Inhibitor of DNA binding proteins revealed as orchestrators of steady state, stress and malignant hematopoiesis.

Adult mammalian hematopoiesis is a dynamic cellular process that provides a continuous supply of myeloid, lymphoid, erythroid/megakaryocyte cells for host survival. This process is sustained by regulating hematopoietic stem cells (HSCs) quiescence, proliferation and activation under homeostasis and stress, and regulating the proliferation and differentiation of downstream multipotent progenitor (MPP) and more committed progenitor cells. Inhibitor of DNA binding (ID) proteins are small helix-loop-helix (HLH) proteins that lack a basic (b) DNA binding domain present in other family members, and function as dominant-negative regulators of other bHLH proteins (E proteins) by inhibiting their transcriptional activity.

ID2 and HIF-1α collaborate to protect quiescent hematopoietic stem cells from activation, differentiation, and exhaustion.

Defining mechanism(s) that maintain tissue stem quiescence is important for improving tissue regeneration, cell therapies, aging, and cancer. We report here that genetic ablation of Id2 in adult hematopoietic stem cells (HSCs) promotes increased HSC activation and differentiation, which results in HSC exhaustion and bone marrow failure over time. Id2Δ/Δ HSCs showed increased cycling, ROS production, mitochondrial activation, ATP production, and DNA damage compared with Id2+/+ HSCs, supporting the conclusion that Id2Δ/Δ HSCs are less quiescent.

Quiescence regulation by normal haematopoietic stem cells and leukaemia stem cells.

The haematopoietic system is maintained by rare haematopoietic stem cells (HSCs), which are quiescent most of the time and only divide occasionally to self-renew and/or to undergo commitment to clonal expansion via the generation of highly proliferative progenitor cells. The latter is responsible for the generation of all mature cells of the system through subsequent lineage commitment and terminal differentiation. Cells with similar properties also exist in leukaemias and are known as leukaemia stem cells (LSCs).

Recruitment of MLL1 complex is essential for SETBP1 to induce myeloid transformation.

Abnormal activation of due to overexpression or missense mutations occurs frequently in various myeloid neoplasms and associates with poor prognosis. Direct activation of transcription by SETBP1 and its missense mutants is essential for their transforming capability; however, the underlying epigenetic mechanisms remain elusive. We found that both SETBP1 and its missense mutant SETBP1(D/N) directly interact with histone methyltransferase MLL1.

Effects of captopril against radiation injuries in the Göttingen minipig model of hematopoietic-acute radiation syndrome.

Our laboratory has demonstrated that captopril, an angiotensin converting enzyme inhibitor, mitigates hematopoietic injury following total body irradiation in mice. Improved survival in mice is correlated with improved recovery of mature blood cells and bone marrow, reduction of radiation-induced inflammation, and suppression of radiation coagulopathy. Here we investigated the effects of captopril treatment against radiation injuries in the Göttingen mini pig model of Hematopoietic-Acute Radiation Syndrome (H-ARS).

Gene Inactivation in Adult Long-Term Hematopoietic Stem Cells Using Inducible Mouse Models.

The availability of mouse models that allow inducible long-term hematopoietic stem cell (LT-HSC)-specific gene deletion in adult mice has been limited. Therefore, analysis of gene function in adult LT-HSCs has mostly relied on models such as the interferon inducible Mx1-Cre model. Unfortunately, the Mx1-Cre strain has significant drawbacks due to lack of specificity towards the hematopoietic system, adverse effects of interferon induction on the interpretation of data, and Cre expression leakage.

is a critical regulator of adult long-term hematopoietic stem cell quiescence.

Regulation of quiescence is critical for the maintenance of adult hematopoietic stem cells (HSCs). Disruption of transcription factor gene during mouse embryonic development has been shown to cause a severe loss of fetal liver HSCs; however, the underlying mechanisms and the function of in adult HSCs remain unclear. To investigate the role of in adult HSCs, we generated a novel conditional knockout mouse model and deleted in adult mouse hematopoietic system using the IFN-inducible Our results show that deletion in the adult mouse hematopoietic system has a less severe effect on HSCs, causing a gradual decline of adult HSC numbers and a concomitant increase in the multipotent progenitor (MPP) compartment.

Pogz deficiency leads to transcription dysregulation and impaired cerebellar activity underlying autism-like behavior in mice.

Several genes implicated in autism spectrum disorder (ASD) are chromatin regulators, including POGZ. The cellular and molecular mechanisms leading to ASD impaired social and cognitive behavior are unclear. Animal models are crucial for studying the effects of mutations on brain function and behavior as well as unveiling the underlying mechanisms.

Id1 and Id3 Maintain Steady-State Hematopoiesis by Promoting Sinusoidal Endothelial Cell Survival and Regeneration.

Investigating mechanisms that regulate endothelial cell (EC) growth and survival is important for understanding EC homeostasis and how ECs maintain stem cell niches. We report here that targeted loss of Id genes in adult ECs results in dilated, leaky sinusoids and a pro-inflammatory state that increases in severity over time. Disruption in sinusoidal integrity leads to increased hematopoietic stem cell (HSC) proliferation, differentiation, migration, and exhaustion.

POGZ Is Required for Silencing Mouse Embryonic β-like Hemoglobin and Human Fetal Hemoglobin Expression.

Fetal globin genes are transcriptionally silenced during embryogenesis through hemoglobin switching. Strategies to derepress fetal globin expression in the adult could alleviate symptoms in sickle cell disease and β-thalassemia. We identified a zinc-finger protein, pogo transposable element with zinc-finger domain (POGZ), expressed in hematopoietic progenitor cells.

Analyzing gene function in adult long-term hematopoietic stem cells using the interferon inducible Mx1-Cre mouse system.

Long-term hematopoietic stem cells (LT-HSCs) have the ability to self-renew and differentiate into all blood cell lineages. Understanding the genetic networks that regulate LT-HSC function in the adult bone marrow requires inducible gene targeting and bone marrow transplantations. In this chapter we describe the use of the inducible Mx1-Cre mouse model to delete genes in LT-HSCs and methodologies for examining the function of LT-HSCs following deletion.

Somatic SETBP1 mutations in myeloid malignancies.

Here we report whole-exome sequencing of individuals with various myeloid malignancies and identify recurrent somatic mutations in SETBP1, consistent with a recent report on atypical chronic myeloid leukemia (aCML). Closely positioned somatic SETBP1 mutations encoding changes in Asp868, Ser869, Gly870, Ile871 and Asp880, which match germline mutations in Schinzel-Giedion syndrome (SGS), were detected in 17% of secondary acute myeloid leukemias (sAML) and 15% of chronic myelomonocytic leukemia (CMML) cases. These results from deep sequencing demonstrate a higher mutational detection rate than reported with conventional sequencing methodology.

Transplantation of mouse fetal liver cells for analyzing the function of hematopoietic stem and progenitor cells.

Hematopoietic stem cells are defined by their ability to self-renew and differentiate through progenitor cell stages into all types of mature blood cells. Gene-targeting studies in mice have demonstrated that many genes are essential for the generation and function of hematopoietic stem and progenitor cells. For definitively analyzing the function of these cells, transplantation studies have to be performed.

Setbp1 promotes the self-renewal of murine myeloid progenitors via activation of Hoxa9 and Hoxa10.

Acquisition of self-renewal capability by myeloid progenitors to become leukemic stem cells during myeloid leukemia development is poorly understood. Here, we show that Setbp1 overexpression efficiently confers self-renewal capability to myeloid progenitors in vitro, causing their immortalization in the presence of stem cell factor and IL-3. Self-renewal after immortalization requires continuous Setbp1 expression.

RapGEF2 is essential for embryonic hematopoiesis but dispensable for adult hematopoiesis.

RapGEF2 is one of many guanine nucleotide exchange factors (GEFs) that specifically activate Rap1. Here, we generated RapGEF2 conditional knockout mice and studied its role in embryogenesis and fetal as well as adult hematopoietic stem cell (HSC) regulation. RapGEF2 deficiency led to embryonic lethality at ~ E11.

Gene expression analysis of hematopoietic progenitor cells identifies Dlg7 as a potential stem cell gene.

Inducible hematopoietic stem/progenitor cell lines represent a model for studying genes involved in self-renewal and differentiation. Here, gene expression was studied in the inducible human CD34+ acute myelogenous leukemia cell line KG1 using oligonucleotide arrays and suppression subtractive cloning. Using this approach, we identified Dlg7, the homolog of the Drosophila Dlg1 tumor suppressor gene, as downregulated at the early stages of KG1 differentiation.

Flt3/Flk-2 ligand in combination with thrombopoietin decreases apoptosis in megakaryocyte development.

The growth factors thrombopoietin (TPO) and Flt3/Flk-2-ligand (FL), either independently or in combination, modulate megakaryocyte development. Our results show that bone marrow CD34+ cells cultured with TPO and FL differentiate at a slower rate into CD41+ cells and are delayed in apoptosis at the later stages of the cultures compared to cells cultured with TPO alone. Our data also show that FL in synergy with TPO may inhibit apoptosis in megakaryocyte development by up-regulating bcl-2 and inducing conformational changes of p53, in MK progenitors.

Flt3/Flk-2-ligand in synergy with thrombopoietin delays megakaryocyte development and increases the numbers of megakaryocyte progenitor cells in serum-free cultures initiated with CD34+ cells.

Megakaryocytopoiesis involves proliferation and maturation of committed precursors that increase their size by polyploidy, a process that is believed to be critical for the efficient production and release of platelets. Thrombopoietin has been shown to act on proliferation, maturation, and survival pathways in megakaryocytopoiesis. Less is known about the role of Flt3/Flk-2-ligand in this development.