Sustained axon regeneration induced by a synergy of PTEN and SOCS3 deletion
Ontology highlight
ABSTRACT: A formidable challenge in neural repair in the adult central nervous system (CNS) is the long distances that regenerating axons often need to travel in order to reconnect with their targets. Thus, a sustained capacity for axon regeneration is critical for achieving functional restoration. Although deletion of either Phosphatase and tensin homolog (PTEN), a negative regulator of mammalian target of rapamycin (mTOR), or suppressor of cytokine signaling 3 (SOCS3), a negative regulator of Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway, in adult retinal ganglion cells (RGCs) individually promoted significant optic nerve regeneration, such regrowth tapered off around two weeks after the crush injury. Remarkably, we now find that simultaneous deletion of both PTEN and SOCS3 enable robust and sustained axon regeneration. We further show that PTEN and SOCS3 regulate two independent pathways that act synergistically to promote enhanced axon regeneration. Gene expression analyses suggest that double deletion not only result in the induction of many growth-related genes, but also allow RGCs to maintain the expression of a repertoire of genes at the physiological level after injury. Our results reveal concurrent activation of mTOR and STAT3 pathways as a key for sustaining long-distance axon regeneration in adult CNS, a crucial step toward functional recovery. RNAs were extracted from FACS sorted YFP positive mouse retinal cells, and gene-profiled using affymetrix 1.0 ST expression arrays. Three hybridizations were performed for each group (Wild type after crush, PTEN Knockout+crush, SOCS3 Knockout+crush, and PTEN/SOCS3 double knockout+crush) with RNA samples collected from three independent FACS purifications. Data were analyzed using dChIP and SAM.
Project description:A formidable challenge in neural repair in the adult central nervous system (CNS) is the long distances that regenerating axons often need to travel in order to reconnect with their targets. Thus, a sustained capacity for axon regeneration is critical for achieving functional restoration. Although deletion of either Phosphatase and tensin homolog (PTEN), a negative regulator of mammalian target of rapamycin (mTOR), or suppressor of cytokine signaling 3 (SOCS3), a negative regulator of Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway, in adult retinal ganglion cells (RGCs) individually promoted significant optic nerve regeneration, such regrowth tapered off around two weeks after the crush injury. Remarkably, we now find that simultaneous deletion of both PTEN and SOCS3 enable robust and sustained axon regeneration. We further show that PTEN and SOCS3 regulate two independent pathways that act synergistically to promote enhanced axon regeneration. Gene expression analyses suggest that double deletion not only result in the induction of many growth-related genes, but also allow RGCs to maintain the expression of a repertoire of genes at the physiological level after injury. Our results reveal concurrent activation of mTOR and STAT3 pathways as a key for sustaining long-distance axon regeneration in adult CNS, a crucial step toward functional recovery.
Project description:Axon regeneration holds great promise for neural repair of CNS axonopathies, including glaucoma. Pten deletion in retinal ganglion cell (RGC) promotes potent optic nerve regeneration, but only a small population of Pten-null RGCs are actually regenerating RGCs (regRGCs); most surviving RGCs (surRGCs) remain non-regenerative. Here we developed a strategy to specifically label and purify regRGCs and surRGCs respectively from the same Pten deletion mice after optic nerve crush, in which they differ only in their regeneration capability. Smart-Seq2 single cell transcriptome analysis revealed novel regeneration-associated genes that significantly promote axon regeneration. The most potent of these, Anxa2, acts synergistically with its ligand tPA in Pten deletion-induced axon regeneration. Anxa2, its downstream effector ILK, and Mpp1 dramatically protect RGC somata and axons and preserves visual function in a clinically relevant model of glaucoma, demonstrating the exciting potential of this innovative strategy to identify novel effective neural repair candidates.
Project description:Axon regeneration holds great promise for neural repair of CNS axonopathies, including glaucoma. Pten deletion in retinal ganglion cell (RGC) promotes potent optic nerve regeneration, but only a small population of Pten-null RGCs are actually regenerating RGCs (regRGCs); most surviving RGCs (surRGCs) remain non-regenerative. Here we developed a strategy to specifically label and purify regRGCs and surRGCs respectively from the same Pten deletion mice after optic nerve crush, in which they differ only in their regeneration capability. Smart-Seq2 single cell transcriptome analysis revealed novel regeneration-associated genes that significantly promote axon regeneration. The most potent of these, Anxa2, acts synergistically with its ligand tPA in Pten deletion-induced axon regeneration. Anxa2, its downstream effector ILK, and Mpp1 dramatically protect RGC somata and axons and preserves visual function in a clinically relevant model of glaucoma, demonstrating the exciting potential of this innovative strategy to identify novel effective neural repair candidates.
Project description:Axon regeneration holds great promise for neural repair of CNS axonopathies, including glaucoma. Pten deletion in retinal ganglion cell (RGC) promotes potent optic nerve regeneration, but only a small population of Pten-null RGCs are actually regenerating RGCs (regRGCs); most surviving RGCs (surRGCs) remain non-regenerative. Here we developed a strategy to specifically label and purify regRGCs and surRGCs respectively from the same Pten deletion mice after optic nerve crush, in which they differ only in their regeneration capability. Smart-Seq2 single cell transcriptome analysis revealed novel regeneration-associated genes that significantly promote axon regeneration. The most potent of these, Anxa2, acts synergistically with its ligand tPA in Pten deletion-induced axon regeneration. Anxa2, its downstream effector ILK, and Mpp1 dramatically protect RGC somata and axons and preserves visual function in a clinically relevant model of glaucoma, demonstrating the exciting potential of this innovative strategy to identify novel effective neural repair candidates.
Project description:Axon regeneration holds great promise for neural repair of CNS axonopathies, including glaucoma. Pten deletion in retinal ganglion cell (RGC) promotes potent optic nerve regeneration, but only a small population of Pten-null RGCs are actually regenerating RGCs (regRGCs); most surviving RGCs (surRGCs) remain non-regenerative. Here we developed a strategy to specifically label and purify regRGCs and surRGCs respectively from the same Pten deletion mice after optic nerve crush, in which they differ only in their regeneration capability. Smart-Seq2 single cell transcriptome analysis revealed novel regeneration-associated genes that significantly promote axon regeneration. The most potent of these, Anxa2, acts synergistically with its ligand tPA in Pten deletion-induced axon regeneration. Anxa2, its downstream effector ILK, and Mpp1 dramatically protect RGC somata and axons and preserves visual function in a clinically relevant model of glaucoma, demonstrating the exciting potential of this innovative strategy to identify novel effective neural repair candidates.
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.
Project description:Neurons of the central nervous system (CNS) display only a limited ability to survive and regenerate their axons after an injury. In mice, 85% of retinal ganglion cells (RGCs) die within 2 weeks of axotomy by optic nerve crush (ONC) and only few survivors regenerate axons. In the past years, a multitude of interventions have been identified to improve RGC survival and regeneration after an injury, however, each only protects a subset of neurons and stimulates axon regrowth in an even smaller set.. Here, we sought out to elucidate the molecular mechanisms underlying this selective responsiveness and investigated genes regulated by three well established survival and regeneration-promoting interventions – activation of the MTOR pathway via deletion of its inhibitor Pten, activation of the Jak/Stat-pathway by deletion of its endogenous inhibitor Socs3, and overexpression of the neurotrophic cytokine CNTF. Analysis of the transcriptomes from >125,000 single RGCs at various time points after ONC showed that while broad survival of all RGC types could be induced with each intervention, type-independent axon regeneration was only overcome with the manipulation of multiple pathways. Those RGCs were able to mitigate the injury response and simultaneously upregulated survival and regeneration associated programs (prior and after injury). Four independent ways of analysis identified these programs to be differentially regulated among RGCs, with distinct signatures for degenerating, surviving and regenerating cells. Finally, testing some genes associated with the regeneration-program in vivo identified potential future therapeutic targets to promote neuroprotection and axonal regeneration.
Project description:Neurons of the central nervous system (CNS) display only a limited ability to survive and regenerate their axons after an injury. In mice, 85% of retinal ganglion cells (RGCs) die within 2 weeks of axotomy by optic nerve crush (ONC) and only few survivors regenerate axons. In the past years, a multitude of interventions have been identified to improve RGC survival and regeneration after an injury, however, each only protects a subset of neurons and stimulates axon regrowth in an even smaller set.. Here, we sought out to elucidate the molecular mechanisms underlying this selective responsiveness and investigated genes regulated by three well established survival and regeneration-promoting interventions – activation of the MTOR pathway via deletion of its inhibitor Pten, activation of the Jak/Stat-pathway by deletion of its endogenous inhibitor Socs3, and overexpression of the neurotrophic cytokine CNTF. Analysis of the transcriptomes from >125,000 single RGCs at various time points after ONC showed that while broad survival of all RGC types could be induced with each intervention, type-independent axon regeneration was only overcome with the manipulation of multiple pathways. Those RGCs were able to mitigate the injury response and simultaneously upregulated survival and regeneration associated programs (prior and after injury). Four independent ways of analysis identified these programs to be differentially regulated among RGCs, with distinct signatures for degenerating, surviving and regenerating cells. Finally, testing some genes associated with the regeneration-program in vivo identified potential future therapeutic targets to promote neuroprotection and axonal regeneration.
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:The central nervous system (CNS) projection neurons fail to spontaneously regenerate injured axons. Targeting the developmentally regulated genes in order to reactivate embryonic intrinsic axon growth capacity, or targeting tumor suppressor genes such as Pten, promote axon regeneration in a subset of injured retinal ganglion cells (RGCs). The subset of RGCs that regenerate axons in response to inhibition of Pten was narrowed-down to the Opn4+ intrinsically photosensitive (ip) and α subtypes of RGCs. Here, we used single cell RNA-sequencing (scRNA-seq) to investigate why only a subset of injured RGCs regenerate axons in response to Pten knockdown (KD), and to characterize the relationship between axon regeneration promoted by targeting Pten and the developmental decline in intrinsic axon growth capacity. We found that, only the most similar to embryonic state ipRGC subtypes C33 and C40 regenerated axons in response to Pten KD, which dedifferentiated them even further towards an embryonic state. We also found that genes downstream of Pten KD, specifically in the RGCs that regenerated axons, include mitochondria-associated developmentally regulated and non-developmentally regulated Dynlt1a and Lars2, respectively, which promoted axon regeneration on their own. Overall, we show that injury itself reverts transcriptome towards an embryonic state only in some neuronal subtypes and not sufficiently close to embryonic state to confer response to Pten KD, whereas certain mature neuronal subtypes are similar to embryonic state even without injury, which primes them to regenerate axons in response to Pten KD, that dedifferentiates them further towards an embryonic state and upregulates mitochondria-associated Dynlt1a and Lars2.