Myeloid translocation gene 16 is required for maintenance of haematopoietic stem cell quiescence

Abstract

The t(8;21) and t(16;21) that are associated with acute myeloid leukaemia disrupt two closely related genes termed Myeloid Translocation Genes 8 (MTG8) and 16 (MTG16), respectively. Many of the transcription factors that recruit Mtg16 regulate haematopoietic stem and progenitor cell functions and are required to maintain stem cell self-renewal potential. Accordingly, we found that Mtg16-null bone marrow (BM) failed in BM transplant assays. Moreover, when removed from the animal, Mtg16-deficient stem cells continued to show defects in stem cell self-renewal assays, suggesting a requirement for Mtg16 in this process. Gene expression analysis indicated that Mtg16 was required to suppress the expression of several key cell-cycle regulators including E2F2, and chromatin immunoprecipitation assays detected Mtg16 near an E2A binding site within the first intron of E2F2. BrdU incorporation assays indicated that in the absence of Mtg16 more long-term stem cells were in the S phase, even after competitive BM transplantation where normal stem and progenitor cells are present, suggesting that Mtg16 plays a role in the maintenance of stem cell quiescence.

MTG16 is a tumor suppressor in colitis-associated carcinoma

“…Expression of genes critical to stem cell function is often perturbed in the process of carcinogenesis (i.e., APC, p53, KRAS) (18,19). As MTG16 contributes to hematopoietic stem cell function (20) and is critical to intestinal injury responses (10), we reasoned that MTG16 contributes to inflammatory carcinogenesis. To determine if its expression levels were altered in tumors generated via inflammatory carcinogenesis modeling, we treated WT mice using the scheme outlined in Figure 1A using standard azoxymethane (AOM)/DSS dosing (12.5 mg/kg AOM i.p.…”

“…To date, we have learned a great deal about the biological functions of MTG16 through the analysis of Mtg16 -/-mouse phenotypes. In addition to hematopoietic stem cell defects (20), these mice have increased enterocyte proliferation, altered intestinal differentiation, protection against radiation enteritis (12), and develop severe colitis after DSS-induced injury (10), indicating that MTG16 is a key contributor to intestinal epithelial homeostasis.…”

“…MTG16 is required for hematopoietic progenitor cell fate decisions and early progenitor differentiation (27). Accordingly, Mtg16 -/-bone marrow fails to rescue WT mice from lethal irradiation (20). Because MTG16 is critical in hematopoietic stem cell function and Mtg16 -/-colons exhibited greater inflammation and overall injury compared with WT, we characterized the intratumoral inflammatory cell infiltrate by immunohistochemistry.…”

“…It is well established that MTG16 is a regulator of hematopoietic stem cell function (20,27). To test whether the increased tumorigenesis observed in Mtg16 -/-mice was due to an MTG16 hematopoietic cell-autonomous effect, we transferred WT bone marrow into irradiated Mtg16 -/-and WT mice and subjected these mice to the AOM/DSS inflammatory carcinogenesis protocol ( Figure 8A).…”

Tgif1 Regulates Quiescence and Self-Renewal of Hematopoietic Stem Cells

“…The generation, maintenance, and genotyping of Tgif1 ϩ/Ϫ mice (C57BL/6, CD45.2 ϩ ) have been previously described (2,32 BrdU incorporation and apoptosis analysis. For bromodeoxyuridine (BrdU) incorporation assays, mice were sacrificed 2 h after intraperitoneal injection of 1 mg BrdU (33). Bone marrow lineage-negative cells were isolated using a MACS lineage cell depletion kit (Miltenyi Biotech, Germany).…”