Non-canonical Wnt signaling and lymphostromal interactions: impact of Frizzled6/Vangl2 on stem/progenitor cell function

成人免疫系统的所有细胞都来自少数骨髓造血干细胞(HSC)，这些细胞位于专门的口袋或壁龛中，周围是被认为调节HSC功能的其他细胞。HSC除了能够发育为不同的血细胞谱系外，还具有独特的自我更新能力。它们罕见的细胞分裂是不对称的，导致产生一个与母细胞相同的子代HSC，以及一个失去了几个干细胞特征的祖细胞。这种自我更新依赖于HSC-NICE的相互作用，对于循环血细胞的持续生成是必不可少的。该领域最大的技术挑战之一是开发在培养中扩大HSC的方法，同时限制其自我更新能力的丧失。我们相信，更好地了解生态位环境将有助于确定更好的培养条件。Wnt-信号蛋白家族对HSCNiche相互作用的调节是我实验室的主要主题之一。特别是，我最近的结果发现了一条非传统的信号通路，参与调节小鼠骨髓中的HSC数量。其中一个涉及的分子是细胞表面受体蛋白Frizzled6，我们最近的工作发现它是应激状态下HSC功能的重要调节因子。众所周知，该途径调节皮肤中的细胞取向和细胞与细胞的相互作用。我们认为，同样的信号也可能参与了HSCs与骨髓龛细胞的相互作用，并控制着HSCs在龛内的方向，从而影响其自我更新。因此，我们的长期目标是确定参与HSC-NICE相互作用并可用于维持HSC在培养中的关键的膜相关Wnt信号分子。目前的研究建议集中在Frizzled6影响HSC-NICE相互作用的机制、HSC在NICE内的定位以及其他相关蛋白在细胞内的定位。我们还将评估另一种已知的与Frizzled6在其他细胞类型中相互作用和协作的表面蛋白的作用。总之，这里提出的工作将提高我们对调节HSC在骨髓中定位的机制的理解。此外，这些研究应该有助于识别新的生长因子以促进HSC在培养中的扩增，并开发小鼠模型，以促进对非传统Wnt信号的进一步研究。

All cells of the adult immune system are derived from a small number of bone marrow hematopoietic stem cells (HSC) that are found in specialized pockets or niches, surrounded by other cells that are believed to regulate HSC function. In addition to being able to develop into the different blood cell lineages, HSC also have the unique ability to self-renew. Their infrequent cell divisions are asymmetrical, resulting in the generation of one daughter HSC, identical to the mother cell, and one progenitor cell that has lost several stem cell characteristics. This self-renewal is dependent on HSC-niche interactions and is essential for the continuous generation of circulating blood cells. One of the greatest technical challenges in the field is to develop methods for HSC expansion in culture while limiting the loss of their self-renewal capacity. We believe that a better understanding of the niche environment would help identify better culture conditions.Regulation of HSCniche interactions by the Wnt-family of signaling proteins is one of the main overarching themes in my laboratory. In particular, my recent results have identified a non-traditional signaling pathway that is involved in the regulation of HSC numbers in mouse bone marrow. One of the molecules involved is the cell surface receptor protein Frizzled6 that our recent work identifies as an essential regulator of HSC function under stress. The pathway is known to regulate cellular orientation and cell-cell interaction in the skin. We propose that the same signals could also be involved in the interaction of HSCs with the bone marrow niche cells and control the orientation of HSCs inside the niche, thus influencing their self-renewal. Our long-term goal, therefore, is to identify the key membrane-associated Wnt signaling molecules involved in HSC-niche interactions and that could be used for maintaining HSCs in culture.The current research proposal focuses on the mechanisms by which Frizzled6 could influence HSC-niche interactions, HSC orientation inside the niche, and the localization of other associated proteins inside the cell. We will also evaluate the role of another surface protein known to interact and collaborate with Frizzled6 in other cell types. Together the work proposed here will improve our understanding of the mechanisms that regulate HSC localization in the bone marrow. Furthermore, these studies should lead to the identification of novel growth factors for HSC expansion in culture and the development of mouse models to facilitate further research on non-traditional Wnt signaling.