Project description:TET-family dioxygenases oxidize 5-methylcytosine (5mC) in DNA, and exert tumor suppressor activity in many types of cancers. Even in the absence of TET coding region mutations, TET loss-of-function is strongly associated with cancer. We show that acute elimination of TET function induces the rapid development of an aggressive, fully-penetrant and cell-autonomous myeloid leukemia in mice, pointing to a causative role for TET-loss-of-function in this myeloid malignancy. Phenotypic and transcriptional profiling showed aberrant differentiation of hematopoietic stem/ progenitor cells, impaired erythroid and lymphoid differentiation and strong skewing to the myeloid lineage, with only a mild relation to changes in DNA modification. We also observed progressive accumulation of DNA damage and strong impairment of DNA break repair, suggesting a key role for TET proteins in maintaining genomic integrity.
Project description:To explore oncogene addiction programs in a genetically defined leukemia context we developed an AML mouse model driven by a conditional MLL-AF9 allele together with oncogenic Ras, which enabled us to examine the consequences of MLL-AF9 inhibition in established disease. In order to produce a tightly regulated system that was easy to monitor, we constructed two retroviral vectors containing dsRed-linked MLL-AF9 under control of a tetracycline response element promoter, and KrasG12D or NrasG12D linked to the “Tet-off” tet-transactivator, which activates TRE expression in a doxycycline repressible manner. Leukemias were generated by retroviral cotransduction of both vectors into hematopoietic stem and progenitor cells, which were transplanted into syngeneic mice. Cells harboring both constructs induced aggressive myelomonocytic leukemia. Five independent primary leukemia cell lines were established from bone marrow of terminal mice. Treatment of these lines with doxycycline rapidly turned off MLL-AF9 expression, and induced terminal myeloid differentiation and complete disease remission in vivo. To identify molecular mechanisms underlying addiction to MLL-AF9, we analyzed global gene expression changes following doxycycline-induced suppression of MLL-AF9. Independent primary acute myeloid leukemia lines induced by cotransduction of Tet-off MLL-AF9 together with either KrasG12D or NrasG12D were grown in culture and treated with doxycycline for 6 days to inactivate MLL-AF9 expression. In addition, primary acute myeloid leukemia lines with constitutive MLL-AF9 and KrasG12D were included to control for the effects of doxycycline. Untreated and treated cells were harvested for RNA extraction and hybridization to Affymetrix arrays.
Project description:The three mammalian TET dioxygenases oxidize the methyl group of 5-methylcytosine (5mC) in DNA, and the oxidised methylcytosines are essential intermediates in all known pathways of DNA demethylation. To define the in vivo consequences of complete TET deficiency, we inducibly deleted all three Tet genes in the mouse genome. Tet1/2/3 inducible TKO (iTKO) mice succumbed to acute myeloid leukaemia by 4-5 weeks. Single-cell RNA sequencing of Tet iTKO bone marrow cells revealed the appearance of new myeloid cell populations characterised by a striking increase in expression of all members of the stefin/cystatin gene cluster on mouse chromosome 16. In patients with acute myeloid leukaemia, high stefin/cystatin gene expression correlates with poor clinical outcomes. Increased expression of the clustered stefin/cystatin genes was associated with a heterochromatin-to-euchromatin compartment switch with readthrough transcription downstream of the clustered stefin/cystatin genes as well as other highly expressed genes but only minor changes in DNA methylation. Our data highlight new roles for TET enzymes that are distinct from their established function in DNA demethylation, and instead involve increased transcriptional readthrough and changes in three-dimensional genome organisation.
Project description:The three mammalian TET dioxygenases oxidize the methyl group of 5-methylcytosine (5mC) in DNA, and the oxidised methylcytosines are essential intermediates in all known pathways of DNA demethylation. To define the in vivo consequences of complete TET deficiency, we inducibly deleted all three Tet genes in the mouse genome. Tet1/2/3 inducible TKO (iTKO) mice succumbed to acute myeloid leukaemia by 4-5 weeks. Single-cell RNA sequencing of Tet iTKO bone marrow cells revealed the appearance of new myeloid cell populations characterised by a striking increase in expression of all members of the stefin/cystatin gene cluster on mouse chromosome 16. In patients with acute myeloid leukaemia, high stefin/cystatin gene expression correlates with poor clinical outcomes. Increased expression of the clustered stefin/cystatin genes was associated with a heterochromatin-to-euchromatin compartment switch with readthrough transcription downstream of the clustered stefin/cystatin genes as well as other highly expressed genes but only minor changes in DNA methylation. Our data highlight new roles for TET enzymes that are distinct from their established function in DNA demethylation, and instead involve increased transcriptional readthrough and changes in three-dimensional genome organisation.
Project description:The three mammalian TET dioxygenases oxidize the methyl group of 5-methylcytosine (5mC) in DNA, and the oxidised methylcytosines are essential intermediates in all known pathways of DNA demethylation. To define the in vivo consequences of complete TET deficiency, we inducibly deleted all three Tet genes in the mouse genome. Tet1/2/3 inducible TKO (iTKO) mice succumbed to acute myeloid leukaemia by 4-5 weeks. Single-cell RNA sequencing of Tet iTKO bone marrow cells revealed the appearance of new myeloid cell populations characterised by a striking increase in expression of all members of the stefin/cystatin gene cluster on mouse chromosome 16. In patients with acute myeloid leukaemia, high stefin/cystatin gene expression correlates with poor clinical outcomes. Increased expression of the clustered stefin/cystatin genes was associated with a heterochromatin-to-euchromatin compartment switch with readthrough transcription downstream of the clustered stefin/cystatin genes as well as other highly expressed genes but only minor changes in DNA methylation. Our data highlight new roles for TET enzymes that are distinct from their established function in DNA demethylation, and instead involve increased transcriptional readthrough and changes in three-dimensional genome organisation.
Project description:The three mammalian TET dioxygenases oxidize the methyl group of 5-methylcytosine (5mC) in DNA, and the oxidised methylcytosines are essential intermediates in all known pathways of DNA demethylation. To define the in vivo consequences of complete TET deficiency, we inducibly deleted all three Tet genes in the mouse genome. Tet1/2/3 inducible TKO (iTKO) mice succumbed to acute myeloid leukaemia by 4-5 weeks. Single-cell RNA sequencing of Tet iTKO bone marrow cells revealed the appearance of new myeloid cell populations characterised by a striking increase in expression of all members of the stefin/cystatin gene cluster on mouse chromosome 16. In patients with acute myeloid leukaemia, high stefin/cystatin gene expression correlates with poor clinical outcomes. Increased expression of the clustered stefin/cystatin genes was associated with a heterochromatin-to-euchromatin compartment switch with readthrough transcription downstream of the clustered stefin/cystatin genes as well as other highly expressed genes but only minor changes in DNA methylation. Our data highlight new roles for TET enzymes that are distinct from their established function in DNA demethylation, and instead involve increased transcriptional readthrough and changes in three-dimensional genome organisation.
Project description:The three mammalian TET dioxygenases oxidize the methyl group of 5-methylcytosine (5mC) in DNA, and the oxidised methylcytosines are essential intermediates in all known pathways of DNA demethylation. To define the in vivo consequences of complete TET deficiency, we inducibly deleted all three Tet genes in the mouse genome. Tet1/2/3 inducible TKO (iTKO) mice succumbed to acute myeloid leukaemia by 4-5 weeks. Single-cell RNA sequencing of Tet iTKO bone marrow cells revealed the appearance of new myeloid cell populations characterised by a striking increase in expression of all members of the stefin/cystatin gene cluster on mouse chromosome 16. In patients with acute myeloid leukaemia, high stefin/cystatin gene expression correlates with poor clinical outcomes. Increased expression of the clustered stefin/cystatin genes was associated with a heterochromatin-to-euchromatin compartment switch with readthrough transcription downstream of the clustered stefin/cystatin genes as well as other highly expressed genes but only minor changes in DNA methylation. Our data highlight new roles for TET enzymes that are distinct from their established function in DNA demethylation, and instead involve increased transcriptional readthrough and changes in three-dimensional genome organisation.
Project description:The three mammalian TET dioxygenases oxidize the methyl group of 5-methylcytosine (5mC) in DNA, and the oxidised methylcytosines are essential intermediates in all known pathways of DNA demethylation. To define the in vivo consequences of complete TET deficiency, we inducibly deleted all three Tet genes in the mouse genome. Tet1/2/3 inducible TKO (iTKO) mice succumbed to acute myeloid leukaemia by 4-5 weeks. Single-cell RNA sequencing of Tet iTKO bone marrow cells revealed the appearance of new myeloid cell populations characterised by a striking increase in expression of all members of the stefin/cystatin gene cluster on mouse chromosome 16. In patients with acute myeloid leukaemia, high stefin/cystatin gene expression correlates with poor clinical outcomes. Increased expression of the clustered stefin/cystatin genes was associated with a heterochromatin-to-euchromatin compartment switch with readthrough transcription downstream of the clustered stefin/cystatin genes as well as other highly expressed genes but only minor changes in DNA methylation. Our data highlight new roles for TET enzymes that are distinct from their established function in DNA demethylation, and instead involve increased transcriptional readthrough and changes in three-dimensional genome organisation.