Project description:Growth factor independent 1 (Gfi1) is a transcriptional repressor originally identified as a common integration site in Moloney-murine-leukemia-virus-induced T-cell leukemia. Gfi1-/- mice display increased apoptosis of developing thymocytes and T lymphopenia; however, there are contradictory reports of the absolute number of Gfi1-/- early T lineage progenitors. We used floxed alleles of Gfi1 crossed to various T-cell-specific Cre transgenes to map the requirements for Gfi1 during lymphoid priming and development. We show that Gfi1 is necessary for the proper formation and function of both lymphoid-primed multipotent progenitors and early T lineage progenitors. These defects correlate with a global inability of Gfi1-/- progenitors to enforce the activation of lymphoid genes including IL7R, Rag1, Flt3 and Notch1. Forced expression of intracellular Notch1 fails to rescue the Gfi1-/- defective lymphoid gene signature or Gfi1-/- T cell development. Instead, activation of Notch1 in Gfi1-/- cells results in a potent synthetic lethal phenotype that is most dramatic in immature thymocytes, but absent in mature peripheral T cells where developmental transcriptional programs are silent. Moreover, we find that the requirement for Gfi1-transcriptional integration of Notch-driven lymphoid transcriptional programs is cell autonomous. Our data indicate that Gfi1 is required at multiple independent stages of lymphoid development. In hematopoietic progenitors Gfi1 is necessary to integrate Notch1 signaling, mediate lymphoid priming, the formation of early T lineage progenitors and subsequent T lineage commitment. Lineage negative cells were purified by magnetic beads from RosaCreERT2 Gfi1 ex4-5 floxed mice and an activated Notch1 signal was introduced using a GFP+ retroviral vector. GFP+ progenitors were FACS-sorted and cultured in semi-solid media for one week to allow sufficient time to to instruct lymphoid differentiation, then replated in 1uM 4-OHT or EtOH control. After an additional 7 days, CFU were disrupted and RNA was isolated for global gene expression using microarrays.
Project description:Growth factor independent 1 (Gfi1) is a transcriptional repressor originally identified as a common integration site in Moloney-murine-leukemia-virus-induced T-cell leukemia. Gfi1-/- mice display increased apoptosis of developing thymocytes and T lymphopenia; however, there are contradictory reports of the absolute number of Gfi1-/- early T lineage progenitors. We used floxed alleles of Gfi1 crossed to various T-cell-specific Cre transgenes to map the requirements for Gfi1 during lymphoid priming and development. We show that Gfi1 is necessary for the proper formation and function of both lymphoid-primed multipotent progenitors and early T lineage progenitors. These defects correlate with a global inability of Gfi1-/- progenitors to enforce the activation of lymphoid genes including IL7R, Rag1, Flt3 and Notch1. Forced expression of intracellular Notch1 fails to rescue the Gfi1-/- defective lymphoid gene signature or Gfi1-/- T cell development. Instead, activation of Notch1 in Gfi1-/- cells results in a potent synthetic lethal phenotype that is most dramatic in immature thymocytes, but absent in mature peripheral T cells where developmental transcriptional programs are silent. Moreover, we find that the requirement for Gfi1-transcriptional integration of Notch-driven lymphoid transcriptional programs is cell autonomous. Our data indicate that Gfi1 is required at multiple independent stages of lymphoid development. In hematopoietic progenitors Gfi1 is necessary to integrate Notch1 signaling, mediate lymphoid priming, the formation of early T lineage progenitors and subsequent T lineage commitment.
Project description:Hematopoietic stem cells (HSCs) and lymphoid-primed multi-potential progenitors (LMPPs) are able to initiate both lymphoid and myeloid differentiation. We show here that the transcriptional repressor Gfi1 (growth factor independence 1) implements a specific gene expression program in HSCs and LMPPs that is critical for their survival and lymphoid differentiation potential. We present evidence that Gfi1 is required to maintain expression of genes involved in lymphoid development such as Flt-3, IL7R, Ebf1, Rag1, CCR9 and Notch1 and controls myeloid lineage commitment by regulating expression of genes such as Hoxa9 or M-CSFR. Gfi1 also inhibits apoptosis in HSCs by repressing pro-apoptotic genes such as Bax or Bak. As a consequence, Gfi1-/- mice show defects in self renewal, survival and both myeloid and lymphoid development of HSCs and LMPPs. Co-expression of a Bcl-2 transgene can partially restore the function of HSCs in Gfi1-/- mice, but not the defects in early lymphoid development. Of interest, Gfi1-/- x Bcl-2 transgenic mice show an accelerated expansion of myeloid cells and succumb to a fatal myeloproliferative disease resembling chronic myelomonocytic leukemia (CMML). Our data show that Gfi1 protects HSCs against apoptosis, ensures the proper development of LMPPs and plays a role in the development of myeloid leukemia. We used microarrays to detail the global gene expression changes following knockout of Gfi1 in mouse LSK cells We compared LSK cells isolated from Gfi1 knockout mice with wildtype cells to determine global gene expression changes by microarray analysis
Project description:Hematopoietic stem cells (HSCs) and lymphoid-primed multi-potential progenitors (LMPPs) are able to initiate both lymphoid and myeloid differentiation. We show here that the transcriptional repressor Gfi1 (growth factor independence 1) implements a specific gene expression program in HSCs and LMPPs that is critical for their survival and lymphoid differentiation potential. We present evidence that Gfi1 is required to maintain expression of genes involved in lymphoid development such as Flt-3, IL7R, Ebf1, Rag1, CCR9 and Notch1 and controls myeloid lineage commitment by regulating expression of genes such as Hoxa9 or M-CSFR. Gfi1 also inhibits apoptosis in HSCs by repressing pro-apoptotic genes such as Bax or Bak. As a consequence, Gfi1-/- mice show defects in self renewal, survival and both myeloid and lymphoid development of HSCs and LMPPs. Co-expression of a Bcl-2 transgene can partially restore the function of HSCs in Gfi1-/- mice, but not the defects in early lymphoid development. Of interest, Gfi1-/- x Bcl-2 transgenic mice show an accelerated expansion of myeloid cells and succumb to a fatal myeloproliferative disease resembling chronic myelomonocytic leukemia (CMML). Our data show that Gfi1 protects HSCs against apoptosis, ensures the proper development of LMPPs and plays a role in the development of myeloid leukemia. We used microarrays to detail the global gene expression changes following knockout of Gfi1 in mouse LSK cells
Project description:Using (conditional) Gfi1 knock-out mice we show that ablation of the transcriptional repressor Gfi1 cures mice from lymphoid leukemia and reduces the expansion of primary human T-ALL xenografts in mice. We find that Gfi1 alters the p53 dependent transcriptional activation of a substantial subset of known p53 target genes and thus sets a threshold for cell death. We used Affymetrix mouse Gene-1.0-ST arrays to define the changes in the gene expression pattern of wt or Gfi1-KO thymocytes (Gfi1-fl/fl X MX-CRE, induced by pIpC) that were either untreated (WT, GfiKO thymocytes), irradiated (WT_irr, Gfi1KO_irr), ENU transformed (WT_Tum, Gfi1KO_Tum), or transformed by Notch1-CT and ENU-induced to enhance tumorigenesis (WT_Notch_Tum, Gfi1KO_Notch_Tum). The study should determine how loss of Gfi1 alters the gene expression pattern in irradiated or tumor derived thymocytes
Project description:Cellular binary fate decisions require the progeny to silence genes associated with the alternative fate. The major subsets of alpha:beta T cells have been extensively studied as a model system for fate decisions. While the transcription factor RUNX3 is required for the initiation of Cd4 silencing in CD8 T cell progenitors, it is not required to maintain the silencing of Cd4 and other helper T lineage genes. The other runt domain containing protein, RUNX1, silences Cd4 in an earlier T cell progenitor, but this silencing is reversed whereas the gene silencing after RUNX3 expression is not reverse. Therefore, we hypothesized that RUNX3 and not RUNX1 recruits other factors that maintains the silencing of helper T lineage genes in CD8 T cells. To this end, we performed a proteomics screen of RUNX1 and RUNX3 to determine candidate silencing factors.
Project description:GFI1 is a transcriptional regulator expressed in lymphoid cells, and an "oncorequisite" factor required for development and maintenance of T-lymphoid leukemia. GFI1 deletion causes hypersensitivity to ionizing radiation, for which the molecular mechanism remains unknown. Here, we demonstrate that GFI1 is required in T cells for the regulation of key DNA damage signalling and repair proteins. Specifically, GFI1 interacts with the arginine methyltransferase PRMT1 and its substrates MRE11 and 53BP1. We demonstrate that GFI1 enables PRMT1 to bind and methylate MRE11 and 53BP1, which is necessary for their function in the DNA damage response. Thus, our results provide evidence that GFI1 can adopt non-transcriptional roles, mediating the post-translational modification of proteins involved in DNA repair. These findings have direct implications for treatment responses in tumours overexpressing GFI1 and suggest that GFI1's activity may be a therapeutic target in these malignancies.
Project description:Introgressed variants from other species can be an important source of genetic variation because they may arise rapidly, can include multiple mutations on a single haplotype, and have often been pretested by selection in the species of origin. Although introgressed alleles are generally deleterious, several studies have reported introgression as the source of adaptive alleles-including the rodenticide-resistant variant of Vkorc1 that introgressed from Mus spretus into European populations of Mus musculus domesticus. Here, we conducted bidirectional genome scans to characterize introgressed regions into one wild population of M. spretus from Spain and three wild populations of M. m. domesticus from France, Germany, and Iran. Despite the fact that these species show considerable intrinsic postzygotic reproductive isolation, introgression was observed in all individuals, including in the M. musculus reference genome (GRCm38). Mus spretus individuals had a greater proportion of introgression compared with M. m. domesticus, and within M. m. domesticus, the proportion of introgression decreased with geographic distance from the area of sympatry. Introgression was observed on all autosomes for both species, but not on the X-chromosome in M. m. domesticus, consistent with known X-linked hybrid sterility and inviability genes that have been mapped to the M. spretus X-chromosome. Tract lengths were generally short with a few outliers of up to 2.7 Mb. Interestingly, the longest introgressed tracts were in olfactory receptor regions, and introgressed tracts were significantly enriched for olfactory receptor genes in both species, suggesting that introgression may be a source of functional novelty even between species with high barriers to gene flow.
Project description:Using (conditional) Gfi1 knock-out mice we show that ablation of the transcriptional repressor Gfi1 cures mice from lymphoid leukemia and reduces the expansion of primary human T-ALL xenografts in mice. We find that Gfi1 alters the p53 dependent transcriptional activation of a substantial subset of known p53 target genes and thus sets a threshold for cell death. We used Affymetrix mouse Gene-1.0-ST arrays to define the changes in the gene expression pattern of wt or Gfi1-KO thymocytes (Gfi1-fl/fl X MX-CRE, induced by pIpC) that were either untreated (WT, GfiKO thymocytes), irradiated (WT_irr, Gfi1KO_irr), ENU transformed (WT_Tum, Gfi1KO_Tum), or transformed by Notch1-CT and ENU-induced to enhance tumorigenesis (WT_Notch_Tum, Gfi1KO_Notch_Tum).