RESUMO
Significant progress has been made in elucidating the basic principles that govern neuronal specification in the developing central nervous system. In contrast, much less is known about the origin of astrocytic diversity. Here, we demonstrate that a restricted pool of progenitors in the mouse spinal cord, expressing the transcription factor Dbx1, produces a subset of astrocytes, in addition to interneurons. Ventral p0-derived astrocytes (vA0 cells) exclusively populate intermediate regions of spinal cord with extraordinary precision. The postnatal vA0 population comprises gray matter protoplasmic and white matter fibrous astrocytes and a group of cells with strict radial morphology contacting the pia. We identified that vA0 cells in the lateral funiculus are distinguished by the expression of reelin and Kcnmb4. We show that Dbx1 mutants have an increased number of vA0 cells at the expense of p0-derived interneurons. Manipulation of the Notch pathway, together with the alteration in their ligands seen in Dbx1 knockouts, suggest that Dbx1 controls neuron-glial balance by modulating Notch-dependent cell interactions. In summary, this study highlights that restricted progenitors in the dorsal-ventral neural tube produce region-specific astrocytic subgroups and that progenitor transcriptional programs highly influence glial fate and are instrumental in creating astrocyte diversity.
Assuntos
Astrócitos , Medula Espinal , Animais , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Interneurônios/metabolismo , Subunidades beta do Canal de Potássio Ativado por Cálcio de Condutância Alta/metabolismo , Camundongos , Neuroglia/metabolismo , Transdução de Sinais/genética , Medula Espinal/metabolismoRESUMO
The dentate gyrus (DG) of the hippocampus plays a key role in memory formation, and it is known to be modulated by septal projections. By performing electrophysiology and optogenetics, we evaluated the role of cholinergic modulation in the processing of afferent inputs in the DG. We show that mature granule cells (GCs), but not adult-born immature neurons, have increased responses to afferent perforant path stimuli upon cholinergic modulation. This is due to a highly precise reconfiguration of inhibitory circuits, differentially affecting Parvalbumin and Somatostatin interneurons, resulting in a nicotinic-dependent perisomatic disinhibition of GCs. This circuit reorganization provides a mechanism by which mature GCs could escape the strong inhibition they receive, creating a window of opportunity for plasticity. Indeed, coincident activation of perforant path inputs with optogenetic release of acetylcholine produces a long-term potentiated response in GCs, essential for memory formation.
Assuntos
Acetilcolina/farmacologia , Giro Denteado/metabolismo , Interneurônios/metabolismo , Inibição Neural/efeitos dos fármacos , Transmissão Sináptica/efeitos dos fármacos , Animais , Camundongos , Camundongos Transgênicos , OptogenéticaRESUMO
Generation of neuronal types at the right time, location, and number is essential for building a functional nervous system. Significant progress has been reached in understanding the mechanisms that govern neuronal diversity. Cerebrospinal fluid-contacting neurons (CSF-cNs), an intriguing spinal cord central canal population, are produced during advanced developmental stages, simultaneous with glial and ependymal cells. It is unknown how CSF-cNs are specified after the neurogenesis-to-gliogenesis switch. Here, we identify delayed Ascl1 expression in mouse spinal progenitors during the gliogenic phase as key in CSF-cN differentiation. With fate mappings and time-controlled deletions, we demonstrate that CSF-cNs derive from Ascl1-expressing cells and that Ascl1 triggers late neurogenesis in the amniote spinal cord. Ascl1 abrogation transforms prospective CSF-cN progenitors into ependymocytes. These results demonstrate that late spinal progenitors have the potential to produce neurons and that Ascl1 initiates CSF-cN differentiation, controlling the precise neuronal and nonneuronal composition of the spinal central canal.
Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Epêndima/metabolismo , Neurogênese , Neurônios/metabolismo , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Epêndima/citologia , Camundongos , Neurônios/citologia , Medula Espinal/citologia , Medula Espinal/embriologia , Medula Espinal/metabolismo , Peixe-ZebraRESUMO
Locomotion is common to all animals and is essential for survival. Neural circuits located in the spinal cord have been shown to be necessary and sufficient for the generation and control of the basic locomotor rhythm by activating muscles on either side of the body in a specific sequence. Activity in these neural circuits determines the speed, gait pattern, and direction of movement, so the specific locomotor pattern generated relies on the diversity of the neurons within spinal locomotor circuits. Here, we review findings demonstrating that developmental genetics can be used to identify populations of neurons that comprise these circuits and focus on recent work indicating that many of these populations can be further subdivided into distinct subtypes, with each likely to play complementary functions during locomotion. Finally, we discuss data describing the manner in which these populations interact with each other to produce efficient, task-dependent locomotion.
Assuntos
Interneurônios/fisiologia , Locomoção/fisiologia , Rede Nervosa/anatomia & histologia , Rede Nervosa/fisiologia , Medula Espinal/citologia , Medula Espinal/fisiologia , Animais , Humanos , Neurônios Motores/fisiologia , Rede Nervosa/diagnóstico por imagem , Rede Nervosa/crescimento & desenvolvimento , Medula Espinal/diagnóstico por imagem , Medula Espinal/crescimento & desenvolvimentoRESUMO
Considerable progress has been made in understanding the mechanisms that control the production of specialized neuronal types. However, how the timing of differentiation contributes to neuronal diversity in the developing spinal cord is still a pending question. In this study, we show that cerebrospinal fluid-contacting neurons (CSF-cNs), an anatomically discrete cell type of the ependymal area, originate from surprisingly late neurogenic events in the ventral spinal cord. CSF-cNs are identified by the expression of the transcription factors Gata2 and Gata3, and the ionic channels Pkd2l1 and Pkd1l2. Contrasting with Gata2/3(+) V2b interneurons, differentiation of CSF-cNs is independent of Foxn4 and takes place during advanced developmental stages previously assumed to be exclusively gliogenic. CSF-cNs are produced from two distinct dorsoventral regions of the mouse spinal cord. Most CSF-cNs derive from progenitors circumscribed to the late-p2 and the oligodendrogenic (pOL) domains, whereas a second subset of CSF-cNs arises from cells bordering the floor plate. The development of these two subgroups of CSF-cNs is differentially controlled by Pax6, they adopt separate locations around the postnatal central canal and they display electrophysiological differences. Our results highlight that spatiotemporal mechanisms are instrumental in creating neural cell diversity in the ventral spinal cord to produce distinct classes of interneurons, motoneurons, CSF-cNs, glial cells and ependymal cells.
Assuntos
Líquido Cefalorraquidiano/metabolismo , Neurônios/citologia , Medula Espinal/embriologia , Medula Espinal/fisiologia , Animais , Diferenciação Celular , Linhagem da Célula , Eletrofisiologia , Proteínas do Olho/genética , Feminino , Fatores de Transcrição Forkhead/genética , Fator de Transcrição GATA2/genética , Genótipo , Imuno-Histoquímica , Hibridização In Situ , Interneurônios/citologia , Camundongos , Neurônios Motores/citologia , Células-Tronco/citologiaRESUMO
V3 spinal interneurons (INs) are a group of excitatory INs that play a crucial role in producing balanced and stable gaits in vertebrate animals. In the developing mouse spinal cord, V3 INs arise from the most ventral progenitor domain and form anatomically distinctive subpopulations in adult spinal cords. They are marked by the expression of transcription factor Sim1 postmitotically, but the function of Sim1 in V3 development remains unknown. Here, we used Sim1(Cre) ;tdTomato mice to trace the fate of V3 INs in a Sim1 mutant versus control genetic background during development. In Sim1 mutants, V3 INs are produced normally and maintain a similar position and organization as in wild types before E12.5. Further temporal analysis revealed that the V3 INs in the mutants failed to migrate properly to form V3 subgroups along the dorsoventral axis of the spinal cord. At birth, in the Sim1 mutant the number of V3 INs in the ventral subgroup was normal, but they were significantly reduced in the dorsal subgroup with a concomitant increase in the intermediate subgroup. Retrograde labeling at lumbar level revealed that loss of Sim1 led to a reduction in extension of contralateral axon projections both at E14.5 and P0 without affecting ipsilateral axon projections. These results demonstrate that Sim1 is essential for proper migration and the guidance of commissural axons of the spinal V3 INs.
Assuntos
Axônios/fisiologia , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Movimento Celular/fisiologia , Interneurônios/fisiologia , Proteínas Repressoras/metabolismo , Medula Espinal/embriologia , Medula Espinal/fisiologia , Animais , Animais Recém-Nascidos , Axônios/patologia , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Hibridização In Situ , Interneurônios/patologia , Vértebras Lombares , Camundongos Transgênicos , Mutação , Técnicas de Rastreamento Neuroanatômico , Proteínas Repressoras/genética , Medula Espinal/patologia , Vértebras TorácicasRESUMO
Developing granule cells (GCs) of the adult dentate gyrus undergo a critical period of enhanced activity and synaptic plasticity before becoming mature. The impact of developing GCs on the activity of preexisting dentate circuits remains unknown. Here we combine optogenetics, acute slice electrophysiology, and in vivo chemogenetics to activate GCs at different stages of maturation to study the recruitment of local target networks. We show that immature (4-week-old) GCs can efficiently drive distal CA3 targets but poorly activate proximal interneurons responsible for feedback inhibition (FBI). As new GCs transition toward maturity, they reliably recruit GABAergic feedback loops that restrict spiking of neighbor GCs, a mechanism that would promote sparse coding. Such inhibitory loop impinges only weakly in new cohorts of young GCs. A computational model reveals that the delayed coupling of new GCs to FBI could be crucial to achieve a fine-grain representation of novel inputs in the dentate gyrus.
Assuntos
Região CA3 Hipocampal/metabolismo , Giro Denteado/metabolismo , Retroalimentação Fisiológica/fisiologia , Interneurônios/metabolismo , Plasticidade Neuronal/fisiologia , Neurônios/metabolismo , Animais , Giro Denteado/citologia , Giro Denteado/crescimento & desenvolvimento , Neurônios GABAérgicos/metabolismo , Camundongos , Neurônios/citologia , Optogenética , Parvalbuminas/metabolismo , Técnicas de Patch-ClampRESUMO
The development of the nervous system is critically dependent on the production of functionally diverse neuronal cell types at their correct locations. In the embryonic neural tube, dorsoventral signaling has emerged as a fundamental mechanism for generating neuronal diversity. In contrast, far less is known about how different neuronal cell types are organized along the rostrocaudal axis. In the developing mouse and chick neural tube, hindbrain serotonergic neurons and spinal glutamatergic V3 interneurons are produced from ventral p3 progenitors, which possess a common transcriptional identity but are confined to distinct anterior-posterior territories. In this study, we show that the expression of the transcription factor Neurogenin3 (Neurog3) in the spinal cord controls the correct specification of p3-derived neurons. Gain- and loss-of-function manipulations in the chick and mouse embryo show that Neurog3 switches ventral progenitors from a serotonergic to V3 differentiation program by repressing Ascl1 in spinal p3 progenitors through a mechanism dependent on Hes proteins. In this way, Neurog3 establishes the posterior boundary of the serotonergic system by actively suppressing serotonergic specification in the spinal cord. These results explain how equivalent p3 progenitors within the hindbrain and the spinal cord produce functionally distinct neuron cell types.
Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/fisiologia , Diferenciação Celular , Proteínas do Tecido Nervoso/fisiologia , Rombencéfalo/citologia , Neurônios Serotoninérgicos/citologia , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/biossíntese , Embrião de Galinha , Regulação da Expressão Gênica no Desenvolvimento , Interneurônios/fisiologia , Camundongos , Proteínas do Tecido Nervoso/biossíntese , Proteínas Repressoras/biossíntese , Proteínas Repressoras/fisiologia , Rombencéfalo/metabolismo , Medula Espinal/metabolismo , Medula Espinal/fisiologia , Células-Tronco/metabolismo , Células-Tronco/fisiologiaRESUMO
Reciprocal activation of flexor and extensor muscles constitutes the fundamental mechanism that tetrapod vertebrates use for locomotion and limb-driven reflex behaviors. This aspect of motor coordination is controlled by inhibitory neurons in the spinal cord; however, the identity of the spinal interneurons that serve this function is not known. Here, we show that the production of an alternating flexor-extensor motor rhythm depends on the composite activities of two classes of ventrally located inhibitory neurons, V1 and V2b interneurons (INs). Abrogating V1 and V2b IN-derived neurotransmission in the isolated spinal cord results in a synchronous pattern of L2 flexor-related and L5 extensor-related locomotor activity. Mice lacking V1 and V2b inhibition are unable to articulate their limb joints and display marked deficits in limb-driven reflex movements. Taken together, these findings identify V1- and V2b-derived neurons as the core interneuronal components of the limb central pattern generator (CPG) that coordinate flexor-extensor motor activity.
Assuntos
Extremidades/fisiologia , Interneurônios/fisiologia , Locomoção/fisiologia , Atividade Motora/fisiologia , Inibição Neural/fisiologia , Reflexo/fisiologia , Potenciais de Ação/efeitos dos fármacos , Potenciais de Ação/genética , Potenciais de Ação/fisiologia , Animais , Animais Recém-Nascidos , Toxina da Cólera/metabolismo , Embrião de Mamíferos , Lateralidade Funcional/efeitos dos fármacos , Lateralidade Funcional/genética , Locomoção/efeitos dos fármacos , Locomoção/genética , Camundongos , Camundongos Transgênicos , Atividade Motora/efeitos dos fármacos , Atividade Motora/genética , Músculo Esquelético/citologia , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/fisiologia , Mutação/genética , Inibição Neural/efeitos dos fármacos , Inibição Neural/genética , Neurotransmissores/farmacologia , Reflexo/efeitos dos fármacos , Medula Espinal/citologia , Cauda/inervaçãoRESUMO
Our understanding of the neural control of locomotion has been greatly enhanced by the ability to identify and manipulate genetically defined populations of interneurons that comprise the locomotor central pattern generator (CPG). To date, the dI6 interneurons are one of the few populations that settle in the ventral region of the postnatal spinal cord that have not been investigated. In the present study, we utilized a novel transgenic mouse line to electrophysiologically characterize dI6 interneurons located close to the central canal and study their function during fictive locomotion. The majority of dI6 cells investigated were found to be rhythmically active during fictive locomotion and could be divided into two electrophysiologically distinct populations of interneurons. The first population fired rhythmic trains of action potentials that were loosely coupled to ventral root output and contained several intrinsic membrane properties of rhythm-generating neurons, raising the possibility that these cells may be involved in the generation of rhythmic activity in the locomotor CPG. The second population fired rhythmic trains of action potentials that were tightly coupled to ventral root output and lacked intrinsic oscillatory mechanisms, indicating that these neurons may be driven by a rhythm-generating network. Together these results indicate that dI6 neurons comprise an important component of the locomotor CPG that participate in multiple facets of motor behavior.
Assuntos
Interneurônios/fisiologia , Medula Espinal/fisiologia , Potenciais de Ação/fisiologia , Animais , Animais Recém-Nascidos , Feminino , Proteínas de Homeodomínio/genética , Locomoção/fisiologia , Masculino , Potenciais da Membrana/fisiologia , Camundongos , Camundongos Transgênicos , Técnicas de Patch-Clamp/métodos , Periodicidade , Proteínas/genética , RNA não Traduzido , Medula Espinal/citologia , Raízes Nervosas Espinhais/fisiologiaRESUMO
The LIM homeodomain transcription factor Islet1 (Isl1) is expressed in multiple organs and plays essential roles during embryogenesis. Isl1 is required for the survival and specification of spinal cord motor neurons. Due to early embryonic lethality and loss of motor neurons, the role of Isl1 in other aspects of motor neuron development remains unclear. In this study, we generated Isl1 mutant mouse lines expressing graded doses of Isl1. Our study has revealed essential roles of Isl1 in multiple aspects of motor neuron development, including motor neuron cell body localization, motor column formation and axon growth. In addition, Isl1 is required for survival of cranial ganglia neurons.
Assuntos
Desenvolvimento Embrionário/fisiologia , Proteínas de Homeodomínio/metabolismo , Neurônios Motores/metabolismo , Medula Espinal/metabolismo , Animais , Axônios/metabolismo , Proteínas de Homeodomínio/genética , Proteínas com Homeodomínio LIM , Camundongos , Camundongos Transgênicos , Medula Espinal/embriologia , Fatores de TranscriçãoRESUMO
The development of the amygdala, a central structure of the limbic system, remains poorly understood. We found that two spatially distinct and early-specified telencephalic progenitor pools marked by the homeodomain transcription factor Dbx1 are major sources of neuronal cell diversity in the mature mouse amygdala. We found that Dbx1-positive cells of the ventral pallium generate the excitatory neurons of the basolateral complex and cortical amygdala nuclei. Moreover, Dbx1-derived cells comprise a previously unknown migratory stream that emanates from the preoptic area (POA), a ventral telencephalic domain adjacent to the diencephalic border. The Dbx1-positive, POA-derived population migrated specifically to the amygdala and, as defined by both immunochemical and electrophysiological criteria, generated a unique subclass of inhibitory neurons in the medial amygdala nucleus. Thus, this POA-derived population represents a previously unknown progenitor pool dedicated to the limbic system.
Assuntos
Tonsila do Cerebelo/citologia , Tonsila do Cerebelo/embriologia , Proteínas de Homeodomínio/metabolismo , Neurônios/citologia , Nicho de Células-Tronco/citologia , Células-Tronco/citologia , Tonsila do Cerebelo/fisiologia , Animais , Movimento Celular/fisiologia , Feminino , Técnicas de Introdução de Genes , Proteínas de Homeodomínio/genética , Integrases/genética , Óperon Lac , Masculino , Potenciais da Membrana/fisiologia , Camundongos , Camundongos Mutantes , Camundongos Transgênicos , Inibição Neural/fisiologia , Técnicas de Patch-Clamp , Gravidez , Área Pré-Óptica/citologia , Área Pré-Óptica/embriologia , Área Pré-Óptica/fisiologia , Nicho de Células-Tronco/fisiologia , Células-Tronco/fisiologiaRESUMO
A robust and well-organized rhythm is a key feature of many neuronal networks, including those that regulate essential behaviors such as circadian rhythmogenesis, breathing, and locomotion. Here we show that excitatory V3-derived neurons are necessary for a robust and organized locomotor rhythm during walking. When V3-mediated neurotransmission is selectively blocked by the expression of the tetanus toxin light chain subunit (TeNT), the regularity and robustness of the locomotor rhythm is severely perturbed. A similar degeneration in the locomotor rhythm occurs when the excitability of V3-derived neurons is reduced acutely by ligand-induced activation of the allatostatin receptor. The V3-derived neurons additionally function to balance the locomotor output between both halves of the spinal cord, thereby ensuring a symmetrical pattern of locomotor activity during walking. We propose that the V3 neurons establish a regular and balanced motor rhythm by distributing excitatory drive between both halves of the spinal cord.
Assuntos
Interneurônios/fisiologia , Atividade Motora/fisiologia , Neurônios Motores/fisiologia , Equilíbrio Postural/fisiologia , Medula Espinal/fisiologia , Caminhada/fisiologia , Potenciais de Ação/genética , Potenciais de Ação/fisiologia , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Fatores de Transcrição Hélice-Alça-Hélice Básicos/fisiologia , Camundongos , Camundongos Transgênicos , Atividade Motora/genética , Rede Nervosa/fisiologia , Proteínas Repressoras/genética , Proteínas Repressoras/fisiologiaRESUMO
The neuronal networks that generate vertebrate movements such as walking and swimming are embedded in the spinal cord. These networks, which are referred to as central pattern generators (CPGs), are ideal systems for determining how ensembles of neurons generate simple behavioural outputs. In spite of efforts to address the organization of the locomotor CPG in walking animals, little is known about the identity and function of the spinal interneuron cell types that contribute to these locomotor networks. Here we use four complementary genetic approaches to directly address the function of mouse V1 neurons, a class of local circuit inhibitory interneurons that selectively express the transcription factor Engrailed1. Our results show that V1 neurons shape motor outputs during locomotion and are required for generating 'fast' motor bursting. These findings outline an important role for inhibition in regulating the frequency of the locomotor CPG rhythm, and also suggest that V1 neurons may have an evolutionarily conserved role in controlling the speed of vertebrate locomotor movements.
Assuntos
Locomoção/fisiologia , Neurônios Motores/fisiologia , Medula Espinal/citologia , Medula Espinal/fisiologia , Potenciais de Ação , Animais , Proteínas do Olho/genética , Deleção de Genes , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Interneurônios/fisiologia , Locomoção/genética , Camundongos , Fator de Transcrição PAX6 , Fatores de Transcrição Box Pareados/deficiência , Fatores de Transcrição Box Pareados/genética , Receptores de Neuropeptídeos/metabolismo , Proteínas Repressoras/genética , Fatores de Tempo , Transgenes/genética , Caminhada/fisiologiaRESUMO
The molecular programs that specify progenitors in the dorsal spinal cord remain poorly defined. The homeodomain transcription factor Gsh2 is expressed in the progenitors of three dorsal interneuron subtypes, dI3, dI4 and dI5 neurons, whereas Gsh1 is only expressed in dI4 and dI5 progenitors. Mice lacking Gsh2 exhibit a selective loss of dI3 interneurons that is accompanied by an expansion of the dI2 progenitor domain. In Gsh2 mutant embryos, expression of the proneural bHLH protein Mash1 is downregulated in dI3 neural progenitors, with Mash1 mutants exhibiting a concordant reduction in dI3 neurons. Conversely, overexpression of Gsh2 and Mash1 leads to the ectopic production of dI3 neurons and a concomitant repression of Ngn1 expression. Our results provide evidence that genetic interactions involving repression of Ngn1 by Gsh2 promote the differentiation of dI3 neurons from class A progenitors.
Assuntos
Diferenciação Celular/fisiologia , Regulação para Baixo/fisiologia , Proteínas de Homeodomínio/fisiologia , Interneurônios/citologia , Proteínas do Tecido Nervoso/metabolismo , Medula Espinal/embriologia , Fatores de Transcrição/metabolismo , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos , Diferenciação Celular/genética , Regulação da Expressão Gênica no Desenvolvimento/fisiologia , Inibidores do Crescimento/fisiologia , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Interneurônios/metabolismo , Camundongos , Proteínas do Tecido Nervoso/antagonistas & inibidores , Proteínas do Tecido Nervoso/biossíntese , Células-Tronco/citologia , Células-Tronco/fisiologia , Fatores de Transcrição/antagonistas & inibidores , Fatores de Transcrição/biossínteseRESUMO
Mammary gland morphogenesis and differentiation are mediated through the combined activities of systemic hormones and locally synthesized growth factors. Activin, a member of the transforming growth factor (TGF)-beta superfamily, is known to regulate the growth and differentiation of several cell types. In the present study, we investigated the role of activin in rat mammary gland on different stages of development. We found that activin A in vitro inhibits the proliferation of isolated acini, and this effect increases with the development of the gland. This factor also produces in vitro an inhibition of the final differentiation of acini obtained from 19th day pregnant rats. We also report the expression of activin receptors IIA and IIB mRNA in whole rat mammary gland and acini, with decreased levels of expression of type IIA (in both compartments) and IIB (in acini) during pregnancy and lactogenesis. In addition, we show that activin betaB-subunit mRNA decreases throughout pregnancy, and that the mRNA levels of follistatin (Fst) (its ligand protein) are high in cycling rats and at the beginning of pregnancy and diminish thereafter, having the acini higher levels of expression. Our data show that activin betaB-subunit, follistatin and ActRIIA and IIB transcripts are expressed in rat mammary gland at appropriate times and locations during development, allowing an interplay that might regulate activin action on growth and differentiation of the gland.
Assuntos
Ativinas/fisiologia , Folistatina/biossíntese , Subunidades beta de Inibinas/fisiologia , Glândulas Mamárias Animais/crescimento & desenvolvimento , Receptores de Ativinas/biossíntese , Receptores de Ativinas/genética , Ativinas/genética , Ativinas/farmacologia , Animais , Caseínas/biossíntese , Caseínas/genética , Diferenciação Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Feminino , Folistatina/genética , Folistatina/farmacologia , Regulação da Expressão Gênica , Subunidades beta de Inibinas/biossíntese , Subunidades beta de Inibinas/genética , Subunidades beta de Inibinas/farmacologia , Inibinas/biossíntese , Inibinas/genética , Lactação/fisiologia , Glândulas Mamárias Animais/efeitos dos fármacos , Glândulas Mamárias Animais/fisiologia , Gravidez , RNA Mensageiro/análise , RNA Mensageiro/metabolismo , Ratos , Ratos Sprague-Dawley , Fator de Crescimento Transformador beta/farmacologiaRESUMO
The sequential stepping of left and right limbs is a fundamental motor behavior that underlies walking movements. This relatively simple locomotor behavior is generated by the rhythmic activity of motor neurons under the control of spinal neural networks known as central pattern generators (CPGs) that comprise multiple interneuron cell types. Little, however, is known about the identity and contribution of defined interneuronal populations to mammalian locomotor behaviors. We show a discrete subset of commissural spinal interneurons, whose fate is controlled by the activity of the homeobox gene Dbx1, has a critical role in controlling the left-right alternation of motor neurons innervating hindlimb muscles. Dbx1 mutant mice lacking these ventral interneurons exhibit an increased incidence of cobursting between left and right flexor/extensor motor neurons during drug-induced locomotion. Together, these findings identify Dbx1-dependent interneurons as key components of the spinal locomotor circuits that control stepping movements in mammals.
Assuntos
Interneurônios/metabolismo , Atividade Motora/genética , Medula Espinal/metabolismo , Caminhada/fisiologia , Animais , Genes fos/genética , Genes fos/fisiologia , Proteínas de Homeodomínio/biossíntese , Proteínas de Homeodomínio/genética , Técnicas In Vitro , Camundongos , Camundongos Mutantes , Atividade Motora/fisiologia , Desempenho Psicomotor/fisiologiaRESUMO
We studied the expression of TGF-beta/T(beta)R system and its biological role in tumor development, in M3 and MM3 murine mammary adenocarcinomas with different metastasizing capability and in LM3 and LMM3 derived cell lines. All the studied cells secreted TGF-beta(s) and expressed T(beta)Rs. While the proliferation of the poorly metastatic M3 cells was significantly inhibited by 4 ng/ml TGF-beta(s), the highly metastatic MM3 cells were only slightly inhibited in response to the highest dose used. LM3 and LMM3 cells, highly invasive and metastatic, were totally refractory to TGF-beta antiproliferative effect. The role of TGF-beta in modulating key proteolytic cascades in tumor progression was also studied. TGF-beta(s) enhanced metalloproteinases production in all the studied cells while induced a stimulatory net effect on plasmin system activity only in the more metastatic cells. Our results in this murine mammary tumor lineage support the concept that dissociation of TGF-beta regulated growth control versus proteolytic enzyme pathways promotes tumor dissemination.
Assuntos
Adenocarcinoma/imunologia , Adenocarcinoma/fisiopatologia , Regulação Neoplásica da Expressão Gênica , Neoplasias Mamárias Animais/imunologia , Neoplasias Mamárias Animais/fisiopatologia , Metástase Neoplásica/fisiopatologia , Fator de Crescimento Transformador beta/farmacologia , Animais , Diferenciação Celular , Divisão Celular , Progressão da Doença , Metaloproteases/farmacologia , Camundongos , Células Tumorais CultivadasRESUMO
Tumour necrosis factor-alpha (TNF-alpha) has been proposed as an intraovarian modulator of granulosa cell function. The effect of TNF-alpha on DNA synthesis in cultured rat granulosa cells was examined. Tumour necrosis factor-alpha stimulated thymidine incorporation when added in the presence of transforming growth factor-beta (TGF-beta). In contrast, the co-mitogenic effect of follicle-stimulating hormone (FSH) and TGF-beta was inhibited in a dose-dependent manner by TNF-alpha. Inhibition of FSH-dependent DNA synthesis by TNF-alpha was also found when cultures were co-stimulated with activin A. The inhibitory action of TNF-alpha on FSH-treated cultures was not associated with changes in cell viability. The inhibitory effects of TNF-alpha could not be solely explained by a decrease in cAMP levels, since TNF-alpha was also able to inhibit the stimulation by dibutyryl-cAMP and TGF-beta on granulosa cell DNA synthesis. These results suggest that TNF-alpha regulation of granulosa cell growth is elicited either independently or downstream from gonadotrophin-induced cAMP production. The actions of TNF-alpha could be only partially mimicked by a cell-permeable analogue of ceramide, thus indicating that actions of this cytokine can not be fully ascribed to an activation of sphingomyelinase. Data presented here indicate that, in addition to its previously demonstrated inhibitory effects on gonadotrophin-induced cell differentiation, TNF-alpha may also exert a marked inhibition on hormonally stimulated immature granulosa cell proliferation. In contrast to this inhibitory action, this cytokine could amplify the mitogenic action of putative intraovarian growth regulators such as TGF-beta. These observations add further support to the notion that TNF-alpha plays a physiological role as a paracrine modulator of follicle development and may be also relevant to the alteration of ovarian function during physiopathological processes.