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MYBL2 is a sub-haploinsufficient tumor suppressor gene in myeloid malignancy.

Heinrichs S, Conover LF, Bueso-Ramos CE, Kilpivaara O, Stevenson K, Neuberg D, Loh ML, Wu WS, Rodig SJ, Garcia-Manero G, Kantarjian HM, Look AT - Elife (2013)

Bottom Line: Here we show that MYBL2, a gene within the 20q CDR, is expressed at sharply reduced levels in CD34+ cells from most MDS cases (65%; n = 26), whether or not they harbor 20q abnormalities.In a murine competitive reconstitution model, Mybl2 knockdown by RNAi to 20-30% of normal levels in multipotent hematopoietic progenitors resulted in clonal dominance of these 'sub-haploinsufficient' cells, which was reflected in all blood cell lineages.We conclude that downregulation of MYBL2 activity below levels predicted by classical haploinsufficiency underlies the clonal expansion of hematopoietic progenitors in a large fraction of human myeloid malignancies.

View Article: PubMed Central - PubMed

Affiliation: Institute of Transfusion Medicine , University Hospital Essen , Essen , Germany ; Department of Pediatric Oncology , Dana-Farber Cancer Institute , Boston , United States.

ABSTRACT
A common deleted region (CDR) in both myelodysplastic syndromes (MDS) and myeloproliferative neoplasms (MPN) affects the long arm of chromosome 20 and has been predicted to harbor a tumor suppressor gene. Here we show that MYBL2, a gene within the 20q CDR, is expressed at sharply reduced levels in CD34+ cells from most MDS cases (65%; n = 26), whether or not they harbor 20q abnormalities. In a murine competitive reconstitution model, Mybl2 knockdown by RNAi to 20-30% of normal levels in multipotent hematopoietic progenitors resulted in clonal dominance of these 'sub-haploinsufficient' cells, which was reflected in all blood cell lineages. By 6 months post-transplantation, the reconstituted mice had developed a clonal myeloproliferative/myelodysplastic disorder originating from the cells with aberrantly reduced Mybl2 expression. We conclude that downregulation of MYBL2 activity below levels predicted by classical haploinsufficiency underlies the clonal expansion of hematopoietic progenitors in a large fraction of human myeloid malignancies. DOI:http://dx.doi.org/10.7554/eLife.00825.001.

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Related in: MedlinePlus

Cell cycle analysis.Cell cycle phase distribution was determined by standard Propidium Iodide staining in control bone marrow cells and in sorted, RFP-negative cells (no Mybl2 RNAi) and in sorted, RFP-positive cells (Mybl2 knockdown).DOI:http://dx.doi.org/10.7554/eLife.00825.020
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fig6s2: Cell cycle analysis.Cell cycle phase distribution was determined by standard Propidium Iodide staining in control bone marrow cells and in sorted, RFP-negative cells (no Mybl2 RNAi) and in sorted, RFP-positive cells (Mybl2 knockdown).DOI:http://dx.doi.org/10.7554/eLife.00825.020

Mentions: The results confirmed expansion of the Mybl2-knockdown cell population compared to control bone marrow cells (Figures 5C and 6D; Figure 8—figure supplement 1C), which surpassed even the percentage of GFP+ cells in the blood (Figure 5—figure supplement 3). Lineage analysis showed that this expansion included lymphocytes as well as myeloid cells (Figure 5D–F), indicating clonal dominance originating from transduced multilineage long-term repopulating cells. Cells of the myeloid lineage were most prominently affected, as the frequency of GFP+ cells in the Gr1+/Mac1+ population exceeded 90% in three of five experimental animals. Bone marrow erythropoiesis was reduced by Mybl2 knockdown, as indicated by the decreased percentages of Ter119+ cells (Figures 5G–I and 6E; Figure 8—figure supplement 1D). As expected, analysis by Western blotting and QRT-PCR of bone marrow cells expressing the M3 Mybl2-shRNA as a single hairpin showed that Mybl2 expression levels were reduced to approximately 20–30% of control levels after long-term reconstitution (Figure 6F). We did not observe any effect of this level of Mybl2 knockdown on the cell cycle-phase distribution of bone marrow cells from mice 6–7 months post-transplantation (Figure 6—figure supplement 2), indicating that this level of decreased Mybl2 expression does not induce a delay in the G2-to-M-phase transition.


MYBL2 is a sub-haploinsufficient tumor suppressor gene in myeloid malignancy.

Heinrichs S, Conover LF, Bueso-Ramos CE, Kilpivaara O, Stevenson K, Neuberg D, Loh ML, Wu WS, Rodig SJ, Garcia-Manero G, Kantarjian HM, Look AT - Elife (2013)

Cell cycle analysis.Cell cycle phase distribution was determined by standard Propidium Iodide staining in control bone marrow cells and in sorted, RFP-negative cells (no Mybl2 RNAi) and in sorted, RFP-positive cells (Mybl2 knockdown).DOI:http://dx.doi.org/10.7554/eLife.00825.020
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3713455&req=5

fig6s2: Cell cycle analysis.Cell cycle phase distribution was determined by standard Propidium Iodide staining in control bone marrow cells and in sorted, RFP-negative cells (no Mybl2 RNAi) and in sorted, RFP-positive cells (Mybl2 knockdown).DOI:http://dx.doi.org/10.7554/eLife.00825.020
Mentions: The results confirmed expansion of the Mybl2-knockdown cell population compared to control bone marrow cells (Figures 5C and 6D; Figure 8—figure supplement 1C), which surpassed even the percentage of GFP+ cells in the blood (Figure 5—figure supplement 3). Lineage analysis showed that this expansion included lymphocytes as well as myeloid cells (Figure 5D–F), indicating clonal dominance originating from transduced multilineage long-term repopulating cells. Cells of the myeloid lineage were most prominently affected, as the frequency of GFP+ cells in the Gr1+/Mac1+ population exceeded 90% in three of five experimental animals. Bone marrow erythropoiesis was reduced by Mybl2 knockdown, as indicated by the decreased percentages of Ter119+ cells (Figures 5G–I and 6E; Figure 8—figure supplement 1D). As expected, analysis by Western blotting and QRT-PCR of bone marrow cells expressing the M3 Mybl2-shRNA as a single hairpin showed that Mybl2 expression levels were reduced to approximately 20–30% of control levels after long-term reconstitution (Figure 6F). We did not observe any effect of this level of Mybl2 knockdown on the cell cycle-phase distribution of bone marrow cells from mice 6–7 months post-transplantation (Figure 6—figure supplement 2), indicating that this level of decreased Mybl2 expression does not induce a delay in the G2-to-M-phase transition.

Bottom Line: Here we show that MYBL2, a gene within the 20q CDR, is expressed at sharply reduced levels in CD34+ cells from most MDS cases (65%; n = 26), whether or not they harbor 20q abnormalities.In a murine competitive reconstitution model, Mybl2 knockdown by RNAi to 20-30% of normal levels in multipotent hematopoietic progenitors resulted in clonal dominance of these 'sub-haploinsufficient' cells, which was reflected in all blood cell lineages.We conclude that downregulation of MYBL2 activity below levels predicted by classical haploinsufficiency underlies the clonal expansion of hematopoietic progenitors in a large fraction of human myeloid malignancies.

View Article: PubMed Central - PubMed

Affiliation: Institute of Transfusion Medicine , University Hospital Essen , Essen , Germany ; Department of Pediatric Oncology , Dana-Farber Cancer Institute , Boston , United States.

ABSTRACT
A common deleted region (CDR) in both myelodysplastic syndromes (MDS) and myeloproliferative neoplasms (MPN) affects the long arm of chromosome 20 and has been predicted to harbor a tumor suppressor gene. Here we show that MYBL2, a gene within the 20q CDR, is expressed at sharply reduced levels in CD34+ cells from most MDS cases (65%; n = 26), whether or not they harbor 20q abnormalities. In a murine competitive reconstitution model, Mybl2 knockdown by RNAi to 20-30% of normal levels in multipotent hematopoietic progenitors resulted in clonal dominance of these 'sub-haploinsufficient' cells, which was reflected in all blood cell lineages. By 6 months post-transplantation, the reconstituted mice had developed a clonal myeloproliferative/myelodysplastic disorder originating from the cells with aberrantly reduced Mybl2 expression. We conclude that downregulation of MYBL2 activity below levels predicted by classical haploinsufficiency underlies the clonal expansion of hematopoietic progenitors in a large fraction of human myeloid malignancies. DOI:http://dx.doi.org/10.7554/eLife.00825.001.

Show MeSH
Related in: MedlinePlus