Signals directing the migration of hematopoietic progenitor into the thymus

描述（由申请人提供）：允许祖细胞从血液运输到胸腺的分子信号尚不清楚。我们实验室正在进行的工作表明，不同的造血祖细胞从血液中进入胸腺的能力不同。因此，下游的多能祖细胞（MPPs）而不是造血干细胞（hsc）都在血液中循环，但如果将MPPs放入血液中，只有MPPs能够在胸腺内定居。我们进一步分离了MPP，发现只有表达淋巴特异性基因RAG1和RAG2的MPP的早期淋巴祖亚群（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。这项拨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和不能在胸腺内定居的rag阴性mpp和hsc之间受到调节。我们的数据进一步表明，CCR9的调控表达对于elp在胸腺内的生理定居能力很重要。然而，我们的初步数据也表明，额外的分子必须参与elp经历调节胸腺沉降的能力。在Aim 1中，我们提出鉴定除CCR9外，在造血干细胞和mpp之间表达受调控的分子。在目标2中，我们建议进行遗传功能获得实验，以确定CCR9和其他已鉴定的分子是否足以使胸腺归巢到通常不能进行这种迁移的祖细胞，如造血干细胞；并进行功能丧失实验，以确定这些分子是否在胸腺内循环造血祖细胞的沉淀中发挥生理作用。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，例如改善骨髓移植后胸腺内T细胞重建和衰老。关键人员。看到指令。根据需要使用延续页，以下列格式提供所需的信息。从首席调查员开始。按字母顺序列出所有其他重要人员，姓氏在前。名称eRA Commons用户名项目组织角色Avinash Bhandoola Avinash美国宾州大学P.I.其他重要贡献者项目组织角色Paul E. Love美国国立卫生研究院医学博士合作者Wolfgang Weninger费城Wistar研究所合作者Donald A. Baldwin宾夕法尼亚大学合作者指示成年小鼠胸腺内造血祖细胞沉积的信号是未知的。我们建议鉴定能够在胸腺内定居的造血祖细胞表达的归巢分子，并确定这些分子在胸腺定居过程中的作用。这些实验将允许胸腺沉降祖细胞的分子定义，并可能使临床环境中T谱系重建的治疗增强，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.