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。产生适当数量的功能性血细胞， 谱系需要细胞内在的发育程序，但这些程序需要细胞外在的指导， 正确传达这些细胞生理需求的机制。细胞表面和细胞内的聚糖 细胞外环境位于细胞外信号传递的间期。总体 程序假说是细胞内在和外在聚糖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转移酶ST 6 GAL 1也是细胞外环境的居民。我们 初步数据表明，细胞外或外源性ST 6 GAL 1，以及可能的其他 骨髓中的糖基转移酶影响多水平血细胞的造血决定 发展在骨髓外，血小板活化后释放所需的唾液酸供体底物 来驱动外源性唾液酸转移酶催化。与项目1一起，我们将探讨这样一个想法， 巨核细胞（血小板的前体）通过类似的机制控制骨髓外源性唾液酸化。 与项目3一起，我们发现了糖胺聚糖之间完全出乎意料的相互作用， 与ST 6 GAL 1的细胞外基质的成分，我们已经确定了一些GAG模拟物与ST 6 GAL 1， 调节靶细胞上外源性ST 6 GAL 1唾液酸化的显著能力。 具有高度异质性表现和各种潜在驱动突变的造血紊乱是 克隆性髓系疾病如骨髓增生性肿瘤（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， 循环血小板数量和功能。我们的初步数据表明， 与这些疾病患者的血小板相关，这表明骨髓发生了根本性的变化， 环境和产生血小板的巨核细胞。我们假设糖基化，特别是 外源性糖基化，调节血细胞稳态，最终影响细胞的数量和功能。 在健康和疾病中循环血细胞。我们将在三个具体目标中检验这一假设，以1）理解 外源性ST 6 GAL 1如何调节HSPC维持; 2）了解骨髓中的外源性唾液酸化如何 调节;和3）启动关于糖基化在临床MDS和MPN中以及在临床MDS和MPN中如何修饰的首次研究。 小鼠模型。这项拟议的研究有望对外源性糖基化产生变革性的理解 在维持血细胞生成的关键细胞-生态位相互作用中。这也是一个开创性的调查， 临床MDS和MPN的糖科学，具有新的治疗和诊断潜力。

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.