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Project description:Acute Lymphoblastic Leukemia (ALL) caused by chromosomal translocation involving the Mixed Lineage Leukemia (MLL) gene remains a poor prognosis disease, especially in infants. The most common MLL-rearrangement in infant ALL (iALL), MLL-AF4, originates in utero where the properties of fetal target cells likely provide a permissive landscape for transformation. We describe the first faithful MLL-AF4 iALL model derived by CRISPR-Cas9 genome editing of primary human fetal liver (FL) cells. Using this model, we demonstrate that H3K79me2/3 is increased during transformation as a direct consequence of MLL-AF4 binding, but correlates weakly with changes in gene expression. DOT1L, the only known H3K79 methyltransferase, does not form part of the MLL-AF4 complex. Instead, we identify PAF1 as a key protein recruited by the MLL-AF4 complex, which in turn can recruit DOT1L. These results explain the previously unclear link between MLL-AF4 binding and increased H3K79me2/3, and introduce an iALL-specific model for future drug studies.
2021-10-25 | GSE162032 | GEO
Project description:A novel human fetal model of infant ALL reveals a link between MLL-AF4, PAF1 and increased H3K79me2/3
| PRJNA680337 | ENA
Project description:A novel human fetal model of infant ALL reveals a link between MLL-AF4, PAF1 and increased H3K79me2/3 [RNA-seq]
| PRJNA680335 | ENA
Project description:Although 90% of children with acute lymphoblastic leukemia (ALL) are now cured, the prognosis for infant-ALL remains dismal. Infant-ALL is usually caused by a single genetic hit that arises in utero: an MLL/KMT2A gene rearrangement (MLL-r). This is sufficient to induce a uniquely aggressive and treatment-refractory leukemia compared to older children. The reasons for disparate outcomes in patients of different ages with identical driver mutations are unknown. Using the most common MLL-r in infant-ALL, MLL-AF4, as a disease model, we show that fetal-specific gene expression programs are maintained in MLL-AF4 infant-ALL but not in MLL-AF4 childhood-ALL. We use CRISPR-Cas9 gene editing of primary human fetal liver hematopoietic cells to produce a t(4;11)/MLL-AF4 translocation, which replicates the clinical features of infant-ALL and drives infant-ALL-specific and fetal-specific gene expression programs. These data support the hypothesis that fetal-specific gene expression programs cooperate with MLL-AF4 to initiate and maintain the distinct biology of infant-ALL.
| S-EPMC8616957 | biostudies-literature
Project description:Although 90% of children with acute lymphoblastic leukemia (ALL) are now cured, the prognosis of infant-ALL (diagnosis within the first year of life) remains dismal. Infant-ALL is usually caused by a single genetic hit that arises in utero: rearrangement of the MLL/KMT2A gene (MLL-r). This is sufficient to give rise to a uniquely aggressive and treatment-refractory leukemia compared to older children with the same MLL-r. The reasons for disparate outcomes in patients of different ages with identical molecular drivers are unknown. This paper addresses the hypothesis that fetal-specific gene expression programs co-operate with MLL-AF4 to initiate and maintain infant-ALL. Using direct comparison of fetal and adult HSC and progenitor transcriptomes we identify fetal-specific gene expression programs in primary human cells. We show that MLL-AF4-driven infant-ALL, but not MLL-AF4 childhood-ALL, displays expression of fetal-specific genes. In a direct test of this observation, we find that CRISPR-Cas9 gene editing of primary human fetal liver cells (to produce a t(4;11)/MLL-AF4 translocation) replicates the clinical features of infant-ALL and drives infant-ALL-specific and fetal-specific gene expression programs. These data strongly support the hypothesis that fetal-specific gene expression programs co-operate with MLL-AF4 to initiate and maintain the distinct biology of infant ALL.
2021-10-25 | GSE162034 | GEO
Project description:Previously, we identified SETD2 loss-of-function mutations in 22% of MLL-rearranged (MLLr) acute leukemia patients, implicating a mechanism for cooperativity between SETD2 mutations and MLL fusions. However, the detailed mechanism of how SETD2-H3K36me3 downregulation accelerates MLLr leukemia remains unclear. Here, we show that in MLLr leukemia, both H3K79me2 and H3K36me3 are aberrantly elevated and co-enriched in a group of genes. SETD2 inactivation leads to a global reduction of H3K36me3 and a further elevation of H3K79me2, but does not change the expression of known MLL fusion target genes. Instead, this pattern of histone changes is associated with transcriptional deregulation of a novel set of genes; downregulating tumor suppressors (for example, ASXL1) and upregulating oncogenes (for example, ERG). Taken together, our findings reveal a global crosstalk between the oncogenic DOT1L-H3K79me2 axis and the tumor suppressive SETD2-H3K36me3 axis in gene regulation, provide molecular insights into how SETD2 mutations accelerate MLLr leukemogenesis through differential regulation of additional tumor suppressors and oncogenes.
| S-EPMC6277029 | biostudies-literature
Project description:The most frequent MLL-gene rearrangement found in leukemia is a reciprocal translocation with AF4 on chromosome 4 resulting in the formation of the MLL-AF4 and the AF4-MLL fusion genes. The oncogenic role of MLL-AF4 is documented but the significance of the reciprocal product - AF4-MLL in leukemia is less clear. In the human leukemia cell lines - RS4;11 and SEMK2-M1, both of which express MLL-AF4 and AF4-MLL, we knocked down the expression of AF4-MLL using siRNA. Loss of AF4-MLL had no effect on the growth of either RS4;11 or SEMK2-M1 cells. Furthermore, in SEMK2-M1 cells there were no changes in cell cycle or apoptosis with loss of AF4-MLL. In contrast, knockdown of MLL-AF4 significantly inhibited growth of both RS4;11 and SEMK2-M1. Additionally, in SEMK2-M1 cells, loss of MLL-AF4 led to G2/M cell cycle arrest and increased apoptosis. Overall, these results demonstrate that in t(4;11) leukemia, the MLL-AF4 fusion protein is critical for leukemia cell proliferation and survival while the AF4-MLL fusion product is dispensable.
| S-EPMC3011030 | biostudies-literature
Project description:MLL-AF4+ blasts from infant B-ALL, CB-derived CD34+CD38-CD19-CD33- HSC, CB-derived CD34+CD19+CD33- B-cell HPCs and CB-derived CD34+CD33+CD19- myeloid HPCs. We used microarray to estudy gene expression profile comparing ALL vs HSC, HPC and myeloid HPSC. We used highly FACS-purified (purity>98%) MLL-AF4+ blasts from infant B-ALL, CB-derived CD34+CD38-CD19-CD33- HSC, CB-derived CD34+CD19+CD33- B-cell HPCs and CB-derived CD34+CD33+CD19- myeloid HPCs. For each independent sample technical duplicates were always performed. Total RNA was extracted using TRIol reagent, and quantified on a Nanodrop spectrophotometer and Bioanalyzer. High-quality RNA was reverse transcribed and the obtained cDNA was used as a template to synthesize biotinylanted cDNA, then was fragmented and hybridized as duplicates/triplicates to HG-U133 plus2.0 GeneChips (Affymetrix) according to manufacturer's guideline.
2016-03-22 | E-GEOD-79450 | biostudies-arrayexpress
Project description:MLL gene rearrangements (MLLr) are a common cause of aggressive, incurable acute lymphoblastic leukemias (ALL) in infants and children, most of which originate in utero. The most common MLLr produces an MLL-AF4 fusion protein. MLL-AF4 promotes leukemogenesis by activating key target genes, mainly through recruitment of DOT1L and increased histone H3 lysine-79 methylation (H3K79me2/3). One key MLL-AF4 target gene is PROM1, which encodes CD133 (Prominin-1). CD133 is a pentaspan transmembrane glycoprotein that represents a potential pan-cancer target as it is found on multiple cancer stem cells. Here we demonstrate that aberrant PROM1/CD133 expression is essential for leukemic cell growth, mediated by direct binding of MLL-AF4. Activation is controlled by an intragenic H3K79me2/3 enhancer element (KEE) leading to increased enhancer-promoter interactions between PROM1 and the nearby gene TAPT1. This dual locus regulation is reflected in a strong correlation of expression in leukemia. We find that in PROM1/CD133 non-expressing cells, the PROM1 locus is repressed by polycomb repressive complex 2 (PRC2) binding, associated with reduced expression of TAPT1, partially due to loss of interactions with the PROM1 locus. Together, these results provide the first detailed analysis of PROM1/CD133 regulation that explains CD133 expression in MLLr ALL.
| S-EPMC7116565 | biostudies-literature
Project description:MLL gene rearrangements (MLLr) are a common cause of aggressive, incurable acute lymphoblastic leukemias (ALL) in infants and children, most of which originate in utero. The most common MLLr produces an MLL-AF4 fusion protein. MLL-AF4 promotes leukemogenesis by activating key target genes, mainly through recruitment of DOT1L and increased histone H3 lysine-79 methylation (H3K79me2/3). One key MLL-AF4 target gene is PROM1, which encodes CD133 (Prominin-1). CD133 is a pentaspan transmembrane glycoprotein that represents a potential pan-cancer target as it is found on multiple cancer stem cells. Here we demonstrate that aberrant PROM1/CD133 expression is essential for leukemic cell growth, mediated by direct binding of MLL-AF4. Activation is controlled by an intragenic H3K79me2/3 enhancer element (KEE) leading to increased enhancer-promoter interactions between PROM1 and the nearby gene TAPT1. This dual locus regulation is reflected in a strong correlation of expression in leukemia. We find that in PROM1/CD133 non-expressing cells, the PROM1 locus is repressed by polycomb repressive complex 2 (PRC2) binding, associated with reduced expression of TAPT1, partially due to loss of interactions with the PROM1 locus. Together, these results provide the first detailed analysis of PROM1/CD133 regulation that explains CD133 expression in MLLr ALL.
| S-EPMC7787973 | biostudies-literature