Project 2: Extracellular Glycosylation and Blood Cell Production

项目2--项目摘要 维持造血对生命至关重要。在所有人中产生适当数量的功能血细胞 谱系需要细胞内的发育程序，但这些程序需要细胞外的指导 正确地传达这些细胞的生理需求的机制。细胞表面和细胞内的葡聚糖 细胞外环境存在于细胞-外在信号传递的界面上。最重要的是 程序假说是细胞内在和外在的糖链介导的机制调节维持， 造血细胞的分化和功能。 糖基转移酶，如唾液酸基转移酶ST6GAL1，也存在于细胞外环境中。我们的 初步数据表明细胞外ST6GAL1或外源性ST6GAL1，以及可能的其他 骨髓中的糖基转移酶在多个血细胞水平上影响造血决定 发展。在骨髓外，血小板在激活时释放所需的唾液酸供体底物。 驱动外源性唾液酸转移酶的催化作用。与项目1一起，我们将探讨 巨核细胞是血小板的前体，通过类似的机制控制骨髓的外源性唾液酸化。 与项目3一起，我们发现了糖胺聚糖之间完全意想不到的相互作用 含有ST6GAL1的细胞外基质的成分，我们已经鉴定了一些与GAG类似的成分 显著调节靶细胞上外源性ST6GAL1唾液酸化的能力。 具有高度异质性表现和不同潜在驱动因素突变的造血功能障碍是 定义克隆性髓系疾病的特征，如骨髓增生性肿瘤(MPN)和骨髓增生异常 综合征(MDS)。然而，MPN和MDS的一个关键共同特征是发育不良的巨核细胞 循环中的血小板数量和功能。我们的初步数据指向不同的糖基化信号 与这些疾病患者的血小板有关，表明骨髓发生了根本变化 环境和产生血小板的巨核细胞。我们假设糖基化，尤其是 外源性糖基化，调节血细胞稳态，最终影响血管内皮细胞的数量和功能 健康和疾病中的循环血细胞。我们将在三个具体目标上检验这一假设，以1)理解 外源性ST6GAL1如何调节HSPC的维持；2)了解骨髓中外源性唾液酸化是如何 3)首次研究糖基化如何在临床MDS和MPN以及在 老鼠模型。这项拟议的研究有望对外源性糖基化产生变革性的理解。 在细胞-利基相互作用中，对维持血细胞生产至关重要。这也是一项开创性的调查 临床MDS和MPN的血糖科学，具有新的治疗和诊断的潜力。

Project 2 – Project Summary Maintaining hematopoiesis is critical for life. Generating the proper numbers of functional blood cells across all lineages requires cell-intrinsic developmental programs, but these programs require guidance from cell-extrinsic mechanisms that correctly convey the physiologic needs for these cells. Glycans on the cell surface and in the extracellular milieu reside at the interphase through which the cell-extrinsic cues are conveyed. The overarching Program Hypothesis is that cell-intrinsic and extrinsic glycan-mediated mechanisms regulate maintenance, differentiation, and function of hematopoietic cells. Glycosyltransferases such as the sialyltransferase ST6GAL1 are also residents of the extracellular milieu. Our preliminary data point to a role for the extracellular, or extrinsic ST6GAL1, and possibly other glycosyltransferases in the marrow to influence hematopoietic decisions on multiple levels of blood cell development. Outside of the marrow, platelets upon activation release the sialic acid donor substrate required to drive extrinsic sialyltransferase catalysis. Together with Project 1, we will explore the idea that megakaryocytes, the precursors of platelets, control marrow extrinsic sialylation by a similar mechanism. Together with Project 3, we have uncovered a totally unexpected interaction between glycosaminoglycan components of the extracellular matrix with ST6GAL1, and we have identified a number of GAG-mimetics with striking ability to modulate extrinsic ST6GAL1 sialylation on target cells. Disturbed hematopoiesis with highly heterogenous presentation and varied underlying driver mutations is the defining hallmark of clonal myeloid diseases such as myeloproliferative neoplasms (MPN) and myelodysplastic syndromes (MDS). However, a key common feature of MPN and MDS is dysplastic megakaryocytes with altered circulating platelet numbers and function. Our preliminary data point to distinct glycosylation signatures associated with platelets from patients of these diseases, suggesting fundamental alterations to the bone marrow environment and the megakaryocytes that produce the platelets. We hypothesize that glycosylation, especially extrinsic glycosylation, regulates blood cell homeostasis, ultimately impacting the number and function of circulating blood cells in health and in disease. We will test this hypothesis in three Specific Aims to 1) understand how extrinsic ST6GAL1 regulates HSPC maintenance; 2) understand how extrinsic sialylation in the marrow is regulated; and 3) initiate a first-time study on how glycosylation is modified in clinical MDS and MPN and in mouse models. The proposed study is expected to yield transformative understanding of extrinsic glycosylation in cell-niche interactions critical to maintaining blood cell production. This is also a pioneering investigation into the glycoscience of clinical MDS and MPN, with potential for novel therapeutics and diagnostics.