Genome-Wide Analysis of Transcriptional Reprogramming in Mouse Models of Acute Myeloid Leukaemia

Abstract

Acute leukaemias are commonly caused by mutations that corrupt the transcriptional circuitry of haematopoietic stem/progenitor cells. However, the mechanisms underlying large-scale transcriptional reprogramming remain largely unknown. Here we investigated transcriptional reprogramming at genome-scale in mouse retroviral transplant models of acute myeloid leukaemia (AML) using both gene-expression profiling and ChIP-sequencing. We identified several thousand candidate regulatory regions with altered levels of histone acetylation that were characterised by differential distribution of consensus motifs for key haematopoietic transcription factors including Gata2, Gfi1 and Sfpi1/Pu.1. In particular, downregulation of Gata2 expression was mirrored by abundant GATA motifs in regions of reduced histone acetylation suggesting an important role in leukaemogenic transcriptional reprogramming. Forced re-expression of Gata2 was not compatible with sustained growth of leukaemic cells thus suggesting a previously unrecognised role for Gata2 in downregulation during the development of AML. Additionally, large scale human AML datasets revealed significantly higher expression of GATA2 in CD34+ cells from healthy controls compared with AML blast cells. The integrated genome-scale analysis applied in this study represents a valuable and widely applicable approach to study the transcriptional control of both normal and aberrant haematopoiesis and to identify critical factors responsible for transcriptional reprogramming in human cancer.

Low-level GATA2 overexpression promotes myeloid progenitor self-renewal and blocks lymphoid differentiation in mice

“…Consistent with this possibility, GATA2 is overexpressed in the BM of both pediatric and adult acute myeloid leukemia patients, and aberrant GATA2 expression is also observable in leukemic blasts [7][8][9][10]. Patients in remission display GATA2 levels that return to normal, whereas patients with resistant disease display continued GATA2 overexpression [8].…”

“…Interestingly, GATA2 activity elevation in leukemic blasts is lower than the high levels observed endogenously in BM CD34 þ cells [10], raising the possibility that elevated lowlevel and high-level expression might have different cellular effects. In an attempt to better understand the effects of GATA2 on lineage maturation, we developed a Tamoxifen (TAM)-inducible GATA2-estrogen receptor (ERT) construct that would provide us with a means to regulate activity.…”

The human GFI136N variant induces epigenetic changes at the Hoxa9 locus and accelerates K-RAS driven myeloproliferative disorder in mice

“…[40][41][42][43][44][45][46][47][48][49][50] As an example, we show here how an SNP that causes the expression of a variant form of a transcription factor (GFI136N) leads to specific epigenetic alterations and as a result of these changes might render myeloid precursors more susceptible to develop more quickly into preleukemic cells when an oncogenic event has occurred. To our knowledge, this is the first report of a mouse model, in which the introduction of a human coding SNP accelerates a myeloproliferative disease by inducing epigenetic changes.…”

GATA2 finds its macrophage niche

“…However, quantitative alterations in GATA2 expression, possibly secondary to the primary lesions, have been described. For example, CD34 pos cells from patients with aplastic anemia 10 and blasts from acute myeloid leukemia (AML) 11 are both characterized by reduced levels of GATA2. In addition, although hypomorphic GATA2 mutations do not induce a strong phenotype in mice, 12 genome-wide analyses of transcriptional reprogramming of mouse models of AML have identified GATA2 as one of the few key transcription factors whose expression is reduced in these leukemic blasts.…”

“…In addition, although hypomorphic GATA2 mutations do not induce a strong phenotype in mice, 12 genome-wide analyses of transcriptional reprogramming of mouse models of AML have identified GATA2 as one of the few key transcription factors whose expression is reduced in these leukemic blasts. 11 A preliminary report presented as a "late breaking" abstract at the 2010 American Society of Hematology annual meeting mapped mutations in the coding region of GATA2 in 4 patients with myelodysplatic syndrome (MDS) that did not report immunodeficiency. 13 This report also provided an initial characterization of the biologic consequences of the mutations on the DNA binding properties of GATA2 that included reduced affinity for the c-Fms promoter.…”