Project description:T cell development is accompanied by epigenetic changes that ensure the silencing of stem cell-related, and the activation of lymphocyte-specific programs. How transcription factors influence these changes remains unclear. We show that the Ikaros transcription factor interacts with the Polycomb Repressive Complex 2 (PRC2) in CD4-CD8- thymocytes, and allows its binding to >200 developmentally-regulated genes, many of which are expressed in hematopoietic stem cells. Loss of Ikaros in CD4-CD8- cells leads to diminished histone H3 Lys27 (H3K27) trimethylation and ectopic expression of these genes. Ikaros binding triggers PRC2 recruitment and H3K27 trimethylation. Furthermore, Ikaros interacts with PRC2 independently of the Nucleosome Remodeling and Deacetylation complex. Our results identify Ikaros as a fundamental regulator of PRC2 function in developing T cells. Genome-wide comparison of different histone modifications, Ikaros, Suz12 and NuRD binding in different stages of T cell development in WT and Ikaros mutant mice. Profiling of H3K27me3 in DN1, DN2, DN3, DN4 and DP thymocytes and hematopoietic stem and progenitor cells (LSK cells) of WT and Ikaros mutant mice. Profiling of H3K4me3 and H3ac in WT and Ikaros mutant DP thymocytes. Global analysis of Ikaros binding in WT DN3, DN4 and DP cells, Suz12 binding in WT and Ikaros mutant DN3 cells, and Mta2 and Mi2beta binding in WT DN3 cells. Genome-wide profiling of Ikaros binding and H3K27me3 upon Ikaros activation in Ikaros-deficient leukemic T cells.
Project description:A transcriptome study in mouse hematopoietic stem cells was performed using a sensitive SAGE method, in an attempt to detect medium and low abundant transcripts expressed in these cells. Among a total of 31,380 unique transcript, 17,326 (55%) known genes were detected, 14,054 (45%) low-copy transcripts that have no matches to currently known genes. 3,899 (23%) were alternatively spliced transcripts of the known genes and 3,754 (22%) represent anti-sense transcripts from known genes.
Project description:A transcriptome study in mouse hematopoietic stem cells was performed using a sensitive SAGE method, in an attempt to detect medium and low abundant transcripts expressed in these cells. Among a total of 31,380 unique transcript, 17,326 (55%) known genes were detected, 14,054 (45%) low-copy transcripts that have no matches to currently known genes. 3,899 (23%) were alternatively spliced transcripts of the known genes and 3,754 (22%) represent anti-sense transcripts from known genes. Mouse hematopoietic stem cells were purified from bone marrow cells using negative and positive selection with a Magnetic-Activated Cell Sorter (MACS). total RNA and mRNA were purified from the purified cells using Trizol reagent and magnetic oligo dT beads. Double strand cDNAs were synthesized using a cDNA synthesis kit and anchored oligo dT primers. After NlaIII digestion, 3’ cDNAs were isolated and amplified through 16-cycle PCR. SAGE tags were released from the 3’ cDNA after linker ligation. Ditags were formed, concatemerized and cloned into a pZERO vector. Sequencing reactions were performed with the ET sequencing terminator kit. Sequences were collected using a Megabase 1000 sequencer. SAGE tag sequences were extracted using SAGE 2000 software.
Project description:The Ikaros zink finger transcription factor is a critical regulator of the hematopietic system, and plays an important role in the regulation of the development and function of several blood cell lineages. We used microarrays to characterize how Ikaros deficieny affects global transcription in the hematopoietic stem and progenitor cells from wild-type and Ikaros mutant mice. lin- Sca1+ c-Kit+ (LSK) cells, that contains the hematopoietic stem cells and the multipotent progenitor cells, were sorted by FACS from the bone marrow of 6-7 weeks old WT and IkL/L mutant mice. Total RNA extracted from these cells was subjected to transcriptome analysis.
Project description:The DNA-binding protein, Ikaros, functions as a potent tumor suppressor and hematopoietic regulator. However, the mechanisms by which Ikaros functions in the nucleus remain largely undefined, due in part to its atypical DNA-binding properties and partnership with the poorly understood Mi-2/NuRD complex. In this study, we extended our analysis of thymocyte development and lymphomagenesis in a mouse strain containing a specific deletion of Ikaros zinc finger 4, which exhibits a select subset of abnormalities observed in Ikaros null mice. By examining thymopoiesis in vivo and in vitro, numerous abnormalities were observed. RNA-sequencing revealed that each developmental stage is characterized by mis-regulation of a limited number of genes, with a strong preference for genes modulated in a stage-specific manner. Strikingly, individual genes and pathways rarely exhibited Ikaros-dependence at all developmental stages. Instead, the most consistent feature of aberrantly expressed genes was a reduced magnitude of expression level change during a developmental transition. These results and others suggest that Ikaros may not be a dedicated and consistent activator or repressor of a defined set of genes. Instead, its primary function may be to support the dynamic range of gene expression changes during developmental transitions via atypical molecular mechanisms that remain undefined. RNA-Seq of T cells at varying developmental stages and T cells expressing activated Notch in WT and Ikzf1-dF4/dF4 mutant backgrounds
Project description:Summary Purpose: By means of high-throughput data analysis (high-throughput sequencing or next-generation sequencing -NGS-), we addressed the effect of the absence of Ikaros and the Notch pathway activation in mouse fetal liver erythroid cells. Specifically, the goals of this study are (i) to characterize the transcriptome of erythroid cells in the absence of Ikaros, when the Notch pathway is activated or not (by RNA-seq); (ii) to identify patterns in the modification of gene regulation according to the variable conditions; and (iii) to obtain information on mechanisms involved in the variation of gene regulation. Methods: Erythroid cells obtained from Ikaros wild type (WT) or Ikaros knockout (Null) mouse fetal livers at the embryonic stage e14.5. These cells were co-cultured for 48 h on OP9 or OP9-DL1 cells. mRNA profiles were generated by NGS, in biological triplicate, using Illumina cBot 2 System. The quality of the raw reads was assessed with FASTQC. Report show no pool imbalance. After examining the quality of the raw reads, no trimming was deemed necessary. The reads were aligned to the GRCm38/mm10 genome with TopHat. The raw alignment counts were calculated with htseq-count. DESeq2 calculates the differential expression of genes directly from the raw alignment counts calculated with htseq-count. The output from DESeq2 includes the raw counts normalized relative to the total number of reads. The log2 fold change is an estimate of the fold change between the conditions, based on the distribution of the reads. qRT-PCR validation was performed using specific primer sets in real-time PCR with SYBR Green. Results. Based on expression profiles, all samples clustered correctly. The differential expression analysis was perform with all samples. For subsequent analysis, 2452 differentially expressed genes were identified in Ikaros WT vs Ikaros null cells cultured on OP9 cells, using a log2 ≥ 1 and a p value <0.005. Additionally, 2847 differentially expressed genes were identified in Ikaros WT vs Ikaros Null cells cultured on OP9-DL1 cells, using a log2 ≥ 1 and a p value <0.005. Among genes activated by Notch (cells cultured on OP9-DL1), 616 genes were repressed in the absence of Ikaros (Ikaros Null vs WT cells; log2≥ -0.8 and a p value <0.005) and 1558 genes were overexpressed in in the absence of Ikaros (Ikaros Null vs WT cells: log2≥ 0.8 and a p value <0.005), using adjusted p value <0.005. Modified expression or immunoprecipitation of several gene transcripts was confirmed with qRT-PCR. Conclusions (Summary): The results obtained demonstrate that Ikaros can favour repression of Notch target genes but can also be required for proper activation on Notch targets upon Notch pathway activation.