Session: 501. Hematopoietic Stem and Progenitor Cells and Hematopoiesis: Basic and Translational: Poster III
Hematology Disease Topics & Pathways:
hematopoiesis, Biological Processes
Here, we created a separation of function mouse model to study the non-canonical functions of Jarid2 in hematopoiesis. Through CRISPR/Cas9 gene targeting, we created a genetic knock in mouse model by mutating lysine 116 to alanine (K116A), a point mutation that cannot be methylated by PRC2. We generated a Vav-cre:Jarid2fl/K116A (K116A) mouse model, that express one K116A mutated copy of Jarid2, while the other floxed copy will be conditionally knocked out by Vav-cre recombinase system in hematopoietic stem and progenitor cells (HSPCs). We hypothesized if Jarid2K116A HSPCs functionally phenocopy Vav-Cre:Jarid2fl/fl (Jarid2-KO) HSPCs then the function of Jarid2 in these cells is largely PCR2-dependent. However, if the output of Jarid2-K116A HSPCs resembles that of Vav-Cre:Jarid2fl/+ (Jarid2-HET) HSPCs, then this suggests Jarid2 has previously undescribed non-canonical functions in hematopoiesis.
To characterize the functional effects of this mutation, we performed competitive transplantation of stem and progenitor subsets. Transplantation of MPP1 (Lineage-/c-Kit+/Sca1+/CD135-/CD48-/CD150-) cells revealed that Jarid2-K116A MPPs behaved similarly to Jarid2-KO MPPs. Recipients of both Jarid2-K116A and Jarid2-KO MPPs displayed higher peripheral blood (53% and 60%, respectively) and bone marrow (33% and 43%, respectively) engraftment compared to the control (12% and 3%, respectively) and Jarid2-HET (37.5% and 11%, respectively) MPPs. Additionally, Jarid2-K116A mutation enhanced donor MPP1 chimerism over recipient cells and promoted MPP1 self-renewal, similarly to what we previously described for Jarid2-KO MPP1 cells. These results suggest that Jarid2 function in MPP1 cells is largely dependent on PRC2. However, competitive transplantation of Jarid2-K116A HSCs (HSCs; Lineage-/c-Kit+/Sca1+/CD135-/CD48-/CD150+) revealed a striking phenotype. Jarid2-K116A HSCs showed a neomorphic phenotype compared to control, Jarid2-HET and Jarid2-KO HSCs in both primary and secondary transplantations. Jarid2-K116A mutation significantly enhanced the peripheral blood and bone marrow myeloid engraftment (both 40% increase). Furthermore, Jarid2-K116A enhanced HSC fitness and self-renewal with these mutant HSCs able to gain increased chimerism in the HSC pool and increased donor-derived HSC number in the bone marrow of recipient mice (Figure 1). These results suggest that the unmethylated version of Jarid2-K116 exerts a neomorphic effect on HSC function confirming the importance of the post-translational modification at the K116 residue of Jarid2 in hematopoiesis. Thus far, our studies suggest that Jarid2 function is dependent on PRC2 in MPPs, but may act independently of PRC2 in HSCs. Ongoing studies are focused on examining the importance of PCR2-related Jarid2 function in malignant hematopoiesis, and determining if the ratio of methylated to unmethylated JARID2 influences leukemic transformation of human chronic myeloid disorders.
Disclosures: Celik: Incyte Corporation: Current Employment, Current equity holder in publicly-traded company. Challen: Incyte: Consultancy, Other: Sponsored Research agreements.
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