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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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Gene set enrichment analysis (GSEA) of the expression profile of CD34+ cells upon MYBL2 knockdown.The highest scoring subset using the ‘gene ontology processes’ gene sets of MSigDB (v3.0) was the ‘mitosis’ gene set (left panel). Gene sets reflecting distinct phases of the cell cycle were used to determine the prominent cycle phase, and the gene set ‘G2/M’ had the highest score (right panel).DOI:http://dx.doi.org/10.7554/eLife.00825.009
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fig2s2: Gene set enrichment analysis (GSEA) of the expression profile of CD34+ cells upon MYBL2 knockdown.The highest scoring subset using the ‘gene ontology processes’ gene sets of MSigDB (v3.0) was the ‘mitosis’ gene set (left panel). Gene sets reflecting distinct phases of the cell cycle were used to determine the prominent cycle phase, and the gene set ‘G2/M’ had the highest score (right panel).DOI:http://dx.doi.org/10.7554/eLife.00825.009

Mentions: To address whether reduced levels of MYBL2 expression actively contribute to the MDS phenotype or merely constitute a compensatory response to other abnormalities, we asked if reduced MYBL2 transcriptional activity is reflected in the MDS gene expression signature. To model gene dose insufficiency by RNA interference (RNAi), we used a set of eight shRNA-expression vectors in the MDS/AML cell line SKM1, which reduced MYBL2 expression to 5–30% of the endogenous MYBL2 levels (Figure 2A), approximating the endogenous levels we had identified in CD34+ cells from patients (Figure 1B). To identify the genes most highly correlated with decreased MYBL2 expression, we introduced our shRNA-expression vectors into normal primary human CD34+ cells and measured gene expression at 48 hr post-transduction. Nearly all differentially expressed genes were downregulated after MYBL2 knockdown (81 of 89 genes; Figure 2B and Figure 2—figure supplement 1). Because these results are based on eight different MYBL2-specific shRNAs, each with different knockdown efficiency, this analysis ensures the robustness of the data and eliminates potentially confounding off-target effects by individual shRNAs. Gene set enrichment analysis (GSEA) (Subramanian et al., 2005) identified mitosis as the key biological process reflected by the MYBL2 gene signature, specifically the G2-to-M phase transition (Figure 2—figure supplement 2) (Whitfield et al., 2002; Zhu et al., 2004; Shepard et al., 2005). Individual genes and their functions included the G2 cell cycle regulator cyclin B (CCNB1 and CCNB2), the early mitotic regulator FBXO5 and the coregulator of chromosome architecture CDCA2 (Supplementary file 1B).10.7554/eLife.00825.007Figure 2.Identification of an MYBL2-regulated gene expression signature and its enrichment in CD34+ cells from MDS patients.


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)

Gene set enrichment analysis (GSEA) of the expression profile of CD34+ cells upon MYBL2 knockdown.The highest scoring subset using the ‘gene ontology processes’ gene sets of MSigDB (v3.0) was the ‘mitosis’ gene set (left panel). Gene sets reflecting distinct phases of the cell cycle were used to determine the prominent cycle phase, and the gene set ‘G2/M’ had the highest score (right panel).DOI:http://dx.doi.org/10.7554/eLife.00825.009
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig2s2: Gene set enrichment analysis (GSEA) of the expression profile of CD34+ cells upon MYBL2 knockdown.The highest scoring subset using the ‘gene ontology processes’ gene sets of MSigDB (v3.0) was the ‘mitosis’ gene set (left panel). Gene sets reflecting distinct phases of the cell cycle were used to determine the prominent cycle phase, and the gene set ‘G2/M’ had the highest score (right panel).DOI:http://dx.doi.org/10.7554/eLife.00825.009
Mentions: To address whether reduced levels of MYBL2 expression actively contribute to the MDS phenotype or merely constitute a compensatory response to other abnormalities, we asked if reduced MYBL2 transcriptional activity is reflected in the MDS gene expression signature. To model gene dose insufficiency by RNA interference (RNAi), we used a set of eight shRNA-expression vectors in the MDS/AML cell line SKM1, which reduced MYBL2 expression to 5–30% of the endogenous MYBL2 levels (Figure 2A), approximating the endogenous levels we had identified in CD34+ cells from patients (Figure 1B). To identify the genes most highly correlated with decreased MYBL2 expression, we introduced our shRNA-expression vectors into normal primary human CD34+ cells and measured gene expression at 48 hr post-transduction. Nearly all differentially expressed genes were downregulated after MYBL2 knockdown (81 of 89 genes; Figure 2B and Figure 2—figure supplement 1). Because these results are based on eight different MYBL2-specific shRNAs, each with different knockdown efficiency, this analysis ensures the robustness of the data and eliminates potentially confounding off-target effects by individual shRNAs. Gene set enrichment analysis (GSEA) (Subramanian et al., 2005) identified mitosis as the key biological process reflected by the MYBL2 gene signature, specifically the G2-to-M phase transition (Figure 2—figure supplement 2) (Whitfield et al., 2002; Zhu et al., 2004; Shepard et al., 2005). Individual genes and their functions included the G2 cell cycle regulator cyclin B (CCNB1 and CCNB2), the early mitotic regulator FBXO5 and the coregulator of chromosome architecture CDCA2 (Supplementary file 1B).10.7554/eLife.00825.007Figure 2.Identification of an MYBL2-regulated gene expression signature and its enrichment in CD34+ cells from MDS patients.

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