Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-05-31T20:52:30Z No. of bitstreams: 1 BrunaSoaresLandeira_TESE.pdf: 8601965 bytes, checksum: a68be4513e6834f5aaf48800f8ea90d7 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-06-01T22:19:30Z (GMT) No. of bitstreams: 1 BrunaSoaresLandeira_TESE.pdf: 8601965 bytes, checksum: a68be4513e6834f5aaf48800f8ea90d7 (MD5) / Made available in DSpace on 2017-06-01T22:19:30Z (GMT). No. of bitstreams: 1 BrunaSoaresLandeira_TESE.pdf: 8601965 bytes, checksum: a68be4513e6834f5aaf48800f8ea90d7 (MD5) Previous issue date: 2017-04-11 / O c?rtex cerebral de mam?feros ? histologicamente organizado em diferentes camadas de neur?nios excitat?rios que possuem diversos padr?es de conex?o com alvos corticais e subcorticais. Durante o desenvolvimento, essas camadas corticais se estabelecem sequencialmente atrav?s de uma intrincada combina??o de especifica??o neuronal e migra??o em um padr?o radial conhecida como ?de dentro para fora?: neur?nios infragranulares s?o gerados primeiro do que os neur?nios granulares e supragranulares. Nas ?ltimas d?cadas, diversos genes codificando fatores de transcri??o envolvidos na especifica??o de neur?nios destinados a diferentes camadas corticais foram identificados. Todavia, a influ?ncia dos neur?nios infragranulares sobre a especifica??o das coortes neuronais subsequentes permanece pouco entendida. Para investigar os poss?veis efeitos da abla??o de neur?nios infragranulares sobre a especifica??o de neur?nios supragranulares, n?s induzimos a morte seletiva de neur?nios corticais das camadas V e VI antes da gera??o dos neur?nios destinados ?s camadas II-IV. Nossos dados revelam que um dia ap?s a abla??o, progenitores continuaram a gerar neur?nios destinados a camada VI que expressam o fator de transcri??o TBR1, enquanto praticamente nenhum neur?nio expressando TBR1 foi gerado na mesma etapa do desenvolvimento em controles com a mesma idade. Curiosamente, alguns neur?nios TBR1-positivos gerados ap?s a abla??o de neur?nios infragranulares se estabeleceram em camadas corticais superficiais, como esperado para neur?nios supragranulares gerados neste est?gio, sugerindo que a migra??o de neur?nios corticais pode ser controlada independentemente da sua especifica??o molecular. Al?m disso, n?s observamos um aumento em neur?nios de camada V que expressam CTIP2 e neur?nios calosos que expressam SATB2 ? custa da diminui??o neur?nios de camada IV em animais P0. Quando estes animais se tornam adultos jovens (P30) o aumento de neur?nios SATB2 e CTIP2 n?o existe mais, todavia encontramos esses neur?nios distribu?dos de forma diferente na ?rea somatossensorial dos animais que sofreram abla??o. Experimentos in vitro revelaram que a organiza??o citoarquitet?nica laminar do c?rtex ? necess?ria para gerar novamente os neur?nios TBR1+ que foram eliminados anteriormente. Al?m disso, experimentos in vitro indicam que em condi??o de baixa densidade celular os neur?nios tem seu fen?tipo alterado, expressando v?rios fatores de transcri??o ao mesmo tempo. Em conjunto, nossos dados indicam a exist?ncia de um mecanismo regulat?rio entre neur?nios infragranulares e progenitores envolvidos na gera??o de neur?nios supragranulares e/ou entre neur?nios infragranulares e neur?nios p?s-mit?ticos gerados em seguida. Este mecanismo poderia ajudar a controlar o n?mero de neur?nios em diferentes camadas e contribuir para o estabelecimento de diferentes ?reas corticais. / The cerebral cortex of mammals is histologically organized into in different layers of excitatory neurons that have distinct patterns of connections with cortical or subcortical targets. During development, these cortical layers are sequentially established through an intricate combination of neuronal specification and migration in a radial pattern known as "inside-out": deep-layer neurons are generated prior to upper-layer neurons. In the last few decades, several genes encoding transcription factors involved in the specification of neurons destined to different cortical layers have been identified. However, the influence of early-generated neurons in to the specification of subsequent neuronal cohorts remains unclear. To investigate the possible effects early born neurons ablation on the specification of late born neurons, we induced the selective death of cortical neurons from layers V and VI neurons before the generation of neurons destined to layers II, III and IV. Our data shows that oneday after ablation, progenitors resumed generation of layer VI neurons expressing the transcription factor TBR1, whereas virtually no TBR1-expressing neuron was generated at the same developmental stage in age-matched controls. Interestingly, many TBR1-positive neurons generated after deep-layer ablation settled within superficial cortical layers, as expected for upper-layer neurons generated at that stage, suggesting that migration post-mitotic neurons is independent of fate-specification. Furthermore, we observed an increase in layer V neurons expressing CTIP2 and cortico-cortical neurons expressing SATB2 at the expense of layer IV neurons in P0 animals. When these animals became young adults (P30) the increase os SATB2 and CTIP2 neurons is no longer observed, however these neurons are distributed in a different way in somatosensory areas from ablated animals. In vitro experiments show that the laminar cytoarchitectural organization of the cortex is necessary to regenerate the previously deleted TBR1 + neurons. In addition, in vitro experiments indicate that in a condition of low cell density the neurons phnotype is altered, they express several transcription factors at the same time. Together, our data indicate the existence of feedback mechanism either from early-generated neurons to progenitors involved in the generation of upper-layer neurons or from deep-layer neurons to postmitotic neurons generated subsequently. This mechanism could help to control the number of neurons in different layers and contribute to the establishment of different cortical areas.