Publications
76 results found
Quadrato G, Elnaggar MY, Di Giovanni S, 2014, Adult neurogenesis in brain repair: cellular plasticity vs. cellular replacement, FRONTIERS IN NEUROSCIENCE, Vol: 8, ISSN: 1662-453X
- Author Web Link
- Cite
- Citations: 24
Stern S, Haverkamp S, Sinske D, et al., 2013, The Transcription Factor Serum Response Factor Stimulates Axon Regeneration through Cytoplasmic Localization and Cofilin Interaction., The Journal Of Neuroscience, Vol: 33, Pages: 18836-18848
Hart ML, Neumayer KMH, Vaegler M, et al., 2013, Cell-based therapy for the deficient urinary sphincter., Curr Urol Rep, Vol: 14, Pages: 476-487
When sterile culture techniques of mammalian cells first became state of the art, there was tremendous anticipation that such cells could be eventually applied for therapeutic purposes. The discovery of adult human stem or progenitor cells further motivated scientists to pursue research in cell-based therapies. Although evidence from animal studies suggests that application of cells yields measurable benefits, in urology and many other disciplines, progenitor-cell-based therapies are not yet routinely clinically available. Stress urinary incontinence (SUI) is a condition affecting a large number of patients. The etiology of SUI includes, but is not limited to, degeneration of the urinary sphincter muscle tissue and loss of innervation, as well as anatomical and biomechanical causes. Therefore, different regimens were developed to treat SUI. However, at present, a curative functional treatment is not at hand. A progenitor-cell-based therapy that can tackle the etiology of incontinence, rather than the consequences, is a promising strategy. Therefore, several research teams have intensified their efforts to develop such a therapy for incontinence. Here, we introduce candidate stem and progenitor cells suitable for SUI treatment, show how the functional homogeneity and state of maturity of differentiated cells crucial for proper tissue integration can be assessed electrophysiologically prior to their clinical application, and discuss the trophic potential of adult mesenchymal stromal (or stem) cells in regeneration of neuronal function.
Lindner R, Puttagunta R, Di Giovanni S, 2013, Epigenetic regulation of axon outgrowth and regeneration in CNS injury: the first steps forward., Neurotherapeutics, Vol: 10, Pages: 771-781
Inadequate axonal sprouting and lack of regeneration limit functional recovery following neurologic injury, such as stroke, brain, and traumatic spinal cord injury. Recently, the enhancement of the neuronal regenerative program has led to promising improvements in axonal sprouting and regeneration in animal models of axonal injury. However, precise knowledge of the essential molecular determinants of this regenerative program remains elusive, thus limiting the choice of fully effective therapeutic strategies. Given that molecular regulation of axonal outgrowth and regeneration requires carefully orchestrated waves of gene expression, both temporally and spatially, epigenetic changes may be an ideal regulatory mechanism to address this unique need. While recent evidence suggests that epigenetic modifications could contribute to the regulation of axonal outgrowth and regeneration following axonal injury in models of stroke, and spinal cord and optic nerve injury, a number of unanswered questions remain. Such questions require systematic investigation of the epigenetic landscape between regenerative and non-regenerative conditions for the potential translation of this knowledge into regenerative strategies in human spinal and brain injury, as well as stroke.
Forsberg K, Wuttke A, Quadrato G, et al., 2013, The tumor suppressor p53 fine-tunes reactive oxygen species levels and neurogenesis via PI3 kinase signaling., J Neurosci, Vol: 33, Pages: 14318-14330
Mounting evidence points to a role for endogenous reactive oxygen species (ROS) in cell signaling, including in the control of cell proliferation, differentiation, and fate. However, the function of ROS and their molecular regulation in embryonic mouse neural progenitor cells (eNPCs) has not yet been clarified. Here, we describe that physiological ROS are required for appropriate timing of neurogenesis in the developing telencephalon in vivo and in cultured NPCs, and that the tumor suppressor p53 plays a key role in the regulation of ROS-dependent neurogenesis. p53 loss of function leads to elevated ROS and early neurogenesis, while restoration of p53 and antioxidant treatment partially reverse the phenotype associated with premature neurogenesis. Furthermore, we describe that the expression of a number of neurogenic and oxidative stress genes relies on p53 and that both p53 and ROS-dependent induction of neurogenesis depend on PI3 kinase/phospho-Akt signaling. Our results suggest that p53 fine-tunes endogenous ROS levels to ensure the appropriate timing of neurogenesis in eNPCs. This may also have implications for the generation of tumors of neurodevelopmental origin.
Quadrato G, Di Giovanni S, 2013, Waking up the sleepers: shared transcriptional pathways in axonal regeneration and neurogenesis., Cell Mol Life Sci, Vol: 70, Pages: 993-1007
In the last several years, relevant progress has been made in our understanding of the transcriptional machinery regulating CNS repair after acute injury, such as following trauma or stroke. In order to survive and functionally reconnect to the synaptic network, injured neurons activate an intrinsic rescue program aimed to increase their plasticity. Perhaps, in the attempt to switch back to a plastic and growth-competent state, post-mitotic neurons wake up and re-express a set of transcription factors that are also critical for the regulation of their younger brothers, the neural stem cells. Here, we review and discuss the transcriptional pathways regulating both axonal regeneration and neurogenesis highlighting the connection between the two. Clarification of their common molecular substrate may help simultaneous targeting of both neurogenesis and axonal regeneration with the hope to enhance functional recovery following CNS injury.
Floriddia EM, Rathore KI, Tedeschi A, et al., 2012, p53 Regulates the Neuronal Intrinsic and Extrinsic Responses Affecting the Recovery of Motor Function following Spinal Cord Injury, The Journal of Neuroscience, Vol: 32, Pages: 13956-13970, ISSN: 0270-6474
<jats:p>Following spinal trauma, the limited physiological axonal sprouting that contributes to partial recovery of function is dependent upon the intrinsic properties of neurons as well as the inhibitory glial environment. The transcription factor p53 is involved in DNA repair, cell cycle, cell survival, and axonal outgrowth, suggesting p53 as key modifier of axonal and glial responses influencing functional recovery following spinal injury. Indeed, in a spinal cord dorsal hemisection injury model, we observed a significant impairment in locomotor recovery in p53<jats:sup>−/−</jats:sup>versus wild-type mice. p53<jats:sup>−/−</jats:sup>spinal cords showed an increased number of activated microglia/macrophages and a larger scar at the lesion site. Loss- and gain-of-function experiments suggested p53 as a direct regulator of microglia/macrophages proliferation. At the axonal level, p53<jats:sup>−/−</jats:sup>mice showed a more pronounced dieback of the corticospinal tract (CST) and a decreased sprouting capacity of both CST and spinal serotoninergic fibers.<jats:italic>In vivo</jats:italic>expression of p53 in the sensorimotor cortex rescued and enhanced the sprouting potential of the CST in p53<jats:sup>−/−</jats:sup>mice, while, similarly, p53 expression in p53<jats:sup>−/−</jats:sup>cultured cortical neurons rescued a defect in neurite outgrowth, suggesting a direct role for p53 in regulating the intrinsic sprouting ability of CNS neurons. In conclusion, we show that p53 plays an important regulatory role at both extrinsic and intrinsic levels affecting the recovery of motor function following spinal cord injury. Therefore, we propose p53 as a novel potential multilevel therapeutic target for spinal cord injury.</jats:p>
Ferreira LMR, Floriddia EM, Quadrato G, et al., 2012, Neural regeneration: lessons from regenerating and non-regenerating systems., Mol Neurobiol, Vol: 46, Pages: 227-241
One only needs to see a salamander regrowing a lost limb to become fascinated by regeneration. However, the lack of robust axonal regeneration models for which good cellular and molecular tools exist has hampered progress in the field. Nevertheless, the nervous system has been revealed to be an excellent model to investigate regeneration. There are conspicuous differences in neuroregeneration capacity between amphibia and warm-blooded animals, as well as between the central and the peripheral nervous systems in mammals. Exploration of such discrepancies led to significant discoveries on the basic tenets of neuroregeneration in the last two decades, identifying several positive and negative regulators of axonal regeneration. Implications of these findings to the comprehension of mammalian regeneration and to the development of spinal cord injury therapies are also addressed.
Beck H, Flynn K, Lindenberg KS, et al., 2012, Serum Response Factor (SRF)-cofilin-actin signaling axis modulates mitochondrial dynamics, Proceedings of the National Academy of Sciences, Vol: 109, ISSN: 0027-8424
<jats:p>Aberrant mitochondrial function, morphology, and transport are main features of neurodegenerative diseases. To date, mitochondrial transport within neurons is thought to rely mainly on microtubules, whereas actin might mediate short-range movements and mitochondrial anchoring. Here, we analyzed the impact of actin on neuronal mitochondrial size and localization. F-actin enhanced mitochondrial size and mitochondrial number in neurites and growth cones. In contrast, raising G-actin resulted in mitochondrial fragmentation and decreased mitochondrial abundance. Cellular F-actin/G-actin levels also regulate serum response factor (SRF)-mediated gene regulation, suggesting a possible link between SRF and mitochondrial dynamics. Indeed, SRF-deficient neurons display neurodegenerative hallmarks of mitochondria, including disrupted morphology, fragmentation, and impaired mitochondrial motility, as well as ATP energy metabolism. Conversely, constitutively active SRF-VP16 induced formation of mitochondrial networks and rescued huntingtin (HTT)-impaired mitochondrial dynamics. Finally, SRF and actin dynamics are connected via the actin severing protein cofilin and its slingshot phosphatase to modulate neuronal mitochondrial dynamics. In summary, our data suggest that the SRF-cofilin-actin signaling axis modulates neuronal mitochondrial function.</jats:p>
Di Giovanni S, Rathore K, 2012, p53-dependent pathways in neurite outgrowth and axonal regeneration, Cell and Tissue Research, Vol: 349, Pages: 87-95, ISSN: 0302-766X
Quadrato G, Benevento M, Alber S, et al., 2012, Nuclear factor of activated T cells (NFATc4) is required for BDNF-dependent survival of adult-born neurons and spatial memory formation in the hippocampus, Proceedings of the National Academy of Sciences, Vol: 109, ISSN: 0027-8424
<jats:p> New neurons generated in the adult dentate gyrus are constantly integrated into the hippocampal circuitry and activated during encoding and recall of new memories. Despite identification of extracellular signals that regulate survival and integration of adult-born neurons such as neurotrophins and neurotransmitters, the nature of the intracellular modulators required to transduce those signals remains elusive. Here, we provide evidence of the expression and transcriptional activity of nuclear factor of activated T cell c4 (NFATc4) in hippocampal progenitor cells. We show that NFATc4 calcineurin-dependent activity is required selectively for survival of adult-born neurons in response to BDNF signaling. Indeed, cyclosporin A injection and stereotaxic delivery of the BDNF scavenger TrkB-Fc in the mouse dentate gyrus reduce the survival of hippocampal adult-born neurons in wild-type but not in NFATc4 <jats:sup>−/−</jats:sup> mice and do not affect the net rate of neural precursor proliferation and their fate commitment. Furthermore, associated with the reduced survival of adult-born neurons, the absence of NFATc4 leads to selective defects in LTP and in the encoding of hippocampal-dependent spatial memories. Thus, our data demonstrate that NFATc4 is essential in the regulation of adult hippocampal neurogenesis and identify NFATc4 as a central player of BDNF–driven prosurvival signaling in hippocampal adult-born neurons. </jats:p>
Quadrato G, Di Giovanni S, 2012, Gatekeeper between quiescence and differentiation: p53 in axonal outgrowth and neurogenesis., Int Rev Neurobiol, Vol: 105, Pages: 71-89
The transcription factor and tumor suppressor gene p53 regulates a wide range of cellular processes including DNA damage/repair, cell cycle progression, apoptosis, and cell metabolism. In the past several years, a specific novel role for p53 in neuronal biology has emerged. p53 orchestrates the polarity of self-renewing divisions in neural stem cells both during embryonic development and in adulthood and coordinates the timing for cell fate specification. In postmitotic neurons, p53 regulates neurite outgrowth and postinjury axonal regeneration via neurotrophin-dependent and -independent signaling by both transcriptional and posttranslational control of growth cone remodeling. This review provides an insight into the molecular mechanisms upstream and downstream p53 both during neural development and following axonal injury. Their understanding may provide therapeutic targets to enhance neuroregeneration following nervous system injury.
Floriddia E, Nguyen T, Di Giovanni S, 2011, Chromatin immunoprecipitation from dorsal root ganglia tissue following axonal injury., J Vis Exp
Axons in the central nervous system (CNS) do not regenerate while those in the peripheral nervous system (PNS) do regenerate to a limited extent after injury (Teng et al., 2006). It is recognized that transcriptional programs essential for neurite and axonal outgrowth are reactivated upon injury in the PNS (Makwana et al., 2005). However the tools available to analyze neuronal gene regulation in vivo are limited and often challenging. The dorsal root ganglia (DRG) offer an excellent injury model system because both the CNS and PNS are innervated by a bifurcated axon originating from the same soma. The ganglia represent a discrete collection of cell bodies where all transcriptional events occur, and thus provide a clearly defined region of transcriptional activity that can be easily and reproducibly removed from the animal. Injury of nerve fibers in the PNS (e.g. sciatic nerve), where axonal regeneration does occur, should reveal a set of transcriptional programs that are distinct from those responding to a similar injury in the CNS, where regeneration does not take place (e.g. spinal cord). Sites for transcription factor binding, histone and DNA modification resulting from injury to either PNS or CNS can be characterized using chromatin immunoprecipitation (ChIP). Here, we describe a ChIP protocol using fixed mouse DRG tissue following axonal injury. This powerful combination provides a means for characterizing the pro-regeneration chromatin environment necessary for promoting axonal regeneration.
Gaub P, Joshi Y, Wuttke A, et al., 2011, The histone acetyltransferase p300 promotes intrinsic axonal regeneration, Brain, Vol: 134, Pages: 2134-2148, ISSN: 0006-8950
Puttagunta R, Schmandke A, Floriddia EM, et al., 2011, RA-RAR-β counteracts myelin-dependent inhibition of neurite outgrowth via Lingo-1 repression, Journal of Cell Biology, Vol: 193, Pages: 1147-1156, ISSN: 0021-9525
After an acute central nervous system injury, axonal regeneration is limited as the result of a lack of neuronal intrinsic competence and the presence of extrinsic inhibitory signals. The injury fragments the myelin neuronal insulating layer, releasing extrinsic inhibitory molecules to signal through the neuronal membrane- bound Nogo receptor (NgR) complex. In this paper, we show that a neuronal transcriptional pathway can interfere with extrinsic inhibitory myelin-dependent signaling, thereby promoting neurite outgrowth. Specifically, retinoic acid (RA), acting through the RA receptor β (RAR-β), inhibited myelin-activated NgR signaling through the transcriptional repression of the NgR complex member Lingo-1. We show that suppression of Lingo-1 was required for RA-RAR-β to counteract extrinsic inhibition of neurite outgrowth. Furthermore, we confirm in vivo that RA treatment after a dorsal column overhemisection injury inhibited Lingo-1 expression, specifically through RAR-β. Our findings identify a novel link between RA-RAR-β- dependent proaxonal outgrowth and inhibitory NgR complex-dependent signaling, potentially allowing for the development of molecular strategies to enhance axonal regeneration after a central nervous system injury. © 2011 Puttagunta et al.
Erharhaghen J, Bartz M, Di Giovanni S, et al., 2011, An unusual location of deep venous thrombosis associated with ischemic stroke and persistent foramen ovale., Case Rep Neurol, Vol: 3, Pages: 160-164
Up to 40% of ischemic strokes have no known cause (cryptogenic). The prevalence of persistent foramen ovale (PFO) amongst patients with cryptogenic stroke (CS) is twice as high as that of the normal population, therefore suggesting a causal relationship between the two entities. However, PFO by itself is not sufficient to cause stroke, as an embolic source is needed. This source is often unknown, making the causal relationship between CS and PFO hard to demonstrate. The most frequent, although still seldom, identifiable cause of embolism in an otherwise cryptogenic stroke associated with PFO is a deep venous thrombosis (DVT) of the lower extremities. Here, we present a unique case of brachiocephalic venous DVT associated with PFO and ischemic stroke in a young patient. As the search for DVT in patients with PFO and stroke is often limited to the lower extremities, this case may suggest that an unspecified number of DVTs are overlooked. Our report lends support to paradoxical embolism as a mechanism of stroke in patients with PFO and does, at least in selected cases, suggest a more detailed search for DVT beyond the lower extremities.
Puttagunta R, Di Giovanni S, 2011, Retinoic acid signaling in axonal regeneration., Front Mol Neurosci, Vol: 4
Following an acute central nervous system (CNS) injury, axonal regeneration and functional recovery are extremely limited. This is due to an extrinsic inhibitory growth environment and the lack of intrinsic growth competence. Retinoic acid (RA) signaling, essential in developmental dorsoventral patterning and specification of spinal motor neurons, has been shown through its receptor, the transcription factor RA receptor β2 (RARβ2), to induce axonal regeneration following spinal cord injury (SCI). Recently, it has been shown that in dorsal root ganglion neurons (DRGs), cAMP levels were greatly increased by lentiviral RARβ2 expression and contributed to neurite outgrowth. Moreover, RARβagonists, in cerebellar granule neurons (CGN) and in the brain in vivo, induced phosphoinositide 3-kinase dependent phosphorylation of AKT that was involved in RARβ-dependent neurite outgrowth. More recently, RA-RARβpathways were shown to directly transcriptionally repress a member of the inhibitory Nogo receptor (NgR) complex, Lingo-1, under an axonal growth inhibitory environment in vitro as well as following spinal injury in vivo. This perspective focuses on these newly discovered molecular mechanisms and future directions in the field.
Gaub P, Tedeschi A, Puttagunta R, et al., 2010, HDAC inhibition promotes neuronal outgrowth and counteracts growth cone collapse through CBP/p300 and P/CAF-dependent p53 acetylation., Cell Death Differ, Vol: 17, Pages: 1392-1408
Neuronal outgrowth is guided by both extrinsic and intrinsic factors, involving transcriptional regulation. The acetylation of histones and transcription factors, which facilitates promoter accessibility, ultimately promotes transcription, and depends on the balance between histone deacetylases (HDACs) and histone acetyltransferases (HATs) activities. However, a critical function for specific acetylation modifying enzymes in neuronal outgrowth has yet to be investigated. To address this issue, we have used an epigenetic approach to facilitate gene expression in neurons, by using specific HDAC inhibitors. Neurons treated with a combination of HDAC and transcription inhibitors display an acetylation and transcription-dependent increase in outgrowth and a reduction in growth cone collapse on both 'permissive' (poly-D-lysine, PDL) and 'non-permissive' substrates (myelin and chondroitin sulphate proteoglycans (CSPGs)). Next, we specifically show that the expression of the histone acetyltransferases CBP/p300 and P/CAF is repressed in neurons by inhibitory substrates, whereas it is triggered by HDAC inhibition on both permissive and inhibitory conditions. Gene silencing and gain of function experiments show that CBP/p300 and P/CAF are key players in neuronal outgrowth, acetylate histone H3 at K9-14 and the transcription factor p53, thereby initiating a pro-neuronal outgrowth transcriptional program. These findings contribute to the growing understanding of transcriptional regulation in neuronal outgrowth and may lay the molecular groundwork for the promotion of axonal regeneration after injury.
Biermann J, Grieshaber P, Goebel U, et al., 2010, Valproic acid-mediated neuroprotection and regeneration in injured retinal ganglion cells., Invest Ophthalmol Vis Sci, Vol: 51, Pages: 526-534
PURPOSE: Valproic acid (VPA) has been demonstrated to have neuroprotective effects in neurodegenerative conditions. VPA inhibits histone-deacetylases (HDAC) and delays apoptosis in degenerating neurons. The authors investigated whether VPA delays retinal ganglion cell (RGC) death and enhances axonal regeneration after optic nerve crush (ONC). Furthermore, potential molecular targets involved in VPA-mediated protection were analyzed. METHODS: ONC was performed on the left eye of rats, which received VPA or Ringer's solution subcutaneously (SC; 300 mg/kg twice daily) or intravitreally (single postlesional injection). Densities of fluorogold-labeled RGC were analyzed in retinal flatmounts after 5 or 8 days. Retinal tissue was also harvested and processed to quantify axon growth in retinal explants; evaluate caspase-3 activity; analyze transcription factor cAMP response element binding protein (CREB); and determine acetylated histone 3 and 4, as well as phosphorylated extracellular signal-regulated kinase (pERK) 1/2. RESULTS: Five and 8 days after ONC, 93% and 58% RGC survived after subcutaneous VPA treatment in comparison to Ringer's solution (62% and 37% viable RGC), respectively (P < 0.001). Likewise, a single intravitreal injection of VPA immediately after injury significantly delayed apoptosis in RGC (P = 0.0016). Injured RGC treated with VPA showed better regeneration of their axons in culture (196 axons/explant) than the crushed controls receiving Ringer (115 axons/explant). RGC axons of the right control eyes regenerated more after VPA treatment. VPA-mediated neuroprotection and neuroregeneration were accompanied by decreased caspase-3 activity, CREB induction, pERK1/2 activation, but not by altered histone-acetylation. CONCLUSIONS: VPA provided neuroprotection and axonal regrowth after ONC. Alterations were observed in several pathways; however, the precise mechanism of VPA-mediated protection is not yet fully understood.
Tedeschi A, Nguyen T, Steele SU, et al., 2009, The tumor suppressor p53 transcriptionally regulates cGKI expression during neuronal maturation and is required for cGMP-dependent growth cone collapse., J Neurosci, Vol: 29, Pages: 15155-15160
The cGMP-dependent protein kinase type I (cGKI) has multiple functions including a role in axonal growth and pathfinding of sensory neurons, and counteracts Semaphorin 3A (Sema3A)-induced growth cone collapse. Within the nervous system, however, the transcriptional regulation of cGKI is still obscure. Recently, the transcription factor and tumor suppressor p53 has been reported to promote neurite outgrowth by regulating the gene expression of factors that promote growth cone extension, but specific p53 targets genes that may counteract growth cone collapse have not been identified so far. Here, we show that p53 promotes cGKI expression in neuronal-like PC-12 cells and primary neurons by occupying specific regulatory elements in a chromatin environment during neuronal maturation. Importantly, we demonstrate that p53-dependent expression of cGKI is required for the ability of cGMP to counteract growth cone collapse. Growth cone retraction mediated by Sema3A is overcome by cGMP only in wild-type, but not in p53-null dorsal root ganglia. Reconstitution of p53 levels is sufficient to recover both cGKI expression and the ability of cGMP to counteract growth cone collapse, while cGKI overexpression rescues growth cone collapse in p53-null primary neurons. In conclusion, this study identifies p53 as a transcription factor that regulates the expression of cGKI during neuronal maturation and cGMP-dependent inhibition of growth cone collapse.
Di Giovanni S, 2009, Molecular targets for axon regeneration: focus on the intrinsic pathways., Expert Opin Ther Targets, Vol: 13, Pages: 1387-1398
Axonal damage and degeneration are prominent components of acute neurological disorders such as stroke, brain and spinal cord injuries, leading to the dysfunction of neuronal networks, which is largely responsible for the impaired neurological function. In the CNS, injured axons not only degenerate but are unable to regenerate and have a limited capacity to sprout and re-establish lost connections. Therefore, axonal damage often results in long term disability. Strategies aimed at fostering neurological recovery by promoting axonal sprouting and regeneration have largely targeted the glial inhibitory environment that develops following central nervous system injury. However, experimental evidence suggests that providing a favorable environment may not be the sole and sufficient means for functional regeneration, and that activating the limited intrinsic potential of neurons to sprout and regenerate may represent an alternative and complementary therapeutic approach. Experimental data that show how the modulation of the intrinsic potential of neurons can promote axonal sprouting and regeneration in the CNS are presented and discussed. These data may suggest future therapeutic opportunities to promote recovery in acute neurological disorders.
Nguyen T, Lindner R, Tedeschi A, et al., 2009, NFAT-3 is a transcriptional repressor of the growth-associated protein 43 during neuronal maturation., J Biol Chem, Vol: 284, Pages: 18816-18823, ISSN: 0021-9258
Transcription is essential for neurite and axon outgrowth during development. Recent work points to the involvement of nuclear factor of activated T cells (NFAT) in the regulation of genes important for axon growth and guidance. However, NFAT has not been reported to directly control the transcription of axon outgrowth-related genes. To identify transcriptional targets, we performed an in silico promoter analysis and found a putative NFAT site within the GAP-43 promoter. Using in vitro and in vivo experiments, we demonstrated that NFAT-3 regulates GAP-43, but unexpectedly, does not promote but represses the expression of GAP-43 in neurons and in the developing brain. Specifically, in neuron-like PC-12 cells and in cultured cortical neurons, the overexpression of NFAT-3 represses GAP-43 activation mediated by neurotrophin signaling. Using chromatin immunoprecipitation assays, we also show that prior to neurotrophin activation, endogenous NFAT-3 occupies the GAP-43 promoter in PC-12 cells, in cultured neurons, and in the mouse brain. Finally, we observe that NFAT-3 is required to repress the physiological expression of GAP-43 and other pro-axon outgrowth genes in specific developmental windows in the mouse brain. Taken together, our data reveal an unexpected role for NFAT-3 as a direct transcriptional repressor of GAP-43 expression and suggest a more general role for NFAT-3 in the control of the neuronal outgrowth program.
Tedeschi A, Di Giovanni S, 2009, The non-apoptotic role of p53 in neuronal biology: enlightening the dark side of the moon., EMBO Rep, Vol: 10, Pages: 576-583
The transcription factor p53 protects neurons from transformation and DNA damage through the induction of cell-cycle arrest, DNA repair and apoptosis in a range of in vitro and in vivo conditions. Indeed, p53 has a crucial role in eliciting neuronal cell death during development and in adult organisms after exposure to a range of stressors and/or DNA damage. Nevertheless, accumulating evidence challenges this one-sided view of the role of p53 in the nervous system. Here, we discuss how-unexpectedly-p53 can regulate the proliferation and differentiation of neural progenitor cells independently of its role in apoptosis, and p53 post-translational modifications might promote neuronal maturation, as well as axon outgrowth and regeneration, following neuronal injury. We hope to encourage a more comprehensive view of the non-apoptotic functions of p53 during neural development, and to warn against oversimplifications regarding its role in neurons. In addition, we discuss how further insight into the p53-dependent modulation of these mechanisms is necessary to elucidate the decision-making processes between neuronal cell death and differentiation during development, and between neuronal degeneration and axonal regeneration after injury.
Tedeschi A, Nguyen T, Puttagunta R, et al., 2009, A p53-CBP/p300 transcription module is required for GAP-43 expression, axon outgrowth, and regeneration., Cell Death Differ, Vol: 16, Pages: 543-554
Transcription regulates axon outgrowth and regeneration. However, to date, no transcription complexes have been shown to control axon outgrowth and regeneration by regulating axon growth genes. Here, we report that the tumor suppressor p53 and its acetyltransferases CBP/p300 form a transcriptional complex that regulates the axonal growth-associated protein 43, a well-characterized pro-axon outgrowth and regeneration protein. Acetylated p53 at K372-3-82 drives axon outgrowth, GAP-43 expression, and binds specific elements on the neuronal GAP-43 promoter in a chromatin environment through CBP/p300 signaling. Importantly, in an axon regeneration model, both CBP and p53 K372-3-82 are induced following axotomy in facial motor neurons, where p53 K372-3-82 occupancy of GAP-43 promoter is enhanced as shown by in vivo chromatin immunoprecipitation. Finally, by comparing wild-type and p53 null mice, we demonstrate that the p53/GAP-43 transcriptional module is specifically switched on during axon regeneration in vivo. These data contribute to the understanding of gene regulation in axon outgrowth and may suggest new molecular targets for axon regeneration.
Nguyen T, Di Giovanni S, 2008, NFAT signaling in neural development and axon growth., Int J Dev Neurosci, Vol: 26, Pages: 141-145, ISSN: 0736-5748
The NFAT (nuclear factor of activated T-cells) family of transcription factors functions as integrators of multiple signaling pathways by binding to chromatin in combination with other transcription factors and coactivators to regulate genes central for many developmental systems. Recent experimental evidence has shown that the calcineurin/NFAT signaling pathway is important in axonal growth and guidance during vertebrate development. In fact, studies with triple NFATc2/c3/c4 mutant mice demonstrate that the extension and organization of sensory axon projection and commissural axon growth are both dependent upon NFAT activity. Neurotrophin and L-type calcium channel signaling modulate intracellular calcium levels to regulate the nuclear import and transcriptional activity of NFAT by activating the phosphatase calcineurin. The rephosphorylation and subsequent export of NFAT from the nucleus is mediated by several kinases, including GSK-3beta, which contribute to the fine tuning of NFAT transcriptional activity in neurons. However, currently, no direct transcriptional targets for NFAT have been identified in a chromatin environment in the nervous system. Undiscovered are also the binding partners of NFAT that might combinatorially regulate specific genes important for neuronal development. This review will discuss the current knowledge related to NFAT signaling in the nervous system development and the potential for future research directions.
Byrnes KR, Stoica BA, Fricke S, et al., 2007, Cell cycle activation contributes to post-mitotic cell death and secondary damage after spinal cord injury., Brain, Vol: 130, Pages: 2977-2992
Spinal cord injury (SCI) causes delayed secondary biochemical alterations that lead to tissue loss and associated neurological dysfunction. Up-regulation of cell cycle proteins occurs in both neurons and glia after SCI and may contribute to these changes. The present study examined the role of cell cycle activation on secondary injury after severe SCI in rat. SCI caused cell cycle protein up-regulation associated with neuronal and oligodendroglial apoptosis, glial scar formation and microglial activation. Treatment with the cell cycle inhibitor flavopiridol reduced cell cycle protein induction and significantly improved functional recovery versus vehicle-treated controls at 21 and 28 days post-injury. Treatment also significantly reduced lesion volume, as measured by MRI and histology, decreased astrocytic reactivity, attenuated neuronal and oligodendroglial apoptosis and reduced the production of factors associated with microglial activation. Thus, flavopiridol treatment improves outcome after SCI by inhibiting cell cycle pathways, resulting in beneficial multifactorial actions on neurons and glia.
Di Giovanni S, Knights CD, Rao M, et al., 2006, The tumor suppressor protein p53 is required for neurite outgrowth and axon regeneration., EMBO J, Vol: 25, Pages: 4084-4096, ISSN: 0261-4189
Axon regeneration is substantially regulated by gene expression and cytoskeleton remodeling. Here we show that the tumor suppressor protein p53 is required for neurite outgrowth in cultured cells including primary neurons as well as for axonal regeneration in mice. These effects are mediated by two newly identified p53 transcriptional targets, the actin-binding protein Coronin 1b and the GTPase Rab13, both of which associate with the cytoskeleton and regulate neurite outgrowth. We also demonstrate that acetylation of lysine 320 (K320) of p53 is specifically involved in the promotion of neurite outgrowth and in the regulation of the expression of Coronin 1b and Rab13. Thus, in addition to its recognized role in neuronal apoptosis, surprisingly, p53 is required for neurite outgrowth and axonal regeneration, likely through a different post-translational pathway. These observations may suggest a novel therapeutic target for promoting regenerative responses following peripheral or central nervous system injuries.
Di Giovanni S, 2006, Regeneration following spinal cord injury, from experimental models to humans: where are we?, Expert Opin Ther Targets, Vol: 10, Pages: 363-376
Regeneration in the adult CNS following injury is extremely limited. Traumatic spinal cord injury causes a permanent neurological deficit followed by a very limited recovery due to failed regeneration attempts. In fact, it is now clear that the spinal cord intrinsically has the potential to regenerate, but cellular loss and the presence of an inhibitory environment strongly limit tissue regeneration and functional recovery. The molecular mechanisms responsible for failed regeneration are starting to be unveiled. This gain in knowledge led to the design of therapeutic strategies aimed to limit the tissue scar, to enhance the proregeneration versus the inhibitory environment, and to replace tissue loss, including the use of stem cells. They have been very successful in several animal models, although results are still controversial in humans. Nonetheless, novel experimental approaches hold great promise for use in humans.
Knights CD, Catania J, Di Giovanni S, et al., 2006, Distinct p53 acetylation cassettes differentially influence gene-expression patterns and cell fate., J Cell Biol, Vol: 173, Pages: 533-544, ISSN: 0021-9525
The activity of the p53 gene product is regulated by a plethora of posttranslational modifications. An open question is whether such posttranslational changes act redundantly or dependently upon one another. We show that a functional interference between specific acetylated and phosphorylated residues of p53 influences cell fate. Acetylation of lysine 320 (K320) prevents phosphorylation of crucial serines in the NH(2)-terminal region of p53; only allows activation of genes containing high-affinity p53 binding sites, such as p21/WAF; and promotes cell survival after DNA damage. In contrast, acetylation of K373 leads to hyperphosphorylation of p53 NH(2)-terminal residues and enhances the interaction with promoters for which p53 possesses low DNA binding affinity, such as those contained in proapoptotic genes, leading to cell death. Further, acetylation of each of these two lysine clusters differentially regulates the interaction of p53 with coactivators and corepressors and produces distinct gene-expression profiles. By analogy with the "histone code" hypothesis, we propose that the multiple biological activities of p53 are orchestrated and deciphered by different "p53 cassettes," each containing combination patterns of posttranslational modifications and protein-protein interactions.
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.