Brg1 Coordinates Multiple Processes During Retinogenesis and is a Tumor Suppressor in Retinoblastoma
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ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE74181 | GEO | 2015/12/02
SECONDARY ACCESSION(S): PRJNA299271
REPOSITORIES: GEO
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Project description:Retinal development requires precise temporal and spatial coordination of cell cycle exit, cell-fate specification, cell migration and differentiation. When this process is disrupted, retinoblastoma, a developmental tumor of the retina, can form. Epigenetic modulators are central to precisely coordinating developmental events, and many epigenetic processes have been implicated in cancer. Studying epigenetic mechanisms in development is challenging because they often regulate multiple cellular processes; therefore, elucidating the primary molecular mechanisms involved can be difficult. Here we explore the role of Brg1 in retinal development and retinoblastoma by using molecular and cellular approaches. Brg1 regulated retinal size by controlling cell cycle length, cell cycle exit, and cell survival during development. Brg1 was not required for cell-fate specification but was required for photoreceptor differentiation and cell adhesion/polarity programs that contribute to proper retinal lamination during development. The combination of defective cell differentiation and lamination led to retinal degeneration in Brg1-deficient retinae. Despite the hypocellularity, premature cell cycle exit, increased cell death, and extended cell cycle length, retinal progenitor cells persisted in Brg1-deficient retinae, thereby making them more susceptible to retinoblastoma. ChIP-seq analysis provided insight into the underlying molecular mechanisms of these complex Brg1-regulated cellular processes during retinal development.
2015-12-02 | GSE74268 | GEO
Project description:During vertebrate retinogenesis, the precise balance between retinoblast proliferation and differentiation is spatially and temporally regulated through a number of intrinsic factors and extrinsic signaling pathways. Moreover, there are complex gene regulatory network interactions between these intrinsic factors and extrinsic pathways, which ultimately function to determine when retinoblasts exit the cell cycle and terminally differentiate. We recently uncovered a cell non-autonomous role for the intrinsic HLH factor, Id2a, in regulating retinoblast proliferation and differentiation, with Id2a-deficient retinae containing an abundance of proliferative retinoblasts and an absence of terminally differentiated retinal neurons and glia. Here, we report that Id2a function is necessary and sufficient to limit Notch pathway activity during retinogenesis. Id2a-deficient retinae possess elevated levels of Notch pathway component gene expression, while retinae overexpressing id2a possess reduced expression of Notch pathway component genes. Attenuation of Notch signaling activity by DAPT or by morpholino knockdown of Notch1a is sufficient to rescue both the proliferative and differentiation defects in Id2a-deficient retinae. In addition to regulating Notch pathway activity, through an RNA-Seq and differential gene expression analysis of Id2a-deficient retinae, we identify a number of additional intrinsic and extrinsic regulatory pathway components whose expression is regulated by Id2a. These data highlight the integral role played by Id2a in the gene regulatory network governing the transition from retinoblast proliferation to terminal differentiation during vertebrate retinogenesis. Two biological replicates for both Id2aMM and Id2aMO samples
2012-08-27 | E-GEOD-38786 | biostudies-arrayexpress
Project description:To study the development of human retina, we used single cell RNAseq at key fetal stages and followed the development of the major cell types, as well as populations of transitional cells. We also analyzed stem cell (hPSC)-derived retinal organoids; although organoids have a very similar cellular composition at equivalent ages to the fetal retina, there are some differences in gene expression of particular cell types. Moreover, the inner retinal lamination is disrupted in more advanced stages of organoids when compared with fetal retina. To determine whether the disorganization in the inner retina was due to the culture conditions, we analyzed retinal development in fetal retina maintained under similar conditions. These retinospheres develop for at least 6 months, displaying better inner retinal lamination than retinal organoids. Our scRNAseq comparisons between fetal retina, retinal organoids and retinospheres provide a new resource for developing better in vitro models for retinal disease.
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Project description:During vertebrate retinogenesis, the precise balance between retinoblast proliferation and differentiation is spatially and temporally regulated through a number of intrinsic factors and extrinsic signaling pathways. Moreover, there are complex gene regulatory network interactions between these intrinsic factors and extrinsic pathways, which ultimately function to determine when retinoblasts exit the cell cycle and terminally differentiate. We recently uncovered a cell non-autonomous role for the intrinsic HLH factor, Id2a, in regulating retinoblast proliferation and differentiation, with Id2a-deficient retinae containing an abundance of proliferative retinoblasts and an absence of terminally differentiated retinal neurons and glia. Here, we report that Id2a function is necessary and sufficient to limit Notch pathway activity during retinogenesis. Id2a-deficient retinae possess elevated levels of Notch pathway component gene expression, while retinae overexpressing id2a possess reduced expression of Notch pathway component genes. Attenuation of Notch signaling activity by DAPT or by morpholino knockdown of Notch1a is sufficient to rescue both the proliferative and differentiation defects in Id2a-deficient retinae. In addition to regulating Notch pathway activity, through an RNA-Seq and differential gene expression analysis of Id2a-deficient retinae, we identify a number of additional intrinsic and extrinsic regulatory pathway components whose expression is regulated by Id2a. These data highlight the integral role played by Id2a in the gene regulatory network governing the transition from retinoblast proliferation to terminal differentiation during vertebrate retinogenesis.
2012-08-27 | GSE38786 | GEO
Project description:Retinal cells are specified in a zebrafish recessive mutant called young (yng) but they fail to terminally differentiate; i.e. extend neurites and make synaptic contacts. A point mutation in a brahma-related gene 1 (brg1) is responsible for this phenotype. In this microarray study, a three-factor factorial design was utilized to investigate the effects of 1) mutation, 2) change in time (36 vs. 52hpf), and 3) change in tissue (retina vs. whole embryos), and their interactions on gene expression. Significant probesets were inferred by using both specific contrasts of the fitted Analysis of Variance (ANOVA) models and a corresponding 2-fold expression cutoff. The probesets were grouped into three broad categories: 1) Brg1-regulated retinal differentiation genes (731 probsets), 2) Retinal specific genes but independent of Brg1 regulation (3038 probesets) and 3) Genes regulated by Brg1 but outside the retina (107 probesets). Four gene groups/pathways including neurite outgrowth regulators, Delta-Notch signalling molecules, Irx family members and specific cell cycle regulators were identified in the first group, and their relevance for retinal differentiation functionally validated. This study demonstrates that an approach such as ours can identify relevant genes and pathways involved in retinal development as well as the development of other tissues at the same time. Keywords: Development, retina, terminal differentiation, chromatin remodeling, factorial anlaysis
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Project description:It is widely believed that the molecular and cellular features of a tumor reflect its cell-of-origin and can thus provide clues about treatment targets. The retinoblastoma cell-of-origin has been debated for over a century. Here we report that human and mouse retinoblastomas have molecular, cellular, and neurochemical features of multiple cell classes, principally amacrine/horizontal interneurons, retinal progenitor cells, and photoreceptors. Importantly, single-cell gene expression array analysis showed that these multiple cell type–specific developmental programs are coexpressed in individual retinoblastoma cells, which creates a progenitor/neuronal hybrid cell. Importantly, neurotransmitter receptors, transporters, and biosynthetic enzymes are expressed in human retinoblastoma, and targeted disruption of these pathways reduces retinoblastoma growth in vivo and in vitro. Our finding that retinoblastoma tumor cells express multiple neuronal differentiation programs that are normally incompatible in development suggests that the pathways that control retinal development and establish distinct cell types are perturbed during tumorigenesis. Therefore, the cell-of-origin for retinoblastoma cannot be inferred from the features of the tumor cells themselves. However, we now have a detailed understanding of the neuronal pathways that are deregulated in retinoblastoma and targeting the catecholamine and indolamine receptors or downstream components could provide useful therapeutic approaches in future studies. This example highlights the importance of comprehensive molecular, cellular and physiological characterization of human cancers with single cell resolution as we incorporate molecular targeted therapy into treatment regimens. 55 primary pediatric retinoblastoma tumors were collected and assayed and compared to with 3 passaged xenografts and 4 RB cell lines
2011-06-07 | E-GEOD-29683 | biostudies-arrayexpress
Project description:It is widely believed that the molecular and cellular features of a tumor reflect its cell-of-origin and can thus provide clues about treatment targets. The retinoblastoma cell-of-origin has been debated for over a century. Here we report that human and mouse retinoblastomas have molecular, cellular, and neurochemical features of multiple cell classes, principally amacrine/horizontal interneurons, retinal progenitor cells, and photoreceptors. Importantly, single-cell gene expression array analysis showed that these multiple cell type–specific developmental programs are coexpressed in individual retinoblastoma cells, which creates a progenitor/neuronal hybrid cell. Importantly, neurotransmitter receptors, transporters, and biosynthetic enzymes are expressed in human retinoblastoma, and targeted disruption of these pathways reduces retinoblastoma growth in vivo and in vitro. Our finding that retinoblastoma tumor cells express multiple neuronal differentiation programs that are normally incompatible in development suggests that the pathways that control retinal development and establish distinct cell types are perturbed during tumorigenesis. Therefore, the cell-of-origin for retinoblastoma cannot be inferred from the features of the tumor cells themselves. However, we now have a detailed understanding of the neuronal pathways that are deregulated in retinoblastoma and targeting the catecholamine and indolamine receptors or downstream components could provide useful therapeutic approaches in future studies. This example highlights the importance of comprehensive molecular, cellular and physiological characterization of human cancers with single cell resolution as we incorporate molecular targeted therapy into treatment regimens. 20 single cells isolated from primary pediatric retinoblastoma tumors were assayed to asses the within tumor consistency of expression signals
2011-06-07 | E-GEOD-29684 | biostudies-arrayexpress
Project description:The zebrafish eye develops from a neuroepithelial layer of retinal progenitors, which then become postmitotic and differentiate into the mature retinal cell types. After 72hpf, the embryonic development of the retina is completed, since all major cell types are present and arranged in the characteristic lamination of the vertebrate retina. At this point, the cells located in the central retina have already exited the cell cycle and almost all growth comes from astem cell niche located at the periphery of the retina, called the ciliary marginal zone (CMZ). The CMZ is an heterogeneous region composed of stem cells, which continuously supply the CMZ with intermediate progenitors, that gradually proliferate and differentiate moving towards the central retina, a process that spatially recapitulates the temporal progression of embryonic development. The aim of this project is to characterise the transcriptome of the stem cells and the proliferative progenitors in order to build gene networks within each compartment, and subsequently characterise the mechanisms by which a stem cell gives rise to a differentiated cell in a post-embryonic retina This data is part of a pre-publication release. For information on the proper use of pre-publication data shared by the Wellcome Trust Sanger Institute (including details of any publication moratoria), please see http://www.sanger.ac.uk/datasharing/
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2012-12-05 | E-GEOD-38762 | biostudies-arrayexpress
Project description:The two catalytic subunits of the SWI/SNF chromatin remodeling complex - Brg1 and Brm - have been often implicated as essential components of common biological processes, suggesting a functional redundancy between these two proteins. For instance, earlier works indicated that both proteins are required for the activation of the myogenic program. However, their mutually exclusive pattern of incorporation in SWI/SNF complexes with variable composition and functional heterogeneity predicts that Brg1- and Brm-based SWI/SNF complexes execute specific functions to coordinate gene expression in multistep programs, such as skeletal myogenesis. We detected a distinct expression profile of Brg1 and Brm during the myogenic program, with Brm being upregulated in differentiating myocytes. Genetic knockdown of either Brg1 or Brm in skeletal myoblasts, followed by gene expression analysis, revealed discrete functions during myogenic differentiation. While Brm is required for the exit from the cell cycle at the early stages of differentiation, by repressing CyclinD1 transcription, Brg1 is required for the activation of muscle gene transcription. Interestingly, at later stages of differentiation Brg1 and Brm cooperate to the activation of a cluster of common target genes. Thus, Brg1 and Brm appear to coordinate activation and repression of distinct subsets of genes during initial phase myogenesis, and converge to cooperatively activate the expression of muscle genes at later stages. C2C12 myoblasts treated with siBRM or siBRG1 or siSCR in growth medium (GM) and differentiated by medium replacemnte (DM ). Celles were collected at 18h and 48h from the onset of DM for RNA extraction and microarray analysis. Arrays were used to generate 6 data sets in duplicate.To address the question of which genes were regulated by BRM and/or BRG1 the fold changes in gene expression were calculated between Scrambled siRNA and the BRM or BRG1 siRNA. The experiments were repeated at 2 different time points (18 hours and 48 hours) .
2015-01-14 | E-GEOD-44993 | biostudies-arrayexpress