Translational profiling of retinal ganglion cell optic nerve regeneration in Xenopus laevis
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ABSTRACT: Unlike adult mammals, adult frogs regrow and regenerate their optic nerve following a crush injury. Using Translational Ribosome Affinity Purification (TRAP), a method to isolate mRNAs actively undergoing translation in a target cell population, we have generated a transcriptional profile by RNA-Seq for retinal ganglion cells (RGC) during the period of recovery following an optic nerve injury. Based on bioinformatics analysis using the JGI 9.1 Xenopus laevis gene models, our results reveal a profound shift in the composition of actively translating mRNAs during the early stages of RGC regeneration: as factors involved in cell signaling are rapidly downregulated, and those involved in core metabolism are upregulated. We identified one highly upregulated gene in response to injury, uchl1, which coupled to downregulation of the synucleins (snca, scng), was previously implicated in neurodegenerative diseases. Our injury-screen in Xenopus identified a previously unknown gene, gng8, as being associated with the regenerative process. Our generated online database provides the Xenopus community a valuable resource for the identification of genes involved in the regeneration process to target for future functional studies.
Project description:It is well-established that neurons in the adult mammalian central nervous system are terminally differentiated and, if injured, will be unable to regenerate their connections. In contrast to mammals, zebrafish and other teleosts display a robust neuroregenerative response. Following optic nerve crush (ONX), retinal ganglion cells (RGC) regrow their axons to synapse with topographically correct targets in the optic tectum, such that vision is restored in ~21 days. What accounts for these differences between teleostean and mammalian responses to neural injury is not fully understood. A time course analysis of global gene expression patterns in the zebrafish eye after optic nerve crush can help to elucidate cellular and molecular mechanisms that contribute to a successful neuroregeneration. We used microarrays to detail the global gene expression patterns underlying a successful regeneration or the optic nerve following injury. Experiment Overall Design: Microarray analysis was performed on total RNA extracted from whole eye following optic nerve crush (ONX) or sham surgery at defined intervals (4, 12, & 21 days).
Project description:It is well-established that neurons in the adult mammalian central nervous system are terminally differentiated and, if injured, will be unable to regenerate their connections. In contrast to mammals, zebrafish and other teleosts display a robust neuroregenerative response. Following optic nerve crush (ONX), retinal ganglion cells (RGC) regrow their axons to synapse with topographically correct targets in the optic tectum, such that vision is restored in ~21 days. What accounts for these differences between teleostean and mammalian responses to neural injury is not fully understood. A time course analysis of global gene expression patterns in the zebrafish eye after optic nerve crush can help to elucidate cellular and molecular mechanisms that contribute to a successful neuroregeneration. We used microarrays to detail the global gene expression patterns underlying a successful regeneration or the optic nerve following injury.
Project description:To identify a novel clinically-relevant therapy, fluvastatin and matrix bound nanovesicles (MBV) were focused in this study. We found that fluvastatin and MBV synergistically enhance optic nerve regeneration and RGC protection after optic nerve injury in mouse. To identify the molecular mechanisms underlying enhancement of RGC protection and axon regeneration after optic nerve injury, bulk RNA sequencing analysis of the whole retina treated with MBV, fluvastatin and the combination of MBV and fluvastatin or PBS as a control two days after optic nerve crush, was performed. Bulk RNA-seq analysis revealed that genes and cellular pathways related to inflammation, were robustly altered.
Project description:CNS injuries of the anuran amphibian, Xenopus laevis, are uniquely befitted for studying the molecular compositions of neuronal regeneration of retinal ganglion cells (RGC) due to a functional recovery of optic axons disparate to adult mammalian analogues. RGCs and their optic nerve axons undergo irreversible neurodegeneration in glaucoma and associated optic neuropathies, resulting in blindness in mammals. Conversely, Xenopus demonstrates RGC lifetime-spanning regenerative capabilities after optic nerve crush, inciting opportunities to compare de novo regeneration and develop efficient pharmaceutical approaches for vision restoration. Studies revealing lipidome alterations during optic nerve regeneration are sparse and could serve as a solid foundation for these underlying molecular changes. We profile the lipid changes in a transgenic line of 1 year old Xenopus laevis Tg(islet2b:gfp) frogs that were either left untreated (naïve) or had a monocular surgery of either a left optic crush injury (crush) or sham surgery (sham). Matching controls of uninjured right optic nerves were also collected (control). Tg(islet2b:gfp) frogs were allowed to recover for 7,12,18, and 27 days post optic nerve crush. Following euthanasia, the optic nerves were collected for lipidomic analysis. A modified Bligh and Dyer method [PMID: 13671378] was used for lipid extraction, followed by untargeted mass spectrometry lipid profiling with a Q-Exactive Orbitrap Liquid Chromatography-Mass Spectrometer (LC MS-MS) coupled with Vanquish Horizon Binary UHPLC LC-MS system.
Project description:The failure of adult CNS neurons to survive and regenerate their axons after injury or in neurodegenerative disease remains a major target for basic and clinical neuroscience. Recent data demonstrated in the adult mouse that exogenous expression of Sry-related high-mobility-box 11 (Sox11) promotes optic nerve regeneration after optic nerve injury, but exacerbates the death of a subset of retinal ganglion cells, alpha-RGCs. During development, Sox11 is required for RGC differentiation from retinal progenitor cells (RPCs), and we found that mutation of a single residue to prevent sumoylation at K91 increased nuclear localization and RGC differentiation in vitro. Here we explored whether this Sox11 manipulation similarly has stronger effects on RGC survival and optic nerve regeneration. In vitro, we found that non-SUMOylatable Sox11 K91A leads to RGC death and suppresses axon outgrowth in primary neurons. We furthermore found that Sox11 K91A more strongly promotes axon regeneration but also increases RGC death after optic nerve injury in vivo in adult mouse. RNA-seq data showed that Sox11 and Sox11 K91A increase the expression of key signaling pathway genes associated with axon growth and regeneration but downregulated Spp1 and Opn4 expression in RGC cultures, consistent with negatively regulating the survival of α-RGCs and ipRGCs. Thus Sox11 and its sumoylation site at K91 regulate gene expression, survival and axon growth in RGCs and may be explored further as potential regenerative therapies for optic neuropathy.
Project description:We used optic nerve injury as a model to study early signaling events in the neuronal soma following axonal injury. Optic nerve injury results in the selective death of retinal ganglion cells (RGCs). The time course of cell death takes place over a period of days with the earliest detection of RGC death at about 48 hr post injury. We hypothesized that in the period immediately following axonal injury, there are changes in the soma that signal surrounding glia and neurons and that start programmed cell death. In the current study, we investigated early changes in cellular signaling and gene expression that occur within the first 6 hrs post optic nerve injury. We detected differences in phosphoproteins and gene expression within this time period that we used to interpret temporal events. Our studies revealed that the entire retina has been signaled by the RGC soma within 30 min after optic nerve injury and that pathways that modulate cell death are likely to be active in RGCs within 6 hrs following axonal injury Experiment Overall Design: In the treated animals, axons of the optic nerve were crushed with fine forceps for 10 sec, 1 mm posterior to the globe, under direct visualization, within an intact meningeal sheath. Controls were contralateral eyes from the same animals in each group that had not been injured. After 6 hr eyes were enucleated and processed for tissue sectionin
Project description:Retinal ganglion cell (RGC) death is the final consequence of many blinding diseases, where there is considerable variation in the time course and severity of RGC loss. Indeed, this process appears to be influenced by a wide variety of genetic and environmental factors. In this study we explored the genetic basis for differences in ganglion cell death in two inbred strains of mice. We found that RGCs are more susceptible to death following optic nerve crush in C57BL/6J mice (54% survival) than in DBA2/J mice (62% survival). Using the Illumina Mouse-6 microarray, we identified 1,580 genes with significant change in expression following optic nerve crush in these two strains of mice. Our analysis of the changes occurring after optic nerve crush demonstrated that the greatest amount of change (44% of the variance) was due to the injury itself. This included changes associated with ganglion cell death, reactive gliosis, and abortive regeneration. The second pattern of gene changes (23% of the variance) was primarily related to differences in gene expressions observed between the C57BL/6J and DBA/2J mouse strains. The remaining changes in gene expression represent interactions between the effects of optic nerve crush and the genetic background of the mouse. We extracted one genetic network from this dataset that appears to be related to tissue remodeling. One of the most intriguing sets of changes included members of the crystallin family of genes, which may represent a signature of pathways modulating the susceptibility of cells to death. Differential responses to optic nerve crush between two widely used strains of mice were used to define molecular networks associated with ganglion cell death and reactive gliosis. These results form the basis for our continuing interest in the modifiers of retinal injury. 18 Samples: 9 per strain (C57BL/6J & DBA/2J); 3 conditions per strain
Project description:Loss of specialized neurons in neurodegenerative diseases and after nerve injury is mediated in a neuronal subtype- and region-specific fashion. However, little is known about what molecular contexts define selective vulnerability. Here, we demonstrate that retinal ganglion cells (RGCs) in the mouse peripheral ventrotemporal (VT) retina are the most susceptible to optic nerve injury. Mechanistically, we show that the ventral-specific molecule, the serotonin transporter (SERT) is upregulated on VT axons within one day after injury and loss of SERT attenuates VT RGC death and promotes axon regeneration. From RNA-seq analysis, the transmembrane protein Gpnmb has been identified as a target downregulated by SERT. Moreover, GPNMB is involved in RGC protection and axon regeneration. Together, our studies reveal the serotonin transporter as a determinant of selective vulnerability.
Project description:To investigate the role of aldose reductase (AR) inhibition using Sorbinil on retinal microglia (RMG) activation, retinal ganglion cell (RGC) survival, and axon regeneration after optic nerve trauma. We observed that AR inhibition using Sorbinil attenuates RMG activation and subsequently promotes RGC survival and delays axon degeneration one week after optic nerve crush.
Project description:Irreversible blindness from glaucoma and optic neuropathies is attributed to retinal ganglion cells (RGCs) losing the ability to regenerate axons. While several transcription factors and proteins have demonstrated enhancement of axon regeneration after optic nerve injury, mechanisms contributing to the age-related decline in axon regenerative capacity remains elusive. Here, we show that microRNAs are differentially expressed during RGC development, and identify microRNA-19a (miR-19a) as a heterochronic marker; developmental decline of miR-19a relieves suppression of PTEN, a key regulator of axon regeneration, and serves as a temporal indicator of decreasing axon regenerative capacity. Intravitreal injection of miR-19a promotes axon regeneration after optic nerve crush in adult mice, and increases axon extension in RGCs isolated from aged human donors. This uncovers a previously unrecognized involvement of the miR-19a-PTEN axis in RGC axon regeneration, and demonstrates therapeutic potential of microRNA-mediated restoration of axon regenerative capacity via intravitreal injection in patients with optic neuropathies.