Project description:Stem Cell Leukemia (Scl or Tal1) and Lymphoblastic Leukemia 1 (Lyl1) are highly related members of the basic helix-loop-helix (bHLH) family of transcription factors that are co- expressed in hematopoietic stem cells and the erythro-megakaryocytic lineages. Previous studies suggest that Scl is essential for hematopoietic development including primitive erythropoiesis. However, analysis of single-cell RNA-sequencing data of early embryos showed that primitive erythroid cells express both Scl and Lyl1. Therefore, to determine whether Lyl1 has a functional role in erythropoiesis, we crossed conditional Scl mice with transgenic mice expressing a Cre recombinase under the control of the Epo receptor, active in erythroid progenitors. Surprisingly, embryos with markedly reduced expression of Scl from E9.5 survived to adulthood. In contrast, mice with reduced expression of Scl and absence of Lyl1 (double knockout; DKO) died at E10.5 due to progressive loss of erythropoiesis. Consistent with a phenocopy of Gata1-null mice, gene expression profiling of DKO yolk sacs prior to the loss of erythrocytes (E9.5) revealed loss of Gata1 and many of the known target genes of the SCL-GATA1 complex. ChIP-seq analyses showed that LYL1 exclusively bound a small subset of SCL targets including GATA1. Together, these data show for the first time that Scl and Lyl1 share functional roles in primitive erythropoiesis.
Project description:This SuperSeries is composed of the SubSeries listed below. Germline GATA1 mutations resulting in the production of an amino-truncated protein termed GATA1s (for M-bM-^@M-^\shortM-bM-^@M-^]) cause congenital hypoplastic anemia. Similar somatic mutations promote transient myeloproliferative disease and acute megakaryoblastic leukemia in trisomy 21 patients. Here we show that induced pluripotent stem cells (iPSCs) from patients with GATA1-truncating mutations exhibit impaired erythroid potential but enhanced megakaryopoiesis and myelopoiesis, faithfully recapitulating the major phenotypes of associated diseases. Similarly, GATA1s promotes megakaryopoiesis but not erythropoiesis in developmentally arrested Gata1- murine megakaryocyte-erythroid progenitors derived from murine embryonic stem cells (ESCs). Transcriptome studies demonstrate a selective deficiency in the ability of GATA1s to activate erythroid-expressed genes within populations of hematopoietic progenitors. Although its DNA binding domain is intact, chromatin immunoprecipitation studies show that GATA1s binding at specific erythroid regulatory regions is impaired, while binding at many non-erythroid sites, including megakaryocytic and myeloid target genes, is normal. These observations point to lineage specific GATA1 co-factor associations essential for normal chromatin occupancy and provide mechanistic insights into how GATA1s mutations cause human disease. More broadly, our studies underscore the value of ESCs and iPSCs to recapitulate and study disease phenotypes. Refer to individual Series
Project description:This SuperSeries is composed of the SubSeries listed below. Germline GATA1 mutations resulting in the production of an amino-truncated protein termed GATA1s (for “short”) cause congenital hypoplastic anemia. Similar somatic mutations promote transient myeloproliferative disease and acute megakaryoblastic leukemia in trisomy 21 patients. Here we show that induced pluripotent stem cells (iPSCs) from patients with GATA1-truncating mutations exhibit impaired erythroid potential but enhanced megakaryopoiesis and myelopoiesis, faithfully recapitulating the major phenotypes of associated diseases. Similarly, GATA1s promotes megakaryopoiesis but not erythropoiesis in developmentally arrested Gata1- murine megakaryocyte-erythroid progenitors derived from murine embryonic stem cells (ESCs). Transcriptome studies demonstrate a selective deficiency in the ability of GATA1s to activate erythroid-expressed genes within populations of hematopoietic progenitors. Although its DNA binding domain is intact, chromatin immunoprecipitation studies show that GATA1s binding at specific erythroid regulatory regions is impaired, while binding at many non-erythroid sites, including megakaryocytic and myeloid target genes, is normal. These observations point to lineage specific GATA1 co-factor associations essential for normal chromatin occupancy and provide mechanistic insights into how GATA1s mutations cause human disease. More broadly, our studies underscore the value of ESCs and iPSCs to recapitulate and study disease phenotypes.
Project description:DS children have a 500-fold increased risk for developing acute megakaryoblastic leukemia (AMKL). Around 10% of DS newborns have a transient myeloproliferative disorder (TMD) that resolves spontaneously. Somatic mutations acquired during fetal hematopoiesis in the GATA1 transcription factor are detected in megakaryoblasts from all the DS TMDs or AMKLs. GATA1 is an X chromosome transcription factor essential for the development of multiple hematopoietic lineages. Loss of GATA1 results in embryonic lethality due to severe anemia. The GATA1 mutations result in the expression of a shorter isoform, GATA1s. Replacement of GATA1 with GATA1s causes transient proliferation of immature fetal megakaryocytic progenitors. The Hsa21 ETS transcription factor, ERG, is expressed in megakaryocytes and erythrocytes and is involved in several types of cancer. Mutation in GATA1 gene leading to expression of the short isoform (GATA1s) that occurs on the background of trisomy 21 is regarded as one of the driving forces for megakaryocytic expansion observed in DS fetal livers. ERG, which is located on chromosome 21, is considered one of the leading candidates to cooperate with GATA1 mutation in the generation of DS AMKL. To study the in vivo cooperation between ERG and GATA1 isoforms, we crossed the ERG transgenic mice with the GATA1s Knock-in mice (GATA null background). We found that males expressing both ERG and the short isoform of GATA1(GATA1s) died in uterus between embryonic days E121/2 and E141/2.We studied erythropoiesis and megakaryopoiesis in fetal livers from the different genotypes generated from our cross. We used expression array to study the specific interaction of ERG with the different GATA1 isoforms in fetal livers from E121/2 and E141/2 and identify ERG, GATA1 and GATA1s target genes by comparing sets of genes that are activated or repressed in the presence of ERG and the two isoforms of GATA1.
Project description:In this project, we studied a mouse model of human Down Syndrome (DS) megakaryocytic leukemia involving mutations in the GATA1 transcription factor (called GATA1s mutation). The model was generated through retroviral insertional mutagenesis in Gata1s mutant fetal liver progenitors. In this study, we analyzed the dependency of these leukemic cells on the Gata1s mutant protein. Here we report Gata1s mutant leukemic cells were dependent on this mutant protein. Introduction of the full-length Gata1 protein to these cells led to their reduced proliferation and increased differentiation along the megakaryocytic lineage. We transduced leukemic cells with Gata1/estrogen receptor fusion cDNA (Gata1-ER) and generated stable cell lines. Addition of beta-estradiol to culture medium led to activation of the full-length Gata1 protein in synchronized leukemic cells. Gene expression profiles were collected at multiple time points.
Project description:DS children have a 500-fold increased risk for developing acute megakaryoblastic leukemia (AMKL). Around 10% of DS newborns have a transient myeloproliferative disorder (TMD) that resolves spontaneously. Somatic mutations acquired during fetal hematopoiesis in the GATA1 transcription factor are detected in megakaryoblasts from all the DS TMDs or AMKLs. GATA1 is an X chromosome transcription factor essential for the development of multiple hematopoietic lineages. Loss of GATA1 results in embryonic lethality due to severe anemia. The GATA1 mutations result in the expression of a shorter isoform, GATA1s. Replacement of GATA1 with GATA1s causes transient proliferation of immature fetal megakaryocytic progenitors. The Hsa21 ETS transcription factor, ERG, is expressed in megakaryocytes and erythrocytes and is involved in several types of cancer. Mutation in GATA1 gene leading to expression of the short isoform (GATA1s) that occurs on the background of trisomy 21 is regarded as one of the driving forces for megakaryocytic expansion observed in DS fetal livers. ERG, which is located on chromosome 21, is considered one of the leading candidates to cooperate with GATA1 mutation in the generation of DS AMKL. To study the in vivo cooperation between ERG and GATA1 isoforms, we crossed the ERG transgenic mice with the GATA1s Knock-in mice (GATA null background). We found that males expressing both ERG and the short isoform of GATA1(GATA1s) died in uterus between embryonic days E121/2 and E141/2.We studied erythropoiesis and megakaryopoiesis in fetal livers from the different genotypes generated from our cross.
Project description:In this project, we studied a mouse model of human Down Syndrome (DS) megakaryocytic leukemia involving mutations in the GATA1 transcription factor (called GATA1s mutation). The model was generated through retroviral insertional mutagenesis in Gata1s mutant fetal liver progenitors. In this study, we analyzed the dependency of these leukemic cells on the Gata1s mutant protein. Here we report Gata1s mutant leukemic cells were dependent on this mutant protein. Introduction of the full-length Gata1 protein to these cells led to their reduced proliferation and increased differentiation along the megakaryocytic lineage.
Project description:Erythro-myeloid progenitors (EMP) and their progeny were labeled with YFP in mouse embryos using genetic fate mapping (constitutive Csf1r-iCre;Rosa26-eYFP or inducible Csf1r-MeriCreMer;Rosa26-eYFP injected at embryonic day E8.5 with 4-hydroxytamoxifen). EMP-derived progenitors (Lin- Kit+ YFP+) were sorted by FACS for single-cell transcriptomic analysis using the MARS-Seq approach. The purpose was to uncover heterogeneity and differentiation trajectories of EMP by comparing their transcriptional status at different developmental timepoints (E9.5, E10.5 and E12.5) and across niches (yolk sac and fetal liver).
Project description:The goal of this study is to derive a mouse model of human Down Syndrome (DS) megakaryocytic leukemia involving mutations in the hematopoietic transcription factor, GATA1 (called GATA1s mutation). We achieved this through transduction of Gata1s mutant fetal progenitors by MSCV-based retrovirus expressing a GFP marker, followed by in vitro selection (for immortalized cell lines), and then in vivo selection (for transformed cell lines) through transplantation. Here we report one such cell line [T6(6)] that gives rise to megakaryocytic leukemia (M7 leukemia) upon transplantation.