RESUMO
Sensory stimuli drive the maturation and function of the mammalian nervous system in part through the activation of gene expression networks that regulate synapse development and plasticity. These networks have primarily been studied in mice, and it is not known whether there are species- or clade-specific activity-regulated genes that control features of brain development and function. Here we use transcriptional profiling of human fetal brain cultures to identify an activity-dependent secreted factor, Osteocrin (OSTN), that is induced by membrane depolarization of human but not mouse neurons. We find that OSTN has been repurposed in primates through the evolutionary acquisition of DNA regulatory elements that bind the activity-regulated transcription factor MEF2. In addition, we demonstrate that OSTN is expressed in primate neocortex and restricts activity-dependent dendritic growth in human neurons. These findings suggest that, in response to sensory input, OSTN regulates features of neuronal structure and function that are unique to primates.
Assuntos
Evolução Molecular , Proteínas Musculares/metabolismo , Neocórtex/metabolismo , Neurônios/metabolismo , Fatores de Transcrição/metabolismo , Transcriptoma , Animais , Sequência de Bases , Osso e Ossos/metabolismo , Dendritos/metabolismo , Elementos Facilitadores Genéticos/genética , Feminino , Humanos , Fatores de Transcrição MEF2/metabolismo , Macaca mulatta , Masculino , Camundongos , Dados de Sequência Molecular , Proteínas Musculares/genética , Músculos/metabolismo , Neocórtex/citologia , Neurônios/citologia , Especificidade de Órgãos , Especificidade da Espécie , Fatores de Transcrição/genéticaRESUMO
Experience-dependent gene transcription is required for nervous system development and function. However, the DNA regulatory elements that control this program of gene expression are not well defined. Here we characterize the enhancers that function across the genome to mediate activity-dependent transcription in mouse cortical neurons. We find that the subset of enhancers enriched for monomethylation of histone H3 Lys4 (H3K4me1) and binding of the transcriptional coactivator CREBBP (also called CBP) that shows increased acetylation of histone H3 Lys27 (H3K27ac) after membrane depolarization of cortical neurons functions to regulate activity-dependent transcription. A subset of these enhancers appears to require binding of FOS, which was previously thought to bind primarily to promoters. These findings suggest that FOS functions at enhancers to control activity-dependent gene programs that are critical for nervous system function and provide a resource of functional cis-regulatory elements that may give insight into the genetic variants that contribute to brain development and disease.
Assuntos
Regulação da Expressão Gênica/genética , Neurônios/fisiologia , 2-Amino-5-fosfonovalerato/farmacologia , Animais , Proteína de Ligação a CREB/metabolismo , Embrião de Mamíferos , Antagonistas de Aminoácidos Excitatórios/farmacologia , Regulação da Expressão Gênica/efeitos dos fármacos , Estudo de Associação Genômica Ampla , Humanos , Histona Desmetilases com o Domínio Jumonji/metabolismo , Fatores de Transcrição MEF2/genética , Fatores de Transcrição MEF2/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Mutação/genética , Neurônios/efeitos dos fármacos , Proteínas Oncogênicas v-fos/metabolismo , Cloreto de Potássio/farmacologia , Bloqueadores dos Canais de Sódio/farmacologia , Tetrodotoxina/farmacologia , Fatores de Tempo , Córtex Visual/citologiaRESUMO
EphB receptor tyrosine kinases control multiple steps in nervous system development. However, it remains unclear whether EphBs regulate these different developmental processes directly or indirectly. In addition, given that EphBs signal through multiple mechanisms, it has been challenging to define which signaling functions of EphBs regulate particular developmental events. To address these issues, we engineered triple knock-in mice in which the kinase activity of three neuronally expressed EphBs can be rapidly, reversibly and specifically blocked. We found that the tyrosine kinase activity of EphBs was required for axon guidance in vivo. In contrast, EphB-mediated synaptogenesis occurred normally when the kinase activity of EphBs was inhibited, suggesting that EphBs mediate synapse development by an EphB tyrosine kinase-independent mechanism. Taken together, our data indicate that EphBs control axon guidance and synaptogenesis by distinct mechanisms and provide a new mouse model for dissecting EphB function in development and disease.