Unknown,Transcriptomics,Genomics,Proteomics

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Transcription profiling of human neuroblastoma cell line expressing PHOX2B

ABSTRACT: Neuroblastoma is an embryonal tumour of the peripheral sympathetic nervous system (SNS). One of the master regulator genes for peripheral SNS differentiation, the homeobox transcription factor PHOX2B, is mutated in familiar and sporadic neuroblastomas. Here we report that inducible expression of PHOX2B in the neuroblastoma cell line SJNB-8 down-regulates MSX1, a homeobox gene important for embryonic neural crest development. Inducible expression of MSX1 in SJNB-8 caused inhibition of both cell proliferation and colony formation in soft agar. Affymetrix micro- array and Northern blot analysis demonstrated that MSX1 strongly up-regulated the Delta-Notch pathway. These experiments describe for the first time regulation of the Delta-Notch pathway by MSX1, and connect these genes to the PHOX2B oncogene, indicative of a role in neuroblastoma biology. Experiment Overall Design: Time course experiments of two independent clones (K2 and K5), with 2 or 4 time points, respectively.

ORGANISM(S): Homo sapiens

SUBMITTER: Rogier Versteeg

PROVIDER: E-GEOD-9339 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:The spatial and temporal control of gene expression during development requires the concerted actions of sequence-specific transcriptional regulators and epigenetic chromatin modifiers, which are thought to function within precise nuclear compartments. However, how these activities are coordinated within the dynamic context of the nuclear environment is still largely unresolved. Here we show that transcriptional repression by the Msx1 homeoprotein coordinates recruitment of Polycomb to genomic targets with localization to the nuclear periphery. Using genome-wide ChIP-Seq analyses to identify genomic binding sites for Msx1, we find that repressed target genes are enriched at the nuclear periphery in myoblast cells. We further show that the interaction of Msx1 with the Polycomb repressive complex PRC2 is required for transcriptional repression and regulation of myoblast differentiation, and promotes increased tri-methylation of lysine 27 on histone H3 (H3K27me3) at Msx1 target genes. Furthermore, Msx1 genomic binding promotes the dynamic spatial redistribution of the H3K27me3 repressive mark to the nuclear periphery in developing embryos in vivo. Thus, our findings suggest a hitherto unappreciated spatial coordination of transcription factor binding, Polycomb recruitment, and subnuclear localization in regulation of developmentgene expression programs. In order to identify genes regulated by Msx1, we infected C2C12 myoblast cells with a retrovirus expressing a tamoxifen-regulated Msx1 protein, Msx1-ER (or with empty vector as a control), followed by induction with 0.2 nM of tamoxifen or vehicle (DMSO) for 6 hours. Regulated genes were identified as those that changed in expression upon tamoxifen induction of the Msx1-ER protein but did not change in the empty vector control. Experiments were performed in triplicate for each of the four experimental conditions (Msx1-ER + tamoxifen, Msx1-ER - tamoxifen, empty vector control + tamoxifen, empty vector control - tamoxifen), for a total of 12 independent array samples. This submission represents the transcriptome component of the study.

Project description:Homeobox genes encode transcription factors regulating basic processes in cell differentiation during embryogenesis and in the adult. Recently, we have reported the NKL-code which describes physiological expression patterns of nine NKL homeobox genes in early hematopoiesis and in lymphopoiesis including main stages of T-, B- and NK-cell development. Aberrant activity of NKL homeobox genes is involved in the generation of hematological malignancies including T-cell leukemia. Here, we searched for deregulated NKL homeobox genes in main entities of T-cell lymphomas comprising peripheral T-cell lymphoma (PTCL), angioimmunoblastic T-cell lymphoma (AITL), anaplastic large cell lymphoma (ALCL), adult T-cell leukemia/lymphoma (ATLL), hepatospleenic T-cell lymphoma (HSTL), and NK/T-cell lymphoma (NKTL). Our data revealed in all types altogether 19 aberrantly overexpressed genes, demonstrating that deregulated NKL homeobox genes play a significant role in T-cell lymphomas as well. For detailed analyses we focused on NKL homeobox gene MSX1 which is normally expressed in NK-cells and aberrantly activated in T-cell leukemia. This gene was overexpressed in subsets of HSTL patients and HSTL-derived sister cell lines DERL-2 and DERL-7 which served as models to identify mechanisms of deregulation. We performed genomic and expression profiling and whole genome sequencing and revealed mutated and deregulated gene candidates including the fusion gene CD53-PDGFRB exclusively expressed in DERL-2. Subsequent knockdown experiments allowed the construction of an aberrant network involved in MSX1 deregulation containing chromatin factors AUTS2 and H3B/H3.1, PDGF- and BMP-signalling pathways, and homeobox genes NKX2-2 and PITX1. The gene encoding AUTS2 is located at 7q11 and may represent a basic target of the HSTL hallmark aberration i(7q). Our data indicate both oncogenic and tumor suppressor functions of MSX1 in HSTL, reflecting its activity in early lineage differentiation of T- and NK-cells and the presence of NK-cell like characteristics in malignant HSTL cells. In this context, NKL homeobox gene MSX1 may represent a selective target in HSTL tumor evolution. Together, the data highlight an oncogenic role of deregulated NKL homeobox genes in T-cell lymphoma and identified MSX1 as a novel player in HSTL, involved in aberrant NK- and T-cell differentiation.

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Transcription profiling of human neuroblastoma cell line expressing PHOX2B

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