rod, cone, and pineal photoreceptor cells, we used the transgenic zebrafish lines, Tg(rho:egfp)ja2Tg, Tg(gnat2:egfp)ja23Tg, and Tg(exorh:EGFP)ja1Tg, which express EGFP in rods, all cone subtypes, and pineal rod cells, respectively. Retinas were dissected from dark-adapted adult fish under dim red light. The isolated retinas were digested with trypsin in Ca2+-free Ringer’s solution. The reaction was terminated by adding soybean trypsin inhibitor and fetal bovine serum. The dissociated EGFP-positive cells were isolated with a fluorescence activating cell sorter (FACSAria, BD Biosciences) by the following three parameters: forward scatter, side scatter and green fluorescence. Goal was to determine differentially expressed genes among three types of photoreceptor cells.
Project description:Cone photoreceptors are the primary initiator of visual transduction in the human retina. Dysfunction or death of rod photoreceptors precedes cone loss in many retinal and macular degenerative diseases, suggesting a rod-dependent trophic support for cone survival. Rod differentiation and homeostasis are dependent on the basic motif leucine zipper transcription factor NRL. The loss of Nrl in mice (Nrl-/-) results in a retina with predominantly S-opsin containing cones that exhibit molecular and functional characteristics of WT cones. Here we report that Nrl-/- retina undergoes a rapid but transient period of degeneration in early adulthood, with cone apoptosis, retinal detachment, alterations in retinal vessel structure, and activation and translocation of retinal microglia. However, cone degeneration stabilizes by four months of age, resulting in a thinned but intact outer nuclear layer with residual cones expressing S- and M-opsins and a preserved photopic ERG. At this stage, microglia translocate back to the inner retina and reacquire a quiescent morphology. Gene profiling analysis during the period of transient degeneration reveals misregulation of stress response and inflammation genes, implying their involvement in cone death. The Nrl-/- retina illustrates the long-term viability of cones in the absence of rods and may serve as a model for elucidating mechanisms of cone homeostasis and degeneration that would be relevant to understanding diseases of the cone-dominant human macula.