RESUMEN

BACKGROUND: Cerebral Palsy (CP) is a major cause of motor and cognitive disability in children due to injury to the developing brain. Early intensive sensorimotor rehabilitation has been shown to change brain structure and reduce CP symptoms severity. We combined environmental enrichment (EE) and treadmill training (TT) to observe the effects of a one-week program of sensorimotor stimulation (EETT) in animals exposed to a CP model and explored possible mechanisms involved in the functional recovery. METHODS: Pregnant Wistar rats were injected with Lipopolysaccharide (LPS - 200 µg/kg) intraperitoneally at embryonic days 18 and 19. At P0, pups of both sexes were exposed to 20' anoxia at 37 °C. From P2 to P21, hindlimbs were restricted for 16 h/day during the dark cycle. EETT lasted from P21 to P27. TT - 15 min/day at 7 cm/s. EE - 7 days in enriched cages with sensorimotor stimulus. Functional 3D kinematic gait analysis and locomotion were analyzed. At P28, brains were collected for ex-vivo MRI and histological assessment. Neurotrophins and key proteins involved in CNS function were assessed by western blotting. RESULTS: CP model caused gross and skilled locomotor disruption and altered CNS neurochemistry. EETT reversed locomotor dysfunction with minor effects over gait kinematics. EETT also decreased brain inflammation and glial activation, preserved myelination, upregulated BDNF signaling and modulated the expression of proteins involved in excitatory synaptic function in the brain and spinal cord. CONCLUSIONS: Using this translational approach based on intensive sensorimotor rehabilitation, we highlight pathways engaged in the early developmental processes improving neurological recovery observed in CP.

Asunto(s)

Parálisis Cerebral , Modelos Animales de Enfermedad , Locomoción , Plasticidad Neuronal , Ratas Wistar , Animales , Parálisis Cerebral/rehabilitación , Parálisis Cerebral/fisiopatología , Plasticidad Neuronal/fisiología , Ratas , Femenino , Locomoción/fisiología , Masculino , Encéfalo/metabolismo , Encéfalo/fisiopatología , Embarazo , Recuperación de la Función/fisiología , Encefalitis/metabolismo , Encefalitis/fisiopatología , Encefalitis/rehabilitación , Marcha/fisiología , Condicionamiento Físico Animal/fisiología , Condicionamiento Físico Animal/métodos , Enfermedades Neuroinflamatorias/metabolismo , Enfermedades Neuroinflamatorias/fisiopatología

RESUMEN

Here, we introduce the Tabulae Paralytica-a compilation of four atlases of spinal cord injury (SCI) comprising a single-nucleus transcriptome atlas of half a million cells, a multiome atlas pairing transcriptomic and epigenomic measurements within the same nuclei, and two spatial transcriptomic atlases of the injured spinal cord spanning four spatial and temporal dimensions. We integrated these atlases into a common framework to dissect the molecular logic that governs the responses to injury within the spinal cord1. The Tabulae Paralytica uncovered new biological principles that dictate the consequences of SCI, including conserved and divergent neuronal responses to injury; the priming of specific neuronal subpopulations to upregulate circuit-reorganizing programs after injury; an inverse relationship between neuronal stress responses and the activation of circuit reorganization programs; the necessity of re-establishing a tripartite neuroprotective barrier between immune-privileged and extra-neural environments after SCI and a failure to form this barrier in old mice. We leveraged the Tabulae Paralytica to develop a rejuvenative gene therapy that re-established this tripartite barrier, and restored the natural recovery of walking after paralysis in old mice. The Tabulae Paralytica provides a window into the pathobiology of SCI, while establishing a framework for integrating multimodal, genome-scale measurements in four dimensions to study biology and medicine.

Asunto(s)

Núcleo Celular , Epigenómica , Multiómica , Neuronas , Análisis de la Célula Individual , Traumatismos de la Médula Espinal , Transcriptoma , Animales , Femenino , Masculino , Ratones , Atlas como Asunto , Núcleo Celular/metabolismo , Neuronas/patología , Neuronas/metabolismo , Parálisis/genética , Parálisis/patología , Parálisis/rehabilitación , Parálisis/terapia , Recuperación de la Función , Médula Espinal/patología , Traumatismos de la Médula Espinal/genética , Traumatismos de la Médula Espinal/patología , Traumatismos de la Médula Espinal/rehabilitación , Traumatismos de la Médula Espinal/terapia , Caminata , Anatomía Artística , Vías Nerviosas , Terapia Genética

RESUMEN

Axon regeneration can be induced across anatomically complete spinal cord injury (SCI), but robust functional restoration has been elusive. Whether restoring neurological functions requires directed regeneration of axons from specific neuronal subpopulations to their natural target regions remains unclear. To address this question, we applied projection-specific and comparative single-nucleus RNA sequencing to identify neuronal subpopulations that restore walking after incomplete SCI. We show that chemoattracting and guiding the transected axons of these neurons to their natural target region led to substantial recovery of walking after complete SCI in mice, whereas regeneration of axons simply across the lesion had no effect. Thus, reestablishing the natural projections of characterized neurons forms an essential part of axon regeneration strategies aimed at restoring lost neurological functions.

Asunto(s)

Axones , Regeneración Nerviosa , Parálisis , Recuperación de la Función , Traumatismos de la Médula Espinal , Caminata , Animales , Ratones , Axones/fisiología , Regeneración Nerviosa/genética , Regeneración Nerviosa/fisiología , Neuronas/fisiología , Parálisis/fisiopatología , Traumatismos de la Médula Espinal/fisiopatología , Conectoma

RESUMEN

A spinal cord injury interrupts pathways from the brain and brainstem that project to the lumbar spinal cord, leading to paralysis. Here we show that spatiotemporal epidural electrical stimulation (EES) of the lumbar spinal cord1-3 applied during neurorehabilitation4,5 (EESREHAB) restored walking in nine individuals with chronic spinal cord injury. This recovery involved a reduction in neuronal activity in the lumbar spinal cord of humans during walking. We hypothesized that this unexpected reduction reflects activity-dependent selection of specific neuronal subpopulations that become essential for a patient to walk after spinal cord injury. To identify these putative neurons, we modelled the technological and therapeutic features underlying EESREHAB in mice. We applied single-nucleus RNA sequencing6-9 and spatial transcriptomics10,11 to the spinal cords of these mice to chart a spatially resolved molecular atlas of recovery from paralysis. We then employed cell type12,13 and spatial prioritization to identify the neurons involved in the recovery of walking. A single population of excitatory interneurons nested within intermediate laminae emerged. Although these neurons are not required for walking before spinal cord injury, we demonstrate that they are essential for the recovery of walking with EES following spinal cord injury. Augmenting the activity of these neurons phenocopied the recovery of walking enabled by EESREHAB, whereas ablating them prevented the recovery of walking that occurs spontaneously after moderate spinal cord injury. We thus identified a recovery-organizing neuronal subpopulation that is necessary and sufficient to regain walking after paralysis. Moreover, our methodology establishes a framework for using molecular cartography to identify the neurons that produce complex behaviours.

Asunto(s)

Neuronas , Parálisis , Traumatismos de la Médula Espinal , Médula Espinal , Caminata , Animales , Humanos , Ratones , Neuronas/fisiología , Parálisis/genética , Parálisis/fisiopatología , Parálisis/terapia , Médula Espinal/citología , Médula Espinal/fisiología , Médula Espinal/fisiopatología , Traumatismos de la Médula Espinal/genética , Traumatismos de la Médula Espinal/fisiopatología , Traumatismos de la Médula Espinal/terapia , Caminata/fisiología , Estimulación Eléctrica , Región Lumbosacra/inervación , Rehabilitación Neurológica , Análisis de Secuencia de ARN , Perfilación de la Expresión Génica

RESUMEN

A spinal cord injury disrupts communication between the brain and the circuits in the spinal cord that regulate neurological functions. The consequences are permanent paralysis, loss of sensation and debilitating dysautonomia. However, the majority of circuits located above and below the injury remain anatomically intact, and these circuits can reorganize naturally to improve function. In addition, various neuromodulation therapies have tapped into these processes to further augment recovery. Emerging research is illuminating the requirements to reconstitute damaged circuits. Here, we summarize these natural and targeted reorganizations of circuits after a spinal cord injury. We also advocate for new concepts of reorganizing circuits informed by multi-omic single-cell atlases of recovery from injury. These atlases will uncover the molecular logic that governs the selection of 'recovery-organizing' neuronal subpopulations, and are poised to herald a new era in spinal cord medicine.

Asunto(s)

Traumatismos de la Médula Espinal , Humanos , Traumatismos de la Médula Espinal/terapia , Sensación , Encéfalo

RESUMEN

After spinal cord injury, tissue distal to the lesion contains undamaged cells that could support or augment recovery. Targeting these cells requires a clearer understanding of their injury responses and capacity for repair. Here, we use single nucleus RNA sequencing to profile how each cell type in the lumbar spinal cord changes after a thoracic injury in mice. We present an atlas of these dynamic responses across dozens of cell types in the acute, subacute, and chronically injured spinal cord. Using this resource, we find rare spinal neurons that express a signature of regeneration in response to injury, including a major population that represent spinocerebellar projection neurons. We characterize these cells anatomically and observed axonal sparing, outgrowth, and remodeling in the spinal cord and cerebellum. Together, this work provides a key resource for studying cellular responses to injury and uncovers the spontaneous plasticity of spinocerebellar neurons, uncovering a potential candidate for targeted therapy.

Asunto(s)

Traumatismos de la Médula Espinal , Animales , Axones/metabolismo , Cerebelo/metabolismo , Ratones , Regeneración Nerviosa/fisiología , Neuronas/metabolismo , Médula Espinal/metabolismo , Traumatismos de la Médula Espinal/patología

RESUMEN

Optoelectronic systems can exert precise control over targeted neurons and pathways throughout the brain in untethered animals, but similar technologies for the spinal cord are not well established. In the present study, we describe a system for ultrafast, wireless, closed-loop manipulation of targeted neurons and pathways across the entire dorsoventral spinal cord in untethered mice. We developed a soft stretchable carrier, integrating microscale light-emitting diodes (micro-LEDs), that conforms to the dura mater of the spinal cord. A coating of silicone-phosphor matrix over the micro-LEDs provides mechanical protection and light conversion for compatibility with a large library of opsins. A lightweight, head-mounted, wireless platform powers the micro-LEDs and performs low-latency, on-chip processing of sensed physiological signals to control photostimulation in a closed loop. We use the device to reveal the role of various neuronal subtypes, sensory pathways and supraspinal projections in the control of locomotion in healthy and spinal-cord injured mice.

Asunto(s)

Optogenética , Tecnología Inalámbrica , Animales , Encéfalo/fisiología , Ratones , Neuronas/fisiología , Médula Espinal/fisiología

RESUMEN

Differential expression analysis in single-cell transcriptomics enables the dissection of cell-type-specific responses to perturbations such as disease, trauma, or experimental manipulations. While many statistical methods are available to identify differentially expressed genes, the principles that distinguish these methods and their performance remain unclear. Here, we show that the relative performance of these methods is contingent on their ability to account for variation between biological replicates. Methods that ignore this inevitable variation are biased and prone to false discoveries. Indeed, the most widely used methods can discover hundreds of differentially expressed genes in the absence of biological differences. To exemplify these principles, we exposed true and false discoveries of differentially expressed genes in the injured mouse spinal cord.

Asunto(s)

Exactitud de los Datos , Modelos Estadísticos , RNA-Seq/métodos , Análisis de la Célula Individual/métodos , Animales , Variación Biológica Individual , Variación Biológica Poblacional , Conjuntos de Datos como Asunto , Regulación de la Expresión Génica , Humanos , Ratones , RNA-Seq/estadística & datos numéricos , Conejos , Ratas , Análisis de la Célula Individual/estadística & datos numéricos , Porcinos

RESUMEN

Spinal cord injury (SCI) induces haemodynamic instability that threatens survival1-3, impairs neurological recovery4,5, increases the risk of cardiovascular disease6,7, and reduces quality of life8,9. Haemodynamic instability in this context is due to the interruption of supraspinal efferent commands to sympathetic circuits located in the spinal cord10, which prevents the natural baroreflex from controlling these circuits to adjust peripheral vascular resistance. Epidural electrical stimulation (EES) of the spinal cord has been shown to compensate for interrupted supraspinal commands to motor circuits below the injury11, and restored walking after paralysis12. Here, we leveraged these concepts to develop EES protocols that restored haemodynamic stability after SCI. We established a preclinical model that enabled us to dissect the topology and dynamics of the sympathetic circuits, and to understand how EES can engage these circuits. We incorporated these spatial and temporal features into stimulation protocols to conceive a clinical-grade biomimetic haemodynamic regulator that operates in a closed loop. This 'neuroprosthetic baroreflex' controlled haemodynamics for extended periods of time in rodents, non-human primates and humans, after both acute and chronic SCI. We will now conduct clinical trials to turn the neuroprosthetic baroreflex into a commonly available therapy for people with SCI.

Asunto(s)

Barorreflejo , Biomimética , Hemodinámica , Prótesis e Implantes , Traumatismos de la Médula Espinal/fisiopatología , Traumatismos de la Médula Espinal/terapia , Animales , Modelos Animales de Enfermedad , Femenino , Humanos , Masculino , Vías Nerviosas , Primates , Ratas , Ratas Endogámicas Lew , Sistema Nervioso Simpático/citología , Sistema Nervioso Simpático/fisiología

RESUMEN

Neural control of movement cannot be fully understood without careful consideration of interactions between the neural and biomechanical components. Recent advancements in mouse molecular genetics allow for the identification and manipulation of constituent elements underlying the neural control of movement. To complement experimental studies and investigate the mechanisms by which the neural circuitry interacts with the body and the environment, computational studies modeling motor behaviors in mice need to incorporate a model of the mouse musculoskeletal system. Here, we present the first fully articulated musculoskeletal model of the mouse. The mouse skeletal system has been developed from anatomical references and includes the sets of bones in all body compartments, including four limbs, spine, head and tail. Joints between all bones allow for simulation of full 3D mouse kinematics and kinetics. Hindlimb and forelimb musculature has been implemented using Hill-type muscle models. We analyzed the mouse whole-body model and described the moment-arms for different hindlimb and forelimb muscles, the moments applied by these muscles on the joints, and their involvement in limb movements at different limb/body configurations. The model represents a necessary step for the subsequent development of a comprehensive neuro-biomechanical model of freely behaving mice; this will close the loop between the neural control and the physical interactions between the body and the environment.

RESUMEN

We present Augur, a method to prioritize the cell types most responsive to biological perturbations in single-cell data. Augur employs a machine-learning framework to quantify the separability of perturbed and unperturbed cells within a high-dimensional space. We validate our method on single-cell RNA sequencing, chromatin accessibility and imaging transcriptomics datasets, and show that Augur outperforms existing methods based on differential gene expression. Augur identified the neural circuits restoring locomotion in mice following spinal cord neurostimulation.

Asunto(s)

Biología Computacional/métodos , Aprendizaje Automático , Análisis de la Célula Individual/métodos , Transcriptoma , Animales , Cromatina/genética , Cromatina/metabolismo , Bases de Datos Genéticas , Perfilación de la Expresión Génica/métodos , Ratones , Red Nerviosa/metabolismo , Ratas , Análisis de Secuencia de ARN , Transcriptoma/genética , Transcriptoma/fisiología , Caminata/fisiología

RESUMEN

After a spinal cord injury, axons fail to regenerate in the adult mammalian central nervous system, leading to permanent deficits in sensory and motor functions. Increasing neuronal activity after an injury using electrical stimulation or rehabilitation can enhance neuronal plasticity and result in some degree of recovery; however, the underlying mechanisms remain poorly understood. We found that placing mice in an enriched environment before an injury enhanced the activity of proprioceptive dorsal root ganglion neurons, leading to a lasting increase in their regenerative potential. This effect was dependent on Creb-binding protein (Cbp)-mediated histone acetylation, which increased the expression of genes associated with the regenerative program. Intraperitoneal delivery of a small-molecule activator of Cbp at clinically relevant times promoted regeneration and sprouting of sensory and motor axons, as well as recovery of sensory and motor functions in both the mouse and rat model of spinal cord injury. Our findings showed that the increased regenerative capacity induced by enhancing neuronal activity is mediated by epigenetic reprogramming in rodent models of spinal cord injury. Understanding the mechanisms underlying activity-dependent neuronal plasticity led to the identification of potential molecular targets for improving recovery after spinal cord injury.

Asunto(s)

Axones/fisiología , Proteína de Unión a CREB/metabolismo , Ambiente , Histonas/metabolismo , Regeneración Nerviosa , Traumatismos de la Médula Espinal/metabolismo , Traumatismos de la Médula Espinal/fisiopatología , Acetilación , Animales , Calcio/metabolismo , Modelos Animales de Enfermedad , Proteína p300 Asociada a E1A/metabolismo , Ganglios Espinales/patología , Ganglios Espinales/fisiopatología , Ratones , Neuronas Motoras/patología , Propiocepción , Recuperación de la Función , Células Receptoras Sensoriales/patología , Transducción de Señal , Traumatismos de la Médula Espinal/patología

RESUMEN

Unilateral or bilateral corticospinal tract injury in the medullary pyramids in adult rats causes anatomical and physiological changes in proprioceptive neurons projecting to the cervical spinal cord accompanied by hyperreflexia and abnormal behavioural movements including spasms. In a previous publication, we showed that "Intramuscular Neurotrophin-3 normalizes low threshold spinal reflexes, reduces spasms and improves mobility after bilateral corticospinal tract injury in rats" (Kathe et al., 2016) [1]. We hypothesize that neurotrophin-3 induces these changes by modifying gene expression in affected cervical dorsal root ganglia (DRG). Therefore in this data article, we analyzed the transcriptomes of cervical DRGs obtained during that previous study from naïve rats and from rats after bilateral pyramidotomy (bPYX) with unilateral intramuscular injections of either AAV1-CMV-NT3 or AAV1-CMV-EGFP applied 24 h after injury (Kathe et al., 2016) [1]. A bioinformatic analysis enabled us to identify genes that are likely to be expressed in TrkC+ neurons after injury and which were regulated by neurotrophin-3 in the direction expected from other datasets involving knockout or overexpression of neurotrophin-3. This dataset will help us and others identify genes in sensory neurons whose expression levels are regulated by neurotrophin-3 treatment. This may help identify novel therapeutic targets to improve sensation and movement after neurological injury. Data has been deposited in the Gene Expression Omnibus (GSE82197), http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?token=avgpicgcjhknzyv&acc=GSE82197.

RESUMEN

Brain and spinal injury reduce mobility and often impair sensorimotor processing in the spinal cord leading to spasticity. Here, we establish that complete transection of corticospinal pathways in the pyramids impairs locomotion and leads to increased spasms and excessive mono- and polysynaptic low threshold spinal reflexes in rats. Treatment of affected forelimb muscles with an adeno-associated viral vector (AAV) encoding human Neurotrophin-3 at a clinically-feasible time-point after injury reduced spasticity. Neurotrophin-3 normalized the short latency Hoffmann reflex to a treated hand muscle as well as low threshold polysynaptic spinal reflexes involving afferents from other treated muscles. Neurotrophin-3 also enhanced locomotor recovery. Furthermore, the balance of inhibitory and excitatory boutons in the spinal cord and the level of an ion co-transporter in motor neuron membranes required for normal reflexes were normalized. Our findings pave the way for Neurotrophin-3 as a therapy that treats the underlying causes of spasticity and not only its symptoms.

Asunto(s)

Locomoción , Factores de Crecimiento Nervioso/metabolismo , Tractos Piramidales/lesiones , Reflejo Anormal/efectos de los fármacos , Espasmo/tratamiento farmacológico , Animales , Modelos Animales de Enfermedad , Terapia Genética/métodos , Inyecciones Intramusculares , Factores de Crecimiento Nervioso/genética , Neurotrofina 3 , Ratas , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Resultado del Tratamiento

RESUMEN

There is an urgent need for a therapy that reverses disability after stroke when initiated in a time frame suitable for the majority of new victims. We show here that intramuscular delivery of neurotrophin-3 (NT3, encoded by NTF3) can induce sensorimotor recovery when treatment is initiated 24 h after stroke. Specifically, in two randomized, blinded preclinical trials, we show improved sensory and locomotor function in adult (6 months) and elderly (18 months) rats treated 24 h following cortical ischaemic stroke with human NT3 delivered using a clinically approved serotype of adeno-associated viral vector (AAV1). Importantly, AAV1-hNT3 was given in a clinically-feasible timeframe using a straightforward, targeted route (injections into disabled forelimb muscles). Magnetic resonance imaging and histology showed that recovery was not due to neuroprotection, as expected given the delayed treatment. Rather, treatment caused corticospinal axons from the less affected hemisphere to sprout in the spinal cord. This treatment is the first gene therapy that reverses disability after stroke when administered intramuscularly in an elderly body. Importantly, phase I and II clinical trials by others show that repeated, peripherally administered high doses of recombinant NT3 are safe and well tolerated in humans with other conditions. This paves the way for NT3 as a therapy for stroke.

Asunto(s)

Neurotrofina 3/administración & dosificación , Neurotrofina 3/uso terapéutico , Recuperación de la Función/efectos de los fármacos , Accidente Cerebrovascular/tratamiento farmacológico , Adenoviridae , Factores de Edad , Animales , Endotelina-1/administración & dosificación , Femenino , Vectores Genéticos/administración & dosificación , Humanos , Inyecciones Intramusculares , Locomoción/efectos de los fármacos , Imagen por Resonancia Magnética , Microinyecciones , Músculo Esquelético/metabolismo , Neuroimagen , Neurotrofina 3/sangre , Neurotrofina 3/metabolismo , Tractos Piramidales/efectos de los fármacos , Ratas , Médula Espinal/metabolismo , Accidente Cerebrovascular/inducido químicamente , Factores de Tiempo

RESUMEN

The corticospinal tract (CST) can be completely severed unilaterally in the medullary pyramids of the rodent brainstem. The CST is a motor tract that has great importance for distal muscle control in humans and, to a lesser extent, in rodents. A unilateral cut of one pyramid results in loss of CST innervation of the spinal cord mainly on the contralateral side of the spinal cord leading to transient motor disability in the forelimbs and sustained loss of dexterity. Ipsilateral projections of the corticospinal tract are minor. We have refined our surgical method to increase the chances of lesion completeness. We describe postsurgical care. Deficits on the Montoya staircase pellet reaching test and the horizontal ladder test shown here are detected up to 8 weeks postinjury. Deficits on the cylinder rearing test are only detected transiently. Therefore, the cylinder test may only be suitable for detection of short term recovery. We show how, electrophysiologically and anatomically, one may assess lesions and plastic changes. We also describe how to analyse fibers from the uninjured CST sprouting across the midline into the deprived areas. It is challenging to obtain >90% complete lesions consistently due to the proximity to the basilar artery in the medulla oblongata and survival rates can be low. Alternative surgical approaches and behavioural testing are described in this protocol. The pyramidotomy model is a good tool for assessing neuroplasticity-inducing treatments, which increase sprouting of intact fibers after injury.

Asunto(s)

Modelos Animales de Enfermedad , Plasticidad Neuronal/fisiología , Tractos Piramidales/cirugía , Ratas , Traumatismos de la Médula Espinal/cirugía , Animales , Tronco Encefálico/fisiopatología , Desnervación/métodos , Miembro Anterior , Masculino

RESUMEN

Recombinant adeno-associated viral (AAV) vectors are one of the most promising therapeutic delivery systems for gene therapy to the central nervous system (CNS). Preclinical testing of novel gene therapies requires the careful design and production of AAV vectors and their successful application in a model of CNS injury. One major limitation of AAV vectors is their limited packaging capacity (<5 kb) making the co-expression of two genes (e.g., from two promoters) difficult. An internal ribosomal entry site has been used to express two genes: However, the second transgene is often expressed at lower levels than the first. In addition to this, achieving high levels of transduction in the CNS can be challenging. In this chapter we describe the cloning of a bicistronic AAV vector that uses the foot-and-mouth disease virus 2A sequence to efficiently express two genes from a single promoter. Bicistronic expression of a therapeutic gene and a reporter gene is desirable so that the axons from transduced neurons can be tracked and, after CNS injury, the amount of axonal sprouting or regeneration quantified. We go on to describe how to perform a pyramidotomy model of CNS injury and the injection of AAV vectors into the sensorimotor cortex to provide efficient transduction and bicistronic gene expression in cortical neurons such that transduced axons are detectable in the dorsal columns of the spinal cord.

Asunto(s)

Sistema Nervioso Central/lesiones , Dependovirus/genética , Expresión Génica , Técnicas de Transferencia de Gen , Vectores Genéticos/uso terapéutico , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Sistema Nervioso Central/metabolismo , Sistema Nervioso Central/fisiología , Clonación Molecular/métodos , Electroporación/métodos , Femenino , Terapia Genética/métodos , Vectores Genéticos/administración & dosificación , Vectores Genéticos/genética , Histocitoquímica/métodos , Inyecciones , Microscopía/métodos , Datos de Secuencia Molecular , Regeneración Nerviosa , Reacción en Cadena de la Polimerasa/métodos

RESUMEN

Mutations in the gene encoding Fused in Sarcoma (FUS) cause amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disorder. FUS is a predominantly nuclear DNA- and RNA-binding protein that is involved in RNA processing. Large FUS-immunoreactive inclusions fill the perikaryon of surviving motor neurons of ALS patients carrying mutations at post-mortem. This sequestration of FUS is predicted to disrupt RNA processing and initiate neurodegeneration. Here, we demonstrate that C-terminal ALS mutations disrupt the nuclear localizing signal (NLS) of FUS resulting in cytoplasmic accumulation in transfected cells and patient fibroblasts. FUS mislocalization is rescued by the addition of the wild-type FUS NLS to mutant proteins. We also show that oxidative stress recruits mutant FUS to cytoplasmic stress granules where it is able to bind and sequester wild-type FUS. While FUS interacts with itself directly by protein-protein interaction, the recruitment of FUS to stress granules and interaction with PABP are RNA dependent. These findings support a two-hit hypothesis, whereby cytoplasmic mislocalization of FUS protein, followed by cellular stress, contributes to the formation of cytoplasmic aggregates that may sequester FUS, disrupt RNA processing and initiate motor neuron degeneration.

Asunto(s)

Esclerosis Amiotrófica Lateral/genética , Esclerosis Amiotrófica Lateral/metabolismo , Nucléolo Celular/metabolismo , Gránulos Citoplasmáticos/metabolismo , Proteína FUS de Unión a ARN/genética , Proteína FUS de Unión a ARN/metabolismo , Estrés Fisiológico , Sustitución de Aminoácidos , Animales , Línea Celular , Humanos , Neuronas Motoras/metabolismo , Mutación , Señales de Localización Nuclear , Unión Proteica , Transporte de Proteínas , Ratas

RESUMEN

Trans-activation response DNA-binding protein (TDP-43) accumulation is the major component of ubiquitinated protein inclusions found in patients with amyotrophic lateral sclerosis, and frontotemporal lobar degeneration with TDP-43 positive ubiquitinated inclusions, recently relabelled the 'TDP-43 proteinopathies'. TDP-43 is predominantly located in the nucleus, however, in disease it mislocalizes to the cytoplasm where it aggregates to form hallmark pathological inclusions. The identification of TDP-43 mutations in familial and sporadic amyotrophic lateral sclerosis cases confirms its pathogenic role; but it is wild-type TDP-43 that is deposited in the vast majority of TDP-43 proteinopathies, implicating other unknown factors for its mislocalization and aggregation. One such mechanism may be defective nuclear import of TDP-43 protein, as a disruption of its nuclear localization signal leads to mislocalization and aggregation of TDP-43 in the cytoplasm. In order to explore the factors that regulate the nuclear import of TDP-43, we used a small interfering RNA library to silence 82 proteins involved in nuclear transport and found that knockdowns of karyopherin-beta1 and cellular apoptosis susceptibility protein resulted in marked cytoplasmic accumulation of TDP-43. In glutathione S-transferase pull-down assays, TDP-43 bound to karyopherin-alphas, thereby confirming the classical nuclear import pathway for the import of TDP-43. Analysis of the expression of chosen nuclear import factors in post-mortem brain samples from patients with TDP-43 positive frontotemporal lobar degeneration, and spinal cord samples from patients with amyotrophic lateral sclerosis, revealed a considerable reduction in expression of cellular apoptosis susceptibility protein in frontotemporal lobar degeneration. We propose that cellular apoptosis susceptibility protein associated defective nuclear transport may play a mechanistic role in the pathogenesis of the TDP-43 positive frontotemporal lobar degeneration.

Asunto(s)

Transporte Activo de Núcleo Celular/fisiología , Citoplasma/metabolismo , Proteínas de Unión al ADN/metabolismo , Degeneración Lobar Frontotemporal/metabolismo , Anciano , Esclerosis Amiotrófica Lateral/metabolismo , Animales , Encéfalo/metabolismo , Línea Celular , Línea Celular Tumoral , Proteína de Susceptibilidad a Apoptosis Celular/metabolismo , Femenino , Glutatión Transferasa/metabolismo , Humanos , Masculino , Ratones , Persona de Mediana Edad , Transducción de Señal/genética , Médula Espinal/metabolismo , alfa Carioferinas/metabolismo , beta Carioferinas/metabolismo