Activation of neurotrophic factor signaling is a promising therapy for neurodegeneration. However, the transient nature of ligand-dependent activation limits its effectiveness. In this study, we ...solved this problem by inventing a system that forces membrane localization of the intracellular domain of tropomyosin receptor kinase B (iTrkB), which results in constitutive activation without ligands. Our system overcomes the small size limitation of the genome packaging in adeno-associated virus (AAV) and allows high expression of the transgene. Using AAV-mediated gene therapy in the eyes, we demonstrate that iTrkB expression enhances neuroprotection in mouse models of glaucoma and stimulates robust axon regeneration after optic nerve injury. In addition, iTrkB expression in the retina was also effective in an optic tract transection model, in which the injury site is near the superior colliculus. Regenerating axons successfully formed pathways to their brain targets, resulting in partial recovery of visual behavior. Our system may also be applicable to other trophic factor signaling pathways and lead to a significant advance in the field of gene therapy for neurotrauma and neurodegenerative disorders, including glaucoma.
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Harada and colleagues developed a system that forces membrane localization of the intracellular domain of TrkB (iTrkB), which results in constitutive activation without ligands. AAV-mediated delivery of iTrkB into the eyes induced neuroprotection and robust optic nerve regeneration in mouse models of glaucoma and optic nerve injury.
We uncovered a role for ERK signaling in GABA release, long-term potentiation (LTP), and learning, and show that disruption of this mechanism accounts for the learning deficits in a mouse model for ...learning disabilities in neurofibromatosis type I (NF1). Our results demonstrate that neurofibromin modulates ERK/synapsin I-dependent GABA release, which in turn modulates hippocampal LTP and learning. An
Nf1 heterozygous null mutation, which results in enhanced ERK and synapsin I phosphorylation, increased GABA release in the hippocampus, and this was reversed by pharmacological downregulation of ERK signaling. Importantly, the learning deficits associated with the
Nf1 mutation were rescued by a subthreshold dose of a GABA
A antagonist. Accordingly, Cre deletions of
Nf1 showed that only those deletions involving inhibitory neurons caused hippocampal inhibition, LTP, and learning abnormalities. Importantly, our results also revealed lasting increases in GABA release triggered by learning, indicating that the mechanisms uncovered here are of general importance for learning.
Background Indirect evidence suggests that loss of brain-derived neurotrophic factor (BDNF) from forebrain regions contributes to an individual’s vulnerability for depression, whereas upregulation of ...BDNF in these regions is suggested to mediate the therapeutic effect of antidepressants. Methods We have tested this hypothesis by generating two independent lines of conditional BDNF knockout mice in which the BDNF gene is deleted selectively in forebrain. Results We show that male conditional knockouts exhibit hyperactivity but normal depression-related behaviors. In contrast, female conditional knockouts display normal locomotor activity but a striking increase in depression-like behavior. We also demonstrate that loss of BDNF in both male and female mice attenuates the actions of the antidepressant desipramine in the forced swim test. Conclusions These gender differences in depression-related behaviors in BDNF conditional knockout mice provide direct evidence for a role of BDNF in depression. The results also support the view that forebrain BDNF may be essential in mediating antidepressant efficacy.
The phosphoinositide signaling system is a crucial regulator of neural development, cell survival, and plasticity. Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) negatively regulates ...phosphatidylinositol 3-kinase signaling and downstream targets. Nse- Cre Pten conditional knockout mice, in which Pten is ablated in granule cells of the dentate gyrus and pyramidal neurons of the hippocampal CA3, but not CA1, recapitulate many of the symptoms of humans with inactivating PTEN mutations, including progressive hypertrophy of the dentate gyrus and deficits in hippocampus-based social and cognitive behaviors. However, the impact of Pten loss on activity-dependent synaptic plasticity in this clinically relevant mouse model of Pten inactivation remains unclear. Here, we show that two phosphatidylinositol 3-kinase- and protein synthesis-dependent forms of synaptic plasticity, theta burst-induced long-term potentiation and metabotropic glutamate receptor (mGluR)-dependent long-term depression, are dysregulated at medial perforant path-to-dentate gyrus synapses of young Nse- Cre Pten conditional knockout mice before the onset of visible morphological abnormalities. In contrast, long-term potentiation and mGluR-dependent long-term depression are normal at CA3–CA1 pyramidal cell synapses at this age. Our results reveal that deletion of Pten in dentate granule cells dysregulates synaptic plasticity, a defect that may underlie abnormal social and cognitive behaviors observed in humans with Pten inactivating mutations and potentially other autism spectrum disorders.
Glioblastoma multiforme (GBM) is the most lethal form of brain cancer with a median survival of only 12 to 15 months. Current standard treatment consists of surgery followed by chemoradiation. The ...poor survival of patients with GBM is due to aggressive tumor invasiveness, an inability to remove all tumor tissue, and an innate tumor chemo- and radioresistance. Ataxia-telangiectasia mutated (ATM) is an excellent target for radiosensitizing GBM because of its critical role in regulating the DNA damage response and p53, among other cellular processes. As a first step toward this goal, we recently showed that the novel ATM kinase inhibitor KU-60019 reduced migration, invasion, and growth, and potently radiosensitized human glioma cells in vitro.
Using orthotopic xenograft models of GBM, we now show that KU-60019 is also an effective radiosensitizer in vivo. Human glioma cells expressing reporter genes for monitoring tumor growth and dispersal were grown intracranially, and KU-60019 was administered intratumorally by convection-enhanced delivery or osmotic pump.
Our results show that the combined effect of KU-60019 and radiation significantly increased survival of mice 2- to 3-fold over controls. Importantly, we show that glioma with mutant p53 is much more sensitive to KU-60019 radiosensitization than genetically matched wild-type glioma.
Taken together, our results suggest that an ATM kinase inhibitor may be an effective radiosensitizer and adjuvant therapy for patients with mutant p53 brain cancers.
Neurotrophin growth factors support neuronal survival and function. In this study, we show that the expression of the neurotrophin receptor TrkB is induced on astrocytes in white matter lesions in ...multiple sclerosis (MS) patients and mice with experimental autoimmune encephalomyelitis (EAE). Surprisingly, mice lacking TrkB specifically in astrocytes were protected from EAE-induced neurodegeneration. In an in vitro assay, astrocytes stimulated with the TrkB agonist brain-derived neurotrophic factor (BDNF) released nitric oxide (NO), and conditioned medium from activated astrocytes had detrimental effects on the morphology and survival of neurons. This neurodegenerative process was amplified by NO produced by neurons. NO synthesis in the central nervous system during EAE depended on astrocyte TrkB. Together, these findings suggest that TrkB expression on astrocytes may represent a new target for neuroprotective therapies in MS.
The tumor predisposition disorder neurofibromatosis type I (NF1) is one of the most common genetic disorders of the nervous system. It is caused by mutations in the Nf1 tumor-suppressor gene, which ...encodes a GTPase-activating protein (GAP) that negatively regulates p21-RAS. Development of malignant nerve tumors and neurofibromas occurs frequently in NF1. However, little is known about the molecular mechanisms mediating the initiation and progression of these complex tumors, or the identity of the specific cell type that gives rise to dermal or cutaneous neurofibromas. In this study, we identify a population of stem/progenitor cells residing in the dermis termed skin-derived precursors (SKPs) that, through loss of Nf1, form neurofibromas. We propose that SKPs, or their derivatives, are the cell of origin of dermal neurofibroma. We also provide evidence that additional signals from nonneoplastic cells in the tumor microenvironment play essential roles in neurofibromagenesis.
Summary Background Plexiform neurofibromas are slow-growing chemoradiotherapy-resistant tumours arising in patients with neurofibromatosis type 1 (NF1). Currently, there are no viable therapeutic ...options for patients with plexiform neurofibromas that cannot be surgically removed because of their proximity to vital body structures. We undertook an open-label phase 2 trial to test whether treatment with imatinib mesylate can decrease the volume burden of clinically significant plexiform neurofibromas in patients with NF1. Methods Eligible patients had to be aged 3–65 years, and to have NF1 and a clinically significant plexiform neurofibroma. Patients were treated with daily oral imatinib mesylate at 220 mg/m2 twice a day for children and 400 mg twice a day for adults for 6 months. The primary endpoint was a 20% or more reduction in plexiform size by sequential volumetric MRI imaging. Clinical data were analysed on an intention-to-treat basis; a secondary analysis was also done for those patients able to take imatinib mesylate for 6 months. This trial is registered with ClinicalTrials.gov , number NCT01673009. Findings Six of 36 patients (17%, 95% CI 6–33), enrolled on an intention-to-treat basis, had an objective response to imatinib mesylate, with a 20% or more decrease in tumour volume. Of the 23 patients who received imatinib mesylate for at least 6 months, six (26%, 95% CI 10–48) had a 20% or more decrease in volume of one or more plexiform tumours. The most common adverse events were skin rash (five patients) and oedema with weight gain (six). More serious adverse events included reversible grade 3 neutropenia (two), grade 4 hyperglycaemia (one), and grade 4 increases in aminotransferase concentrations (one). Interpretation Imatinib mesylate could be used to treat plexiform neurofibromas in patients with NF1. A multi-institutional clinical trial is warranted to confirm these results. Funding Novartis Pharmaceuticals, the Indiana University Simon Cancer Centre, and the Indiana University Herman B Wells Center for Pediatric Research.
Neurofibromatosis type 1: modeling CNS dysfunction Gutmann, David H; Parada, Luis F; Silva, Alcino J ...
The Journal of neuroscience,
2012-Oct-10, 2012-10-10, 20121010, Letnik:
32, Številka:
41
Journal Article
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Neurofibromatosis type 1 (NF1) is the most common monogenic disorder in which individuals manifest CNS abnormalities. Affected individuals develop glial neoplasms (optic gliomas, malignant ...astrocytomas) and neuronal dysfunction (learning disabilities, attention deficits). Nf1 genetically engineered mouse models have revealed the molecular and cellular underpinnings of gliomagenesis, attention deficit, and learning problems with relevance to basic neurobiology. Using NF1 as a model system, these studies have revealed critical roles for the NF1 gene in non-neoplastic cells in the tumor microenvironment, the importance of brain region heterogeneity, novel mechanisms of glial growth regulation, the neurochemical bases for attention deficit and learning abnormalities, and new insights into neural stem cell function. Here we review recent studies, presented at a symposium at the 2012 Society for Neuroscience annual meeting, that highlight unexpected cell biology insights into RAS and cAMP pathway effects on neural progenitor signaling, neuronal function, and oligodendrocyte lineage differentiation.
Neuronal activity enhances the elaboration of newborn neurons as they integrate into the synaptic circuitry of the adult brain. The role microRNAs play in the transduction of neuronal activity into ...growth and synapse formation is largely unknown. MicroRNAs can influence the expression of hundreds of genes and thus could regulate gene assemblies during processes like activity-dependent integration. Here, we developed viral-based methods for the in vivo detection and manipulation of the activity-dependent microRNA, miR-132, in the mouse hippocampus. We find, using lentiviral and retroviral reporters of miR-132 activity, that miR-132 is expressed at the right place and right time to influence the integration of newborn neurons. Retroviral knockdown of miR-132 using a specific 'sponge' containing multiple target sequences impaired the integration of newborn neurons into the excitatory synaptic circuitry of the adult brain. To assess potential miR-132 targets, we used a whole-genome microarray in PC12 cells, which have been used as a model of neuronal differentiation. miR-132 knockdown in PC12 cells resulted in the increased expression of hundreds of genes. Functional grouping indicated that genes involved in inflammatory/immune signaling were the most enriched class of genes induced by miR-132 knockdown. The correlation of miR-132 knockdown to increased proinflammatory molecular expression may indicate a mechanistic link whereby miR-132 functions as an endogenous mediator of activity-dependent integration in vivo.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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