RESUMEN
What changes need to occur in a primary tumor to make it metastatic? Denny et al. address this question for small cell lung cancer (SCLC), finding that changes in genomic accessibility mediated by a single transcription factor, NFIB, comprise at least one mechanism influencing metastasis.
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Línea Celular Tumoral , Cromatina , Humanos , Neoplasias Pulmonares , Metástasis de la Neoplasia , Carcinoma Pulmonar de Células Pequeñas/genética , Factores de Transcripción/genéticaRESUMEN
ASCL1 is a neuroendocrine lineage-specific oncogenic driver of small cell lung cancer (SCLC), highly expressed in a significant fraction of tumors. However, â¼25% of human SCLC are ASCL1-low and associated with low neuroendocrine fate and high MYC expression. Using genetically engineered mouse models (GEMMs), we show that alterations in Rb1/Trp53/Myc in the mouse lung induce an ASCL1+ state of SCLC in multiple cells of origin. Genetic depletion of ASCL1 in MYC-driven SCLC dramatically inhibits tumor initiation and progression to the NEUROD1+ subtype of SCLC. Surprisingly, ASCL1 loss promotes a SOX9+ mesenchymal/neural crest stem-like state and the emergence of osteosarcoma and chondroid tumors, whose propensity is impacted by cell of origin. ASCL1 is critical for expression of key lineage-related transcription factors NKX2-1, FOXA2, and INSM1 and represses genes involved in the Hippo/Wnt/Notch developmental pathways in vivo. Importantly, ASCL1 represses a SOX9/RUNX1/RUNX2 program in vivo and SOX9 expression in human SCLC cells, suggesting a conserved function for ASCL1. Together, in a MYC-driven SCLC model, ASCL1 promotes neuroendocrine fate and represses the emergence of a SOX9+ nonendodermal stem-like fate that resembles neural crest.
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Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Factor de Transcripción SOX9/genética , Carcinoma Pulmonar de Células Pequeñas/genética , Animales , Animales Modificados Genéticamente , Modelos Animales de Enfermedad , Regulación Neoplásica de la Expresión Génica/genética , Humanos , Ratones , Cresta Neural/citología , Carcinoma Pulmonar de Células Pequeñas/fisiopatología , Células Madre/citologíaRESUMEN
Peripheral somatosensory input is modulated in the dorsal spinal cord by a network of excitatory and inhibitory interneurons. PTF1A is a transcription factor essential in dorsal neural tube progenitors for specification of these inhibitory neurons. Thus, mechanisms regulating Ptf1a expression are key for generating neuronal circuits underlying somatosensory behaviors. Mutations targeted to distinct cis-regulatory elements for Ptf1a in mice, tested the in vivo contribution of each element individually and in combination. Mutations in an autoregulatory enhancer resulted in reduced levels of PTF1A, and reduced numbers of specific dorsal spinal cord inhibitory neurons, particularly those expressing Pdyn and Gal Although these mutants survive postnatally, at â¼3-5 wk they elicit a severe scratching phenotype. Behaviorally, the mutants have increased sensitivity to itch, but acute sensitivity to other sensory stimuli such as mechanical or thermal pain is unaffected. We demonstrate a requirement for positive transcriptional autoregulatory feedback to attain the level of the neuronal specification factor PTF1A necessary for generating correctly balanced neuronal circuits.
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Retroalimentación Fisiológica/fisiología , Regulación de la Expresión Génica/fisiología , Neuronas/fisiología , Prurito/genética , Factores de Transcripción/genética , Animales , Sistemas CRISPR-Cas , Elementos de Facilitación Genéticos/genética , Ratones , Mutación , Neuronas/citología , Médula Espinal , Factores de Transcripción/metabolismoRESUMEN
Tumor heterogeneity of a primary histologic cancer type has major implications for cancer research and therapeutics. An important and understudied aspect of this heterogeneity is the role of transcription factors that serve as "lineage oncogenes" in a tumor type. A demonstration that different subgroups have distinct dependencies on lineage-specific transcription factors is highlighted in a relatively homogenous cancer type: the pulmonary neuroendocrine cancer small cell lung carcinoma (SCLC). Identification of these factors is providing new insights into the origin of the heterogeneity and subtype-specific vulnerabilities in SCLC and provides a template for studying heterogeneity in other cancer types.
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Carcinoma Neuroendocrino/fisiopatología , Neoplasias Pulmonares/fisiopatología , Carcinoma Pulmonar de Células Pequeñas/fisiopatología , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Linaje de la Célula , Heterogeneidad Genética , Humanos , MutaciónRESUMEN
During development, transcription factors select distinct gene programs, providing the necessary regulatory complexity for temporal and tissue-specific gene expression. How related factors retain specificity, especially when they recognize the same DNA motifs, is not understood. We address this paradox using basic helix-loop-helix (bHLH) transcription factors ASCL1, ASCL2, and MYOD1, crucial mediators of lineage specification. In vivo, these factors recognize the same DNA motifs, yet bind largely different genomic sites and regulate distinct transcriptional programs. This suggests that their ability to identify regulatory targets is defined either by the cellular environment of the partially defined lineages in which they are endogenously expressed, or by intrinsic properties of the factors themselves. To distinguish between these mechanisms, we directly compared the chromatin binding properties of this subset of bHLH factors when ectopically expressed in embryonic stem cells, presenting them with a common chromatin landscape and cellular components. We find that these factors retain distinct binding sites; thus, specificity of binding is an intrinsic property not requiring a restricted landscape or lineage-specific cofactors. Although the ASCL factors and MYOD1 have some distinct DNA motif preference, it is not sufficient to explain the extent of the differential binding. All three factors can bind inaccessible chromatin and induce changes in chromatin accessibility and H3K27ac. A reiterated pattern of DNA binding motifs is uniquely enriched in inaccessible chromatin at sites bound by these bHLH factors. These combined properties define a subclass of lineage-specific bHLH factors and provide context for their central roles in development and disease.
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Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Proteínas de Unión al ADN/genética , Proteína MioD/genética , Secuencia de Aminoácidos/genética , Sitios de Unión , Cromatina/genética , Regulación de la Expresión Génica , Genoma , Humanos , Motivos de Nucleótidos/genética , Unión Proteica/genéticaRESUMEN
Glioblastomas (GBMs) are incurable brain tumors with a high degree of cellular heterogeneity and genetic mutations. Transcription factors that normally regulate neural progenitors and glial development are aberrantly coexpressed in GBM, conferring cancer stem-like properties to drive tumor progression and therapeutic resistance. However, the functional role of individual transcription factors in GBMs in vivo remains elusive. Here, we demonstrate that the basic-helix-loop-helix transcription factor ASCL1 regulates transcriptional targets that are central to GBM development, including neural stem cell and glial transcription factors, oncogenic signaling molecules, chromatin modifying genes, and cell cycle and mitotic genes. We also show that the loss of ASCL1 significantly reduces the proliferation of GBMs induced in the brain of a genetically relevant glioma mouse model, resulting in extended survival times. RNA-seq analysis of mouse GBM tumors reveal that the loss of ASCL1 is associated with downregulation of cell cycle genes, illustrating an important role for ASCL1 in controlling the proliferation of GBM.
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Neoplasias Encefálicas , Glioblastoma , Animales , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Neoplasias Encefálicas/genética , Regulación Neoplásica de la Expresión Génica , Genes cdc , Ratones , Factores de Transcripción/metabolismoRESUMEN
Amacrine interneurons play a critical role in the processing of visual signals within the retina. They are highly diverse, representing 30 or more distinct subtypes. Little is known about how amacrine subtypes acquire their unique gene expression and morphological features. We characterized the gene expression pattern of the zinc-finger transcription factor Prdm13 in the mouse. Consistent with a developmental role, Prdm13 was expressed by Ptf1a+ amacrine and horizontal precursors. Over time, Prdm13 expression diverged from the transiently expressed Ptf1a and marked just a subset of amacrine cells in the adult retina. While heterogeneous, we show that most of these Prdm13+ amacrine cells express the transcription factor Ebf3 and the calcium binding protein calretinin. Loss of Prdm13 did not affect the number of amacrine cells formed during development. However, we observed a modest loss of amacrine cells and increased apoptosis that correlated with the onset timing of Ebf3 expression. Adult Prdm13 loss-of-function mice had 25% fewer amacrine cells, altered calretinin expression, and a lack of Ebf3+ amacrines. Forcing Prdm13 expression in retinal progenitor cells did not significantly increase amacrine cell formation, Ebf3 or calretinin expression, and appeared detrimental to the survival of photoreceptors. Our data show that Prdm13 is not required for amacrine fate as a class, but is essential for the formation of Ebf3+ amacrine cell subtypes. Rather than driving subtype identity, Prdm13 may act by restricting competing fate programs to maintain identity and survival.
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Células Amacrinas/metabolismo , Apoptosis/fisiología , Regulación del Desarrollo de la Expresión Génica/fisiología , N-Metiltransferasa de Histona-Lisina/biosíntesis , Células Madre/metabolismo , Factores de Transcripción/biosíntesis , Células Amacrinas/citología , Animales , Calbindina 2/biosíntesis , Calbindina 2/genética , Supervivencia Celular/fisiología , N-Metiltransferasa de Histona-Lisina/genética , Ratones , Ratones Transgénicos , Células Madre/citología , Factores de Transcripción/genéticaRESUMEN
The spinal cord integrates and relays somatosensory input, leading to complex motor responses. Research over the past couple of decades has identified transcription factor networks that function during development to define and instruct the generation of diverse neuronal populations within the spinal cord. A number of studies have now started to connect these developmentally defined populations with their roles in somatosensory circuits. Here, we review our current understanding of how neuronal diversity in the dorsal spinal cord is generated and we discuss the logic underlying how these neurons form the basis of somatosensory circuits.
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Neuronas/metabolismo , Sensación/fisiología , Médula Espinal/metabolismo , Factores de Transcripción/metabolismo , Animales , Humanos , Interneuronas/citología , Interneuronas/metabolismo , Modelos Teóricos , Neuronas/citología , Sensación/genética , Factores de Transcripción/genéticaRESUMEN
Subependymal nodules (SENs) and subependymal giant cell astrocytomas (SEGAs) are common brain lesions found in patients with tuberous sclerosis complex (TSC). These brain lesions present a mixed glioneuronal phenotype and have been hypothesized to originate from neural stem cells. However, this hypothesis has not been tested empirically. Here, we report that loss of Tsc1 in mouse subventricular zone (SVZ) neural stem/progenitor cells (NSPCs) results in formation of SEN- and SEGA-like structural abnormalities in the lateral ventricle, the consequence of abnormal migration of NSPCs following Tsc1 loss.
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Ventrículos Laterales/patología , Mutación/genética , Células-Madre Neurales/patología , Proteínas Supresoras de Tumor/genética , Animales , Astrocitoma/patología , Neoplasias Encefálicas/patología , Diferenciación Celular , Movimiento Celular/genética , Ventrículos Laterales/citología , Ratones , Ratones Noqueados , Células-Madre Neurales/citología , Esclerosis Tuberosa/patología , Proteína 1 del Complejo de la Esclerosis TuberosaRESUMEN
NG2-glia are highly proliferative oligodendrocyte precursor cells (OPCs) that are widely distributed throughout the central nervous system (CNS). During development, NG2-glia predominantly differentiate into oligodendrocytes (OLs) to myelinate axon fibers, but they can also remain as OPCs persisting into the mature CNS. Interestingly, NG2-glia in the gray matter (GM) are intrinsically different from those in the white matter (WM) in terms of proliferation, differentiation, gene expression, and electrophysiological properties. Here we investigate the role of the transcriptional regulator, ASCL1, in controlling NG2-glia distribution and development in the GM and WM. In the spinal cord, ASCL1 levels are higher in WM NG2-glia than those in the GM. This differential level of ASCL1 in WM and GM NG2-glia is maintained into adult stages. Long-term clonal lineage analysis reveals that the progeny of single ASCL1+ oligodendrocyte progenitors (OLPs) and NG2-glia are primarily restricted to the GM or WM, even though they undergo extensive proliferation to give rise to large clusters of OLs in the postnatal spinal cord. Conditional deletion of Ascl1 specifically in NG2-glia in the embryonic or adult spinal cord resulted in a significant reduction in the proliferation but not differentiation of these cells. These findings illustrate that ASCL1 is an intrinsic regulator of the proliferative property of NG2-glia in the CNS.
Asunto(s)
Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Proliferación Celular/fisiología , Células Precursoras de Oligodendrocitos/metabolismo , Médula Espinal/crecimiento & desarrollo , Médula Espinal/metabolismo , Animales , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Recuento de Células , Regulación del Desarrollo de la Expresión Génica , Sustancia Gris/citología , Sustancia Gris/crecimiento & desarrollo , Sustancia Gris/metabolismo , Ratones Transgénicos , Células Precursoras de Oligodendrocitos/citología , Médula Espinal/citología , Sustancia Blanca/citología , Sustancia Blanca/crecimiento & desarrollo , Sustancia Blanca/metabolismoRESUMEN
V1 interneurons are inhibitory neurons that play an essential role in vertebrate locomotion. The molecular mechanisms underlying their genesis remain, however, largely undefined. Here, we show that the transcription factor Prdm12 is selectively expressed in p1 progenitors of the hindbrain and spinal cord in the frog embryo, and that a similar restricted expression profile is observed in the nerve cord of other vertebrates as well as of the cephalochordate amphioxus. Using frog, chick and mice, we analyzed the regulation of Prdm12 and found that its expression in the caudal neural tube is dependent on retinoic acid and Pax6, and that it is restricted to p1 progenitors, due to the repressive action of Dbx1 and Nkx6-1/2 expressed in the adjacent p0 and p2 domains. Functional studies in the frog, including genome-wide identification of its targets by RNA-seq and ChIP-Seq, reveal that vertebrate Prdm12 proteins act as a general determinant of V1 cell fate, at least in part, by directly repressing Dbx1 and Nkx6 genes. This probably occurs by recruiting the methyltransferase G9a, an activity that is not displayed by the amphioxus Prdm12 protein. Together, these findings indicate that Prdm12 promotes V1 interneurons through cross-repressive interactions with Dbx1 and Nkx6 genes, and suggest that this function might have only been acquired after the split of the vertebrate and cephalochordate lineages.
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Proteínas Portadoras/metabolismo , Regulación del Desarrollo de la Expresión Génica/fisiología , Morfogénesis/fisiología , Proteínas del Tejido Nervioso/metabolismo , Células de Renshaw/fisiología , Xenopus/embriología , Animales , Secuencia de Bases , Embrión de Pollo , Inmunoprecipitación de Cromatina , Biología Computacional , Cartilla de ADN/genética , ADN Complementario/genética , Regulación del Desarrollo de la Expresión Génica/genética , Proteínas de Homeodominio/metabolismo , Inmunohistoquímica , Hibridación in Situ , Ratones , Datos de Secuencia Molecular , Rombencéfalo/metabolismo , Análisis de Secuencia de ARN , Especificidad de la Especie , Médula Espinal/metabolismoRESUMEN
Generating the correct balance of inhibitory and excitatory neurons in a neural network is essential for normal functioning of a nervous system. The neural network in the dorsal spinal cord functions in somatosensation where it modulates and relays sensory information from the periphery. PTF1A is a key transcriptional regulator present in a specific subset of neural progenitor cells in the dorsal spinal cord, cerebellum and retina that functions to specify an inhibitory neuronal fate while suppressing excitatory neuronal fates. Thus, the regulation of Ptf1a expression is critical for determining mechanisms controlling neuronal diversity in these regions of the nervous system. Here we identify a sequence conserved, tissue-specific enhancer located 10.8kb 3' of the Ptf1a coding region that is sufficient to direct expression to dorsal neural tube progenitors that give rise to neurons in the dorsal spinal cord in chick and mouse. DNA binding motifs for Paired homeodomain (Pd-HD) and zinc finger (ZF) transcription factors are required for enhancer activity. Mutations in these sequences implicate the Pd-HD motif for activator function and the ZF motif for repressor function. Although no repressor transcription factor was identified, both PAX6 and SOX3 can increase enhancer activity in reporter assays. Thus, Ptf1a is regulated by active and repressive inputs integrated through multiple sequence elements within a highly conserved sequence downstream of the Ptf1a gene.
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Cerebelo/embriología , Regulación del Desarrollo de la Expresión Génica , Tubo Neural/embriología , Secuencias Reguladoras de Ácidos Nucleicos/genética , Factores de Transcripción/biosíntesis , Factores de Transcripción/genética , Animales , Secuencia de Bases , Diferenciación Celular/fisiología , Embrión de Pollo , Electroporación , Ratones , Ratones Transgénicos , Tubo Neural/metabolismo , Factor de Transcripción PAX6/metabolismo , Retina/embriología , Factores de Transcripción SOXB1/metabolismo , Médula Espinal/embriología , Células Madre/citología , Activación Transcripcional/genética , Dedos de Zinc/genéticaRESUMEN
Glia constitute the majority of cells in the mammalian central nervous system and are crucial for neurological function. However, there is an incomplete understanding of the molecular control of glial cell development. We find that the transcription factor Ascl1 (Mash1), which is best known for its role in neurogenesis, also functions in both astrocyte and oligodendrocyte lineages arising in the mouse spinal cord at late embryonic stages. Clonal fate mapping in vivo reveals heterogeneity in Ascl1-expressing glial progenitors and shows that Ascl1 defines cells that are restricted to either gray matter (GM) or white matter (WM) as astrocytes or oligodendrocytes. Conditional deletion of Ascl1 post-neurogenesis shows that Ascl1 is required during oligodendrogenesis for generating the correct numbers of WM but not GM oligodendrocyte precursor cells, whereas during astrocytogenesis Ascl1 functions in balancing the number of dorsal GM protoplasmic astrocytes with dorsal WM fibrous astrocytes. Thus, in addition to its function in neurogenesis, Ascl1 marks glial progenitors and controls the number and distribution of astrocytes and oligodendrocytes in the GM and WM of the spinal cord.
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Astrocitos/citología , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Linaje de la Célula/fisiología , Oligodendroglía/citología , Médula Espinal/citología , Médula Espinal/embriología , Animales , Astrocitos/metabolismo , Diferenciación Celular/fisiología , Técnica del Anticuerpo Fluorescente , Ratones , Oligodendroglía/metabolismoRESUMEN
The proper balance of excitatory and inhibitory neurons is crucial for normal processing of somatosensory information in the dorsal spinal cord. Two neural basic helix-loop-helix transcription factors (TFs), Ascl1 and Ptf1a, have contrasting functions in specifying these neurons. To understand how Ascl1 and Ptf1a function in this process, we identified their direct transcriptional targets genome-wide in the embryonic mouse neural tube using ChIP-Seq and RNA-Seq. We show that Ascl1 and Ptf1a directly regulate distinct homeodomain TFs that specify excitatory or inhibitory neuronal fates. In addition, Ascl1 directly regulates genes with roles in several steps of the neurogenic program, including Notch signaling, neuronal differentiation, axon guidance and synapse formation. By contrast, Ptf1a directly regulates genes encoding components of the neurotransmitter machinery in inhibitory neurons, and other later aspects of neural development distinct from those regulated by Ascl1. Moreover, Ptf1a represses the excitatory neuronal fate by directly repressing several targets of Ascl1. Ascl1 and Ptf1a bind sequences primarily enriched for a specific E-Box motif (CAGCTG) and for secondary motifs used by Sox, Rfx, Pou and homeodomain factors. Ptf1a also binds sequences uniquely enriched in the CAGATG E-box and in the binding motif for its co-factor Rbpj, providing two factors that influence the specificity of Ptf1a binding. The direct transcriptional targets identified for Ascl1 and Ptf1a provide a molecular understanding of how these DNA-binding proteins function in neuronal development, particularly as key regulators of homeodomain TFs required for neuronal subtype specification.
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Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Redes Reguladoras de Genes , Inhibición Neural , Neuronas/metabolismo , Médula Espinal/citología , Factores de Transcripción/metabolismo , Animales , Secuencia de Bases , Sitios de Unión , Tipificación del Cuerpo/genética , Pollos , Cromatina/metabolismo , Elementos E-Box/genética , Neuronas GABAérgicas/metabolismo , Regulación del Desarrollo de la Expresión Génica , Genoma/genética , Glutamatos/metabolismo , Ratones , Datos de Secuencia Molecular , Tubo Neural/citología , Tubo Neural/embriología , Tubo Neural/metabolismo , Neurogénesis/genética , Neuronas/citología , Motivos de Nucleótidos/genética , Unión Proteica , Médula Espinal/embriologíaRESUMEN
Aggressive neuroendocrine lung cancers, including small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC), represent an understudied tumor subset that accounts for approximately 40,000 new lung cancer cases per year in the United States. No targeted therapy exists for these tumors. We determined that achaete-scute homolog 1 (ASCL1), a transcription factor required for proper development of pulmonary neuroendocrine cells, is essential for the survival of a majority of lung cancers (both SCLC and NSCLC) with neuroendocrine features. By combining whole-genome microarray expression analysis performed on lung cancer cell lines with ChIP-Seq data designed to identify conserved transcriptional targets of ASCL1, we discovered an ASCL1 target 72-gene expression signature that (i) identifies neuroendocrine differentiation in NSCLC cell lines, (ii) is predictive of poor prognosis in resected NSCLC specimens from three datasets, and (iii) represents novel "druggable" targets. Among these druggable targets is B-cell CLL/lymphoma 2, which when pharmacologically inhibited stops ASCL1-dependent tumor growth in vitro and in vivo and represents a proof-of-principle ASCL1 downstream target gene. Analysis of downstream targets of ASCL1 represents an important advance in the development of targeted therapy for the neuroendocrine class of lung cancers, providing a significant step forward in the understanding and therapeutic targeting of the molecular vulnerabilities of neuroendocrine lung cancer.
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Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Carcinoma de Pulmón de Células no Pequeñas/patología , Linaje de la Célula , Tumores Neuroendocrinos/genética , Oncogenes , Carcinoma Pulmonar de Células Pequeñas/genética , Adenocarcinoma/genética , Adenocarcinoma/patología , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Carcinoma de Pulmón de Células no Pequeñas/genética , Línea Celular Tumoral , Supervivencia Celular , Inmunoprecipitación de Cromatina , Regulación Neoplásica de la Expresión Génica , Humanos , Inmunohistoquímica , Tumores Neuroendocrinos/patología , Pronóstico , Proteínas Proto-Oncogénicas c-bcl-2/metabolismo , Carcinoma Pulmonar de Células Pequeñas/patologíaRESUMEN
The intracellular transcriptional milieu wields considerable influence over the induction of neuronal identity. The transcription factor Ptf1a has been proposed to act as an identity "switch" between developmentally related precursors in the spinal cord (Glasgow et al., 2005; Huang et al., 2008), retina (Fujitani et al., 2006; Dullin et al., 2007; Nakhai et al., 2007; Lelièvre et al., 2011), and cerebellum (Hoshino et al., 2005; Pascual et al., 2007; Yamada et al., 2014), where it promotes an inhibitory over an excitatory neuronal identity. In this study, we investigate the potency of Ptf1a to cell autonomously confer a specific neuronal identity outside of its endogenous environment, using mouse in utero electroporation and a conditional genetic strategy to misexpress Ptf1a exclusively in developing cortical pyramidal cells. Transcriptome profiling of Ptf1a-misexpressing cells using RNA-seq reveals that Ptf1a significantly alters pyramidal cell gene expression, upregulating numerous Ptf1a-dependent inhibitory interneuron markers and ultimately generating a gene expression profile that resembles the transcriptomes of both Ptf1a-expressing spinal interneurons and endogenous cortical interneurons. Using RNA-seq and in situ hybridization analyses, we also show that Ptf1a induces expression of the peptidergic neurotransmitter nociceptin, while minimally affecting the expression of genes linked to other neurotransmitter systems. Moreover, Ptf1a alters neuronal morphology, inducing the radial redistribution and branching of neurites in cortical pyramidal cells. Thus Ptf1a is sufficient, even in a dramatically different neuronal precursor, to cell autonomously promote characteristics of an inhibitory peptidergic identity, providing the first example of a single transcription factor that can direct an inhibitory peptidergic fate.
Asunto(s)
Corteza Cerebral/citología , Regulación del Desarrollo de la Expresión Génica/genética , Proteínas del Tejido Nervioso/metabolismo , Células Piramidales/metabolismo , Factores de Transcripción/metabolismo , Transcriptoma/fisiología , Animales , Animales Recién Nacidos , Corteza Cerebral/embriología , Corteza Cerebral/crecimiento & desarrollo , Biología Computacional , Electroporación , Embrión de Mamíferos , Proteínas del Ojo/metabolismo , Proteínas Fluorescentes Verdes/genética , Proteínas Fluorescentes Verdes/metabolismo , Proteínas de Homeodominio/genética , Proteínas de Homeodominio/metabolismo , Antígeno Ki-67/metabolismo , Ratones , Ratones Transgénicos , Proteínas del Tejido Nervioso/genética , Factor de Transcripción PAX6 , Factores de Transcripción Paired Box/metabolismo , Péptidos/genética , Péptidos/metabolismo , Proteínas Represoras/metabolismo , Estadísticas no Paramétricas , Factores de Transcripción/genética , Tubulina (Proteína)/metabolismoRESUMEN
Neural progenitor cells within the developing thalamus are spatially organized into distinct populations. Their correct specification is critical for generating appropriate neuronal subtypes in specific locations during development. Secreted signaling molecules, such as sonic hedgehog (Shh) and Wnts, are required for the initial formation of the thalamic primordium. Once thalamic identity is established and neurogenesis is initiated, Shh regulates the positional identity of thalamic progenitor cells. Although Wnt/ß-catenin signaling also has differential activity within the thalamus during this stage of development, its significance has not been directly addressed. In this study, we used conditional gene manipulations in mice and explored the roles of ß-catenin signaling in the regional identity of thalamic progenitor cells. We found ß-catenin is required during thalamic neurogenesis to maintain thalamic fate while suppressing prethalamic fate, demonstrating that regulation of regional fate continues to require extrinsic signals. These roles of ß-catenin appeared to be mediated at least partly by regulating two basic helix-loop-helix (bHLH) transcription factors, Neurog1 and Neurog2. ß-Catenin and Shh signaling function in parallel to specify two progenitor domains within the thalamus, where individual transcription factors expressed in each progenitor domain were regulated differently by the two signaling pathways. We conclude that ß-catenin has multiple functions during thalamic neurogenesis and that both Shh and ß-catenin pathways are important for specifying distinct types of thalamic progenitor cells, ensuring that the appropriate neuronal subtypes are generated in the correct locations.
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Proteínas Hedgehog/metabolismo , Células Madre/citología , Tálamo/citología , Tálamo/embriología , beta Catenina/metabolismo , Alelos , Animales , Linaje de la Célula , Cruzamientos Genéticos , Femenino , Regulación del Desarrollo de la Expresión Génica , Hibridación in Situ , Ratones , Ratones Transgénicos , Mutación , Neurogénesis , FenotipoRESUMEN
Clara cells of mammalian airways have multiple functions and are morphologically heterogeneous. Although Notch signaling is essential for the development of these cells, it is unclear how Notch influences Clara cell specification and if diversity is established among Clara cell precursors. Here we identify expression of the secretoglobin Scgb3a2 and Notch activation as early events in a program of secretory cell fate determination in developing murine airways. We show that Scgb3a2 expression in vivo is Notch-dependent at early stages and ectopically induced by constitutive Notch1 activation, and also that in vitro Notch signaling together with the pan-airway transcription factor Ttf1 (Nkx2.1) synergistically regulate secretoglobin gene transcription. Furthermore, we identified a subpopulation of secretory precursors juxtaposed to presumptive neuroepithelial bodies (NEBs), distinguished by their strong Scgb3a2 and uroplakin 3a (Upk3a) signals and reduced Ccsp (Scgb1a1) expression. Genetic ablation of Ascl1 prevented NEB formation and selectively interfered with the formation of this subpopulation of cells. Lineage labeling of Upk3a-expressing cells during development showed that these cells remain largely uncommitted during embryonic development and contribute to Clara and ciliated cells in the adult lung. Together, our findings suggest a role for Notch in the induction of a Clara cell-specific program of gene expression, and reveals that the NEB microenvironment in the developing airways is a niche for a distinct subset of Clara-like precursors.