GAP-43 mRNA Research Articles

HnRNPs Interacting with mRNA Localization Motifs Define AxoNAl RNA Regulons

mRNA translation in axons enables neurons to introduce new proteins at sites distant from their cell body. mRNA-protein interactions drive this post-transcriptional regulation, yet knowledge of RNA binding proteins (RBP) in axons is limited. Here we used proteomics to identify RBPs interacting with the axonal localizing motifs of Nrn1, Hmgb1, Actb, and Gap43 mRNAs, revealing many novel RBPs in axons. Interestingly, no RBP is shared between all four RNA motifs, suggesting graded and overlapping specificities of RBP-mRNA pairings. A systematic assessment of axonal mRNAs interacting with hnRNP H1, hnRNP F, and hnRNP K, proteins that bound with high specificity to Nrn1 and Hmgb1, revealed that axonal mRNAs segregate into axon growth-associated RNA regulons based on hnRNP interactions. Axotomy increases axonal transport of hnRNPs H1, F, and K, depletion of these hnRNPs decreases axon growth and reduces axonal mRNA levels and axonal protein synthesis. Thus, subcellular hnRNP-interacting RNA regulons support neuronal growth and regeneration.

Neuroprotection and neuroregeneration of retinal ganglion cells after intravitreal carbon monoxide release.

PurposeRetinal ischemia induces apoptosis leading to neurodegeneration and vision impairment. Carbon monoxide (CO) in gaseous form showed cell-protective and anti-inflammatory effects after retinal ischemia-reperfusion-injury (IRI). These effects were also demonstrated for the intravenously administered CO-releasing molecule (CORM) ALF-186. This article summarizes the results of intravitreally released CO to assess its suitability as a neuroprotective and neuroregenerative agent.MethodsWater-soluble CORM ALF-186 (25 μg), PBS, or inactivated ALF (iALF) (all 5 μl) were intravitreally applied into the left eyes of rats directly after retinal IRI for 1 h. Their right eyes remained unaffected and were used for comparison. Retinal tissue was harvested 24 h after intervention to analyze mRNA or protein expression of Caspase-3, pERK1/2, p38, HSP70/90, NF-kappaB, AIF-1 (allograft inflammatory factor), TNF-α, and GAP-43. Densities of fluorogold-prelabeled retinal ganglion cells (RGC) were examined in flat-mounted retinae seven days after IRI and were expressed as mean/mm2. The ability of RGC to regenerate their axon was evaluated two and seven days after IRI using retinal explants in laminin-1-coated cultures. Immunohistochemistry was used to analyze the different cell types growing out of the retinal explants.ResultsCompared to the RGC-density in the contralateral right eyes (2804±214 RGC/mm2; data are mean±SD), IRI+PBS injection resulted in a remarkable loss of RGC (1554±159 RGC/mm2), p<0.001. Intravitreally injected ALF-186 immediately after IRI provided RGC protection and reduced the extent of RGC-damage (IRI+PBS 1554±159 vs. IRI+ALF 2179±286, p<0.001). ALF-186 increased the IRI-mediated phosphorylation of MAP-kinase p38. Anti-apoptotic and anti-inflammatory effects were detectable as Caspase-3, NF-kappaB, TNF-α, and AIF-1 expression were significantly reduced after IRI+ALF in comparison to IRI+PBS or IRI+iALF. Gap-43 expression was significantly increased after IRI+ALF. iALF showed effects similar to PBS. The intrinsic regenerative potential of RGC-axons was induced to nearly identical levels after IRI and ALF or iALF-treatment under growth-permissive conditions, although RGC viability differed significantly in both groups. Intravitreal CO further increased the IRI-induced migration of GFAP-positive cells out of retinal explants and their transdifferentiation, which was detected by re-expression of beta-III tubulin and nestin.ConclusionIntravitreal CORM ALF-186 protected RGC after IRI and stimulated their axons to regenerate in vitro. ALF conveyed anti-apoptotic, anti-inflammatory, and growth-associated signaling after IRI. CO’s role in neuroregeneration and its effect on retinal glial cells needs further investigation.

Dynamic m6A modification regulates local translation of mRNA in axons.

N 6-methyladenosine (m6A) is a reversible modification in mRNA and has been shown to regulate processing, translation and decay of mRNA. However, the roles of m6A modification in neuronal development are still not known. Here, we found that the m6A eraser FTO is enriched in axons and can be locally translated. Axon-specific inhibition of FTO by rhein, or compartmentalized siRNA knockdown of Fto in axons led to increases of m6A levels. GAP-43 mRNA is modified by m6A and is a substrate of FTO in axons. Loss-of-function of this non-nuclear pool of FTO resulted in increased m6A modification and decreased local translation of axonal GAP-43 mRNA, which eventually repressed axon elongation. Mutation of a predicted m6A site in GAP-43 mRNA eliminated its m6A modification and exempted regulation of its local translation by axonal FTO. This work showed an example of dynamic internal m6A demethylation of non-nuclear localized mRNA by the demethylase FTO. Regulation of m6A modification of axonal mRNA by axonal FTO might be a general mechanism to control their local translation in neuronal development.

VEGF expression correlates with neuronal differentiation and predicts a favorable prognosis in patients with neuroblastoma

Neuroblastoma (NB) is a childhood cancer with a low survival rate and great metastatic potential. Vascular endothelial growth factor (VEGF), an angiogenesis factor, has been found to be involved in CRT-related neuronal differentiation of NB cells. In this study, we further confirmed the role VEGF in NB through mouse xenograft model and clinical analysis from NB patients. In xenograft experiments, CRT overexpression effectively inhibited the tumor growth. In addition, the mRNA and protein levels of VEGF and differentiation marker GAP-43 were upregulated by induced CRT expression. However, no significant correlation between the expression level of VEGF and microvessel density was observed in human NB tumors, suggesting a novel mechanism of VEGF participating in NB tumorigenesis through an angiogenesis-independent pathway. In NB patients’ samples, mRNA expression levels of CRT and VEGF were positively correlated. Furthermore, positive VEGF expression by immunostaining of NB tumors was found to correlate well with histological grade of differentiation and predicted a favorable prognosis. In conclusion, our findings suggest that VEGF is a favorable prognostic factor of NB and might affect NB tumor behavior through CRT-driven neuronal differentiation rather than angiogenesis that might shed light on a novel therapeutic strategy to improve the outcome of NB.

A Shift from a Pivotal to Supporting Role for the Growth-Associated Protein (GAP-43) in the Coordination of Axonal Structural and Functional Plasticity.

In a number of animal species, the growth-associated protein (GAP), GAP-43 (aka: F1, neuromodulin, B-50, G50, pp46), has been implicated in the regulation of presynaptic vesicular function and axonal growth and plasticity via its own biochemical properties and interactions with a number of other presynaptic proteins. Changes in the expression of GAP-43 mRNA or distribution of the protein coincide with axonal outgrowth as a consequence of neuronal damage and presynaptic rearrangement that would occur following instances of elevated patterned neural activity including memory formation and development. While functional enhancement in GAP-43 mRNA and/or protein activity has historically been hypothesized as a central mediator of axonal neuroplastic and regenerative responses in the central nervous system, it does not appear to be the crucial substrate sufficient for driving these responses. This review explores the historical discovery of GAP-43 (and associated monikers), its transcriptional, post-transcriptional and post-translational regulation and current understanding of protein interactions and regulation with respect to its role in axonal function. While GAP-43 itself appears to have moved from a pivotal to a supporting factor, there is no doubt that investigations into its functions have provided a clearer understanding of the biochemical underpinnings of axonal plasticity.

Stable cell lines of human SH-SY5Y uniformly expressing wild-type or mutant-type FERM domain containing 7 gene

It has been reported that FERM domain containing 7 (FRMD7) may cause X-linked idiopathic congenital nystagmus (ICN). A total of >40 mutations of the FRMD7 gene have been identified, however their pathogenic role remains unclear. In the present study, enhanced green fluorescent protein-tagged wild-type (WT) and mutant (MT) FRMD7 (c. C781>G) were expressed in stably expressing human neuroblastoma SH-SY5Y cells following viral transfection and antibiotic selection. Uniform expression of the FRMD7 fusion proteins was confirmed via fluorescence microscopy and western blotting. The expression profiles of neuron-specific proteins and Rho guanine triphosphatases (GTPases) differed significantly between the wild-type and mutant cell lines. Levels of Mtap2, NF-M, nestin, GAP43 and Rac1 mRNA were significantly increased in MT-FRMD7 cells compared with controls (P<0.01). However, the expression of Rac1 protein did not differ significantly among the two cell lines. Taken together, the results of the current study suggest that MT-FRMD7 influences the expression of neuron-specific genes and Rho GTPases, which may be involved in the pathogenesis of ICN. The FRMD7 stable expression cell line may facilitate future studies investigating the role of this protein in neuronal development.

Xuefu zhuyu decoction improves cognitive impairment in experimental traumatic brain injury via synaptic regulation.

An overarching consequence of traumatic brain injury (TBI) is the cognitive impairment. It may hinder individual performance of daily tasks and determine people's subjective well-being. The damage to synaptic plasticity, one of the key mechanisms of cognitive dysfunction, becomes the potential therapeutic strategy of TBI. In this study, we aimed to investigate whether Xuefu Zhuyu Decoction (XFZYD), a traditional Chinese medicine, provided a synaptic regulation to improve cognitive disorder following TBI. Morris water maze and modified neurological severity scores were performed to assess the neurological and cognitive abilities. The PubChem Compound IDs of the major compounds of XFZYD were submitted into BATMAN-TCM, an online bioinformatics analysis tool, to predict the druggable targets related to synaptic function. Furthermore, we validated the prediction through immunohistochemical, RT-PCR and western blot analyses. We found that XFZYD enhanced neuroprotection, simultaneously improved learning and memory performances in controlled cortical impact rats. Bioinformatics analysis revealed that the improvements of XFZYD implied the Long-term potentiation relative proteins including NMDAR1, CaMKII and GAP-43. The further confirmation of molecular biological studies confirmed that XFZYD upregulated the mRNA and protein levels of NMDAR1, CaMKII and GAP-43. Pharmacological synaptic regulation of XFZYD could provide a novel therapeutic strategy for cognitive impairment following TBI.

6-Hydroxydopamine로 유도된 In Vitro 파킨슨병 모델에서 토란추출물의 Brain Resilience에 미치는 영향

Purpose: The purpose of this study was to investigate the effects of taro extract on brain resilience in in vitro Parkinson’s disease model induced by 6-hydroxydopamine (6-OHDA). Methods: To induce a neuroinflammatory reaction and the in vitro Parkinson’s disease model, SH-SY5Y cells were stimulated with lipopolysaccharide (LPS) and 6-OHDA, respectively. After that, cells were treated with at various concentrations (1, 5, and 10 mg/mL) of taro extract. Then nitric oxide (NO) production, inducible nitric oxide synthase (iNOS), interleukin (IL)-6, synaptophysin (SYP) and growth associated protein (GAP)-43 messenger ribonucleic acid (mRNA) expression level were measured. Results: Taro extract significantly suppressed LPS-induced NO production. Meanwhile, iNOS and IL-6 mRNA expression decreased in a dose-dependent manner. In addition, taro increased the mRNA expression of SYP and GAP-43 mRNA. Conclusion: These findings indicate that taro played an important role in brain resilience by inhibiting neuronal cell death and promoting neurite outgrowth, synaptogenesis, and neural plasticity. The results of this study suggest that taro may contribute to the prevention of neurodegenerative disease and become a new and safe therapeutic strategy for Parkinson’s disease. Key Words: Neuroprotection; Parkinson disease; Resilience; Taro Key Words: ì‹ ê²½ë³´í˜¸; 파킨슨병; íšŒë³µë ¥; í† ëž€

Neural Progenitor Cells Promote Axonal Growth and Alter Axonal mRNA Localization in Adult Neurons.

The inhibitory environment of the spinal cord and the intrinsic properties of neurons prevent regeneration of axons following CNS injury. However, both ascending and descending axons of the injured spinal cord have been shown to regenerate into grafts of embryonic neural progenitor cells (NPCs). Previous studies have shown that grafts composed of glial-restricted progenitors (GRPs) and neural-restricted progenitors (NRPs) can provide a permissive microenvironment for axon growth. We have used cocultures of adult rat dorsal root ganglion (DRG) neurons together with NPCs, which have shown significant enhancement of axon growth by embryonic rat GRP and GRPs/NRPs, both in coculture conditions and when DRGs are exposed to conditioned medium from the NPC cultures. This growth-promoting effect of NPC-conditioned medium was also seen in injury-conditioned neurons. DRGs cocultured with GRPs/NRPs showed altered expression of regeneration-associated genes at transcriptional and post-transcriptional levels. We found that levels of GAP-43 mRNA increased in DRG cell bodies and axons. However, hepcidin antimicrobial peptide (HAMP) mRNA decreased in the cell bodies of DRGs cocultured with GRPs/NRPs, which is distinct from the increase in cell body HAMP mRNA levels seen in DRGs after injury conditioning. Endogenous GAP-43 and β-actin mRNAs as well as reporter RNAs carrying axonally localizing 3'UTRs of these transcripts showed significantly increased levels in distal axons in the DRGs cocultured with GRPs/NRPs. These results indicate that axon growth promoted by NPCs is associated not only with enhanced transcription of growth-associated genes but also can increase localization of some mRNAs into growing axons.

Axonal localization of neuritin/CPG15 mRNA is limited by competition for HuD binding.

HuD protein (also known as ELAVL4) has been shown to stabilize mRNAs with AU-rich elements (ARE) in their 3' untranslated regions (UTRs), including Gap43, which has been linked to axon growth. HuD also binds to neuritin (Nrn1) mRNA, whose 3'UTR contains ARE sequences. Although the Nrn1 3'UTR has been shown to mediate its axonal localization in embryonic hippocampal neurons, it is not active in adult dorsal root ganglion (DRG) neurons. Here, we asked why the 3'UTR is not sufficient to mediate the axonal localization of Nrn1 mRNA in DRG neurons. HuD overexpression increases the ability of the Nrn1 3'UTR to mediate axonal localizing in DRG neurons. HuD binds directly to the Nrn1 ARE with about a two-fold higher affinity than to the Gap43 ARE. Although the Nrn1 ARE can displace the Gap43 ARE from HuD binding, HuD binds to the full 3'UTR of Gap43 with higher affinity, such that higher levels of Nrn1 are needed to displace the Gap43 3'UTR. The Nrn1 3'UTR can mediate a higher level of axonal localization when endogenous Gap43 is depleted from DRG neurons. Taken together, our data indicate that endogenous Nrn1 and Gap43 mRNAs compete for binding to HuD for their axonal localization and activity of the Nrn1 3'UTR.

A Comparative Animal Study of Tendon Grafts Healing After Remnant-Preserving Versus Conventional Anterior Cruciate Ligament Reconstruction.

BackgroundThe aim of this study was to determine if anterior cruciate ligament (ACL) reconstruction by remnant preservation promotes cell proliferation, vascularization, proprioception recovery, and improved biomechanical properties of the tendon grafts.Material/Methods75 New Zealand rabbits were randomly assigned into the control group (group A), conventional ACL reconstruction group (group B), ACL reconstruction using remnant preservation and graft through remnant sleeve technique group (group C), and ACL reconstruction using remnant preservation and remnant tensioning technique group (group D). The remnant and healing of tendon grafts in groups C and D were observed at 3, 6, and 12 weeks after surgery, and the mRNA expression levels of VEGF, NT-3 and GAP-43 in ACL (group A) or tendon graft samples (groups B, C, and D) were determined by real-time PCR. Tendon graft cell count, microvessel density (MVD), and proprioceptors were determined by H&E staining, CD34, and S-100 immunohistochemical staining. The biomechanical properties of the tendon graft at week 12 in groups B, C, and D were examined by using a tensile strength test.ResultsRemnant and tendon grafts were not healed at 3, 6, and 12 weeks after the operation in groups C and D. VEGF, NT-3, and GAP-43 mRNA expressions in groups B, C, and D were higher than those in group A (P<0.05), but no significant difference was observed between groups B, C, and D (P>0.05). Furthermore, tendon graft cell count, MVD, proprioception, and biomechanical properties showed no significant differences (P>0.05) among groups B, C, and D at various time points.ConclusionsThere was no significant difference in cell proliferation, vascularization, proprioception recovery, or biomechanical properties of the tendon grafts between remnant-preserving and conventional ACL reconstruction methods.

The prescriptions from Shenghui soup enhanced neurite growth and GAP-43 expression level in PC12 cells.

BackgroundShenghui soup is a traditional Chinese herbal medicine used in clinic for the treatment of forgetfulness. In order to understanding the prescription principle, the effects of “tonifying qi and strengthening spleen” group (TQSS) including Poria cocos (Schw.) Wolf. and Panax ginseng C.A.Mey and “eliminating phlegm and strengthening intelligence” group (EPSI) composed of Polygala tenuifolia Willd., Acorus calamus L. and Sinapis alba L from the herb complex on neurite growth in PC12 cells, two disassembled prescriptions derived from Shenghui soup and their molecular mechanisms were investigated.MethodsFirstly, CCK-8 kit was used to detect the impact of the two prescriptions on PC12 cell viability; and Flow cytometry was performed to measure the cell apoptosis when PC12 cells were treated with these drugs. Secondly, the effect of the two prescriptions on the differentiation of PC12 cells was observed. Finally, the mRNA and protein expression levels of GAP-43 were analyzed by RT-PCR and western blot, respectively.Results“Tonifying qi and strengthening spleen” prescription decreased cell viability in a dose-dependent manner, but had no significant effect on cell apoptosis. Meanwhile, it could improve neurite growth and elevate the mRNA and protein expression level of GAP-43. “Eliminating phlegm and strengthening intelligence” prescription also exerted the similar effects on cell viability and apoptosis. Furthermore, it could also enhance cell neurite growth, with a higher expression level of GAP-43 mRNA and protein.Conclusion“Tonifying qi and strengthening spleen” and “eliminating phlegm and strengthening intelligence” prescriptions from Shenghui soup have a positive effect on neurite growth. Their effects are related to the up-regulating expression of GAP-43.Electronic supplementary materialThe online version of this article (doi:10.1186/s12906-016-1339-y) contains supplementary material, which is available to authorized users.

Impact of auditory deprivation on rats and plasticity expressionof growth associated protein-43 in auditory cortex

Objective:To explore the molecular mechanism of neural plasticity in the reconstitution following impairment of auditory system,we studied the changing levels of GAP-43 expression in the auditory cortex(AC) in the developing rats and in ototoxicity deafened rats before and after electrical intracochlear stimulation.Method:Auditory brain stem response(ABR) measurements were performed to rats of OAD,NC1,CAD and NC2 group to evaluate hearing function.We studied the changing levels of GAP-43-positive neurons expression in the auditory cortex of the OAD,NC1,EIS1 and EIS2 group and RT-PCR was performed to do semiquantitative analysis.Result:The early electrical intracochlear stimulation elevated GAP-43 level(EIS1,120.00±5.59/HP) in ipsilateral AC instead of in the contralateral AC compared with the non-stimulation group (OAD4W,93.25±4.30/HP),and the two groups had statistical difference(EIS1/OAD4W,129.17%±3.33%,P<0.05).After the late electrical intracochlear stimulation,similar to the early group,the staining level of GAP-43(EIS2,102.50±4.02/HP) in the AC was also higher than the unaffected group(OAD8W,81.67±3.76/HP),and the two groups also had statistical difference(EIS2/OAD8W,123.74%±2.70%,P<0.05).Similarly,the expression of GAP-43 mRNA had the synchronous change with the GAP-43 in the AC.Conclusion:GAP-43 has close correlation with the growth and plasticity of the AC,which can be a significant marker for auditory plasticity.

Mechanism of nonylphenol-induced neurotoxicity in F1 rats during sexual maturity

The purpose of this study was to examine whether gestational and lactational exposure to environmental endocrine disrupting chemical, nonylphenol (NP), in pregnant dams would lead to the alterations in hormone levels in the body, apoptosis and glial fibrillary acidic protein (GFAP) in hippocampus during weaning and sexual maturity periods in pups of rats. Dams were gavaged with NP at dose levels of 25mg/kg/day (low dose), 50mg/kg/day (middle dose), 100mg/kg/day (high dose) and groundnut oil alone (vehicle control) respectively from gestational day 6 to postnatal day (PND) 21. At PND 21, serum testosterone (TT) level significantly decreased in the 50, 100mg/kg NP-treated groups compared with the control (p < 0.01). Serum estradiol (E2) level was increased with the increase in the NP concentration; a dose-effect relationship was revealed (r = 0.462, p < 0.01). At both PND 21 and PND 60, pups exposed to 100mg/kg/day NP had an obviously higher apoptotic rate than control did. We observed a significant positive correlation between the dose of NP and the apoptotic rate (r = 0.836, p < 0.05). The number of GFAP-positive cells in rat hippocampus and integral optical density (IOD) of 100mg/kg/day NP-treated group were much higher than the control group. GFAP mRNA expressions increased at high dose (100mg/kg/day) (p < 0.05), and positive correlations between the GFAP mRNA expressions and NP level was observed (r = 0.586, 0.737, p < 0.05). Both the number of growth-associated protein (GAP)-43 positive cells and IOD were much lower at high dose (100mg/kg/day) than the control at both PND 21 and PND 60 (p < 0.05). The number of GAP-43 positive cells was negatively correlated with the NP exposure dose (r = - 0.562, - 0.649, p < 0.05) at these two time points. GAP-43 mRNA expressions in the hippocampus of pups decreased dramatically at high dose (100mg/kg/day) at both PND 21 and PND 60 compared with the control (p < 0.05). High exposure to NP might inhibit neuronal development and differentiation as indicated by the reduction of the neurotrophic factor GAP-43.

HnRNP-Q1 represses nascent axon growth in cortical neurons by inhibiting Gap-43 mRNA translation.

Posttranscriptional regulation of gene expression by mRNA-binding proteins is critical for neuronal development and function. hnRNP-Q1 is an mRNA-binding protein that regulates mRNA processing events, including translational repression. hnRNP-Q1 is highly expressed in brain tissue, suggesting a function in regulating genes critical for neuronal development. In this study, we have identified Growth-associated protein 43 (Gap-43) mRNA as a novel target of hnRNP-Q1 and have demonstrated that hnRNP-Q1 represses Gap-43 mRNA translation and consequently GAP-43 function. GAP-43 is a neuronal protein that regulates actin dynamics in growth cones and facilitates axonal growth. Previous studies have identified factors that regulate Gap-43 mRNA stability and localization, but it remains unclear whether Gap-43 mRNA translation is also regulated. Our results reveal that hnRNP-Q1 knockdown increased nascent axon length, total neurite length, and neurite number in mouse embryonic cortical neurons and enhanced Neuro2a cell process extension; these phenotypes were rescued by GAP-43 knockdown. Additionally, we have identified a G-quadruplex structure in the 5' untranslated region of Gap-43 mRNA that directly interacts with hnRNP-Q1 as a means to inhibit Gap-43 mRNA translation. Therefore hnRNP-Q1-mediated repression of Gap-43 mRNA translation provides an additional mechanism for regulating GAP-43 expression and function and may be critical for neuronal development.

Regeneration-associated genes decline in chronically injured rat sciatic motoneurons.

Chronic nerve injuries are notorious for their poor regenerative outcomes. Here, we addressed the question of whether the established reduced ability of injured motoneurons to regenerate their axons with time of disconnection with targets (chronic axotomy) is associated with a failure of injured motoneurons to express and sustain their expression of regeneration-associated genes. Sciatic motoneurons were prevented from regenerating by ligation of the transected nerves (chronic axotomy), and then subjected to a second nerve transection (acute axotomy) to mimic the clinical surgical procedure of refreshing the proximal nerve stump prior to delayed nerve repair. The expression of α1-tubulin, actin and GAP-43 mRNA was analysed in axotomized sciatic motoneurons by the use of in situ hybridization followed by autoradiography and silver grain quantification. The expression of these regeneration-associated genes by naive (acutely) axotomized motoneurons declined exponentially, to reach baseline levels within 6 months. These chronically injured motoneurons responded to a refreshment axotomy by elevating the expression of the genes to the same levels as in acutely (i.e. for the first time) axotomized sciatic motoneurons. However, the expression of these declined more rapidly than after acute axotomy. We conclude that a progressive decline in the expression of the regeneration-associated genes in chronically axotomized motoneurons and the even more rapid decline in their expression in response to a refreshment axotomy may explain why the regenerative capacity of chronically axotomized neurons declines with time.

Acute reduction of neuronal RNA binding Elavl2 protein and Gap43 mRNA in mouse hippocampus after kainic acid treatment

Activity-dependent gene regulation in neurons has been hypothesized to be under transcriptional control and to include dramatic increases in immediate early genes (IEGs) after neuronal activity. In addition, several reports have focused on post-transcriptional regulation, which could be mediated by neuronal post-transcriptional regulators, including RNA binding proteins (RNABPs). One such protein family is the neuronal Elavls (nElavls; Elavl2, Elavl3, and Elavl4), whose members are widely expressed in peripheral and central nervous system. Previous reports showed that Elavl3 and 4 are up-regulated following repeated stimulation such as during cocaine administration, a seizure, or a spatial discrimination task. In this study, we focused on Elavl2, a candidate gene for schizophrenia and studied its role in neuronal activity. First we found that Elavl2 has a cell-type specific expression pattern that is highly expressed in hippocampal CA3 pyramidal neurons and hilar interneurons using Elavl2 specific antibody. Second, unexpectedly, we discovered that the Elavl2 protein level in the hippocampus was acutely down-regulated for 3 h after a kainic acid (KA)-induced seizure in the hippocampal CA3 region. In addition, level of Gap43 mRNA, a target mRNA of Elavl2 is decreased 12 h after KA treatment, thus suggesting the involvement of Elavl2 in activity-dependent RNA regulation.

Peripheral neuron plasticity is enhanced by brief electrical stimulation and overrides attenuated regrowth in experimental diabetes

Peripheral nerve regrowth is less robust than commonly assumed, particularly when it accompanies common clinical scenarios such as diabetes mellitus. Brief extracellular electrical stimulation (ES) facilitates the regeneration of peripheral nerves in part through early activation of the conditioning injury response and BDNF. Here, we explored intrinsic neuronal responses to ES to identify whether ES might impact experimental diabetes, where regeneration is attenuated. ES altered several regeneration related molecules including rises in tubulin, Shh (Sonic hedgehog) and GAP43 mRNAs. ES was associated with rises in neuronal intracellular calcium but its strict linkage to regrowth was not confirmed. In contrast, we identified PI3K–PTEN involvement, an association previously linked to diabetic regenerative impairment. Following ES there were declines in PTEN protein and mRNA both in vitro and in vivo and a PI3K inhibitor blocked its action. In vitro, isolated diabetic neurons were capable of mounting robust responsiveness to ES. In vivo, ES improved electrophysiological and behavioral indices of nerve regrowth in a chronic diabetic model of mice with pre-existing neuropathy. Regrowth of myelinated axons and reinnervation of the epidermis were greater following ES than sham stimulation. Taken together, these findings identify a role for ES in supporting regeneration during the challenges of diabetes mellitus.

MRNAs and Protein Synthetic Machinery Localize into Regenerating Spinal Cord Axons When They Are Provided a Substrate That Supports Growth.

Although peripheral nerve axons retain the capacity to locally synthesize proteins into adulthood, previous studies have argued that mature brain and spinal cord axons cannot synthesize proteins. Protein synthesis in peripheral nerve axons is increased during regeneration, and intra-axonally synthesized proteins have been shown to contribute to nerve regeneration. Here, we show that mRNAs and translational machinery are transported into axons regenerating from the spinal cord into the permissive environment of a peripheral nerve graft. Our data raise the possibility that spinal cord axons may make use of localized protein synthesis for regeneration.

Effects of prenatal exposure to silver nanoparticles on spatial cognition and hippocampal neurodevelopment in rats

BackgroundSilver nanoparticles (Ag-NPs) are among the most commonly used nanomaterials and may be exposed to human and ecosystem. Prior in vitro study showed that Ag-NPs compromised neurodevelopment of PC12 cells. This study aims to investigate the effect of prenatal exposure to Ag-NPs on spatial cognition and hippocampal neurodevelopment in rats. MethodsPregnant rats were exposed by intraperitoneal injection to various solutions during pregnancy, including vehicle (water and glycerol mixture, 1:1 in volume), uncoated Ag-NPs (0.427mg Ag perg rat), polyvinylpyrrolidine (PVP)-coated Ag-NPs (0.407mg Ag perg rat), silver nitrate (0.013mg Ag+ and 0.007mg NO3+ per g rat) and sodium nitrate (0.007mg NO3+ perg rat). Pregnant rats without any injection were used as blank control. Male offspring at postnatal day 35 (PND35) were randomly selected for Morris Water Maze (MWM) test. After the MWM test, the rats were decapitated and hippocampus were collected for analysis of tissue structure, silver content, GAP-43 mRNA and protein expressions. ResultsFor the spatial learning in MWM test, since the third test day, the escape latency of rats in the uncoated Ag-NPs group was significantly higher than those in the other groups. The behaviors of rats were not significantly different among the other groups. The averaged silver content in the hippocampus of rats in the uncoated Ag-NPs group was 17.51μg/g, significantly higher than those in the other groups. The hippocampal structure in rats of the uncoated Ag-NPs group was deformed as compared to those in the other groups. Compared with the rats in blank and vehicle controls, the levels of GAP-43 mRNA and protein in the uncoated Ag-NPs, PVP-coated Ag-NPs, silver nitrate and sodium nitrate groups were all significantly decreased. The levels of GAP-43 mRNA and protein of rats in the uncoated Ag-NPs group was significantly lower than those in the later three groups, while there was no significant difference among the later three groups. ConclusionsMaternal exposure to uncoated Ag-NPs during pregnancy impaired spatial cognition in rat offspring. GAP-43 reduction might be involved in the cognitive impairment. The toxicity was mainly associated with release of silver ion. Coating with PVP reduced the toxicity of Ag-NPs.