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Deletion of the Hoxa Cluster in MLL-AF9 Is Incompatible with Leukemia Maintenance: RNAseq-based Quantitative Analysis of Wild Type and Hoxa-del Transcriptomes

ABSTRACT: High HOXA expression correlates with poor clinical outcome in AML, particularly those harboring MLL rearrangements (MLLr). The necessity of the HOXA cluster for the maintenance of MLLr-leukemia has not been elucidated. Primary leukemias were generated by transduction of MLL-AF9 (MA9) into hematopoietic stem and progenitor cells from compound Cre responsive transgenic mice for conditional deletion of the Hoxa locus. Hoxa deletion resulted in reduced proliferation, colony formation and repopulating ability in transplanted mice in which surviving leukemic cells retained at least one copy of the Hoxa cluster (Hoxa-del). Comparative RNA-seq analysis of leukemic MA9-Hoxa-wild type (WT) and MA9-Hoxa-del cells identified a unique gene signature.

ORGANISM(S): Mus musculus

PROVIDER: GSE113200 | GEO | 2021/04/16

REPOSITORIES: GEO

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Project description:T-cell acute lymphoblastic leukemia (T-ALL) is mostly characterized by specific chromosomal abnormalities, some occurring in a mutually exclusive manner possibly delineating specific T-ALL subgroups. One subgroup, including MLL-rearranged, CALM-AF10 or inv(7)(p15q34) cases, is characterized by elevated expression of HOXA genes. Using a gene expression based clustering analysis of 67 T-ALL cases with recurrent molecular genetic abnormalities and 25 samples lacking apparent aberrations, we identified 5 new cases with elevated HOXA levels. Using array-CGH, a cryptic and recurrent deletion, del(9)(q34.11q34.13), was exclusively identified in 3 of these 5 cases. This deletion results in a conserved SET-NUP214 fusion product, that was also identified in the T-ALL cell line LOUCY. SET-NUP214 binds in the promoter regions of specific HOXA genes, where it may interact with CRM1 and DOT1L leading to the transcriptional activation of HOXA genes. Targeted inhibition of SET-NUP214 by siRNA abolished expression of HOXA genes, inhibited proliferation and induced differentiation in LOUCY but not in other T-ALL lines. We conclude that SET-NUP214 may contribute to the pathogenesis of T-ALL by enforcing T-cell differentiation arrest. We combined gene expression profiling and array-CGH analysis to detect a new and recurrent molecular cytogenetic abnormality in T-ALL patients that co-clustered with 5 well-defined HOXA-activated T-ALL samples. We describe the cloning of a recurrent SET-NUP214 fusion product in these samples, and identified a potential mechanism by which SET-NUP214 may activate the HOXA gene cluster as potential leukemogenic event in T-ALL. Experiment Overall Design: For 67 T-ALL patients having one of the major molecular cytogenetic abnormalities (i.e. TAL1 (n=24), LMO2 (n=9), HOXA (n=5), HOX11/TLX1 (n=7), and HOX11L2/TLX3 (n=22)), differentially expressed probesets were calculated from Affymetrix U133plus2.0 data based upon a Wilcoxon analysis and corrected for multiple testing for each probeset. Significant and differentially expressed probesets were obtained for the TAL1, HOX11 and HOX11L2 subgroups. No significant probesets were obtained for the HOXA subgroup or the LMO2 subgroup . As TAL1 and LMO2 both participate in the same transcriptional complex, activation of these genes may both lead to a highly similar expression profile. Combined analysis of TAL1 and LMO2 rearranged cases revealed significant and differentially expressed probesets that, as expected, almost entirely overlapped with the gene signature obtained for the TAL1-subgroup only. Next, we clustered 92 T-ALL cases, that besides the 67 cases as described above further included 25 T-ALL that lacked any of these recurrent abnormalities. Cluster analysis was performed based upon the top 25, 50 or 100 most significant probesets for the TAL1, TAL1/LMO2, HOX11 and HOX11L2 subgroups combined with 15 HOXA probesets identified by Soulier et al (2005)

Project description:Polyamines are aliphatic polycations that have emerged as important determinants of cell growth and viability in rapidly proliferating cells, including in the pathogenic protozoan parasite Leishmania donovani. In L. donovani, the polyamine spermidine is synthesized by the successive conversion of ornithine into putrescine (catalyzed by ornithine decarboxylase or ODC) and putrescine into spermidine (catalyzed by spermidine synthase or SPDSYN). Deletion of either ODC (del-odc) or SPDSYN (del-spdsyn) from the L. donovani genome renders these parasites auxotrophic for polyamines and these mutants are impaired in their ability to survive both in culture and within the mammalian host without the addition of exogenous polyamine supplementation. Significantly, del-odc parasites immediately cease proliferation after putrescine is removed from the culture media and perish within two weeks, while spermidine starved del-spdsyn mutants, which retain intracellular putrescine pools, show a slow-growth phenotype, and persist for several weeks in culture. To elucidate the key differences within the proteome of putrescine-starved del-odc cells and spermidine-starved del-spdsyn parasites, a shotgun quantitative proteomics approach was undertaken using TMT labeling and LC-MS/MS analysis. Briefly, three biological replicates each for mid-log phase del-odc and del-spdsyn promastigotes grown in the presence of exogenous putrescine (for del-odc) or spermidine (for del-spdsyn) supplementation were washed to remove the exogenous polyamine supplementation and incubated in polyamine-free media. At 24 and 48 h, cells from each biological replicate were isolated and prepared for tandem mass tag (TMT) labeling and downstream LC-MS/MS analyses. Peptides were identified using a database generated from the reference genome of L. donovani BPK282A1 strain. Changes in relative protein abundance for the polyamine-starved del-odc and del-spdsyn cell lines at 24 and 48 h were calculated by comparing aggregate total reporter ion intensities for each protein to that of the corresponding polyamine-supplemented 0-h timepoint.

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Deletion of the Hoxa Cluster in MLL-AF9 Is Incompatible with Leukemia Maintenance: RNAseq-based Quantitative Analysis of Wild Type and Hoxa-del Transcriptomes

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