Project description:Because PML-RARA-positive acute promyelocytic leukemia (APL) is a morphologically differentiated leukemia, much speculation has been made about whether its leukemic cell of origin might be committed myeloid precursor (e.g., a promyelocyte) vs. a hematopoietic stem/progenitor cell (HSPC). We originally targeted PML-RARA expression with CTSG regulatory elements, based on the early observation that this gene was maximally expressed in cells with promyelocyte morphology. Here, we show that both Ctsg and PML-RARA targeted to the Ctsg locus (in Ctsg-PML-RARA mice) are detected in the purified KLS cells of these mice (Kit+Lin-Sca+ cells, which are highly enriched for HSPCs), and this expression results in biological effects in multi-lineage competitive repopulation assays. Although PML-RARA is indeed expressed at high levels in the promyelocytes of Ctsg-PML-RARA mice, it does not significantly alter the transcriptional signature of these cells, or induce their self-renewal. In sum, these results suggest that in murine models, PML-RARA acts primarily to affect the function of multi-potent progenitor cells, rather than promyelocytes. Since PML/Pml is normally expressed in the HSPCs of both humans and mice, and since some human APL samples contain TCR rearrangements and express T lineage genes, we suggest that the very early hematopoietic expression of PML-RARA in our mouse model may closely mimic the physiologic expression pattern of PML-RARA in human APL patients. Bone marrow from individual mice expressing PML-RARA from the murine Ctg locus (mCG-PR) and littermate controls was harvested from both femurs and tibia. Standard cell lysis was performed, and total RNA was extracted from the cells and analyzed using the Affymetrix Mouse Exon 1.0 ST platform.
Project description:Membrane-less organelles are condensates formed by phase separation whose functions often remain enigmatic. Upon oxidative stress, PML scaffolds Nuclear Bodies (NBs) to regulate senescence or metabolic adaptation, but their role in pluripotency remains elusive. Here we establish that PML is required for basal SUMO2/3 conjugation in mESCs and oxidative stress-driven sumoylation in mESCs or in vivo. PML NBs create an oxidationprotective environment for UBC9-driven SUMO2/3 conjugation of PML partners, often followed by their poly-ubiquitination and degradation. Differential in vivo proteomics identified several members of the KAP1 complex as PML NB-dependent SUMO2-targets. The latter drives functional activation of this key epigenetic repressor. Accordingly, Pml-/- mESCs reexpress transposable elements and display features of totipotent-like cells, a process further enforced by PML-controlled SUMO2-conjugation of DPPA2. Finally, PML is required for adaptive stress responses in mESCs. Collectively, PML orchestrates mESC fate through SUMO2-conjugation of key transcriptional or epigenetic regulators, raising new mechanistic hypotheses about PML roles in normal or cancer stem cells.
Project description:The therapy-induced PML/RARA catabolism elicits the loss of APL-initiating cell self-renewal through PML NB reformation and P53 activation. These results explain the curative activity of the RA/arsenic combination, the resistance to RA of PLZF/RARA-driven APLs and they raise the prospect that activation of this PML/P53 checkpoint might have therapeutic values in other malignancies. Gene expression profiles of 36 transgenic induced APL and 36 viral transduction APL were hybridized using Affymetrix Mouse Gene 1.0 ST Arrays
Project description:Membrane-less organelles are condensates formed by phase separation whose functions often remain enigmatic. Upon oxidative stress, PML scaffolds Nuclear Bodies (NBs) to regulate senescence or metabolic adaptation, but their role in pluripotency remains elusive. Here we establish that PML is required for basal SUMO2/3 conjugation in mESCs and oxidative stress-driven sumoylation in mESCs or in vivo. PML NBs create an oxidationprotective environment for UBC9-driven SUMO2/3 conjugation of PML partners, often followed by their poly-ubiquitination and degradation. Differential in vivo proteomics identified several members of the KAP1 complex as PML NB-dependent SUMO2-targets. The latter drives functional activation of this key epigenetic repressor. Accordingly, Pml-/- mESCs reexpress transposable elements and display features of totipotent-like cells, a process further enforced by PML-controlled SUMO2-conjugation of DPPA2. Finally, PML is required for adaptive stress responses in mESCs. Collectively, PML orchestrates mESC fate through SUMO2-conjugation of key transcriptional or epigenetic regulators, raising new mechanistic hypotheses about PML roles in normal or cancer stem cells.
Project description:Acute promyelocytic leukemia (APL) is associated with PML-RARA expression and late myeloid maturation arrest. The myeloid restriction of PML-RARA dependent leukemia has been recapitulated in multiple mouse models of APL, including PML-RARA expressed from the Ctsg locus (mCG-PR). However, we report here that Ctsg expression is not limited to promyelocytes (as had previously been thought); Ctsg RNA is detectable in KLS cells, and mCG-PR mice express PML-RARA within the same compartment, an event that alters multilineage hematopoiesis. However, these animals only develop myeloid leukemia (consistent with the myeloid restriction of human PML-RARA-associated leukemia). Our results suggest that APL is shaped by myeloid- and development-specific factors that define the ultimate leukemic phenotype rather than PML-RARA acting in a committed myeloid precursor. Bone marrow from individual mice expressing PML-RARA from the murine Ctg locus (mCG-PR) and littermate controls was harvested from both femurs and tibia. Standard cell lysis was performed and total RNA was extracted from the flow sorted KLS and SLAM cells. A total of 13 specimens including 3 x mCG-PR_KLS_6wks, 2 x mCG-PR_KLS_13wks,2 x mCG-PR_SLAM_7wks, 4 x WT_KLS_12-13wks (control) and 2 x WT_SLAM_6wks (control) were analyzed using Affymetrics Mouse Exon 1.0 ST platform.
Project description:Acute promyeloid leukemia (APL) is characterized by the oncogenic fusion protein PML/RARα, a major etiological agent in APL. Although PML/RARα is critical, the molecular mechanisms remains largely unknown. Here, using an inducible system, we comprehensively analyzed the 3D genome organization in myloid cells and its reorganizationn after PML/RARα induction, and performed additional analysis in patient-derived APL cells with native PML/RARα. We discovered that PML/RARα mediate extensive chromatin interactions genome-wide. Globally, it redefine the chromatin topology of the in myloid genome toward a more condensed configuration in APL cells; locally, it intrude RNAPII-associated interaction dmains, interrupt myeloid-specific transcription factors binding at enhancers and super-enahncers, and lead to transcriptional repression of genes critical for myeloid differentiation and maturation. Together, our results provide novel insights of a topological framework for PML/RARα’s roles in transforming myeloid into leukemia, likely a general mechanism for oncogenic fusion proteins in cancers.
Project description:Acute promyeloid leukemia (APL) is characterized by the oncogenic fusion protein PML/RARα, a major etiological agent in APL. Although PML/RARα is critical, the molecular mechanisms remains largely unknown. Here, using an inducible system, we comprehensively analyzed the 3D genome organization in myloid cells and its reorganizationn after PML/RARα induction, and performed additional analysis in patient-derived APL cells with native PML/RARα. We discovered that PML/RARα mediate extensive chromatin interactions genome-wide. Globally, it redefine the chromatin topology of the in myloid genome toward a more condensed configuration in APL cells; locally, it intrude RNAPII-associated interaction dmains, interrupt myeloid-specific transcription factors binding at enhancers and super-enahncers, and lead to transcriptional repression of genes critical for myeloid differentiation and maturation. Together, our results provide novel insights of a topological framework for PML/RARα’s roles in transforming myeloid into leukemia, likely a general mechanism for oncogenic fusion proteins in cancers.
Project description:Acute promyeloid leukemia (APL) is characterized by the oncogenic fusion protein PML/RARα, a major etiological agent in APL. Although PML/RARα is critical, the molecular mechanisms remains largely unknown. Here, using an inducible system, we comprehensively analyzed the 3D genome organization in myloid cells and its reorganizationn after PML/RARα induction, and performed additional analysis in patient-derived APL cells with native PML/RARα. We discovered that PML/RARα mediate extensive chromatin interactions genome-wide. Globally, it redefine the chromatin topology of the in myloid genome toward a more condensed configuration in APL cells; locally, it intrude RNAPII-associated interaction dmains, interrupt myeloid-specific transcription factors binding at enhancers and super-enahncers, and lead to transcriptional repression of genes critical for myeloid differentiation and maturation. Together, our results provide novel insights of a topological framework for PML/RARα’s roles in transforming myeloid into leukemia, likely a general mechanism for oncogenic fusion proteins in cancers.