Control of B-lineage cell migration during differentiation in bone marrow

描述（由申请人提供）：几十年来，了解淋巴细胞迁移的探索一直是多个实验室面临的挑战。近年来多光子显微镜的发展使人们对次级淋巴器官中淋巴细胞的运动动力学有了一些了解。相比之下，关于骨髓（BM）分化过程中b系细胞迁移和定位的信息仍然几乎完全缺乏。b细胞前体与表达关键信号（如IL-7）的特化BM基质细胞相互作用。伊尔

DESCRIPTION (provided by applicant): The quest for understanding lymphocyte migration has challenged multiple laboratories for several decades now. The recent development of multi-photon microscopes is beginning to shed some light on the dynamics of lymphocyte movement in secondary lymphoid organs. In contrast, there is still an almost complete lack of information on B-lineage cell migration and positioning during differentiation in bone marrow (BM). B-cell precursors interact with specialized BM stromal cells expressing critical signals, such as IL-7. IL 7 is essential for maintaining B-lineage specification and differentiation. Yet, the mechanism, and the dynamics, of early B cell precursor interaction with IL-7+ cells remain uncharacterized. In specific aim 1, we define a strategy for visualizing B cell precursor interactions with IL-7+ stromal cells by intravital multiphoton microscopy. Moreover, we will test the hypothesis that defects in B cell precursor migration and adhesion to IL-7+ cells cripple B cell development and cause of B-lymphopenia. We have previously described movement of developing B cells in BM parenchyma and sinusoids. The mechanism(s) controlling B cell precursor motility in BM remain uncharacterized. In specific aim 2 we propose to characterize the mechanism of B cell precursor migration in BM. In late stages of B cell development, immature B-lymphocytes acquire egress capability and exit BM through the sinusoidal network. A significant body of work has demonstrated that the signaling lipid sphingosine-1-phosphate (S1P), and S1P receptors are critical for lymphocyte egress from primary and secondary lymphoid organs. However, we were, recently, surprised to find a minimal role for S1P and its G?i protein coupled receptor S1P1 in immature B cell egress from BM. In an attempt to further define S1P-independent egress mechanism(s), we propose in specific aim 3 to assess if alternative G?i protein coupled receptor(s) are involved in this process. Finally, we will devise a strategy for visualizing immature B cell egress from BM into sinusoids. Combined these studies will begin to detail a model of the microanatomy of B cell development.