ATF4在造血干细胞衰老过程中的调控作用及机制

The applicant of this project has a solid research foundation in the regulation of hematopoietic stem cells (HSCs) (two Blood papers). The aging of HSCs is closely associated with the aging of the body. HSC aging causes the hematopoietic and immune dysfunction of the body, and the increased incidence of myeloid malignancies. Therefore, it is very necessary to discover the key regulatory factors involved in HSCs aging. Based on our previous study, we found that ATF4-/-HSCs shown the following aging-like phenotypes. (1) ATF4-/- HSCs displays a paradoxical increase in the stem cell pool and a significant decline in stem cell functions (i.e., impaired colony forming ability and decreased long-term and short-term repopulation ability). (2) Differentiation of young ATF4-/- HSCs is skewed toward myeloid lineage, accompanied by a significant decline in the lymphoid compartment. (3) ATF4-/- HSCs exhibit the increased levels of ROS (Reactive oxygen species), which has been associated with the aging phenotype in many cell types. Our aforementioned findings indicate that ATF4 may play a role in HSC aging. We employ in vivo and in vitro experiments to further investigate the roles of ATF4 in HSC aging. Firstly, we will perform β-gal staining to detect the aging status of ATF4-/-HSCs and detect the expression of aging-related genes in ATF4-/-HSCs. Secondly, we will investigate how ATF4 regulates the behaviors (self-renewal, differentiation, proliferation, apoptosis and homing) of HSCs under normal physiological and stress conditions. Thirdly, we will explore the underlying mechanism involved in the aging of ATF4-/- HSCs. We will uncover whether the function of ATF4 in the senescence of HSCs is mediated by its target gene Sirt1 or other abnormally activated signaling pathways. Finally, gene modification and ROS scavenger antioxidant—NAC treatment will be used to define whether the aging phenotype in ATF4-/- HSCs is corrected. The expected findings will provide new targets for the prevention and treatment of aging and aging related diseases.

本项目申请人在造血干细胞（HSCs）调控方面已具备坚实的研究基础（Blood两篇）。HSCs衰老与机体的衰老有着密切联系，HSCs衰老可引起机体造血和免疫功能衰退及肿瘤发生率增加，进一步发现HSCs衰老的关键调控因子至关重要。前期研究我们发现年轻的成年ATF4基因敲除小鼠的HSCs出现衰老样表型，如免疫表型的HSCs数量增加、髓系分化偏移、克隆形成和造血重建能力降低及功能性的HSCs减少，同时HSCs中ROS含量升高，这些提示ATF4可能参与HSCs衰老的调控。本项目将结合体内外实验进一步明确ATF4在HSCs衰老过程中的作用，以及ATF4在生理或应激状况下如何维持HSCs的稳态。其次探讨ATF4能否通过靶基因Sirt1或其它异常活化的信号通路来调节HSCs的衰老，最后采用基因修饰及ROS清除剂NAC处理行回复实验看能否纠正HSCs衰老表型。预期成果将为衰老及衰老相关疾病防治提供新靶标。

HSCs衰老与机体的衰老有着密切联系，HSCs衰老可引起机体造血和免疫功能衰退及肿瘤发生率增加，进一步发现HSCs衰老的关键调控因子至关重要。经过研究我们发现年轻的成年ATF4基因敲除小鼠的HSCs出现衰老样表型，如免疫表型的HSCs数量增加、髓系分化偏移、克隆形成和造血重建能力降低及功能性的HSCs减少，同时HSCs中ROS含量升高，这些提示ATF4参与HSCs衰老的调控。本课题结合体内外实验进一步明确了ATF4在HSCs衰老过程中的作用，以及ATF4在生理或应激状况下如何维持HSCs的稳态；进一步探讨了ATF4能通过靶基因Hif1a来调节ROS从而参与HSCs的衰老，最后采用基因修饰及ROS清除剂NAC处理行回复实验能纠正HSCs衰老表型。此研究还发现ATF4在白血病的发生发展过程中起到关键作用，此研究成果将为衰老及衰老相关疾病防治提供新靶标。