Notch Effects on Hematopoietic Repopulating Cells

描述（由申请人提供）：Notch受体由造血前体细胞广泛表达，并且当这些细胞被诱导过表达Notch 1的组成型活性胞质结构域时或当它们暴露于外源呈递的Notch配体形式时，造血前体的分化被抑制。 我们的研究表明，在工程Notch配体存在下培养人脐带血细胞导致CD 34+前体数量增加，包括能够重新填充免疫缺陷小鼠的那些，并且我们的初步数据表明Notch配体的剂量在确定造血干细胞命运中起着关键作用。 基于这些观察，我们假设使用不同剂量和类型的Notch配体可以用于增强造血重建细胞的自我更新。 为了进一步研究Notch信号传导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Delta 1对CD 34 + CD 38-脐带血前体的生长和分化，特别是对短期和长期NOD/SCID再增殖细胞的产生的剂量依赖性影响（Aim 1）;不同的Notch配体类型是否诱导差异性地影响CD 34 + CD 38-脐带血细胞的增殖和分化的Notch信号传导（Aim 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诱导的Notch靶基因群的差异引起的（目标3）。 我们的总体目标是确定配体诱导的Notch信号传导对造血干细胞增殖和分化的影响，作为操纵这种活性用于治疗应用的方法的基础，特别是用于改善脐带血移植。

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.