RESUMEN
We have previously shown that systemic injection of erythropoietin-producing hepatocellular receptor A7 (EPHA7)-Fc raises serum luteinizing hormone (LH) levels before ovulation in female rats, indicating the induction of EPHA7 in ovulation. In this study, we aimed to identify the mechanism and hypothalamus-pituitary-ovary (HPO) axis level underlying the promotion of LH secretion by EPHA7. Using an ovariectomized (OVX) rat model, in conjunction with low-dose 17ß-estradiol (E2) treatment, we investigated the association between EPHA7-ephrin (EFN)A5 signaling and E2 negative feedback. Various rat models (OVX, E2-treated OVX, and abarelix treated) were injected with the recombinant EPHA7-Fc protein through the caudal vein to investigate the molecular mechanism underlying the promotion of LH secretion by EPHA7. Efna5 was observed strongly expressed in the arcuate nucleus of the female rat by using RNAscope in situ hybridization. Our results indicated that E2, combined with estrogen receptor (ER)α, but not ERß, inhibited Efna5 and gonadotropin-releasing hormone 1 (Gnrh1) expressions in the hypothalamus. In addition, the systemic administration of EPHA7-Fc restrained the inhibition of Efna5 and Gnrh1 by E2, resulting in increased Efna5 and Gnrh1 expressions in the hypothalamus as well as increased serum LH levels. Collectively, our findings demonstrated the involvement of EPHA7-EFNA5 signaling in the regulation of LH and the E2 negative feedback pathway in the hypothalamus, highlighting the functional role of EPHA7 in female reproduction.
Asunto(s)
Efrina-A5/metabolismo , Receptor alfa de Estrógeno/metabolismo , Hormona Liberadora de Gonadotropina/metabolismo , Hipotálamo/metabolismo , Hormona Luteinizante/metabolismo , Precursores de Proteínas/metabolismo , Animales , Núcleo Arqueado del Hipotálamo/efectos de los fármacos , Núcleo Arqueado del Hipotálamo/metabolismo , Efrina-A5/efectos de los fármacos , Efrina-A5/genética , Estradiol/farmacología , Receptor beta de Estrógeno/metabolismo , Estrógenos/farmacología , Retroalimentación Fisiológica/efectos de los fármacos , Retroalimentación Fisiológica/fisiología , Femenino , Hormona Liberadora de Gonadotropina/efectos de los fármacos , Antagonistas de Hormonas/farmacología , Sistema Hipotálamo-Hipofisario/efectos de los fármacos , Sistema Hipotálamo-Hipofisario/metabolismo , Hipotálamo/efectos de los fármacos , Hormona Luteinizante/efectos de los fármacos , Oligopéptidos/farmacología , Ovariectomía , Ovario/efectos de los fármacos , Ovario/metabolismo , Precursores de Proteínas/efectos de los fármacos , Ratas , Receptor EphA7/genética , Receptor EphA7/metabolismo , Receptor EphA7/farmacología , Proteínas RecombinantesRESUMEN
Cortical neurons must be specified and make the correct connections during development. Here, we examine a mechanism initiating neuronal circuit formation in the barrel cortex, a circuit comprising thalamocortical axons (TCAs) and layer 4 (L4) neurons. When Lhx2 is selectively deleted in postmitotic cortical neurons using conditional knockout (cKO) mice, L4 neurons in the barrel cortex are initially specified but fail to form cellular barrels or develop polarized dendrites. In Lhx2 cKO mice, TCAs from the thalamic ventral posterior nucleus reach the barrel cortex but fail to further arborize to form barrels. Several activity-regulated genes and genes involved in regulating barrel formation are downregulated in the Lhx2 cKO somatosensory cortex. Among them, Btbd3, an activity-regulated gene controlling dendritic development, is a direct downstream target of Lhx2. We find that Lhx2 confers neuronal competency for activity-dependent dendritic development in L4 neurons by inducing the expression of Btbd3.
Asunto(s)
Expresión Génica , Proteínas con Homeodominio LIM/metabolismo , Neuronas/metabolismo , Corteza Somatosensorial/fisiología , Factores de Transcripción/metabolismo , Proteínas Adaptadoras Transductoras de Señales/genética , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Adenilil Ciclasas/genética , Adenilil Ciclasas/metabolismo , Animales , Línea Celular Tumoral , Inmunoprecipitación de Cromatina , Efrina-A5/genética , Efrina-A5/metabolismo , Potenciales Evocados , Hibridación in Situ , Proteínas con Dominio LIM/genética , Proteínas con Dominio LIM/metabolismo , Proteínas con Homeodominio LIM/genética , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Proteínas del Tejido Nervioso/genética , Proteínas del Tejido Nervioso/metabolismo , Neuronas/patología , Miembro 2 del Grupo F de la Subfamilia 1 de Receptores Nucleares/genética , Miembro 2 del Grupo F de la Subfamilia 1 de Receptores Nucleares/metabolismo , Técnicas de Placa-Clamp , Regiones Promotoras Genéticas , Tálamo/metabolismo , Factores de Transcripción/genéticaRESUMEN
Functional sensory and motor areas in the developing mammalian neocortex are formed through a complex interaction of cortically intrinsic mechanisms, such as gene expression, and cortically extrinsic mechanisms such as those mediated by thalamic input from the senses. Both intrinsic and extrinsic mechanisms are believed to be involved in cortical patterning and the establishment of areal boundaries in early development; however, the nature of the interaction between intrinsic and extrinsic processes is not well understood. In a previous study, we used a perinatal bilateral enucleation mouse model to test some aspects of this interaction by reweighting sensory input to the developing cortex. Visual deprivation at birth resulted in a shift of intraneocortical connections (INCs) that aligned with ectopic ephrin A5 expression in the same location ten days later at postnatal day (P) 10. A prevailing question remained: Does visual deprivation first induce a change in gene expression, followed by a shift in INCs, or vice versa? In the present study, we address this question by investigating the neuroanatomy and patterns of gene expression in post-natal day (P) 1 and 4 mice following bilateral enucleation at birth. Our results demonstrate a rapid reduction in dorsal lateral geniculate nucleus (dLGN) size and ephrin A5 gene expression 24-hours post-enucleation, with more profound effects apparent at P4. The reduced nuclear size and diminished gene expression mirrors subtle changes in ephrin A5 expression evident in P1 and P4 enucleated neocortex, 11 and 8 days prior to natural eye opening, respectively. Somatosensory and visual INCs were indistinguishable between P1 and P4 mice bilaterally enucleated at birth, indicating that perinatal bilateral enucleation initiates a rapid change in gene expression (within one day) followed by an alteration of sensory INCs later on (second postnatal week). With these results, we gain a deeper understanding of how gene expression and sensory input together regulate cortical arealization and plasticity during early development.
Asunto(s)
Desarrollo Embrionario/genética , Efrina-A5/genética , Neocórtex/metabolismo , Tálamo/metabolismo , Animales , Embrión de Mamíferos , Efrina-A5/biosíntesis , Enucleación del Ojo , Femenino , Regulación del Desarrollo de la Expresión Génica , Cuerpos Geniculados/metabolismo , Ratones , Neocórtex/crecimiento & desarrollo , Embarazo , Corteza Somatosensorial/crecimiento & desarrollo , Corteza Somatosensorial/metabolismo , Tálamo/crecimiento & desarrollo , Visión Ocular/fisiología , Corteza Visual/metabolismo , Corteza Visual/fisiologíaRESUMEN
Many factors influence neurodevelopment. However, their contribution to adult neural function is often unclear. This is often due to complex expression profiles, cell signalling, neuroanatomy, and a lack of effective tests to assess the function of neural circuits in vivo. Ephrin-A2 and ephrin-A5 are cell surface proteins implicated in multiple aspects of neurodevelopment. While the role of ephrin-As in visual, auditory and learning behaviours has been explored, little is known about their role in dopaminergic and neuromotor pathways, despite expression in associated brain regions. Here we probe the function of ephrin-A2 and ephrin-A5 in the development of the dopaminergic and neuromotor pathways using counts of tyrosine hydroxylase (TH) positive cells in the substantia nigra pars compacta (SNpc) and the ventral tegmental area (VTA), the acoustic startle reflex (ASR), and a measure of sensorimotor gating, prepulse inhibition (PPI). Analysis of the ASR and PPI in ephrin-A2 and/or ephrin-A5 knock-out mice revealed that both genes play distinct roles in mediating ASR circuits, but are unlikely to play a role in PPI. Knock-out of either gene resulted in robust changes in startle response magnitude and measures of startle onset and peak latencies. However, ephrin-A2 and ephrin-A5 regulate aspects of the ASR differently: ephrin-A2 KO mice have increased startle amplitude, increased sensitivity and reduced latency to startle, whilst ephrin-A5 KO mice show opposite effects. Neither of the gene knock outs affected PPI, despite ephrin-A5 KO mice showing changes in dopamine cell numbers in nuclei thought to regulate PPI. We propose that majority of the changes observed ephrin-A2 and ephrin-A5 KO mice appear to be mediated by the effects on motor neurons and their muscle targets, rather than changes in auditory sensitivity.
Asunto(s)
Efrina-A2/deficiencia , Efrina-A5/deficiencia , Inhibición Neural/genética , Filtrado Sensorial/genética , Estimulación Acústica , Análisis de Varianza , Animales , Efrina-A2/genética , Efrina-A5/genética , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Porción Compacta de la Sustancia Negra/metabolismo , Tiempo de Reacción/genética , Reflejo de Sobresalto/genética , Tirosina 3-Monooxigenasa/metabolismo , Área Tegmental Ventral/metabolismoRESUMEN
How guidance cues are integrated during the formation of complex axonal tracts remains largely unknown. Thalamocortical axons (TCAs), which convey sensory and motor information to the neocortex, have a rostrocaudal topographic organization initially established within the ventral telencephalon [1-3]. Here, we show that this topography is set in a small hub, the corridor, which contains matching rostrocaudal gradients of Slit1 and Netrin 1. Using in vitro and in vivo experiments, we show that Slit1 is a rostral repellent that positions intermediate axons. For rostral axons, although Slit1 is also repulsive and Netrin 1 has no chemotactic activity, the two factors combined generate attraction. These results show that Slit1 has a dual context-dependent role in TCA pathfinding and furthermore reveal that a combination of cues produces an emergent activity that neither of them has alone. Our study thus provides a novel framework to explain how a limited set of guidance cues can generate a vast diversity of axonal responses necessary for proper wiring of the nervous system.
Asunto(s)
Axones/fisiología , Conos de Crecimiento/fisiología , Factores de Crecimiento Nervioso/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Tálamo/embriología , Tálamo/fisiología , Proteínas Supresoras de Tumor/metabolismo , Animales , Células COS , Corteza Cerebral/embriología , Corteza Cerebral/metabolismo , Chlorocebus aethiops , Efrina-A5/genética , Efrina-A5/metabolismo , Regulación del Desarrollo de la Expresión Génica , Ratones , Ratones Transgénicos , Factores de Crecimiento Nervioso/genética , Proteínas del Tejido Nervioso/genética , Netrina-1 , Receptores Inmunológicos/genética , Receptores Inmunológicos/metabolismo , Semaforina-3A/genética , Semaforina-3A/metabolismo , Proteínas Supresoras de Tumor/genética , beta-Galactosidasa/genética , beta-Galactosidasa/metabolismo , Proteínas RoundaboutRESUMEN
OBJECTIVE: To observe the effect of electro-acupuncture (EA) on dendritic spine and ephrin-A5 and to investigate the action of EA on neural plasticity after acute cerebral ischemic infarction. METHODS: Focal acute cerebral ischemia model was established by middle cerebral artery occlusion (MCAO) with electrocoagulation contralateral method. Ninety male Sprague-Dawley rats were randomly divided into sham operation (SO) group, MCAO group and EA treatment (ET) group. Golgi dying, double immunofluorescence method and RT-PCR were used to detect dendritic spine density, expression patterns of ephrin-A5 and the effect of EA on them at the end of the first, second and fourth week after ischemia. RESULTS: The dendritic spine density in MCAO group significantly decreased after ischemia (p<0.01). The dendritic spine density was raised in ET group in the corresponding time period (p<0.01) and among the ET groups. It was higher at the end of the fourth week than before (p<0.05). The signal of ephrin-A5 was detected mainly in neuron cytoplasm, and the mRNA expression in MCAO group and ET group increased compared to that in SO group (p<0.01). The mRNA expression in ET group at the first week was much higher than that in MCAO group (p<0.01). In ET groups, the mRNA expression of ephrin-A5 was down-regulated along with the time going (p<0.01). CONCLUSION: It is possibly the regulation of the ephrin-A5 expression by which EA treatment improves the neural plasticity at the peri-infarct cerebral cortex in acute cerebral ischemia rat. There may be a time window in EA treatment for acute cerebral ischemia.
Asunto(s)
Isquemia Encefálica/complicaciones , Electroacupuntura/métodos , Infarto de la Arteria Cerebral Media/terapia , Plasticidad Neuronal/fisiología , Enfermedad Aguda , Animales , Espinas Dendríticas/metabolismo , Espinas Dendríticas/patología , Modelos Animales de Enfermedad , Efrina-A5/genética , Efrina-A5/metabolismo , Técnica del Anticuerpo Fluorescente , Infarto de la Arteria Cerebral Media/etiología , Infarto de la Arteria Cerebral Media/fisiopatología , Masculino , ARN Mensajero/genética , ARN Mensajero/metabolismo , Distribución Aleatoria , Ratas , Ratas Sprague-Dawley , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Factores de Tiempo , Resultado del TratamientoRESUMEN
Ephrins-A5 are expressed in the cortical target layer of thalamic afferents at the time when these axons form terminal arbors. Previous in-vitro studies provided evidence that ephrin-A5 supports the branching of thalamic axons, but there is no direct in-vivo evidence for such a growth-promoting effect. Here we examined thalamocortical projections in ephrins-A5 deficient mice. Our results demonstrate that the laminar specificity of thalamic afferents in ephrin-A5 mutants remains preserved, but axonal arbor formation is greatly reduced. Thus, ephrin-A5 specifically regulates branch formation of thalamic axons, but does not affect target layer selection. Ephrin-A5-mutant mice are, therefore, a unique model to study the effects of reduced thalamic innervation on the assembly of cortical circuits and sensory processing.
Asunto(s)
Corteza Cerebral/citología , Corteza Cerebral/embriología , Efrina-A5/fisiología , Tálamo/citología , Tálamo/embriología , Vías Aferentes , Animales , Animales Recién Nacidos , Axones/fisiología , Forma de la Célula , Corteza Cerebral/fisiología , Efrina-A5/genética , Femenino , Regulación del Desarrollo de la Expresión Génica/fisiología , Ratones , Ratones Noqueados , Técnicas de Cultivo de Órganos , Embarazo , Tálamo/fisiologíaRESUMEN
The mechanisms generating precise connections between specific thalamic nuclei and cortical areas remain poorly understood. Using axon tracing analysis of ephrin/Eph mutant mice, we provide in vivo evidence that Eph receptors in the thalamus and ephrins in the cortex control intra-areal topographic mapping of thalamocortical (TC) axons. In addition, we show that the same ephrin/Eph genes unexpectedly control the inter-areal specificity of TC projections through the early topographic sorting of TC axons in an intermediate target, the ventral telencephalon. Our results constitute the first identification of guidance cues involved in inter-areal specificity of TC projections and demonstrate that the same set of mapping labels is used differentially for the generation of topographic specificity of TC projections between and within individual cortical areas.
Asunto(s)
Corteza Cerebral/metabolismo , Efrina-A4/genética , Efrina-A5/genética , Receptor EphA4/genética , Receptor EphA5/genética , Tálamo/metabolismo , Animales , Mapeo Encefálico/métodos , Corteza Cerebral/embriología , Corteza Cerebral/enzimología , Efrina-A4/biosíntesis , Efrina-A4/fisiología , Efrina-A5/biosíntesis , Efrina-A5/fisiología , Femenino , Ligandos , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Vías Nerviosas/embriología , Vías Nerviosas/enzimología , Vías Nerviosas/metabolismo , Vías Nerviosas/fisiología , Receptor EphA4/biosíntesis , Receptor EphA4/fisiología , Receptor EphA5/biosíntesis , Receptor EphA5/fisiología , Tálamo/embriología , Tálamo/enzimologíaRESUMEN
Axon guidance cues of the ephrin ligand family have been hypothesized to regulate the formation of thalamocortical connections, but in vivo evidence for such a role has not been examined directly. To test whether ephrin-mediated repulsive cues participate in sorting the projections originating from distinct thalamic nuclei, we analyzed the organization of somatosensory and anterior cingulate afferents postnatally in mice lacking ephrin-A5 gene expression. Projections from ventrobasal and laterodorsal nuclei to their respective sensory and limbic cortical areas developed normally. However, a portion of limbic thalamic neurons from the laterodorsal nucleus also formed additional projections to somatosensory cortical territories, thus maintaining inappropriate dual projections to multiple cortical regions. These results suggest that ephrin-A5 is not required for the formation of normal cortical projections from the appropriate thalamic nuclei, but rather acts as a guidance cue that restricts limbic thalamic axons from inappropriate neocortical regions.