RESUMO
The RAS-stimulated RAF-MEK-ERK pathway confers epithelial cells with critical motile and invasive capacities during development, tissue regeneration, and carcinoma progression, often via promoting the epithelial-mesenchymal transition (EMT). Many mechanisms by which ERK exerts this control remain elusive. We demonstrate that the ERK-activated kinase RSK is necessary to induce mesenchymal motility and invasive capacities in nontransformed epithelial and carcinoma cells. RSK is sufficient to induce certain motile responses. Expression profiling analysis revealed that a primary role of RSK is to induce transcription of a potent promotile/invasive gene program by FRA1-dependent and -independent mechanisms. The program enables RSK to coordinately modulate the extracellular environment, the intracellular motility apparatus, and receptors mediating communication between these compartments to stimulate motility and invasion. These findings uncover a mechanism whereby the RAS-ERK pathway controls epithelial cell motility by identifying RSK as a key effector, from which emanate multiple highly coordinate transcription-dependent mechanisms for stimulation of motility and invasive properties.
Assuntos
Carcinoma/enzimologia , Movimento Celular , Transdiferenciação Celular , Transformação Celular Neoplásica/metabolismo , Células Epiteliais/enzimologia , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Proteínas Quinases S6 Ribossômicas 90-kDa/metabolismo , Proteínas ras/metabolismo , Animais , Carcinoma/genética , Carcinoma/patologia , Linhagem Celular , Movimento Celular/genética , Transdiferenciação Celular/genética , Transformação Celular Neoplásica/genética , Transformação Celular Neoplásica/patologia , Cães , Células Epiteliais/patologia , Perfilação da Expressão Gênica , Regulação Neoplásica da Expressão Gênica , Genótipo , Humanos , Mesoderma/enzimologia , Mesoderma/patologia , Invasividade Neoplásica , Fenótipo , Proteínas Proto-Oncogênicas c-fos/genética , Proteínas Proto-Oncogênicas c-fos/metabolismo , Transdução de Sinais , Fatores de Tempo , Transcrição Gênica , Transdução GenéticaRESUMO
Hippocampal pyramidal neurons are important for encoding and retrieval of spatial maps and episodic memories. While previous work has shown that Zbtb20 is a cell fate determinant for CA1 pyramidal neurons, the regulatory mechanisms governing this process are not known. In this study, we demonstrate that Zbtb20 binds to genes that control neuronal subtype specification in the developing isocortex, including Cux1, Cux2, Fezf2, Foxp2, Mef2c, Rorb, Satb2, Sox5, Tbr1, Tle4, and Zfpm2. We show that Zbtb20 represses these genes during ectopic CA1 pyramidal neuron development in transgenic mice. These data reveal a novel regulatory mechanism by which Zbtb20 suppresses the acquisition of an isocortical fate during archicortical neurogenesis to ensure commitment to a CA1 pyramidal neuron fate. We further show that the expression pattern of Zbtb20 is evolutionary conserved in the fetal human hippocampus, where it is complementary to the expression pattern of the Zbtb20 target gene Tbr1. Therefore, the disclosed Zbtb20-mediated transcriptional repressor mechanism may be involved in development of the human archicortex.
Assuntos
Regulação da Expressão Gênica no Desenvolvimento/genética , Hipocampo/citologia , Hipocampo/crescimento & desenvolvimento , Rede Nervosa/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Células Piramidais/fisiologia , Fatores de Transcrição/metabolismo , Animais , Animais Recém-Nascidos , Imunoprecipitação da Cromatina , Feto , Perfilação da Expressão Gênica , Humanos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Proteínas do Tecido Nervoso/genética , Análise de Sequência com Séries de Oligonucleotídeos , Fatores de Transcrição/genéticaRESUMO
BACKGROUND: Recently, a number of patients have been described with structural rearrangements at 3q13.31, delineating a novel microdeletion syndrome with common clinical features including developmental delay and other neurodevelopmental disorders (NDD). A smallest region of overlapping deletions (SRO) involved five RefSeq genes, including the transcription factor gene ZBTB20 and the dopamine receptor gene DRD3, considered as candidate genes for the syndrome. METHODS AND RESULTS: We used array comparative genomic hybridization and next-generation mate-pair sequencing to identify key structural rearrangements involving ZBTB20 in two patients with NDD. In a patient with developmental delay, attention-deficit hyperactivity disorder, psychosis, Tourette's syndrome and autistic traits, a de novo balanced t(3;18) translocation truncated ZBTB20. The other breakpoint did not disrupt any gene. In a second patient with developmental delay and autism, we detected the first microdeletion at 3q13.31, which truncated ZBTB20 but did not involve DRD3 or the other genes within the previously defined SRO. Zbtb20 directly represses 346 genes in the developing murine brain. Of the 342 human orthologous ZBTB20 candidate target genes, we found 68 associated with NDD. Using chromatin immunoprecipitation and quantitative PCR, we validated the in vivo binding of Zbtb20 in evolutionary conserved regions in six of these genes (Cntn4, Gad1, Nrxn1, Nrxn3, Scn2a, Snap25). CONCLUSIONS: Our study links dosage imbalance of ZBTB20 to a range of neurodevelopmental, cognitive and psychiatric disorders, likely mediated by dysregulation of multiple ZBTB20 target genes, and provides new knowledge on the genetic background of the NDD seen in the 3q13.31 microdeletion syndrome.
Assuntos
Deleção Cromossômica , Cromossomos Humanos Par 3/genética , Deficiências do Desenvolvimento/genética , Deficiências do Desenvolvimento/patologia , Dosagem de Genes/genética , Proteínas do Tecido Nervoso/genética , Fatores de Transcrição/genética , Imunoprecipitação da Cromatina , Hibridização Genômica Comparativa , Humanos , Proteínas do Tecido Nervoso/metabolismo , Análise de Sequência de DNA/métodos , Estatísticas não Paramétricas , Fatores de Transcrição/metabolismoRESUMO
Expression of the transcriptional repressor Zbtb20 is confined to the hippocampal primordium of the developing dorsal midline cortex in mice. Here, we show that misexpression of Zbtb20 converts projection neurons of the subiculum and postsubiculum (dorsal presubiculum) to CA1 pyramidal neurons that are innervated by Schaffer collateral projections in ectopic strata oriens and radiatum. The Zbtb20-transformed neurons express Bcl11B, Satb2, and Calbindin-D28k, which are markers of adult CA1 pyramidal neurons. Downregulation of Zbtb20 expression by RNA interference impairs the normal maturation of CA1 pyramidal neurons resulting in deficiencies in Calbindin-D28k expression and in reduced apical dendritic arborizations in stratum lacunosum moleculare. Overall, the results show that Zbtb20 is required for various aspects of CA1 pyramidal neuron development such as the postnatal extension of apical dendritic arbors in the distal target zone and the subtype differentiation of Calbindin-D28k-positive subsets. They further suggest that Zbtb20 plays a role in arealization of the midline cortex.
Assuntos
Região CA1 Hipocampal/crescimento & desenvolvimento , Córtex Cerebral/crescimento & desenvolvimento , Regulação da Expressão Gênica no Desenvolvimento/genética , Neurogênese/genética , Células Piramidais/metabolismo , Fatores de Transcrição/fisiologia , Animais , Biomarcadores/metabolismo , Região CA1 Hipocampal/patologia , Calbindina 1 , Calbindinas , Diferenciação Celular/genética , Forma Celular/genética , Córtex Cerebral/patologia , Dendritos/metabolismo , Dendritos/patologia , Regulação para Baixo/genética , Hipertrofia , Camundongos , Células Piramidais/patologia , Proteína G de Ligação ao Cálcio S100/metabolismo , Fatores de Transcrição/deficiência , Fatores de Transcrição/genética , Dedos de Zinco/genéticaRESUMO
Family and twin studies have shown a genetic component to seasonal affective disorder (SAD). A number of candidate gene studies have examined the role of variations within biologically relevant genes in SAD susceptibility, but few genome-wide association studies (GWAS) have been performed to date. The authors aimed to identify genetic risk variants for SAD through GWAS. The authors performed a GWAS for SAD in 1380 cases and 2937 controls of European-American (EA) origin, selected from samples for GWAS of major depressive disorder and of bipolar disorder. Further bioinformatic analyses were conducted to examine additional genomic and biological evidence associated with the top GWAS signals. No susceptibility loci for SAD were identified at a genome-wide significant level. The strongest association was at an intronic variant (rs139459337) within ZBTB20 (odds ratio (OR) = 1.63, p = 8.4 × 10-7), which encodes a transcriptional repressor that has roles in neurogenesis and in adult brain. Expression quantitative trait loci (eQTL) analysis showed that the risk allele "T" of rs139459337 is associated with reduced mRNA expression of ZBTB20 in human temporal cortex (p = 0.028). Zbtb20 is required for normal murine circadian rhythm and for entrainment to a shortened day. Of the 330 human orthologs of murine genes directly repressed by Zbtb20, there were 32 associated with SAD in our sample (at p < 0.05), representing a significant enrichment of ZBTB20 targets among our SAD genetic association signals (fold = 1.93, p = 0.001). ZBTB20 is a candidate susceptibility gene for SAD, based on a convergence of genetic, genomic, and biological evidence. Further studies are necessary to confirm its role in SAD.
Assuntos
Estudo de Associação Genômica Ampla , Proteínas do Tecido Nervoso/genética , Transtorno Afetivo Sazonal/genética , Fatores de Transcrição/genética , População Branca/genética , Alelos , Transtorno Bipolar/genética , Estudos de Casos e Controles , Transtorno Depressivo Maior/genética , Feminino , Predisposição Genética para Doença , Humanos , Modelos Logísticos , Masculino , Polimorfismo de Nucleotídeo Único , Locos de Características Quantitativas , Estados UnidosRESUMO
Transgenic mice, expressing fluorescent proteins in neurons and glia, provide new opportunities for real-time microscopic monitoring of degenerative and regenerative structural changes. We have previously validated and compared a number of quantifiable markers for neuronal damage and cell death in organotypic brain slice cultures, such as cellular uptake of propidium iodide (PI), loss of microtubule-associated protein 2 (MAP2), Fluoro-Jade (FJ) cell staining, and the release of cytosolic lactate dehydrogenase (LDH). An important supplement to these markers would be data on corresponding morphological changes, as well as the opportunity to monitor reversible changes or long-term effects in the event of minor damage. As a first step, we present: a) the developmental expression in organotypic hippocampal brain slice cultures of transgenic fluorescent proteins, useful for the visualisation of neuronal subpopulations and astroglial cells; and b) examples of excitotoxic, glutamate receptor-induced degeneration of hippocampal CA1 pyramidal cells, with corresponding astroglial reactivity in such cultures. The slice cultures were set up according to standard techniques, by using one-week old pups from four transgenic mouse strains which express fluorescent proteins in their neurons and/or astroglial cells. From the time of explantation, and subsequently for up to nine weeks in culture, the transgenic neuronal fluorescence displayed the expected characteristics of a developmental, in vivo-like increase, including both the number and localisation of cells, as well as the intensity of fluorescence. At that stage and later, the transgenic fluorescence clearly permitted the visualisation of cell bodies, larger and smaller dendritic branches, spines and axons. In separate experiments, with a 24-hour exposure of matured sliced cultures to 100 microM of the glutamate agonist, N-methyl-D-aspartate (NMDA), we observed, by time-lapse recording, a gradual, but rapid loss of fluorescent CA1 pyramidal cells, accompanied by astrogliosis of transgene fluorescent astroglial cells. Based on these results, we consider that organotypic brain slice cultures from transgenic mice, with fluorescent neurons and glia, combined with detailed visualisation by time-lapse fluorescence microscopy, have great potential for investigating both major irreversible and minor reversible structural changes in neurons and glia, induced by neurotoxins and other neurodegenerative compounds and conditions.
Assuntos
Antagonistas de Aminoácidos Excitatórios/farmacologia , Proteínas de Fluorescência Verde/metabolismo , Hipocampo/metabolismo , N-Metilaspartato/farmacologia , Degeneração Neural/metabolismo , Técnicas de Cultura de Tecidos/métodos , Animais , Animais Recém-Nascidos , Astrócitos/efeitos dos fármacos , Astrócitos/metabolismo , Astrócitos/patologia , Biomarcadores/metabolismo , Células Cultivadas , Hipocampo/efeitos dos fármacos , Hipocampo/crescimento & desenvolvimento , Camundongos , Camundongos Transgênicos , Microscopia de Fluorescência , Degeneração Neural/induzido quimicamente , Degeneração Neural/patologia , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Neurônios/patologia , Fatores de TempoRESUMO
In the adult neurogenic subventricular zone (SVZ), the behavior of astrocyte-like cells and some of their functions depend on changes in intracellular Ca(2+) levels and tonic GABA(A) receptor activation. However, it is unknown whether, and if so how, GABA(A) receptor activity regulates intracellular Ca(2+) dynamics in SVZ astrocytes. To monitor Ca(2+) activity selectively in astrocyte-like cells, we used two lines of transgenic mice expressing either GFP fused to a Gq-coupled receptor or DsRed under the human glial fibrillary acidic protein (hGFAP) promoter. GABA(A) receptor activation induced Ca(2+) increases in 40-50% of SVZ astrocytes. GABA(A)-induced Ca(2+) increases were prevented with nifedipine and mibefradil, blockers of L- and T-type voltage-gated calcium channels (VGCC). The L-type Ca(2+) channel activator BayK 8644 increased the percentage of GABA(A)-responding astrocyte-like cells to 75%, suggesting that the majority of SVZ astrocytes express functional VGCCs. SVZ astrocytes also displayed spontaneous Ca(2+) activity, the frequency of which was regulated by tonic GABA(A) receptor activation. These data support a role for ambient GABA in tonically regulating intracellular Ca(2+) dynamics through GABA(A) receptors and VGCC in a subpopulation of astrocyte-like cells in the postnatal SVZ.
RESUMO
Hippocampus-associated genes that orchestrate the formation of the compact stratum pyramidale are largely unknown. The BTB (broad complex, tramtrack, bric-a-brac)-zinc finger gene Zbtb20 (also known as HOF, Znf288, Zfp288) encodes two protein isoforms, designated Zbtb20(S) and Zbtb20(L), which are expressed in newborn pyramidal neurons of the presumptive hippocampus in mice. Here, we have generated transgenic mice with ectopic expression of Zbtb20(S) and Zbtb20(L) in immature pyramidal neurons differentiated from multipotent non-hippocampal precursors. The subiculum and posterior retrosplenial areas in these mice were transformed into a three-layered hippocampus-like cortex with a compact homogenous pyramidal cell layer. Severe malformations of lamination occur in neocortical areas, which coincide with a deficiency in expression of cortical lamination markers. The alterations in cortical cytoarchitecture result in behavioral abnormalities suggestive of a deficient processing of visual and spatial memory cues in the cerebral cortex of adult Zbtb20 transgenic mice. Overall, our in vivo data suggest that Zbtb20 functions as a molecular switch for a pathway that induces invariant pyramidal neuron morphogenesis and suppression of cell fate transitions in newborn neurons.
Assuntos
Córtex Cerebral/crescimento & desenvolvimento , Células Piramidais/crescimento & desenvolvimento , Fatores de Transcrição/fisiologia , Animais , Movimento Celular/genética , Córtex Cerebral/citologia , Córtex Cerebral/metabolismo , Hipocampo/citologia , Hipocampo/crescimento & desenvolvimento , Hipocampo/metabolismo , Camundongos , Camundongos Transgênicos , Isoformas de Proteínas/genética , Isoformas de Proteínas/fisiologia , Células Piramidais/citologia , Células Piramidais/metabolismo , Fatores de Transcrição/genética , Dedos de Zinco/genéticaRESUMO
Malignant astrocytomas are common human primary brain tumors that result from neoplastic transformation of astroglia or their progenitors. Here we show that deregulation of the c-Myc pathway in developing astroglia predisposes mice to malignant astrocytomas within 2-3 weeks of age. The genetically engineered murine (GEM) gliomas harbor a molecular signature resembling that of human primary glioblastoma multiforme, including up-regulation of epidermal growth factor receptor and Mdm2. The GEM gliomas seem to originate in an abnormal population of glial fibrillary acidic protein-expressing cells in the ventricular zone and, analogous to human glioblastomas, exhibit molecular and morphological heterogeneity. Levels of connexin 43 in the majority of the tumors are unaltered from normal tissue, indicating that GEM tumors have retained the capacity to establish syncytial networks. In line with this, individual glioma foci are composed of a mixture of actively proliferating cells expressing c-Myc and proliferating cell nuclear antigen and less dividing bystander cells that express glial fibrillary acidic protein and the broad complex tramtrack bric-a-brac/poxvirus and zinc finger domain protein HOF. A subset of the transgenic mice harbored, in addition to brain tumors, vestigial cerebellums in which granule cell migration and radial Bergman glial cell differentiation were disturbed. These observations argue for a window of vulnerability during astrocyte development where c-Myc overexpression is sufficient to trigger the neoplastic process, presumably by inducing the sustained growth of early astroglial cells. This is in contrast to most other transgenic studies in which c-Myc overexpression requires co-operating transgenes for rapid tumor induction.
Assuntos
Neoplasias Encefálicas/metabolismo , Glioma/metabolismo , Proteínas Proto-Oncogênicas c-myc/metabolismo , Animais , Sequência de Bases , Primers do DNA , Imuno-Histoquímica , CamundongosRESUMO
The immunophilin homolog FKBP8 has been implicated in the regulation of apoptosis. Here we show that the 38-kDa form of FKBP8 (FKBP38) derives from a truncated ORF. The extended FKBP8 ORFs are 46 and 44 kDa in mouse and 45 kDa in human. Although the genomic organization of mouse and human FKBP8 is evolutionarily conserved, additional first exons are encoded by the murine locus. A 4.4-kb murine Fkbp8 gene fragment, containing a GC-rich potential promoter, directed expression of a LacZ reporter gene to forebrain neurons in transgenic mice. Expression of the transgene was observed in CA1 pyramidal neurons of the hippocampus in transgenic mice from three lines. One transgenic founder mouse exhibited widespread forebrain expression of the LacZ transgene that resembles the pattern for the endogenous Fkbp8 gene. Thus promoter/enhancer elements for forebrain expression are located around the first exons of the mouse Fkbp8 gene.
Assuntos
Regiões Promotoras Genéticas/genética , Proteínas de Ligação a Tacrolimo/genética , Processamento Alternativo , Sequência de Aminoácidos , Animais , Sequência de Bases , Cerebelo/metabolismo , Corpo Estriado/metabolismo , DNA/química , DNA/genética , Éxons , Feminino , Expressão Gênica , Genes/genética , Hipocampo/metabolismo , Humanos , Hibridização In Situ , Íntrons , Óperon Lac/genética , Masculino , Camundongos , Camundongos Endogâmicos , Camundongos Transgênicos , Dados de Sequência Molecular , Neocórtex/metabolismo , Prosencéfalo/metabolismo , Isoformas de Proteínas/genética , Células Piramidais/metabolismo , Alinhamento de Sequência , Análise de Sequência de DNA , Homologia de Sequência de Aminoácidos , Homologia de Sequência do Ácido Nucleico , Sítio de Iniciação de TranscriçãoRESUMO
BTB/POZ (broad complex tramtrack bric-a-brac/poxvirus and zinc finger) zinc finger factors are a class of nuclear DNA-binding proteins involved in development, chromatin remodeling, and cancer. However, BTB/POZ domain zinc finger factors linked to development of the mammalian cerebral cortex, cerebellum, and macroglia have not been described previously. We report here the isolation and characterization of two novel nuclear BTB/POZ domain zinc finger isoforms, designated HOF(L) and HOF(S), that are specifically expressed in early hippocampal neurons, cerebellar granule cells, and gliogenic progenitors as well as in differentiated glia. During embryonic development of the murine cerebral cortex, HOF expression is restricted to the hippocampal subdivision. Expression coincides with early differentiation of presumptive CA1 and CA3 pyramidal neurons and dentate gyrus granule cells, with a sharp decline in expression at the CA1/subicular border. By using bromodeoxyuridine labeling and immunohistochemistry, we show that HOF expression coincides with immature non-dividing cells and is down-regulated in differentiated cells, suggesting a role for HOF in hippocampal neurogenesis. Consistent with the postulated role of the POZ domain as a site for protein-protein interactions, both HOF isoforms are able to dimerize. The HOF zinc fingers bind specifically to the binding site for the related promyelocytic leukemia zinc finger protein as well as to a newly identified DNA sequence.