Project description:Glucorticoids (GCs) are steroid hormones with a wide range of physiological actions in different cell types and tissues. Their ability to induce apoptosis in malignant cells of the lymphoid lineage is exploited since decades in the treatment of childhood acute lymphoblastic leukemia (ALL), the molecular mechanism of this cell death induction being however still unknown. Using an integrative approach we delineated the transcriptional response of a preB- and a T-ALL model system employing Exon microarrays and identified in vivo interactions of the transcription factor GC receptor (GR) with genes' promoters in the same samples using the ChIP-on-chip technology. We did find differences in GR-DNA interaction in the genes' promoters between the two cell systems and also in extent and kinetics of GC mediated gene regulation. The overall response was stronger in CEM-C7H2 T-ALL cells where it was also accompanied by a stronger autoup-regulation of the GR gene. Considering the differing kinetics we furthermore defined a set of common response genes. These response genes were enriched in apoptosis related gene ontology processes, and about half of them yielded also GR enrichment in the respective promoter regions. Globally, the presence of GR at gene's promoters was higher for GC induced compared to repressed genes, indicating that GR mediates gene repression by interaction with distant enhancer regions or by cross-talk with other transcription factors. In order to identify the genes' GC regulated transcript variants we analyzed the data set also at the level of individual exons and predicted first exons of GC induced isoforms. We could thus define GC regulated variants of response genes, did however also identify first exons not corresponding to any known transcript. We reconfirmed these results for the genes ATP4B, GPR98, TBCD and ZBTB16 and identified for the latter also a novel exon employing 5' nested amplification of cDNA ends. Expression and regulation of this and all downstream exons of ZBTB16 was further verified by real time RT-PCR in 4 different preB-ALL cell lines. Thus, besides potential other novel gene isoforms, GCs induce a novel short transcript variant of ZBTB16 in preB-ALL cells. Finally, the implemented bioinformatic methods may be useful also for other high density microarray data sets to identify alternative splice events and transcript variant expression.

Project description:The beneficial effects of glucocorticoids (GCs) in acute lymphoblastic leukemia (ALL) are based on their ability to induce apoptosis. Omics technologies such as DNA microarray analysis are widely used to study the changes in gene expression and have been successfully implemented in biomarker identification. In addition, time series studies of gene expression enable the identification of correlations between kinetic profiles of glucocorticoid receptor (GR) target genes and diverse modes of transcriptional regulation. This study presents a genome-wide microarray analysis of both our and published Affymetrix HG-U133 Plus 2.0 data in GCs-sensitive and -resistant ALL. GCs-sensitive CCRF-CEM-C7-14 cells were treated with dexamethasone at three time points (0 h, 2 h and 10 h). The treated samples were then compared to the control (0 h). The published data used were as follows: GSE2677: GSM51674: B-ALL-24-24h GSM51675: B-ALL-24-6h GSM51676: B-ALL-24-0h GSM51680: B-ALL-17-24h GSM51681: B-ALL-17-8h GSM51682: B-ALL-17-0h GSM51677: B-ALL-13-24h GSM51678: B-ALL-13-8h GSM51679: B-ALL-13-0h GSM51683: B-ALL-31-24h GSM51684: B-ALL-31-6h GSM51685: B-ALL-31-0h GSM51686: B-ALL-32-24h GSM51687: B-ALL-32-6h GSM51688: B-ALL-32-0h GSM51689: B-ALL-33-24h GSM51690: B-ALL-33-6h GSM51691: B-ALL-33-0h GSM51692: B-ALL-37-24h GSM51693: B-ALL-37-6h GSM51694: B-ALL-37-0h GSM51695: B-ALL-38-24h GSM51696: B-ALL-38-6h GSM51697: B-ALL-38-0h GSM51698: B-ALL-40-24h GSM51699: B-ALL-40-6h GSM51700: B-ALL-40-0h GSM51701: B-ALL-43-24h GSM51702: B-ALL-43-6h GSM51703: B-ALL-43-0h GSM51707: T-ALL-25-24h GSM51708: T-ALL-25-6h GSM51709: T-ALL-25-0h GSM51704: T-ALL-20-24h GSM51705: T-ALL-20-8h GSM51706: T-ALL-20-0h GSM51710: T-ALL-2-24h GSM51711: T-ALL-2-8h GSM51712: T-ALL-2-0h GSE2842 GSM60545: S-Line-PreB-6h-EtOH GSM60546: S-Line-PreB-6h-GC GSM60547: S-Line-PreB-24h-GC GSM60542: S-Line-C7H2-6h-EtOH GSM60543: S-Line-C7H2-6h-GC GSM60544: S-Line-C7H2-24h-GC GSM60560: R-Line-CEMC1-6h-EtOH GSM60561: R-Line-CEMC1-6h-GC GSM60562: R-Line-CEMC1-24h-GC GSM60564: R-Line-C7R1-6h-EtOH GSM60566: R-Line-C7R1-6h-GC GSM60576: R-Line-C7R1dim-low-6h-EtOH GSM60578: R-Line-C7R1dim-low-6h-GC GSM60579: R-Line-C7R1dim-low-24h-GC GSM60581: R-Line-PreB-6h-EtOH GSM60583: R-Line-PreB-6h-GC GSM60584: R-Line-PreB-24h-EtOH GSM60586: R-Line-PreB-24h-GC GSM60548: C-Line-CEMC1-ratGR-6h-EtOH GSM60549: C-Line-CEMC1-ratGR-6h-GC GSM60550: C-Line-CEMC1-ratGR-24h-GC GSM60551: C-Line-C7R1dim-high-6h-EtOH GSM60552: C-Line-C7R1dim-high-6h-GC GSM60553: C-Line-C7R1dim-high-24h-GC

Dataset Information

Transcriptional glucocorticoid-response at the exon level and NR3C1 DNA-binding in childhood leukemia models; NR3C1-DNA binding in NALM6 precursor B-ALL cells.

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