Project description:GFI1B expression identified a multi-lineage ILC subset that retained the capacity for ILC2 development in the lung. We used single cell RNA sequencing (scRNAseq) to analyse the differentially expressed genes in these multipotent lung resident ILC.
Project description:The zinc finger protein and SNAG domain transcription factor Gfi1b is highly expressed in hematopoietic stem cells (HSC) and in megakaryocytes (MKs). Deletion of Gfi1b in mice leads to a drastic expansion of both cell types, suggesting that Gfi1b controls their proliferation. Here we present evidence that Gfi1b exerts this control by modulating the Wnt/beta-catenin signaling pathway. We can show that Gfi1b binds to beta-catenin and is part of a larger complex that contains β-catenin co-factors. Gfi1b activates beta-catenin/TCF mediated transcription and is required for the activity of beta-catenin target gene promoter driven reporter genes in vivo. This is dependent of the ability of Gfi1b to recruit the histone modifying enzyme lysine demethylase 1 (LSD1) to β-catenin containing complexes. Moreover, LSD1 enhances the Gfi1b-mediated activation of beta-catenin/TCF dependent transcription. Both Gfi1b deficient HSCs and MKs show de-regulation of expression of many sets on Wnt/β-catenin target genes and Gfi1b and β-catenin co-occupy the promoters of many common target genes. Finally, activating the Wnt/β-catenin signaling pathway in Gfi1b deficient HSCs and MKs significantly reduces their expansion, which confirms that Gfi1b is a critical factor controlling the cellularity of HSCs and MKs and exerts this function by regulating the Wnt/β-catenin pathway in these cells.
Project description:The transcription factor Growth Factor Independence 1B (GFI1B) recruits Lysine Specific Demethylase 1A (LSD1/KDM1A) to stimulate gene programs relevant for megakaryocyte and platelet biology. Inherited pathogenic GFI1B variants result in thrombocytopenia and bleeding propensities with varying intensity. Whether these affect similar gene programs is unknow. Here we studied transcriptomic effects of four patient-derived GFI1B variants (GFI1BT174N,H181Y,R184P,Q287*) in MEG01 megakaryoblasts. Compared to normal GFI1B, each variant affected different gene programs with GFI1BQ287* uniquely failing to repress myeloid traits. In line with this, single cell RNA-sequencing of induced pluripotent stem cell (iPSC)-derived megakaryocytes revealed a 4.5-fold decrease in the megakaryocyte/myeloid cell ratio in GFI1BQ287* versus normal conditions. Inhibiting the GFI1B-LSD1 interaction with small molecule GSK-LSD1 resulted in activation of myeloid genes in normal iPSC-derived megakaryocytes similar as observed for GFI1BQ287* iPSC-derived megakaryocytes. Thus, GFI1B and LSD1 facilitate gene programs relevant for megakaryopoiesis while simultaneously repressing programs that induce myeloid differentiation.
Project description:Megakaryocytes isolated from Gfi1b flox/flox mice carrying PF4-Cre or not, and from Gfi1b flox/flox mice carrying ROSA-Cre-ERT with or without tamoxifen injection were analyzed for differential expression by RNA-Seq
Project description:We have conducted a screen for factors that downregulate expression of the genes encoding the V(D)J recombinase (RAG1 and RAG2) during B cell development. We have identified the transcription factor Gfi1B as being one of the proteins capable of decreasing RAG transcription when overexpressed in Ableson transormed ProB cell lines. We have yet to determine whether the overexpression of Gfi1B downregulates the RAGs directly, or whether it initiates a signalling programme that results in RAG downregulation. We hypothesize that by comparing global gene expression patterns in cells that overexpress Gfi1B and those that do not, we can distinguish between these possibilities and additionally gain insight into the broader genetic program that may be influenced by Gfi1B during hematopoiesis. Abelson pro-B cells were infected with a retrovirus encoding Gfi1b fused to the estrogen receptor domain. Gfi1b expression was induced by adding tamoxifen to the culture medium for 12h. Three biological replicates of untreated and treated cells were analyzed.
Project description:Dominant-negative mutations in transcription factor Growth Factor Independence-1B (GFI1B) cause a bleeding disorder characterized by a plethora of megakaryocyte and platelet abnormalities. The deregulated molecular mechanisms and pathways are unknown. Here we show that normal and mutant GFI1B interacted most strongly with the LSD1-RCOR-HDAC corepressor complex in megakaryoblasts. Sequestration of this complex by mutant GFI1B and chemical separation of GFI1B from LSD1 induced abnormalities in normal megakaryocytes comparable to those seen in patients. Megakaryocytes derived from GFI1B-mutant induced pluripotent stem cells (iPSC) also phenocopied abnormalities seen in patients. Proteome studies on normal and mutant iPSC-derived megakaryocytes identified a multitude of deregulated pathways downstream of mutant GFI1B. Proteome studies on primary normal and GFI1B-mutant platelets showed reduced expression of proteins implicated in platelet function, and sustained expression of proteins normally downregulated during megakaryocyte differentiation. Thus, GFI1B regulates a broad developmental program during megakaryopoiesis. Mutant GFI1B deregulates this program through LSD1-RCOR-HDAC sequestering.
Project description:Using Gfi1b conditional mice, deletion of gfi1b in the hematopietic system was induced by injecting MxCre tg Gfi1bfl/fl mice with pIpC. 30 days after injection, Cd150 pos, Cd 48 neg, Lin neg Sca and c-kit pos stem cells were sortrted from Gfi1bfl/fl and Mxcre tg Gfi1bfl/fl mice and analysed. We used the mouse Affymetrix Gene ST Array. The study should determine whether loss of Gfi1 alters the gene expression pattern in the hematopietic stem cells.
Project description:Innate lymphoid cells (ILC) represent innate versions of T helper and cytotoxic T cells that differentiate from committed ILC precursors (ILCP). Still, how ILCP relate to mature tissue-resident ILCs remains unclear. We observed that a population of CD117+ ILC from peripheral blood (PB) of healthy donors does not represent any conical ILC subset, but expressed marker (CD117) commonly expressed by hemato-lymphoid progenitors. We therefore hypothesized PB CD117+ ILC might include uncommitted lymphoid precursors. In order to further understand the identity of PB CD117+ ILC, we profiled the transcriptome of highly purified circulating CD117+ ILC compared to CD34+ HSC, the latter representing immature hematopoietic progenitors with multi-lineage potential. Clear differences in gene expression profiles emerged, with a large cluster of 1540 genes expressed at substantially higher levels in CD117+ ILC. In contrast, CD34+ HSC cells highly expressed genes involved in the broad development of diverse hematopoietic lineages. Compared to HSC, CD117+ ILC express high levels of TF that have been shown to be essential for murine ILC development and we did not detect transcripts characteristic of T and B cells development. Transcriptomic analysis suggested that CD117+ ILC represent lymphoid-biased progenitors carrying a TF expression profile resembling a multi-potent ILC precursor (ILCP).