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

描述（由申请人提供）：几十年来，对理解淋巴细胞迁移的探索一直在挑战多个实验室。多光子显微镜的最新发展开始揭示次级淋巴器官中淋巴细胞运动的动力学。相比之下，仍然几乎完全缺乏关于B系细胞在骨髓（BM）中分化期间的迁移和定位的信息。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。IL 7是维持B系特化和分化所必需的。然而，早期B细胞前体与IL-7+细胞相互作用的机制和动力学仍不清楚。在具体目标1中，我们定义了一种通过活体多光子显微镜观察B细胞前体与IL-7+基质细胞相互作用的策略。此外，我们将检验B细胞前体迁移和与IL-7+细胞粘附的缺陷削弱B细胞发育并导致B淋巴细胞减少症的假设。我们以前曾描述过发育中的B细胞在骨髓实质和血窦中的运动。控制BM中B细胞前体运动性的机制尚未得到表征。在具体目标2中，我们提出表征BM中B细胞前体迁移的机制。在B细胞发育的晚期，未成熟的B淋巴细胞获得排出能力并通过窦状隙网络离开BM。大量的工作已经证明，信号脂质鞘氨醇-1-磷酸（S1 P）和S1 P受体对于淋巴细胞从初级和次级淋巴器官的流出至关重要。然而，我们，最近，惊讶地发现一个最小的作用S1 P和它的G？未成熟B细胞从骨髓中排出的I蛋白偶联受体S1 P1。为了进一步定义S1 P独立的出口机制，我们在具体目标3中提出评估替代G？I蛋白偶联受体参与该过程。最后，我们将设计一种策略，用于可视化未成熟的B细胞从骨髓进入窦状隙。结合这些研究将开始详细的B细胞发育的显微解剖模型。

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.