Notch Effects on Hematopoietic Repopulating Cells

描述(申请人提供)：Notch受体广泛表达于造血祖细胞，当这些细胞被诱导过表达Notch1的胞浆结构域或暴露于外源性Notch配体形式时，造血祖细胞的分化受到抑制。我们的研究表明，在基因工程Notch配体存在的情况下培养人脐血细胞可以增加CD34+前体细胞的数量，包括那些能够重新填充免疫缺陷小鼠的CD34+前体细胞，我们的初步数据表明，Notch配体的剂量在决定造血干细胞命运方面起着关键作用。基于这些观察，我们假设使用不同剂量和类型的Notch配体可以增强造血细胞的自我更新。为了进一步研究Notch信号在造血中的作用及其对干细胞增殖和分化的影响，我们将确定：Notch配体Delta1对CD34+CD38-脐带血前体细胞的生长和分化的剂量依赖性效应，特别是对短期和长期NOD/SCID再填充细胞的产生(目标1)；不同类型的Notch配体是否诱导Notch信号，从而对CD34+CD38-脐血细胞的增殖和分化产生不同的影响(目标2)；以及不同剂量或类型的Notch配体诱导不同的细胞命运是否是由于诱导的Notch靶基因簇的不同(目标3)。我们的总体目标是明确配体诱导的Notch信号对造血干细胞增殖和分化的影响，作为控制这一活性的方法的基础，用于治疗应用，特别是改善脐带血移植。

DESCRIPTION (provided by applicant): Notch receptors are widely expressed by hematopoietic precursor cells and the differentiation of hematopoietic precursors is inhibited when these cells are induced to overexpress the constitutively active cytoplasmic domain of Notch1 or when they are exposed to exogenously presented Notch ligand forms. Our studies show that culture of human cord blood cells in the presence of engineered Notch ligand leads to increased numbers of CD34+ precursors, including those able to repopulate immunodeficient mice, and our preliminary data indicate that the dose of Notch ligand plays a critical role in determining hematopoietic stem cell fate. Based on these observations, we hypothesize that the use of different doses and types of Notch ligands can serve to enhance the self-renewal of hematopoietic repopulating cells. To further investigate the role of Notch signaling in hematopoiesis and its effect on stem cell proliferation and differentiation, we will determine: dose-dependent effects of the Notch ligand Delta1 on the growth and differentiation of CD34+CD38- cord blood precursors, in particular on the generation of short- and long-term NOD/SCID repopulating cells (Aim 1); whether different Notch ligand types induce Notch signaling that differentially affects the proliferation and differentiation of CD34+CD38- cord blood cells (Aim 2); and whether induction of different cell fates by different doses or types of Notch ligands results from differences in the constellation of induced Notch target genes (Aim 3). Our overall goal is to define the effects of ligand-induced Notch signaling on hematopoietic stem cell proliferation and differentiation as the basis for methods to manipulate this activity for therapeutic application, in particular, for improving umbilical cord blood transplantation.