Project description:In mammals, retinal damage is followed by Müller glia cell activation and proliferation. While retinal gliosis persists in adult mammals after an insult or disease, some vertebrates, including zebrafish, have the capacity to regenerate. We believe we are the first group to show that gliosis is a fibrotic-like process in mammals’ eyes caused by differential activation of canonical and non-canonical TGFβ signaling pathways.
Project description:Previous studies have demonstrated the dynamic changes in chromatin structure during retinal development that correlate with changes in gene expression. However, a major limitation of those prior studies was the lack of cellular resolution. Here, we integrate single-cell (sc) RNA-seq and scATAC-seq with bulk retinal data sets to identify cell type–specific changes in the chromatin structure during development. Although most genes’ promoter activity is strongly correlated with chromatin accessibility, we discovered several hundred genes that were transcriptionally silent but had accessible chromatin at their promoters. Most of those silent/accessible gene promoters were in the Müller glial cells. The Müller cells are radial glia of the retina and perform a variety of essential functions to maintain retinal homeostasis and respond to stress, injury, or disease. The silent/accessible genes in Müller glia are enriched in pathways related to inflammation, angiogenesis, and other types of cell-cell signaling and were rapidly activated when we tested 15 different physiologically relevant conditions to mimic retinal stress, injury, or disease in human and murine retinae. We refer to these as “pliancy genes” because they allow the Müller glia to rapidly change their gene expression and cellular state in response to different types of retinal insults. The Müller glial cell pliancy program is established during development, and we demonstrate that pliancy genes are necessary and sufficient for regulating inflammation in the murine retina in vivo. In zebrafish, Müller glia can de-differentiate and form retinal progenitor cells that replace lost neurons. The pro-inflammatory pliancy gene cascade is not activated in zebrafish Müller glia following injury, and we propose a model in which species-specific pliancy programs underly the differential response to retinal damage in species that can regenerate retinal neurons (zebrafish) versus those that cannot (humans and mice).
Project description:Previous studies have demonstrated the dynamic changes in chromatin structure during retinal development that correlate with changes in gene expression. However, a major limitation of those prior studies was the lack of cellular resolution. Here, we integrate single-cell (sc) RNA-seq and scATAC-seq with bulk retinal data sets to identify cell type–specific changes in the chromatin structure during development. Although most genes’ promoter activity is strongly correlated with chromatin accessibility, we discovered several hundred genes that were transcriptionally silent but had accessible chromatin at their promoters. Most of those silent/accessible gene promoters were in the Müller glial cells. The Müller cells are radial glia of the retina and perform a variety of essential functions to maintain retinal homeostasis and respond to stress, injury, or disease. The silent/accessible genes in Müller glia are enriched in pathways related to inflammation, angiogenesis, and other types of cell-cell signaling and were rapidly activated when we tested 15 different physiologically relevant conditions to mimic retinal stress, injury, or disease in human and murine retinae. We refer to these as “pliancy genes” because they allow the Müller glia to rapidly change their gene expression and cellular state in response to different types of retinal insults. The Müller glial cell pliancy program is established during development, and we demonstrate that pliancy genes are necessary and sufficient for regulating inflammation in the murine retina in vivo. In zebrafish, Müller glia can de-differentiate and form retinal progenitor cells that replace lost neurons. The pro-inflammatory pliancy gene cascade is not activated in zebrafish Müller glia following injury, and we propose a model in which species-specific pliancy programs underly the differential response to retinal damage in species that can regenerate retinal neurons (zebrafish) versus those that cannot (humans and mice).
Project description:Retinitis pigmentosa (RP) and Leber congenital amaurosis are inherited retinal dystrophies caused by mutations in, among others, the Crumbs homologue 1 (CRB1) gene. CRB1 is required for organizing apical-basal polarity and adhesion between photoreceptors and Müller glial cells. Using human CRB1 patient induced pluripotent stem cells from RP patients we derived CRB1 retinal organoids, with diminished expression of variant CRB1 protein with immunohistochemical analysis. Single cell RNA-sequencing revealed impact on, among others, the endosomal pathway and cell adhesion and migration in CRB1 patient derived retinal organoids compared to isogenic controls. Adeno-associated viral (AAV) vector-mediated hCRB2 or hCRB1 gene augmentation in Müller glial and photoreceptor cells partially restored the histological and differentially expressed genes phenotype. Altogether, we show proof-of-concept that AAV.hCRB1 or AAV.hCRB2 treatment improved the phenotype of CRB1 patient derived retinal organoids, providing essential information for future gene therapy approaches for patients with mutations in the CRB1 gene.
Project description:Müller glia play very important and diverse roles in retinal homeostasis and disease, bur very little is known of their development during human retinal embryogenesis. Since they share several markers with retinal progenitors, they are often considered as a different cell population. In this study we isolated CD29+/CD44+cells from retinal organoids formed by hEPSC cells in vitro, and examined their transcriptome profile at various stages of organoid development to identify their transcriptomic profile.
Project description:Purpose: Müller glia are the only glial cell type produced by the neuroepithelial progenitor cells which generate the vertebrate retina. Müller glia are required to maintain retinal homeostasis and support the survival of retinal neurons. Furthermore, they function as an adult stem cell, mediating retinal regeneration among select vertebrate classes. However, the mechanisms which regulate Müller development are poorly understood as considerable overlap exists in gene expression between retinal progenitor cells and differentiated Müller glia. We investigate the functional role of the LIM homeodomain transcription factor Lhx2 in the specification and development of Müller glia in the mouse. Methods: RNA-Seq was performed in collaboration with the Johns Hopkins School of Medicine Deep Sequencing and Microarray Core Facility. Libraries were prepared using Illumina TruSeq RNA Sample kit (Illumina, San Diego, CA) following manufacturer’s recommended procedure. The PCR amplified library was purified using RNAClean XP magnetic beads (Agencourt, Beverley, MA) and run out on a High Sensitivity DNA Chip (Agilent, Santa Clara, CA) for quality check. We used STAR to align RNA-Seq reads onto Ensembl mouse genome GRCm38, release 72. To generate the stand attribute for alignments containing splice junctions, we used the outSAMstrandField intronMotif program. The spliced alignments without strand definition were removed. Number of reads mapped to exons was counted by htseq-count. Genes expressed at very low levels were omitted from further analysis. Gene expression differences between wildtype and mutant samples, significance (p-value) and false discovery rate (FDR) were computed using the generalized linear models based EdgeR. Results: We observed a substantial reduction in expression of Notch pathway genes including Notch1, the Notch ligands Dll1 and Dll3, as well as gliogenic Notch effector genes such as Hes1, Hes5, Id1 and Sox8 and the Müller-gliogenic factor Rax. We likewise observe a substantial reduction in expression of progenitor-specific genes such as Vsx2 and Fgf15. Furthermore, we observed a decrease in the expression of early-onset glial markers such as Crym , Spon1, and Car2.
Project description:Contrasting with fish or amphibian, retinal regeneration from Müller glial cells is largely limited in mammals. In our quest towards the identification of molecular cues that may boost their stemness potential, we investigated the involvement of the Hippo pathway effector YAP, which we previously found to be upregulated in Müller cells following retinal injury. We report that conditional Yap deletion in Müller cells prevents the upregulation of cell cycle genes that normally accompanies reactive gliosis upon photoreceptor cell death. This occurs as a consequence of defective EGFR signaling. Consistent with a function of YAP in triggering Müller glia cell cycle re-entry, we further show that in Xenopus, a species endowed with efficient regenerative capacity, YAP is required for their injury-dependent proliferative response. Finally, and noteworthy, we reveal that YAP overactivation in mouse Müller cells is sufficient to induce their reprogramming into highly proliferative cells. Overall, we unravel a pivotal role for YAP in tuning Müller cell response to injury and highlight a novel YAP-EGFR axis by which Müller cells exit their quiescence state, a critical step towards regeneration.
Project description:To address the function of Rax in differentiated Müller glial cells, we generated Rax tamoxifen-induced conditional knock-out (Rax iCKO) mice, where Rax can be depleted in mTFP-labeled Müller glial cells upon tamoxifen treatment, by crossing Raxflox/flox mice with Rlbp1-CreERT2 mice and found histological characteristic of reactive gliosis and an enhanced gliosis of Müller glial cells in the Rax iCKO retina under normal and stress conditions, respectively. RNA sequencing using isolated Müller glial cells from the Rax iCKO retina by fluorescence-activated cell sorting demonstrated that reduced expression of suppressor of cytokine signaling-3 (Socs3), whose depletion leads to reactive gliosis in Müller glial cells. Reporter gene assays showed that Rax directly transactivates Socs3 and we observed decreased expression of Socs3 in Müller glial cells of the Rax iCKO retina by immunostaining. Taken together, these results suggest that the Rax homeoprotein suppresses reactive gliosis in Müller glial cells by transactivating Socs3 in vivo. Our results may shed light on the transcriptional regulatory mechanisms underlying Müller glial cell homeostasis.