RESUMO
Stable matching of neurotransmitters with their receptors is fundamental to synapse function and reliable communication in neural circuits. Presynaptic neurotransmitters regulate the stabilization of postsynaptic transmitter receptors. Whether postsynaptic receptors regulate stabilization of presynaptic transmitters has received less attention. Here, we show that blockade of endogenous postsynaptic acetylcholine receptors (AChR) at the neuromuscular junction destabilizes the cholinergic phenotype in motor neurons and stabilizes an earlier, developmentally transient glutamatergic phenotype. Further, expression of exogenous postsynaptic gamma-aminobutyric acid type A receptors (GABAA receptors) in muscle cells stabilizes an earlier, developmentally transient GABAergic motor neuron phenotype. Both AChR and GABAA receptors are linked to presynaptic neurons through transsynaptic bridges. Knockdown of specific components of these transsynaptic bridges prevents stabilization of the cholinergic or GABAergic phenotypes. Bidirectional communication can enforce a match between transmitter and receptor and ensure the fidelity of synaptic transmission. Our findings suggest a potential role of dysfunctional transmitter receptors in neurological disorders that involve the loss of the presynaptic transmitter.
Assuntos
Receptores Colinérgicos , Sinapses , Sinapses/metabolismo , Receptores Colinérgicos/metabolismo , Transmissão Sináptica/fisiologia , Neurônios Motores/metabolismo , Receptores de GABA-A/metabolismo , Ácido gama-Aminobutírico/metabolismo , Neurotransmissores/metabolismo , Colinérgicos , Receptores Pré-SinápticosRESUMO
The balance between neural stem cell proliferation and neuronal differentiation is paramount for the appropriate development of the nervous system. Sonic hedgehog (Shh) is known to sequentially promote cell proliferation and specification of neuronal phenotypes, but the signaling mechanisms responsible for the developmental switch from mitogenic to neurogenic have remained unclear. Here, we show that Shh enhances Ca2+ activity at the neural cell primary cilium of developing Xenopus laevis embryos through Ca2+ influx via transient receptor potential cation channel subfamily C member 3 (TRPC3) and release from intracellular stores in a developmental stage-dependent manner. This ciliary Ca2+ activity in turn antagonizes canonical, proliferative Shh signaling in neural stem cells by down-regulating Sox2 expression and up-regulating expression of neurogenic genes, enabling neuronal differentiation. These discoveries indicate that the Shh-Ca2+-dependent switch in neural cell ciliary signaling triggers the switch in Shh action from canonical-mitogenic to neurogenic. The molecular mechanisms identified in this neurogenic signaling axis are potential targets for the treatment of brain tumors and neurodevelopmental disorders.
Assuntos
Cálcio , Proteínas Hedgehog , Proteínas de Xenopus , Cálcio/metabolismo , Diferenciação Celular , Cílios/metabolismo , Proteínas Hedgehog/metabolismo , Tubo Neural/metabolismo , Neurogênese/fisiologia , Xenopus laevis , AnimaisRESUMO
Canavan disease (CD) is a recessively inherited pediatric leukodystrophy resulting from inactivating mutations to the oligodendroglial enzyme aspartoacylase (ASPA). ASPA is responsible for hydrolyzing the amino acid derivative N-acetyl-L-aspartate (NAA), and without it, brain NAA concentrations increase by 50% or more. Infants and children with CD present with progressive cognitive and motor delays, cytotoxic edema, astroglial vacuolation, and prominent spongiform brain degeneration. ASPA-deficient CD mice (Aspanur7/nur7 ) present similarly with elevated NAA, widespread astroglial dysfunction, ataxia, and Purkinje cell (PC) dendritic atrophy. Bergmann glia (BG), radial astrocytes essential for cerebellar development, are intimately intertwined with PCs, where they regulate synapse stability, functionality, and plasticity. BG damage is common to many neurodegenerative conditions and frequently associated with PC dysfunction and ataxia. Here, we report that, in CD mice, BG exhibit significant morphological alterations, decreased structural associations with PCs, loss of synaptic support proteins, and altered calcium dynamics. We also find that BG dysfunction predates cerebellar vacuolation and PC damage in CD mice. Previously, we developed an antisense oligonucleotide (ASO) therapy targeting Nat8l (N-acetyltransferase-8-like, "Nat8l ASO") that inhibits the production of NAA and reverses ataxia and PC atrophy in CD mice. Here, we show that Nat8l ASO administration in adult CD mice also leads to BG repair. Furthermore, blocking astroglial uptake of NAA is neuroprotective in astroglia-neuron cocultures exposed to elevated NAA. Our findings suggest that restoration of BG structural and functional integrity could be a mechanism for PC regeneration and improved motor function.
Assuntos
Doença de Canavan , Doenças Neurodegenerativas , Humanos , Criança , Lactente , Camundongos , Animais , Doença de Canavan/genética , Doença de Canavan/metabolismo , Doença de Canavan/patologia , Cálcio , Ataxia/patologia , Oligodendroglia/metabolismo , Doenças Neurodegenerativas/patologia , Ácido Aspártico , Atrofia/complicações , Atrofia/patologiaRESUMO
Folate supplementation prevents up to 70% of neural tube defects (NTDs), which result from a failure of neural tube closure during embryogenesis. The elucidation of the mechanisms underlying folate action has been challenging. This study introduces Xenopus laevis as a model to determine the cellular and molecular mechanisms involved in folate action during neural tube formation. We show that knockdown of folate receptor 1 (Folr1; also known as FRα) impairs neural tube formation and leads to NTDs. Folr1 knockdown in neural plate cells only is necessary and sufficient to induce NTDs. Folr1-deficient neural plate cells fail to constrict, resulting in widening of the neural plate midline and defective neural tube closure. Pharmacological inhibition of folate action by methotrexate during neurulation induces NTDs by inhibiting folate interaction with its uptake systems. Our findings support a model in which the folate receptor interacts with cell adhesion molecules, thus regulating the apical cell membrane remodeling and cytoskeletal dynamics necessary for neural plate folding. Further studies in this organism could unveil novel cellular and molecular events mediated by folate and lead to new ways of preventing NTDs.
Assuntos
Polaridade Celular , Receptor 1 de Folato/metabolismo , Placa Neural/citologia , Placa Neural/metabolismo , Tubo Neural/citologia , Tubo Neural/embriologia , Organogênese , Proteínas de Xenopus/metabolismo , Xenopus laevis/embriologia , Animais , Caderinas/metabolismo , Polaridade Celular/efeitos dos fármacos , Forma Celular/efeitos dos fármacos , Embrião não Mamífero/citologia , Embrião não Mamífero/metabolismo , Endocitose/efeitos dos fármacos , Feminino , Receptor 1 de Folato/genética , Regulação da Expressão Gênica no Desenvolvimento/efeitos dos fármacos , Técnicas de Silenciamento de Genes , Marcação de Genes , Humanos , Morfolinos/farmacologia , Tubo Neural/metabolismo , Neurulação/efeitos dos fármacos , Organogênese/efeitos dos fármacos , Proteínas de Xenopus/genética , Xenopus laevis/metabolismoRESUMO
In inflammatory arthritis, the dysregulation of osteoclast activity by proinflammatory cytokines, including TNF, interferes with bone remodeling during inflammation through Ca2+-dependent mechanisms causing pathological bone loss. Ca2+-dependent CREB/c-fos activation via Ca2+-calmodulin kinase IV (CaMKIV) induces transcriptional regulation of osteoclast-specific genes via NFATc1, which facilitate bone resorption. In leukocytes, Ca2+ regulation of NFAT-dependent gene expression oftentimes involves the activity of the Ca2+-activated K+ channel KCa3.1. In this study, we evaluate KCa3.1 as a modulator of Ca2+-induced NFAT-dependent osteoclast differentiation in inflammatory bone loss. Microarray analysis of receptor activator of NF-κB ligand (RANKL)-activated murine bone marrow macrophage (BMM) cultures revealed unique upregulation of KCa3.1 during osteoclastogenesis. The expression of KCa3.1 in vivo was confirmed by immunofluorescence staining on multinucleated cells at the bone surface of inflamed mouse joints. Experiments on in vitro BMM cultures revealed that KCa3.1-/- and TRAM-34 treatment significantly reduced the expression of osteoclast-specific genes (p < 0.05) alongside decreased osteoclast formation (p < 0.0001) in inflammatory (RANKL+TNF) and noninflammatory (RANKL) conditions. In particular, live cell Ca2+ imaging and Western blot analysis showed that TRAM-34 pretreatment decreased transient RANKL-induced Ca2+ amplitudes in BMMs by â¼50% (p < 0.0001) and prevented phosphorylation of CaMKIV. KCa3.1-/- reduced RANKL+/-TNF-stimulated phosphorylation of CREB and expression of c-fos in BMMs (p < 0.01), culminating in decreased NFATc1 protein expression and transcriptional activity (p < 0.01). These data indicate that KCa3.1 regulates Ca2+-dependent NFATc1 expression via CaMKIV/CREB during inflammatory osteoclastogenesis in the presence of TNF, corroborating its role as a target candidate for the treatment of bone erosion in inflammatory arthritis.
Assuntos
Reabsorção Óssea/genética , Reabsorção Óssea/metabolismo , Cálcio/metabolismo , Regulação da Expressão Gênica , Canais de Potássio Ativados por Cálcio de Condutância Intermediária/metabolismo , Fatores de Transcrição NFATC/genética , Osteoclastos/metabolismo , Animais , Proteína de Ligação a CREB/metabolismo , Diferenciação Celular , Células Cultivadas , Camundongos , Camundongos Knockout , Fatores de Transcrição NFATC/metabolismo , Osteoclastos/citologia , Ligação Proteica , Proteínas Proto-Oncogênicas c-fos/metabolismo , Ligante RANK/metabolismoRESUMO
Failure of neural tube closure leads to neural tube defects (NTDs), which can have serious neurological consequences or be lethal. Use of antiepileptic drugs (AEDs) during pregnancy increases the incidence of NTDs in offspring by unknown mechanisms. Here we show that during Xenopus laevis neural tube formation, neural plate cells exhibit spontaneous calcium dynamics that are partially mediated by glutamate signaling. We demonstrate that NMDA receptors are important for the formation of the neural tube and that the loss of their function induces an increase in neural plate cell proliferation and impairs neural cell migration, which result in NTDs. We present evidence that the AED valproic acid perturbs glutamate signaling, leading to NTDs that are rescued with varied efficacy by preventing DNA synthesis, activating NMDA receptors, or recruiting the NMDA receptor target ERK1/2. These findings may prompt mechanistic identification of AEDs that do not interfere with neural tube formation.SIGNIFICANCE STATEMENT Neural tube defects are one of the most common birth defects. Clinical investigations have determined that the use of antiepileptic drugs during pregnancy increases the incidence of these defects in the offspring by unknown mechanisms. This study discovers that glutamate signaling regulates neural plate cell proliferation and oriented migration and is necessary for neural tube formation. We demonstrate that the widely used antiepileptic drug valproic acid interferes with glutamate signaling and consequently induces neural tube defects, challenging the current hypotheses arguing that they are side effects of this antiepileptic drug that cause the increased incidence of these defects. Understanding the mechanisms of neurotransmitter signaling during neural tube formation may contribute to the identification and development of antiepileptic drugs that are safer during pregnancy.
Assuntos
Anticonvulsivantes/toxicidade , Defeitos do Tubo Neural/fisiopatologia , Tubo Neural/fisiologia , Receptores de N-Metil-D-Aspartato/fisiologia , Transdução de Sinais/fisiologia , Animais , Sinalização do Cálcio/efeitos dos fármacos , Sinalização do Cálcio/fisiologia , Movimento Celular , Proliferação de Células , Feminino , Glutamatos/fisiologia , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Placa Neural/citologia , Placa Neural/crescimento & desenvolvimento , Tubo Neural/crescimento & desenvolvimento , Defeitos do Tubo Neural/induzido quimicamente , Transdução de Sinais/efeitos dos fármacos , Ácido Valproico/toxicidade , Xenopus laevisRESUMO
Sonic hedgehog (Shh) is a morphogenic protein that operates through the Gli transcription factor-dependent canonical pathway to orchestrate normal development of many tissues. Because aberrant levels of Gli activity lead to a wide spectrum of diseases ranging from neurodevelopmental defects to cancer, understanding the regulatory mechanisms of Shh canonical pathway is paramount. During early stages of spinal cord development, Shh specifies neural progenitors through the canonical signaling. Despite persistence of Shh as spinal cord development progresses, Gli activity is switched off by unknown mechanisms. In this study we find that Shh inverts its action on Gli during development. Strikingly, Shh decreases Gli signaling in the embryonic spinal cord by an electrical activity- and cAMP-dependent protein kinase-mediated pathway. The inhibition of Gli activity by Shh operates at multiple levels. Shh promotes cytosolic over nuclear localization of Gli2, induces Gli2 and Gli3 processing into repressor forms, and activates cAMP-responsive element binding protein that in turn represses gli1 transcription. The regulatory mechanisms identified in this study likely operate with different spatiotemporal resolution and ensure effective down-regulation of the canonical Shh signaling as spinal cord development progresses. The developmentally regulated intercalation of electrical activity in the Shh pathway may represent a paradigm for switching from canonical to noncanonical roles of developmental cues during neuronal differentiation and maturation.
Assuntos
Regulação da Expressão Gênica no Desenvolvimento , Proteínas Hedgehog/metabolismo , Fatores de Transcrição Kruppel-Like/metabolismo , Transdução de Sinais , Animais , Neoplasias Encefálicas/metabolismo , Cálcio/química , Cálcio/metabolismo , Diferenciação Celular , Proliferação de Células , AMP Cíclico/metabolismo , Proteína de Ligação ao Elemento de Resposta ao AMP Cíclico/metabolismo , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Transferência Ressonante de Energia de Fluorescência , Camundongos , Placa Neural/metabolismo , Neurônios/metabolismo , Proteínas Oncogênicas/metabolismo , Biossíntese de Proteínas , Proteínas Repressoras/metabolismo , Medula Espinal/embriologia , Medula Espinal/metabolismo , Transativadores/metabolismo , Transcrição Gênica , Proteínas de Xenopus/metabolismo , Xenopus laevis/metabolismo , Proteína GLI1 em Dedos de Zinco , Proteína Gli2 com Dedos de Zinco , Proteína Gli3 com Dedos de ZincoRESUMO
The central nervous system is a highly plastic network of cells that constantly adjusts its functions to environmental stimuli throughout life. Transcription-dependent mechanisms modify neuronal properties to respond to external stimuli regulating numerous developmental functions, such as cell survival and differentiation, and physiological functions such as learning, memory, and circadian rhythmicity. The discovery and cloning of the cyclic adenosine monophosphate (cAMP) responsive element binding protein (CREB) constituted a big step toward deciphering the molecular mechanisms underlying neuronal plasticity. CREB was first discovered in learning and memory studies as a crucial mediator of activity-dependent changes in target gene expression that in turn impose long-lasting modifications of the structure and function of neurons. In this chapter, we review the molecular and signaling mechanisms of neural activity-dependent recruitment of CREB and its cofactors. We discuss the crosstalk between signaling pathways that imprints diverse spatiotemporal patterns of CREB activation allowing for the integration of a wide variety of stimuli.
Assuntos
Proteína de Ligação ao Elemento de Resposta ao AMP Cíclico/metabolismo , Plasticidade Neuronal/fisiologia , Neurônios/fisiologia , Transdução de Sinais/fisiologia , Animais , Sistema Nervoso Central , HumanosRESUMO
A gradient of bone morphogenetic proteins (BMPs) along the dorsoventral axis of the spinal cord is necessary for the specification of dorsal neurons. Concurrently, a gradient of calcium-mediated electrical activity is present in the developing spinal cord but in an opposing ventrodorsal direction. Whether BMPs and electrical activity interact in embryonic spinal neurons remains unknown. We show that BMP decreases electrical activity by enhancing p38 MAPK-mediated negative modulation of voltage-gated sodium channels. In turn, electrical activity affects the phosphorylation status and nuclear level of activated Smads, the canonical components of BMP signaling. This interaction between calcium spike activity and BMP signaling regulates the specification of the dorsal commissural spinal neuron phenotype. The present study identifies an unexpected interplay between BMPs and electrical activity that is critical for decoding the morphogen gradient during spinal neuron differentiation.
Assuntos
Proteínas Morfogenéticas Ósseas/metabolismo , Sinalização do Cálcio/fisiologia , Diferenciação Celular/fisiologia , Interneurônios/fisiologia , Nervos Espinhais/citologia , Transmissão Sináptica/fisiologia , Xenopus/embriologia , Análise de Variância , Animais , Western Blotting , Proteínas de Transporte/metabolismo , Interneurônios/metabolismo , Microscopia Confocal , Fosforilação , Proteínas Smad/metabolismo , Canais de Sódio Disparados por Voltagem/metabolismo , Xenopus/metabolismoRESUMO
Evolutionarily conserved hedgehog proteins orchestrate the patterning of embryonic tissues, and dysfunctions in their signaling can lead to tumorigenesis. In vertebrates, Sonic hedgehog (Shh) is essential for nervous system development, but the mechanisms underlying its action remain unclear. Early electrical activity is another developmental cue important for proliferation, migration, and differentiation of neurons. Here we demonstrate the interplay between Shh signaling and Ca(2+) dynamics in the developing spinal cord. Ca(2+) imaging of embryonic spinal cells shows that Shh acutely increases Ca(2+) spike activity through activation of the Shh coreceptor Smoothened (Smo) in neurons. Smo recruits a heterotrimeric GTP-binding protein-dependent pathway and engages both intracellular Ca(2+) stores and Ca(2+) influx. The dynamics of this signaling are manifested in synchronous Ca(2+) spikes and inositol triphosphate transients apparent at the neuronal primary cilium. Interaction of Shh and electrical activity modulates neurotransmitter phenotype expression in spinal neurons. These results indicate that electrical activity and second-messenger signaling mediate Shh action in embryonic spinal neurons.
Assuntos
Sinalização do Cálcio , Proteínas Hedgehog/metabolismo , Medula Espinal/embriologia , Medula Espinal/metabolismo , Proteínas de Xenopus/metabolismo , Animais , Diferenciação Celular , Cílios/metabolismo , Inositol 1,4,5-Trifosfato/metabolismo , Mitose , Neurônios/citologia , Neurônios/metabolismo , Neurotransmissores/metabolismo , Medula Espinal/citologia , Xenopus/embriologia , Xenopus/metabolismoRESUMO
Folate supplementation reduces the occurrence of neural tube defects (NTDs), birth defects consisting in the failure of the neural tube to form and close. The mechanisms underlying NTDs and their prevention by folate remain unclear. Here we show that folate receptor 1 (FOLR1) is necessary for the formation of neural tube-like structures in human-cell derived neural organoids. FOLR1 knockdown in neural organoids and in Xenopus laevis embryos leads to NTDs that are rescued by pteroate, a folate precursor that is unable to participate in metabolism. We demonstrate that FOLR1 interacts with and opposes the function of CD2-associated protein, molecule essential for apical endocytosis and turnover of C-cadherin in neural plate cells. In addition, folates increase Ca2+ transient frequency, suggesting that folate and FOLR1 signal intracellularly to regulate neural plate folding. This study identifies a mechanism of action of folate distinct from its vitamin function during neural tube formation.
Assuntos
Ácido Fólico , Defeitos do Tubo Neural , Humanos , Ácido Fólico/metabolismo , Tubo Neural/metabolismo , Receptor 1 de Folato/genética , Receptor 1 de Folato/metabolismo , Defeitos do Tubo Neural/genética , Defeitos do Tubo Neural/metabolismo , Placa Neural/metabolismoRESUMO
Folate supplementation reduces the occurrence of neural tube defects, one of the most common and serious birth defects, consisting in the failure of the neural tube to form and close early in pregnancy. The mechanisms underlying neural tube defects and folate action during neural tube formation remain unclear. Here we show that folate receptor 1 (FOLR1) is necessary for the formation of neural tube-like structures in human-cell derived neural organoids. Knockdown of FOLR1 in human neural organoids as well as in the Xenopus laevis in vivo model leads to neural tube defects that are rescued by pteroate, a folate precursor that binds to FOLR1 but is unable to participate in metabolic pathways. We demonstrate that FOLR1 interacts with and opposes the function of CD2-associated protein (CD2AP), a molecule that we find is essential for apical endocytosis and the spatiotemporal turnover of the cell adherens junction component C-cadherin in neural plate cells. The counteracting action of FOLR1 on these processes is mediated by regulating CD2AP protein level via a degradation-dependent mechanism. In addition, folate and pteroate increase Ca 2+ transient frequency in the neural plate in a FOLR1-dependent manner, suggesting that folate/FOLR1 signal intracellularly to regulate neural plate folding. This study identifies a mechanism of action of folate distinct from its vitamin function during neural tube formation.
RESUMO
The transition of stem cells from quiescence to proliferation enables tissues to self-repair. The signaling mechanisms driving these stem-cell-status decisions are still unclear. Ca2+ and the extracellular signal-regulated kinase (Erk1/2) are two signaling pathways that have the potential to coordinate multiple signals to promote a specific cellular response. They both play important roles during nervous system development but their roles during spinal cord and muscle regeneration are not fully deciphered. Here we show in Xenopus laevis larvae that both Ca2+ and Erk1/2 signaling pathways are activated after tail amputation. In response to injury, we find that Erk1/2 signaling is activated in neural and muscle stem cells and is necessary for spinal cord and skeletal muscle regeneration. Finally, we show in vivo that Erk1/2 activity is necessary for an injury-induced increase in intracellular store-dependent Ca2+ dynamics in skeletal muscle-associated tissues but that in spinal cord, injury increases Ca2+ influx-dependent Ca2+ activity independent of Erk1/2 signaling. This study suggests that precise temporal and tissue-specific activation of Ca2+ and Erk1/2 pathways is essential for regulating spinal cord and muscle regeneration.
Assuntos
Transdução de Sinais , Traumatismos da Medula Espinal , Animais , Músculo Esquelético , Transdução de Sinais/fisiologia , Xenopus laevis/fisiologiaRESUMO
Inducing regeneration in injured spinal cord represents one of modern medicine's greatest challenges. Research from a variety of model organisms indicates that Hedgehog (Hh) signaling may be a useful target to drive regeneration. However, the mechanisms of Hh signaling-mediated tissue regeneration remain unclear. Here, we examined Hh signaling during post-amputation tail regeneration in Xenopus laevis larvae. We found that while Smoothened (Smo) activity is essential for proper spinal cord and skeletal muscle regeneration, transcriptional activity of the canonical Hh effector Gli is repressed immediately following amputation, and inhibition of Gli1/2 expression or transcriptional activity has minimal effects on regeneration. In contrast, we demonstrate that protein kinase A is necessary for regeneration of both muscle and spinal cord, in concert with and independent of Smo, respectively, and that its downstream effector CREB is activated in spinal cord following amputation in a Smo-dependent manner. Our findings indicate that non-canonical mechanisms of Hh signaling are necessary for spinal cord and muscle regeneration.
Assuntos
Proteínas Hedgehog/metabolismo , Larva/fisiologia , Músculos/fisiologia , Regeneração/fisiologia , Transdução de Sinais/genética , Regeneração da Medula Espinal/fisiologia , Xenopus laevis/fisiologia , Animais , Feminino , Proteínas Hedgehog/genética , Larva/genética , Regeneração/genética , Transdução de Sinais/fisiologia , Regeneração da Medula Espinal/genética , Xenopus laevis/genéticaRESUMO
Neurotransmitters are essential for interneuronal signalling, and the specification of appropriate transmitters in differentiating neurons has been related to intrinsic neuronal identity and to extrinsic signalling proteins. Here we show that altering the distinct patterns of Ca2+ spike activity spontaneously generated by different classes of embryonic spinal neurons in vivo changes the transmitter that neurons express without affecting the expression of markers of cell identity. Regulation seems to be homeostatic: suppression of activity leads to an increased number of neurons expressing excitatory transmitters and a decreased number of neurons expressing inhibitory transmitters; the reverse occurs when activity is enhanced. The imposition of specific spike frequencies in vitro does not affect labels of cell identity but again specifies the expression of transmitters that are inappropriate for the markers they express, during an early critical period. The results identify a new role of patterned activity in development of the central nervous system.
Assuntos
Potenciais de Ação/fisiologia , Regulação da Expressão Gênica , Homeostase , Neurônios/fisiologia , Neurotransmissores/metabolismo , Medula Espinal/citologia , Medula Espinal/embriologia , Animais , Cálcio/metabolismo , Sinalização do Cálcio , Diferenciação Celular , Células Cultivadas , Humanos , Neurônios/citologia , Neurônios/metabolismo , Especificidade de Órgãos , Fenótipo , Canais de Potássio Corretores do Fluxo de Internalização/genética , Canais de Potássio Corretores do Fluxo de Internalização/metabolismo , Ratos , Canais de Sódio/genética , Canais de Sódio/metabolismo , Medula Espinal/metabolismo , Xenopus laevisRESUMO
Ion channels are expressed throughout nervous system development. The type and diversity of conductances and gating mechanisms vary at different developmental stages and with the progressive maturational status of neural cells. The variety of ion channels allows for distinct signaling mechanisms in developing neural cells that in turn regulate the needed cellular processes taking place during each developmental period. These include neural cell proliferation and neuronal differentiation, which are crucial for developmental events ranging from the earliest steps of morphogenesis of the neural tube through the establishment of neuronal circuits. Here, we compile studies assessing the ontogeny of ionic currents in the developing nervous system. We then review work demonstrating a role for ion channels in neural tube formation, to underscore the necessity of the signaling downstream ion channels even at the earliest stages of neural development. We discuss the function of ion channels in neural cell proliferation and neuronal differentiation and conclude with how the regulation of all these morphogenetic and cellular processes by electrical activity enables the appropriate development of the nervous system and the establishment of functional circuits adapted to respond to a changing environment.
RESUMO
Neural crest cells (NCCs) comprise a transient progenitor cell population of neuroepithelial origin that contributes to a variety of cell types throughout vertebrate embryos including most mesenchymal cells of the cranial and facial structures. Consequently, abnormal NCC development underlies a variety of craniofacial defects including orofacial clefts, which constitute some of the most common birth defects. We previously reported the generation of manta ray (mray) mice that carry a loss-of-function allele of the gene encoding the preribosomal factor Pak1ip1. Here we describe cranioskeletal abnormalities in homozygous mray mutants that arise from a loss of NCCs after their specification. Our results show that the localized loss of cranial NCCs in the developing frontonasal prominences is caused by cell cycle arrest and cell death. In addition, and consistent with deficits in ribosome biosynthesis, homozygous mray mutants display decreased protein biosynthesis, further linking Pak1ip1 to a role in ribosome biogenesis.
RESUMO
During vertebrate development, spinal neurons differentiate and connect to generate a system that performs sensorimotor functions critical for survival. Spontaneous Ca2+ activity regulates different aspects of spinal neuron differentiation. It is unclear whether environmental factors can modulate this Ca2+ activity in developing spinal neurons to alter their specialization and ultimately adjust sensorimotor behavior to fit the environment. Here, we show that growing Xenopus laevis embryos at cold temperatures results in an increase in the number of spinal motor neurons in larvae. This change in spinal cord development optimizes the escape response to gentle touch of animals raised in and tested at cold temperatures. The cold-sensitive channel TRPM8 increases Ca2+ spike frequency of developing ventral spinal neurons, which in turn regulates expression of the motor neuron master transcription factor HB9. TRPM8 is necessary for the increase in motor neuron number of animals raised in cold temperatures and for their enhanced sensorimotor behavior when tested at cold temperatures. These findings suggest the environment modulates neuronal differentiation to optimize the behavior of the developing organism.
Assuntos
Locomoção/fisiologia , Neurônios Motores/fisiologia , Xenopus laevis/fisiologia , Animais , Temperatura Baixa , Embrião não Mamífero/fisiologia , Desenvolvimento Embrionário/fisiologia , Medula Espinal , Xenopus laevis/crescimento & desenvolvimentoRESUMO
The vitamin folic acid has been recognized as a crucial environmental factor for nervous system development. From the early fetal stages of the formation of the presumptive spinal cord and brain to the maturation and maintenance of the nervous system during infancy and childhood, folate levels and its supplementation have been considered influential in the clinical outcome of infants and children affected by neurological diseases. Despite the vast epidemiological information recorded on folate function and neural tube defects, neural development and neurodegenerative diseases, the mechanisms of folate action in the developing neural tissue have remained elusive. Here we compiled studies that argue for a unique role for folate in nervous system development and function and its consequences to neural disease and repair. © 2018 Wiley Periodicals, Inc. Develop Neurobiol 78: 391-402, 2018.
Assuntos
Ácido Fólico/metabolismo , Doenças do Sistema Nervoso/metabolismo , Sistema Nervoso/crescimento & desenvolvimento , Sistema Nervoso/metabolismo , Animais , Humanos , Doenças do Sistema Nervoso/etiologiaRESUMO
Dynamic calcium signaling is a well-established precept in biology. Different cell types exhibit spontaneous as well as stimulus-triggered transient changes in the concentration of intracellular calcium. Does this behavior extend to other second messengers? Optical dissection of various signal transduction pathways with fluorescent reporter molecules that enable visualization of changes in concentration of other second messengers is well under way. Recent research using technologically refined probes provides improved temporal and spatial resolution of adenosine 3',5'-monophosphate (cAMP) dynamics to generate insights into the bidirectional interplay between intracellular fluctuations of cAMP and calcium. cAMP oscillations are generated in response to hormones, and cells can recognize and differentially respond to transient versus sustained changes in this second messenger. Second messenger reporters are now available to track multiple players and so provide a dynamic picture of signaling networks.