The role of BAF related complexes in regulatory T cell development and function

项目摘要 调节性T细胞（Treg）在保持免疫系统平衡和预防免疫系统疾病方面起着至关重要的作用。 自身免疫性疾病。Treg功能缺陷导致自身免疫性疾病，包括类风湿性关节炎和类风湿性关节炎。 多发性硬化另一方面，肿瘤内的Treg细胞可以阻断有效的抗肿瘤免疫反应。 Treg细胞谱系的发育和维持依赖于转录因子Foxp3，如 功能丧失突变导致小鼠和人的严重淋巴组织增生性疾病。因此，理解 控制Foxp3诱导和稳定性的机制可能会导致开发新的治疗方法， 自身免疫性疾病和癌症。郑博士和同事最近开发了一种系统来执行基因组- 广泛的CRISPR/Cas9敲除筛选，以鉴定小鼠诱导的和天然的TcB中的Foxp3调节剂。的 公正的筛选结果不仅证实了一些已知的Foxp3调节因子，而且还揭示了许多新的 控制Foxp3表达的因子。新鉴定的Foxp3调节子的基因本体分析揭示了 显著富集编码BAF亚基（SWI/SNF）染色质重塑的多个基因 复合物，表明这种调节剂在Treg发育中的未知作用。在三个BAF相关的 复合物，新描述的GBAF复合物促进Foxp3的表达，而PBAF复合物促进Foxp3的表达。 抑制其表达。此外，对GBAF特异性的含溴结构域蛋白Brd9的缺失 复合物，导致Foxp3表达减少和Treg功能受损。此外，布罗莫结构域 BRD9的抑制剂和化学降解剂的作用类似于Brd9基因缺失，以损害Foxp3表达， Treg抑制功能。RNA-seq和ChIP-seq研究表明，Brd9与Foxp3合作， 其与Foxp3靶基因结合并调节其表达。本研究的总体目标是确定 BAF相关复合物通过与Foxp3的调节和合作在Treg功能中的作用。这一目标 将通过阐明G/PBAF在Foxp3诱导和维持中的作用（目标1），定义 G/PBAF复合物与Foxp3（Aim 2）的生物化学结合，确定GBAF在 Foxp3依赖性转录（Aim 3），并表征破坏G/PBAF的功能后果 在自身免疫性疾病和癌症模型中，研究了TcB亚基的表达（Aim 4）。拟议研究的结果 有望从根本上推进对Foxp3基因表达的表观遗传控制的理解， Treg转录网络。此外，这些研究将提供关键的见解，新的功能， 描述了GBAF络合物及其与PBAF络合物的关系。最后，这项研究的结果可以 提供证据支持使用靶向BAF相关复合物的药物治疗自身免疫性 疾病和癌症。

PROJECT SUMMARY Regulatory T cells (Treg) play a crucial role in keeping the immune system in balance and preventing autoimmune disease. Defective Treg function leads to autoimmune diseases including rheumatoid arthritis and multiple sclerosis. On the other hand, Treg cells inside tumors can block effective anti-tumor immune responses. The development and maintenance of the Treg cell lineage are dependent on the transcription factor Foxp3, as loss of function mutations lead to severe lymphoproliferative disease in mice and humans. Thus, understanding the mechanisms that govern Foxp3 induction and stability may lead to the development of novel therapies for autoimmune disease and cancer. Dr. Zheng and colleagues recently developed a system to perform genome- wide CRISPR/Cas9 knockout screens to identify Foxp3 regulators in mouse induced and natural Tregs. The unbiased screen results not only confirmed a number of known Foxp3 regulators but also revealed many novel factors that control Foxp3 expression. Gene ontology analysis of the newly identified Foxp3 regulators revealed significant enrichment of multiple genes encoding subunits of the BAF (SWI/SNF) chromatin remodeling complexes, indicating an unknown role for this regulator in Treg development. Among the three BAF related complexes, the newly described GBAF complex promotes the expression of Foxp3, whereas the PBAF complex represses its expression. Furthermore, deletion of the bromodomain-containing protein Brd9, specific to GBAF complexes, led to reduced Foxp3 expression and compromised Treg function. Additionally, bromodomain inhibitors and chemical degraders of BRD9 act similarly to Brd9 genetic deletion to impair Foxp3 expression and Treg suppressor function. RNA-seq and ChIP-seq studies suggest that Brd9 cooperates with Foxp3 to potentiate its binding to Foxp3 target genes and regulate their expression. The overall objective of this study is to define the role of BAF related complexes in Treg function through regulation of and cooperation with Foxp3. This goal will be accomplished by elucidating the role of G/PBAF in Foxp3 induction and maintenance (Aim 1), defining the biochemical association of G/PBAF complexes with Foxp3 (Aim 2), identifying the functional role of GBAF in Foxp3-dependent transcription (Aim 3), and characterizing the functional consequences of disrupting G/PBAF subunits in Tregs in autoimmune disease and cancer models (Aim 4). The outcomes of the proposed studies are expected to fundamentally advance the understanding of epigenetic control of Foxp3 gene expression and Treg transcriptional networks. Additionally, these studies will provide key insights into the function of the newly described GBAF complex and its relationship with PBAF complexes. Finally, the outcomes of this research could provide evidence to support using drugs to target BAF related complexes for the treatment of autoimmune diseases and cancer.