RESUMO
Ubiquitous deficiency in the survival motor neuron (SMN) protein causes death of motor neurons-a hallmark of the neurodegenerative disease spinal muscular atrophy (SMA)-through poorly understood mechanisms. Here, we show that the function of SMN in the assembly of spliceosomal small nuclear ribonucleoproteins (snRNPs) regulates alternative splicing of Mdm2 and Mdm4, two nonredundant repressors of p53. Decreased inclusion of critical Mdm2 and Mdm4 exons is most prominent in SMA motor neurons and correlates with both snRNP reduction and p53 activation in vivo. Importantly, increased skipping of Mdm2 and Mdm4 exons regulated by SMN is necessary and sufficient to synergistically elicit robust p53 activation in wild-type mice. Conversely, restoration of full-length Mdm2 and Mdm4 suppresses p53 induction and motor neuron degeneration in SMA mice. These findings reveal that loss of SMN-dependent regulation of Mdm2 and Mdm4 alternative splicing underlies p53-mediated death of motor neurons in SMA, establishing a causal link between snRNP dysfunction and neurodegeneration.
Assuntos
Processamento Alternativo , Neurônios Motores/metabolismo , Atrofia Muscular Espinal/genética , Proteínas Proto-Oncogênicas c-mdm2/genética , Proteínas Proto-Oncogênicas/genética , Animais , Morte Celular , Éxons , Camundongos , Neurônios Motores/patologia , Atrofia Muscular Espinal/metabolismo , Atrofia Muscular Espinal/fisiopatologia , Células NIH 3T3 , Degeneração Neural/metabolismo , Proteínas Proto-Oncogênicas/metabolismo , Proteínas Proto-Oncogênicas c-mdm2/metabolismo , Ribonucleoproteínas Nucleares Pequenas/biossíntese , Proteína Supressora de Tumor p53/metabolismoRESUMO
One striking clinical hallmark in patients with autoantibodies to leucine-rich glioma inactivated 1 (LGI1) is the very frequent focal seizure semiologies, including faciobrachial dystonic seizures (FBDS), in addition to the amnesia. Polyclonal serum IgGs have successfully modelled the cognitive changes in vivo but not seizures. Hence, it remains unclear whether LGI1-autoantibodies are sufficient to cause seizures. We tested this with the molecularly precise monoclonal antibodies directed against LGI1 [LGI1-monoclonal antibodies (mAbs)], derived from patient circulating B cells. These were directed towards both major domains of LGI1, leucine-rich repeat and epitempin repeat, and infused intracerebroventricularly over 7 days into juvenile male Wistar rats using osmotic pumps. Continuous wireless EEG was recorded from a depth electrode placed in hippocampal CA3 plus behavioural tests for memory and hyperexcitability were performed. Following infusion completion (Day 9), post-mortem brain slices were studied for antibody binding and effects on Kv1.1. The LGI1-mAbs bound most strongly in the hippocampal CA3 region and induced a significant reduction in Kv1.1 cluster number in this subfield. By comparison to control-Ab injected rats video-EEG analysis over 9 days revealed convulsive and non-convulsive seizure activity in rats infused with LGI1-mAbs, with a significant number of ictal events. Memory was not impaired in the novel object recognition test. Peripherally-derived human LGI1-mAbs infused into rodent CSF provide strong evidence of direct in vivo epileptogenesis with molecular correlations. These findings fulfill criteria for LGI1-antibodies in seizure causation.
Assuntos
Anticorpos Monoclonais , Autoanticorpos , Peptídeos e Proteínas de Sinalização Intracelular , Ratos Wistar , Animais , Masculino , Ratos , Peptídeos e Proteínas de Sinalização Intracelular/imunologia , Humanos , Convulsões/imunologia , Eletroencefalografia , Proteínas/imunologia , Epilepsia/imunologiaRESUMO
Dysfunction of neuronal circuits is an important determinant of neurodegenerative diseases. Synaptic dysfunction, death, and intrinsic activity of neurons are thought to contribute to the demise of normal behavior in the disease state. However, the interplay between these major pathogenic events during disease progression is poorly understood. Spinal muscular atrophy (SMA) is a neurodegenerative disease caused by a deficiency in the ubiquitously expressed protein SMN and is characterized by motor neuron death, skeletal muscle atrophy, as well as dysfunction and loss of both central and peripheral excitatory synapses. These disease hallmarks result in an overall reduction of neuronal activity in the spinal sensory-motor circuit. Here, we show that increasing neuronal activity by chronic treatment with the FDA-approved potassium channel blocker 4-aminopyridine (4-AP) improves motor behavior in both sexes of a severe mouse model of SMA. 4-AP restores neurotransmission and number of proprioceptive synapses and neuromuscular junctions (NMJs), while having no effects on motor neuron death. In addition, 4-AP treatment with pharmacological inhibition of p53-dependent motor neuron death results in additive effects, leading to full correction of sensory-motor circuit pathology and enhanced phenotypic benefit in SMA mice. Our in vivo study reveals that 4-AP-induced increase of neuronal activity restores synaptic connectivity and function in the sensory-motor circuit to improve the SMA motor phenotype.SIGNIFICANCE STATEMENT Spinal muscular atrophy (SMA) is a neurodegenerative disease, characterized by synaptic loss, motor neuron death, and reduced neuronal activity in spinal sensory-motor circuits. However, whether these are parallel or dependent events is unclear. We show here that long-term increase of neuronal activity by the FDA-approved drug 4-aminopyridine (4-AP) rescues the number and function of central and peripheral synapses in a SMA mouse model, resulting in an improvement of the sensory-motor circuit and motor behavior. Combinatorial treatment of pharmacological inhibition of p53, which is responsible for motor neuron death and 4-AP, results in additive beneficial effects on the sensory-motor circuit in SMA. Thus, neuronal activity restores synaptic connections and improves significantly the severe SMA phenotype.
Assuntos
Transtornos dos Movimentos/tratamento farmacológico , Atrofia Muscular Espinal/tratamento farmacológico , Desempenho Psicomotor/efeitos dos fármacos , Transtornos de Sensação/tratamento farmacológico , 4-Aminopiridina/uso terapêutico , Animais , Morte Celular/efeitos dos fármacos , Camundongos , Camundongos Knockout , Neurônios Motores/efeitos dos fármacos , Transtornos dos Movimentos/etiologia , Transtornos dos Movimentos/psicologia , Atrofia Muscular Espinal/complicações , Atrofia Muscular Espinal/psicologia , Junção Neuromuscular/efeitos dos fármacos , Bloqueadores dos Canais de Potássio/uso terapêutico , Propriocepção/efeitos dos fármacos , Transtornos de Sensação/etiologia , Transtornos de Sensação/psicologia , Proteína 1 de Sobrevivência do Neurônio Motor/genética , Sinapses/efeitos dos fármacos , Transmissão Sináptica/efeitos dos fármacos , Proteína Supressora de Tumor p53/antagonistas & inibidoresRESUMO
Mechanoreception is an essential feature of many sensory modalities. Nevertheless, the mechanisms that govern the conversion of a mechanical force to distinct patterns of action potentials remain poorly understood. Proprioceptive mechanoreceptors reside in skeletal muscle and inform the nervous system of the position of body and limbs in space. We show here that Whirlin/Deafness autosomal recessive 31 (DFNB31), a PDZ-scaffold protein involved in vestibular and auditory hair cell transduction, is also expressed by proprioceptive sensory neurons (pSNs) in dorsal root ganglia in mice. Whirlin localizes to the peripheral sensory endings of pSNs and facilitates pSN afferent firing in response to muscle stretch. The requirement of Whirlin in both proprioceptors and hair cells suggests that accessory mechanosensory signaling molecules define common features of mechanoreceptive processing across sensory systems.
Assuntos
Proteínas de Membrana/metabolismo , Fusos Musculares/fisiologia , Células Receptoras Sensoriais/metabolismo , Transdução de Sinais/fisiologia , Animais , Células Cultivadas , Proteína 2 de Resposta de Crescimento Precoce/genética , Proteína 2 de Resposta de Crescimento Precoce/metabolismo , Gânglios Espinais/citologia , Perfilação da Expressão Gênica , Células Ciliadas Auditivas/metabolismo , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Proteínas Luminescentes/genética , Proteínas de Membrana/genética , Camundongos , Camundongos Transgênicos , Músculo Esquelético/citologia , Condução Nervosa/efeitos dos fármacos , Condução Nervosa/genética , Análise de Sequência com Séries de Oligonucleotídeos , Parvalbuminas/genética , Parvalbuminas/metabolismo , Células Receptoras Sensoriais/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacos , Aglutininas do Germe de Trigo/genética , Aglutininas do Germe de Trigo/metabolismo , Proteínas tau/genética , Proteínas tau/metabolismoRESUMO
PURPOSE: The potential of interactive multimedia to improve biobank informed consent has yet to be investigated. The aim of this study was to test the separate effectiveness of interactivity and multimedia at improving participant understanding and confidence in understanding of informed consent compared with a standard, face-to-face (F2F) biobank consent process. METHODS: A 2 (face-to-face versus multimedia) × 2 (standard versus enhanced interactivity) experimental design was used with 200 patients randomly assigned to receive informed consent. All patients received the same information provided in the biobank's nine-page consent document. RESULTS: Interactivity (F(1,196) = 7.56, P = 0.007, partial η(2) = 0.037) and media (F(1,196) = 4.27, P = 0.04, partial η(2) = 0.021) independently improved participants' understanding of the biobank consent. Interactivity (F(1,196) = 6.793, P = 0.01, partial η(2) = 0.033), but not media (F(1,196) = 0.455, not significant), resulted in increased participant confidence in their understanding of the biobank's consent materials. Patients took more time to complete the multimedia condition (mean = 18.2 min) than the face-to-face condition (mean = 12.6 min). CONCLUSION: This study demonstrated that interactivity and multimedia each can be effective at promoting an individual's understanding and confidence in their understanding of a biobank consent, albeit with additional time investment. Researchers should not assume that multimedia is inherently interactive, but rather should separate the two constructs when studying electronic consent.
Assuntos
Bancos de Espécimes Biológicos/ética , Termos de Consentimento , Consentimento Livre e Esclarecido , Multimídia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Bancos de Espécimes Biológicos/normas , Comunicação , Compreensão , Feminino , Humanos , Masculino , Aplicações da Informática Médica , Pessoa de Meia-Idade , Estudos Prospectivos , Inquéritos e QuestionáriosRESUMO
Diabetic neuropathy (DNP), afflicting sensory and motor nerve fibers, is a major complication in diabetes. The underlying cellular mechanisms of axon degeneration are poorly understood. IGFBP5, an inhibitory binding protein for insulin-like growth factor 1 (IGF1) is highly up-regulated in nerve biopsies of patients with DNP. We investigated the pathogenic relevance of this finding in transgenic mice overexpressing IGFBP5 in motor axons and sensory nerve fibers. These mice develop motor axonopathy and sensory deficits similar to those seen in DNP. Motor axon degeneration was also observed in mice in which the IGF1 receptor (IGF1R) was conditionally depleted in motoneurons, indicating that reduced activity of IGF1 on IGF1R in motoneurons is responsible for the observed effect. These data provide evidence that elevated expression of IGFBP5 in diabetic nerves reduces the availability of IGF1 for IGF1R on motor axons, thus leading to progressive neurodegeneration. Inhibition of IGFBP5 could thus offer novel treatment strategies for DNP.
Assuntos
Axônios/fisiologia , Proteínas de Transporte/metabolismo , Diabetes Mellitus Experimental/fisiopatologia , Neuropatias Diabéticas/fisiopatologia , Neurônios Motores/fisiologia , Degeneração Neural/fisiopatologia , Animais , Axônios/patologia , Crescimento Celular , Sobrevivência Celular/fisiologia , Células Cultivadas , Diabetes Mellitus Experimental/patologia , Neuropatias Diabéticas/patologia , Humanos , Camundongos Transgênicos , Atividade Motora/fisiologia , Neurônios Motores/patologia , Degeneração Neural/patologia , Nervo Frênico/patologia , Nervo Frênico/fisiopatologia , Receptor IGF Tipo 1/metabolismo , Nervo Isquiático/patologia , Nervo Isquiático/fisiopatologia , Sensação/fisiologiaRESUMO
Next generation sequencing offers benefit of improved health through knowledge, but comes with challenges, such as inevitable incidental findings (IFs). The applicability of recommended criteria for disclosure of individual results when applied to disclosure of IFs is not well known. The purpose of this study was to examine how medical genetic specialists, genomic researchers, and Institutional Review Board (IRB) chairs perceive the importance of recommended criteria when applied to genetic/genomic IFs. We conducted telephone interviews with medical genetic specialists (genetic counselors, genetic nurses, medical geneticists, laboratory professionals), genomic researchers, and IRB chairs (N = 103). Respondents rated and discussed the importance of nine recommended criteria regarding disclosure of genetic/genomic IFs. Stakeholders agreed the most important criteria for disclosure were: (1) the IF points to a life-threatening condition; (2) there is a treatment; (3) individuals indicate in writing they wanted to be informed of IFs. Criteria rated less important were: analytic validity, high penetrance, association with a young age of onset and relative risk more than 2.0. Respondents indicated that some technical criteria were confusing, and in need of context. Our findings suggest that development of guidelines regarding management of IF include multiple stakeholders' perspectives and be based on a common language.
Assuntos
Revelação , Aconselhamento GenéticoRESUMO
Intercellular communication between axons and Schwann cells is critical for attaining the complex morphological steps necessary for axon maturation. In the early onset motor neuron disease spinal muscular atrophy (SMA), many motor axons are not ensheathed by Schwann cells nor grow sufficiently in radial diameter to become myelinated. These developmentally arrested motor axons are dysfunctional and vulnerable to rapid degeneration, limiting efficacy of current SMA therapeutics. We hypothesized that accelerating SMA motor axon maturation would improve their function and reduce disease features. A principle regulator of peripheral axon development is neuregulin 1 type III (NRG1-III). Expressed on axon surfaces, it interacts with Schwann cell receptors to mediate axon ensheathment and myelination. We examined NRG1 mRNA and protein expression levels in human and mouse SMA tissues and observed reduced expression in SMA spinal cord and in ventral, but not dorsal root axons. To determine the impact of neuronal NRG1-III overexpression on SMA motor axon development, we bred NRG1-III overexpressing mice to SMA∆7 mice. Neonatally, elevated NRG1-III expression increased SMA ventral root size as well as axon segregation, diameter, and myelination resulting in improved motor axon conduction velocities. NRG1-III was not able to prevent distal axonal degeneration nor improve axon electrophysiology, motor behavior, or survival of older mice. Together these findings demonstrate that early SMA motor axon developmental impairments can be ameliorated by a molecular strategy independent of SMN replacement providing hope for future SMA combinatorial therapeutic approaches.
Assuntos
Atrofia Muscular Espinal , Neuregulina-1 , Animais , Humanos , Camundongos , Axônios/metabolismo , Neurônios Motores/metabolismo , Atrofia Muscular Espinal/genética , Atrofia Muscular Espinal/metabolismo , Bainha de Mielina/metabolismo , Neuregulina-1/genética , Neuregulina-1/metabolismoRESUMO
Proximal spinal muscular atrophy (SMA) is caused by homozygous loss or mutation of the SMN1 gene on human chromosome 5. Depending on the levels of SMN protein produced from a second SMN gene (SMN2), different forms of the disease are distinguished. In patients with milder forms of the disease, type III or type IV SMA that normally reach adulthood, enlargement of motor units is regularly observed. However, the underlying mechanisms are not understood. Smn(+/-) mice, a mouse model of type III/IV SMA, reveal progressive loss of motor neurons and denervation of motor endplates starting at 4 weeks of age. Loss of spinal motor neurons between 1 month and 12 months reaches 40%, whereas muscle strength is not reduced. In these animals, amplitude of single motor unit action potentials in the gastrocnemic muscle is increased more than 2-fold. Confocal analysis reveals pronounced sprouting of innervating motor axons. As ciliary neurotrophic factor (CNTF) is highly expressed in Schwann cells, we investigated its role for a compensatory sprouting response and maintenance of muscle strength in this mouse model. Genetic ablation of CNTF results in reduced sprouting and decline of muscle strength in Smn(+/-) mice. These findings indicate that CNTF is necessary for a sprouting response and thus enhances the size of motor units in skeletal muscles of Smn(+/-) mice. This compensatory mechanism could guide the way to new therapies for this motor neuron disease.
Assuntos
Fator Neurotrófico Ciliar/metabolismo , Atividade Motora/fisiologia , Músculo Esquelético/inervação , Músculo Esquelético/fisiopatologia , Atrofia Muscular Espinal/fisiopatologia , Potenciais de Ação/fisiologia , Animais , Axônios/metabolismo , Axônios/patologia , Fator Neurotrófico Ciliar/deficiência , Modelos Animais de Doenças , Camundongos , Placa Motora/metabolismo , Placa Motora/patologia , Neurônios Motores/patologia , Denervação Muscular , Força Muscular/fisiologia , Músculo Esquelético/patologia , Atrofia Muscular Espinal/patologia , Células de Schwann/metabolismo , Células de Schwann/patologia , Medula Espinal/patologia , Medula Espinal/fisiopatologiaRESUMO
The neuromuscular junction (NMJ) is an essential synapse whose loss is a key hallmark of the neurodegenerative disease spinal muscular atrophy (SMA). Here, we show that activity of the SMA-determining SMN protein in the assembly of U7 small nuclear ribonucleoprotein (snRNP)-which functions in the 3'-end processing of replication-dependent histone mRNAs-is required for NMJ integrity. Co-expression of U7-specific Lsm10 and Lsm11 proteins selectively enhances U7 snRNP assembly, corrects histone mRNA processing defects, and rescues key structural and functional abnormalities of neuromuscular pathology in SMA mice-including NMJ denervation, decreased synaptic transmission, and skeletal muscle atrophy. Furthermore, U7 snRNP dysfunction drives selective loss of the synaptic organizing protein Agrin at NMJs innervating vulnerable muscles of SMA mice. These findings reveal a direct contribution of U7 snRNP dysfunction to neuromuscular pathology in SMA and suggest a role for histone gene regulation in maintaining functional synaptic connections between motor neurons and muscles.
Assuntos
Atrofia Muscular Espinal , Doenças Neurodegenerativas , Agrina/metabolismo , Animais , Histonas/metabolismo , Camundongos , Atrofia Muscular Espinal/metabolismo , Doenças Neurodegenerativas/metabolismo , Junção Neuromuscular/metabolismo , RNA Mensageiro/metabolismo , Ribonucleoproteína Nuclear Pequena U7/química , Ribonucleoproteína Nuclear Pequena U7/metabolismoRESUMO
The activation of the p53 pathway has been associated with neuronal degeneration in different neurological disorders, including spinal muscular atrophy (SMA) where aberrant expression of p53 drives selective death of motor neurons destined to degenerate. Since direct p53 inhibition is an unsound therapeutic approach due carcinogenic effects, we investigated the expression of the cell death-associated p53 downstream targets c-fos, perp and fas in vulnerable motor neurons of SMA mice. Fluorescence in situ hybridization (FISH) of SMA motor neurons revealed c-fos RNA as a promising candidate. Accordingly, we identified p53-dependent nuclear upregulation of c-Fos protein in degenerating motor neurons from the severe SMNΔ7 and intermediate Smn2B/- SMA mouse models. Although motor neuron-specific c-fos genetic deletion in SMA mice did not improve motor neuron survival or motor behavior, p53-dependent c-Fos upregulation marks vulnerable motor neurons in different mouse models. Thus, nuclear c-Fos accumulation may serve as a readout for therapeutic approaches targeting neuronal death in SMA and possibly other p53-dependent neurodegenerative diseases.
RESUMO
Loss of synapses on spinal motor neurons is a major feature of several neurodegenerative diseases; however, analyzing these premotor synapses is challenging because of their small size and high density. This protocol describes confocal and Stimulated Emission Depletion (STED) imaging of murine spinal premotor synapses and their segment-specific quantification by confocal microscopy. We detail the preparation of spinal cord segments, followed by image acquisition and analysis. This protocol enables in-depth analysis of pathological changes in spinal premotor synapses during neurodegeneration. For complete details on the use and execution of this protocol, please refer to Buettner et al. (2021).
Assuntos
Doenças Neurodegenerativas , Medula Espinal , Animais , Camundongos , Microscopia Confocal , Neurônios Motores , Medula Espinal/diagnóstico por imagem , SinapsesRESUMO
Some individuals' understanding of informed consent (IC) information may improve with electronic delivery, but others may benefit from face-to-face (F2F). This randomized, multisite study explores how individuals from diverse backgrounds understand electronic IC documents versus F2F, their confidence in understanding, and enrollment in research. A total of 501 patients at two U.S. biobanks with diverse populations participated. There were no overall differences between electronic and F2F understanding, but F2F predicted higher confidence in understanding and enrollment. Ethnicity and a higher educational level predicted higher understanding and confidence. Study findings suggest that electronic consent may lead to better understanding for non-Hispanic patients of higher socioeconomic status. F2F processes may lead to better understanding and higher enrollment of patients from Hispanic and lower socioeconomic levels. Researchers should carefully consider how they implement electronic IC processes and whether to maintain an F2F process to better address the needs and limitations of some populations.
Assuntos
Bancos de Espécimes Biológicos , Consentimento Livre e Esclarecido , Termos de Consentimento , Eletrônica , HumanosRESUMO
PURPOSE: Despite important recent work, US public attitudes toward specific biobank consent models are not well understood. Public opinion data can help shape efforts to develop ethically sound and publicly trusted mechanisms for informing and consenting prospective biobank donors. The purpose of this study was to explore public perspectives toward a range of consent models currently being used or considered for use among comprehensive US biobanks. METHODS: The study used an exploratory mixed-methods design, using focus groups and telephone surveys. Eligible participants were English-speaking residents in the catchment area of a comprehensive biobank being developed at the University of Iowa. RESULTS: Forty-eight participants in seven focus groups and 751 survey participants were recruited. Biobanks were unfamiliar to almost all study participants but were seen as valuable resources. Most focus group (63%) and survey (67%) participants preferred a prospective opt-in over an opt-out consent approach. Broad, research-unspecific consent was preferred over categorical and study-specific consent models for purposes of approving future research use. CONCLUSION: Many individuals may want to make an active and informed choice at the point of being approached for biobank participation but are prepared to consent broadly to future research use and to forego additional choices as a result.
Assuntos
Bancos de Espécimes Biológicos/ética , Consentimento Livre e Esclarecido/ética , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Grupos Focais , Humanos , Masculino , Competência Mental , Pessoa de Meia-Idade , Opinião Pública , Estados UnidosRESUMO
Spinal muscular atrophy (SMA) is a neurodegenerative disease caused by reduced survival motor neuron (SMN) protein. Recently, SMN dysfunction has been linked to individual aspects of motor circuit pathology in a severe SMA mouse model. To determine whether these disease mechanisms are conserved, we directly compared the motor circuit pathology of three SMA mouse models. The severe SMNΔ7 model exhibits vast motor circuit defects, including degeneration of motor neurons, spinal excitatory synapses, and neuromuscular junctions (NMJs). In contrast, the Taiwanese model shows very mild motor neuron pathology, but early central synaptic loss. In the intermediate Smn 2B/- model, strong pathology of central excitatory synapses and NMJs precedes the late onset of p53-dependent motor neuron death. These pathological events correlate with SMN-dependent splicing dysregulation of specific mRNAs. Our study provides a knowledge base for properly tailoring future studies and identifies central excitatory synaptopathy as a key feature of motor circuit pathology in SMA.
RESUMO
Gene replacement and pre-mRNA splicing modifier therapies represent breakthrough gene targeting treatments for the neuromuscular disease spinal muscular atrophy (SMA), but mechanisms underlying variable efficacy of treatment are incompletely understood. Our examination of severe infantile onset human SMA tissues obtained at expedited autopsy revealed persistence of developmentally immature motor neuron axons, many of which are actively degenerating. We identified similar features in a mouse model of severe SMA, in which impaired radial growth and Schwann cell ensheathment of motor axons began during embryogenesis and resulted in reduced acquisition of myelinated axons that impeded motor axon function neonatally. Axons that failed to ensheath degenerated rapidly postnatally, specifically releasing neurofilament light chain protein into the blood. Genetic restoration of survival motor neuron protein (SMN) expression in mouse motor neurons, but not in Schwann cells or muscle, improved SMA motor axon development and maintenance. Treatment with small-molecule SMN2 splice modifiers beginning immediately after birth in mice increased radial growth of the already myelinated axons, but in utero treatment was required to restore axonal growth and associated maturation, prevent subsequent neonatal axon degeneration, and enhance motor axon function. Together, these data reveal a cellular basis for the fulminant neonatal worsening of patients with infantile onset SMA and identify a temporal window for more effective treatment. These findings suggest that minimizing treatment delay is critical to achieve optimal therapeutic efficacy.
Assuntos
Atrofia Muscular Espinal , Animais , Axônios , Modelos Animais de Doenças , Humanos , Camundongos , Camundongos Transgênicos , Neurônios Motores , Atrofia Muscular Espinal/terapia , Proteína 1 de Sobrevivência do Neurônio Motor/genéticaRESUMO
Mutations in Ribosomal s6 kinase 2 (Rsk2) are associated with severe neuronal dysfunction in Coffin-Lowry syndrome (CLS) patients, flies and mice. So far, the mechanisms of how Rsk2 regulates development, maintenance and activity of neurons are not understood. We have investigated the consequences of Rsk2 deficiency in mouse spinal motoneurons. Survival of isolated Rsk2 deficient motoneurons is not reduced, but these cells grow significantly longer neurites. Conversely, overexpression of a constitutively active form of Rsk2 leads to reduced axon growth. Increased axon growth in Rsk2 deficient neurons was accompanied by higher Erk 1/2 phosphorylation, and the knockout phenotype could be rescued by pharmacological inhibition of MAPK/Erk kinase (Mek). These data indicate that Rsk2 negatively regulates axon elongation via the MAPK pathway. Thus, the functional defects observed in the nervous system of CLS patients and animal models with Rsk2 deficiency might be caused by dysregulated neurite growth rather than primary neurodegeneration.
Assuntos
Axônios/fisiologia , Neurônios Motores , Proteínas Quinases S6 Ribossômicas 90-kDa/metabolismo , Animais , Sobrevivência Celular , Feminino , Humanos , Sistema de Sinalização das MAP Quinases/fisiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Neurônios Motores/citologia , Neurônios Motores/fisiologia , Proteínas Quinases S6 Ribossômicas 90-kDa/genética , Medula Espinal/citologiaRESUMO
Reduced expression of the survival motor neuron (SMN) protein causes the neurodegenerative disease spinal muscular atrophy (SMA). Here, we show that adeno-associated virus serotype 9 (AAV9)-mediated delivery of Stasimon-a gene encoding an endoplasmic reticulum (ER)-resident transmembrane protein regulated by SMN-improves motor function in a mouse model of SMA through multiple mechanisms. In proprioceptive neurons, Stasimon overexpression prevents the loss of afferent synapses on motor neurons and enhances sensory-motor neurotransmission. In motor neurons, Stasimon suppresses neurodegeneration by reducing phosphorylation of the tumor suppressor p53. Moreover, Stasimon deficiency converges on SMA-related mechanisms of p53 upregulation to induce phosphorylation of p53 through activation of p38 mitogen-activated protein kinase (MAPK), and pharmacological inhibition of this kinase prevents motor neuron death in SMA mice. These findings identify Stasimon dysfunction induced by SMN deficiency as an upstream driver of distinct cellular cascades that lead to synaptic loss and motor neuron degeneration, revealing a dual contribution of Stasimon to motor circuit pathology in SMA.
Assuntos
Proteínas de Membrana/metabolismo , Neurônios Motores/patologia , Atrofia Muscular Espinal/etiologia , Células Receptoras Sensoriais/patologia , Proteína 1 de Sobrevivência do Neurônio Motor/fisiologia , Sinapses/patologia , Proteína Supressora de Tumor p53/metabolismo , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismo , Animais , Dependovirus/genética , Proteínas de Membrana/administração & dosagem , Proteínas de Membrana/genética , Camundongos , Camundongos Knockout , Neurônios Motores/metabolismo , Atrofia Muscular Espinal/metabolismo , Atrofia Muscular Espinal/patologia , Células Receptoras Sensoriais/metabolismo , Sinapses/metabolismo , Proteína Supressora de Tumor p53/genética , Proteínas Quinases p38 Ativadas por Mitógeno/genéticaRESUMO
Digital informed consent may better inform individuals about health research and increase participation. In the United States and elsewhere, minorities and rural populations are underrepresented in health research and may benefit from well-designed electronic informed consent (eIC). Seven focus groups were conducted with 50 Caucasian, African American, and rural patients in the United States. Participants were asked their preferences for a paper versus electronic informed consent document. Participants found the e-version easier to use, more interesting, and better for understanding. Minority participants emphasized limited access, computer literacy, and trust barriers to eIC. Rural participants were concerned about accessibility, connectivity, privacy, and confidentiality. People see value in electronic consenting. Researchers should consider barriers to eIC among underrepresented populations before recruitment.
Assuntos
Atitude , Termos de Consentimento , Consentimento Livre e Esclarecido , Pesquisa , Telemedicina , Adulto , Negro ou Afro-Americano , Idoso , Idoso de 80 Anos ou mais , Alfabetização Digital , Confidencialidade , Feminino , Grupos Focais , Humanos , Masculino , Pessoa de Meia-Idade , Grupos Minoritários , Papel , Privacidade , População Rural , Estados Unidos , População BrancaRESUMO
Behavioral deficits in neurodegenerative diseases are often attributed to the selective dysfunction of vulnerable neurons via cell-autonomous mechanisms. Although vulnerable neurons are embedded in neuronal circuits, the contributions of their synaptic partners to disease process are largely unknown. Here we show that, in a mouse model of spinal muscular atrophy (SMA), a reduction in proprioceptive synaptic drive leads to motor neuron dysfunction and motor behavior impairments. In SMA mice or after the blockade of proprioceptive synaptic transmission, we observed a decrease in the motor neuron firing that could be explained by the reduction in the expression of the potassium channel Kv2.1 at the surface of motor neurons. Chronically increasing neuronal activity pharmacologically in vivo led to a normalization of Kv2.1 expression and an improvement in motor function. Our results demonstrate a key role of excitatory synaptic drive in shaping the function of motor neurons during development and the contribution of its disruption to a neurodegenerative disease.