RESUMO
Notch signaling and its downstream gene target HES1 play a critical role in regulating and maintaining cancer stem cells (CSCs), similar to as they do during embryonic development. Here, we report a unique subclass of Notch-independent Hes-1 (NIHes-1)-expressing CSCs in neuroblastoma. These CSCs maintain sustained HES1 expression by activation of HES1 promoter region upstream of classical CBF-1 binding sites, thereby completely bypassing Notch receptor-mediated activation. These stem cells have self-renewal ability and potential to generate tumors. Interestingly, we observed that NIHes-1 CSCs could transition to Notch-dependent Hes-1-expressing (NDHes-1) CSCs where HES1 is expressed by Notch receptor-mediated promoter activation. We observed that NDHes-1-expressing CSCs also had the potential to transition to NIHes-1 CSCs and during this coordinated bidirectional transition, both CSCs gave rise to the majority of the bulk cancer cells, which had an inactive HES1 promoter (PIHes-1). A few of these PIHes-1 cells were capable of reverting into a CSC state. These findings explain the existence of a heterogenic mode of HES1 promoter activation within the IMR-32 neuroblastoma cell line and the potential to switch between them. This article has an associated First Person interview with the first authors of the paper.
Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos , Neuroblastoma , Humanos , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Células-Tronco Neoplásicas/metabolismo , Receptores Notch/metabolismo , Neuroblastoma/genética , Neuroblastoma/metabolismo , Regiões Promotoras Genéticas/genética , Linhagem Celular , Fatores de Transcrição HES-1/genética , Fatores de Transcrição HES-1/metabolismoRESUMO
Intra-retinal axon guidance involves a coordinated expression of transcription factors, axon guidance genes, and secretory molecules within the retina. Pax6, the master regulator gene, has a spatio-temporal expression typically restricted till neurogenesis and fate-specification. However, our observation of persistent expression of Pax6 in mature RGCs led us to hypothesize that Pax6 could play a major role in axon guidance after fate specification. Here, we found significant alteration in intra-retinal axon guidance and fasciculation upon knocking out of Pax6 in E15.5 retina. Through unbiased transcriptome profiling between Pax6fl/fl and Pax6-/- retinas, we revealed the mechanistic insight of its role in axon guidance. Our results showed a significant increase in the expression of extracellular matrix molecules and decreased expression of retinal fate specification and neuron projection guidance molecules. Additionally, we found that EphB1 and Sema5B are directly regulated by Pax6 owing to the guidance defects and improper fasciculation of axons. We conclude that Pax6 expression post fate specification of RGCs is necessary for regulating the expression of axon guidance genes and most importantly for maintaining a conducive ECM through which the nascent axons get guided and fasciculate to reach the optic disc.
Assuntos
Fasciculação Axônica/fisiologia , Orientação de Axônios/fisiologia , Fator de Transcrição PAX6/fisiologia , Células Ganglionares da Retina/fisiologia , Animais , Fasciculação Axônica/genética , Orientação de Axônios/genética , Diferenciação Celular/genética , Diferenciação Celular/fisiologia , Matriz Extracelular/metabolismo , Feminino , Perfilação da Expressão Gênica , Regulação da Expressão Gênica no Desenvolvimento , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Neurogênese/genética , Neurogênese/fisiologia , Fator de Transcrição PAX6/deficiência , Fator de Transcrição PAX6/genética , Gravidez , RNA-Seq , Receptor EphB1/genética , Receptor EphB1/fisiologia , Retina/embriologia , Retina/crescimento & desenvolvimento , Retina/fisiologia , Células Ganglionares da Retina/citologia , Semaforinas/genética , Semaforinas/fisiologiaRESUMO
The role of Wnt5a has been extensively explored in various aspects of development but its role in cerebellar development remains elusive. Here, for the first time we unravel the expression pattern and functional significance of Wnt5a in cerebellar development using Wnt5a-/- and Nestin-Cre mediated conditional knockout mouse models. We demonstrate that loss of Wnt5a results in cerebellar hypoplasia and depletion of GABAergic and glutamatergic neurons. Besides, Purkinje cells of the mutants displayed stunted, poorly branched dendritic arbors. Furthermore, we show that the overall reduction is due to decreased radial glial and granule neuron progenitor cell proliferation. At molecular level we provide evidence for non-canonical mode of action of Wnt5a and its regulation over genes associated with progenitor proliferation. Altogether our findings imply that Wnt5a signaling is a crucial regulator of cerebellar development and would aid in better understanding of cerebellar disease pathogenesis caused due to deregulation of Wnt signaling.
