Novel functions of polysialic acid in kidney and immune cell development

这项建议的目的是揭示聚唾液酸(PolySia)在造血干细胞(HSC)发育、造血和维持免疫平衡中的作用。在第一个资助期，我们鉴定了趋化因子CXCL12为新的PolySia结合蛋白。对缺乏多唾液酸转移酶ST8Sia4的小鼠的初步分析显示，表型变化与CXCR4/CXCL12信号轴缺陷动物的变化相似，包括HSC和免疫动态平衡的改变，以及老年小鼠自身免疫性疾病狼疮性肾炎的发展迹象。在下一个资助期，我们将研究CXCL12的结构与功能的关系，与P8项目密切合作，确定PolySia结合所涉及的关键残基。为了了解多唾液酸化如何促进HSC的发育，我们将扩展我们对构成St8sia4基因敲除小鼠的分析，并用分离的原代细胞进行功能分析。最后，我们将补充P2和P10项目的努力，通过建立B细胞特异性St8Sia4基因敲除小鼠来剖析ST8Sia4缺乏对自身免疫的影响。一个特别的焦点将集中在B细胞聚合唾液酸化对体液免疫反应和狼疮性肾炎的发展的作用。除了与P2、P8和P10的紧密互动外，我们还将与P1、P5和P9密切合作，并将得到P3和P7的支持。

The aim of this proposal is to unravel the role of polysialic acid (polySia) in the development of hematopoietic stem cells (HSC), hematopoiesis, and the maintenance of immune homeostasis. In the first funding period, we identified the chemokine CXCL12 as novel polySia binding protein. Initial analysis of mice lacking the polysialyltransferase ST8Sia4 revealed phenotypic alterations that are reminiscent to changes seen in animals with defects in the CXCR4/CXCL12 signaling axis, including altered HSC and immune homeostasis and signs for the development of the autoimmune disease Lupus nephritis in aged mice. In the next funding period, we will study structure-function relationships of CXCL12 to define, in close collaboration with project P8, key residues involved in polySia binding. To understand how polysialylation contributes to HSC development, we will extend our analyses in constitutive St8sia4 knockout mice and perform functional assays with isolated primary cells. Finally, we will complement efforts of projects P2 and P10 in dissecting the impact of ST8Sia4-deficiency on autoimmunity by generating B-cell specific St8Sia4 knockout mice. A specific focus will be set on the role of B-cell polysialylation for humoral immune response and the development of Lupus nephritis. Besides tight interactions with P2, P8 and P10, we will closely collaborate with P1, P5 and P9, and will get support from P3 and P7.