Arginine methyltransferase PRMT5 is essential for sustaining normal adult hematopoiesis

Abstract

R e s e a R c h a R t i c l e3 5 3 3 jci.orgVolume 125 Number 9 September 2015 levels decreased dramatically, suggesting important posttranscriptional regulation of PRMT5 expression in these cells. Since straight Prmt5-KO mice die before birth (12), we generated Prmt5-conditional KO mice by first crossing Prmt5 FLIP-OUT mice (obtained from the European Mutant Mouse Archive [EMMA]) with Flp recombinase-expressing transgenic (Tg) mice to generate Prmt5-floxed mice, whereby exon 7 of the Prmt5 time PCR (qPCR) ( Figure 1A) and Western blot analysis ( Figure 1B). Prmt5 mRNA and protein levels were readily detected in HSPCs, with little change in mRNA levels in the various stem and progenitor cell populations. However, when cells underwent myeloid, erythroid, or lymphoid differentiation, PRMT5 protein levels decreased to 5% to 24% of the levels seen in HSPCs. Although Prmt5 mRNA was maintained in differentiated B cells, its protein BM cells and found a complete loss of this modification 7 days after Cre induction ( Figure 1C), suggesting that PRMT5 is indeed the major type 2 PRMT in these cells. Deletion of PRMT5 during adult hematopoiesis leads to severe cytopenias. The deletion of PRMT5 in 2-month-old mice had a profound effect on hematopoiesis. Two weeks after the first poly(I:C) injection, the Mx1Cre + Prmt5 fl/fl mice developed severe pallor due to anemia, and most of these PRMT5-deleted mice were moribund 1 to 2 days later, requiring euthanasia. Analysis of the peripheral blood of these mice revealed severe pancytopenia, with a more than 10-fold decrease in wbc, a 5-fold decrease in rbc, and a 100-fold decrease in platelet counts 15 days after Cre induction ( Figure 1D). BM cellularity of the PRMT5-deleted mice was reduced by more than 50% on day 7 and by more than 95% on day 15 ( Figure 1E), consistent with the development of aplastic anemia ( Figure 1G). While PRMT5 loss had little effect on spleen weight (or cellularity) on day 15 (Supplemental Figure 2, A and B), the size and cellularity of the thymus were significantly reduced on day 15 gene was flanked by 2 LoxP sites (Supplemental Figure 1A; mice and Mx1Cre-negative littermate controls. To delete Prmt5 in hematopoietic cells, 2 i.p. injections of poly(I:C) (10 mg/kg on days 0 and 1) were given to both the Mx1Cre -and Mx1Cre + Prmt5-floxed mice. Prmt5 loss was confirmed by PCR analysis of genomic DNA (Supplemental Figure 1B), by quantitative qPCR to detect Prmt5 mRNA (Supplemental Figure 1C), and by Western blot analysis to detect PRMT5 protein (Supplemental Figure 1D). This injection strategy was used in all subsequent experiments. Interestingly, loss of PRMT5 triggered the loss of MEP50 protein (Supplemental Figure 1D), a cofactor that is required for the enzymatic activity of PRMT5 on histones, without changing Mep50 mRNA levels (data not shown). This suggests a probable posttranscriptional effect of PRMT5 on MEP50 protein levels. We also determined the overall level of symmetrically dimethylated arginine in PRMT5-deleted and Prmt5 Δ/Δ mice (n = 3). P...

MTAP deletion confers enhanced dependency on the PRMT5 arginine methyltransferase in cancer cells

“…PRMT5 catalyzes the formation of symmetric dimethyl arginine (sDMA), while most other PRMTs generate asymmetric dimethyl arginine (aDMA) (17, 27, 28). Using an antibody previously shown to recognize sDMAs generated by PRMT5 (29), we observed decreased sDMA levels in MTAP− cells compared to isogenic, MTAP-reconstituted lines (Fig. 4A).…”

Arginine Methylation by PRMT1 Regulates Muscle Stem Cell Fate

“…CARM1/PRMT4-deficient mice have defects in adipogenesis, T cell differentiation, and hematopoiesis (11–13). PRMT5 is essential for mouse development, and whole-body genetic deletion leads to embryonic lethality (14), while conditional knockout of PRMT5 using Nestin-Cre demonstrated a key role in regulating the p53 pathway during neurogenesis (15) and a role for PRMT5 in adult hematopoiesis maintenance was shown using Mx1-Cre (16). Mice with whole-body knockout of PRMT6 are viable; however, the mouse embryo fibroblasts undergo premature senescence (17).…”

Genetic deletion or small-molecule inhibition of the arginine methyltransferase PRMT5 exhibit anti-tumoral activity in mouse models of MLL-rearranged AML

“…Yet another recent study using a small molecule inhibitor of PRMT5, describes a positive feedback loop between PRMT5 and BCR-ABL in chronic myeloid leukemia (22). Although we have recently described the effects of conditional deletion of PRMT5 in mouse hematopoietic stem/progenitor cells and characterized the role of PRMT5 in normal hematopoiesis (23), similar studies have not been performed in the context of MLL -rearranged leukemia. Using mouse models of these aggressive leukemias, here we establish that genetic deletion of PRMT5 or inhibition of PRMT5 methyltransferase activity with a small molecule inhibitor impairs MLL -rearranged leukemia in vitro and in vivo , without affecting the expression of MLL -fusion direct oncogenic targets.…”