Signals directing the migration of hematopoietic progenitor into the thymus

描述(申请人提供)：允许祖细胞从血液运输到胸腺的分子信号知之甚少。我们实验室正在进行的研究表明，不同的造血祖细胞在胸腺内从血液中定居的能力不同。因此，下游多能祖细胞(MPPs)而不是造血干细胞(HSCs)都在血液中循环，但只有MPPs能够在胸腺内定居，如果放入血液中。我们进一步对MPP进行了分离，发现只有表达淋巴特异性基因RAG1和RAG2的MPP的早期淋巴祖细胞亚群(ELP)似乎能够有效地在胸腺内定居，而其他MPP亚群似乎不能迁移到胸腺。这项赠款申请的重点是了解ELP在胸腺内定居的选择性能力的分子基础。到目前为止，我们的数据表明趋化因子受体CCR9的表达在可以在胸腺内定居的ELP和RAG阴性的MPP和不能的HSCs之间受到调节。我们的数据进一步表明，CCR9的调节表达对于ELP在胸腺内生理定居的能力是重要的。然而，我们的初步数据也表明，更多的分子必须参与ELP经历调节胸腺定居的能力。在目标1中，我们建议识别CCR9以外的分子，其表达在HSCs和MPP之间调节。在目标2中，我们建议进行遗传功能获得实验，以确定CCR9和其他已识别的分子是否足以赋予通常无法进行这种迁移的祖细胞(如HSCs)胸腺归巢；并进行功能丧失实验，以确定这些分子是否在生理上对胸腺内循环的造血祖细胞的定居起作用。总之，这些研究将确定在祖细胞生理归巢到胸腺中至关重要的信号，并可能为需要改善胸腺重建的情况下的治疗干预提供新的途径，例如在骨髓移植后改善胸腺内T细胞重建，以及在衰老方面。关键人员。请参阅说明。根据需要使用续页，以如下所示的格式提供所需信息。从首席调查员开始。按字母顺序列出所有其他关键人员，姓氏在前。名字时代公共用户名组织在Avinash Bhandoola阿维纳什项目中的组织角色宾夕法尼亚州P.I.其他重要的贡献者名字组织在项目Paul E.Love National Institutes of Health，MD合作者Wolfgang Veninger Wistar Institute，Philadelphia，PA合作者Donald A.Baldwin University of Pennsylvania，PA合作者唐纳德·A·鲍德温(Donald A.Baldwin)，PA合作者指导成年小鼠胸腺内造血祖细胞定居的信号未知。我们建议鉴定由造血祖细胞表达的能够在胸腺内定居的归巢分子，并确定这些分子在胸腺定居过程中的作用。这些实验将允许对胸腺稳定祖细胞进行分子定义，并可能在临床环境中增强T细胞谱系重建的治疗性，如衰老和骨髓移植。

DESCRIPTION (provided by applicant): The molecular signals that allow progenitors to traffic to the thymus from the blood are very poorly understood. Work ongoing in our laboratory indicates that different hematopoietic progenitors differ in their ability to settle within the thymus from the blood. Hence downstream multipotent progenitors (MPPs) but not hematopoietic stem cells (HSCs) both circulate in blood, but only MPPs are able to settle within the thymus if placed in the blood. We have further fractionated MPPs, and find that only the early lymphoid progenitor subset (ELP) of MPPs, that expresses the lymphoid-specific genes RAG1 and RAG2, appears able to efficiently settle within the thymus, whereas other MPP subsets do not appear able to migrate into the thymus. This grant application is focused on understanding the molecular basis of the selective ability of ELPs to settle within the thymus. Our data thus far suggest that expression of the chemokine receptor CCR9 is regulated between ELPs that can settle within the thymus and RAG-negative MPPs and HSCs that cannot. Our data further indicate that regulated expression of CCR9 is important for the ability of ELPs to physiologically settle within the thymus. However, our preliminary data also indicate that additional molecules must be involved in the ability of ELPs to undergo regulated thymic settling. In Aim 1, we propose to identify molecules in addition to CCR9 whose expression is regulated between HSCs and MPPs. In Aim 2, we propose to perform genetic gain-of-function experiments to determine whether CCR9 and other identified molecules are sufficient to confer thymic homing on progenitors such as HSCs that normally fail to undertake this migration; and to perform loss of function experiments to determine whether such molecules physiologically play a role in the settling of circulating hematopoietic progenitors within the thymus. Together, these studies will identify the signals critically important in the physiological homing of progenitors to the thymus, and may provide new avenues for therapeutic interventions in circumstances where thymic reconstitution needs to be improved, such as improving intrathymic T cell reconstitution following bone marrow transplantation, and in aging. KEY PERSONNEL. See instructions. Use continuation pages as needed to provide the required information in the format shown below. Start with Principal Investigator. List all other key personnel in alphabetical order, last name first. Name eRA Commons User Name Organization Role on Project Avinash Bhandoola AVINASH University of PA P.I. OTHER SIGNIFICANT CONTRIBUTORS Name Organization Role on Project Paul E. Love National Institutes of Health, MD Collaborator Wolfgang Weninger Wistar Institute, Philadelphia, PA Collaborator Donald A. Baldwin University of Pennsylvania, PA Collaborator The signals that direct the settling of hematopoietic progenitors within the thymus of adult mice are unknown. We propose to identify homing molecules expressed by hematopoietic progenitors that are able to settle within the thymus, and to determine the role of these molecules in the process of thymic settling. These experiments will allow a molecular definition of thymus-settling progenitors, and may enable therapeutic enhancement of T lineage reconstitution in clinical settings such as aging and bone marrow transplantation.