Genetic mechanisms which control hematopoietic cell migration

描述(由申请人提供)：造血干细胞(HSC)迁移到骨髓内适当的微环境是骨髓移植(BMT)成功的关键。造血干细胞和造血祖细胞在骨髓移植期间和正常动态期的归巢在一定程度上由选择素控制，选择素是一个由3个黏附分子组成的家族，在炎症、转移和淋巴细胞再循环的环境中对成熟的白细胞募集也是至关重要的。特别是，骨髓干细胞的归巢依赖于骨髓内皮细胞上E-选择素和/或P-选择素的表达，这是进入骨髓内专门的利基环境的必备步骤。选择素的生理配体是碳水化合物，这些多糖是由一些糖基转移酶的顺序作用形成的。所有选择素配体生物合成的末端调控步骤是由11，3岩藻糖基转移酶Fuct-VII介导的，它将岩藻糖残基11，3添加到唾液酸乳糖胺前体上，形成类型(Neu5Ac(12-3)Gal(21-4)[Fuc(11-3)]GlcNAc-R)的结构。这些结构构成了选择素配体的基本元素。缺乏Fuct-VII的小鼠表现出中性粒细胞减少、造血改变以及免疫和炎症反应的严重缺陷，反映了这种酶的广泛关键重要性以及选择素参与的不同过程。在Fuct-VII基因缺失的小鼠中，Fuct-VII的表达模式以及缺乏任何与选择素配体无关的表型表明，该酶专门在选择素配体的生物合成中发挥作用。由于翻译后修饰，如磷酸化，在糖基转移酶活性的调节中没有作用，糖基转移酶的酶活性主要控制在基因表达水平上，如果不是唯一的话。然而，尽管Fuct-VII对于有效的造血、炎症和免疫至关重要，但令人惊讶的是，人们对编码这一关键酶的Fut7基因在不同造血谱系中的表达是如何调节的知之甚少。在这一应用中，我们建议进行实验，全面鉴定控制Fut7基因表达的顺式作用遗传元件，并开发一种转基因的、遗传互补的功能获得方法来测试这些元件在体内的功能。这些结果将为揭示控制Fut7基因表达的转录、遗传和表观遗传机制提供坚实的长期基础。与公众健康相关在骨髓移植过程中，被称为干细胞的特殊血细胞在血液中传播，并对来自组织的化学信号做出反应进入骨髓。这一过程涉及这些干细胞表面的特定糖类，这些糖类与骨髓中血管壁上的特定受体结合。因此，了解这些糖的表达是如何调节的，对于了解骨髓移植是如何工作的以及相关过程是非常重要的。

DESCRIPTION (provided by applicant): Migration of hematopoietic stem cells (HSC) to appropriate microenvironments within the bone marrow is critical to the success of bone marrow transplantation (BMT). Homing of HSC and hematopoietic progenitors both during BMT and during normal homeostasis is controlled in part by selectins, a family of 3 adhesion molecules which are also critical for mature leukocyte recruitment in settings of inflammation, metastasis, and lymphocyte recirculation. In particular, homing of HSC to bone marrow relies on expression of E-selectin and/or P-selectin on bone marrow endothelial cells as an obligate step in entering specialized niches within the marrow. The physiologic ligands for selectins are carbohydrates, and these glycans are formed by the sequential action of a number of glycosyltransferases. The terminal, regulated step in biosynthesis of all selectin ligands is mediated by the 11,3 fucosyltransferase FucT-VII, which adds a fucose residue 11,3 to a sialylated lactosamine precursor to form structures of the type (Neu5Ac(12-3)Gal(21-4)[Fuc(11-3)]GlcNAc-R). These structures constitute essential elements of ligands for selectins. Mice deficient in FucT-VII exhibit neutrophilia, altered hematopoiesis, and severe defects in immune and inflammatory responses, reflecting the broadly critical importance of this enzyme and the diverse set of processes in which selectins participate. The pattern of expression of FucT-VII and the lack of any phenotype unrelated to selectin ligands in FucT-VII null mice suggest that this enzyme is dedicated to function in selectin ligand biosynthesis. Because post-translational modifications such as phosphorylation play no role in the regulation of glycosyltransferase enzymatic activity, the enzymatic activity of glycosyltransferases is controlled primarily, if not exclusively, at the level of gene expression. However, despite the well documented critical importance of FucT-VII for effective hematopoiesis, inflammation and immunity, surprisingly little is known about how expression of the fut7 gene encoding this key enzyme is regulated in different hematopoietic lineages. In this application, we propose experiments to comprehensively identify cis-acting genetic elements which control fut7 gene expression, and to develop a transgenic, genetic complementation gain-of-function approach for testing the functionality of these elements in vivo. These results will provide a solid, long term foundation to unravel transcriptional, genetic, and epigenetic mechanisms which control fut7 gene expression. PUBLIC HEALTH RELEVANCE During a bone marrow transplant, specialized blood cells called stem cells travel through the bloodstream and enter the bone marrow in response to chemical signals from the tissues. This process involves specific sugars on the surface of these stem cells which bind to specific receptors on the blood vessel wall in the bone marrow. Understanding how expression of these sugars is regulated is therefore of high importance to understanding how bone marrow transplantation works as well as related processes.