b1 integrin signaling governs necroptosis via the chromatin remodeling factor CHD4. b1 integrin signaling governs necroptosis via the chromatin remodeling factor CHD4

Fibrosis, characterized by sustained activation of myofibroblasts and excessive extracellular matrix (ECM) deposition, is known to be associated with chronic inflammation. RIPK3, a key kinase mediating TNF-driven necroptosis signaling, is upregulated in fibrosis and contributes to the TNF-mediated inflammation. In biliary duct ligation-induced liver fibrosis, we found that myofibroblasts are the major cell type expressing RIPK3. Genetic ablation of b1 integrins, the major profibrotic ECM receptors in fibroblasts, not only abolished ECM fibrillogenesis but also blunted RIPK3 expression via an epigenetic mechanism mediated by the chromatin remodeling factor CHD4. While the function of CHD4 has been conventionally linked to NuRD and ChAHP complexes, we found that CHD4 potently repressed a set of genes, including Ripk3, with high locus specificity but independent of either the NuRD or ChAHP complex. Thus, our data uncover that b1 integrin intrinsically links fibrotic signaling to RIPK3-driven inflammation via a novel mode of action of CHD4. Overall design: Chromatin accessibility analysis by ATAC-seq of Control, Chd4KO and Gatad2a/b DKO

纤维化（Fibrosis）是以肌成纤维细胞持续激活与细胞外基质（extracellular matrix, ECM）过度沉积为核心特征的病理状态，已知其与慢性炎症密切相关。RIPK3作为介导TNF驱动的坏死性凋亡信号通路的关键激酶，在纤维化进程中表达上调，并参与TNF介导的炎症反应。在胆管结扎诱导的肝纤维化模型中，我们发现肌成纤维细胞是表达RIPK3的主要细胞类群。对成纤维细胞中主要的促纤维化ECM受体β1整合素（b1 integrins）进行遗传敲除后，不仅阻断了ECM纤维形成过程，还通过染色质重塑因子CHD4（chromatin remodeling factor CHD4）介导的表观遗传机制抑制了RIPK3的表达。尽管以往研究普遍认为CHD4的功能与NuRD和ChAHP复合物相关，但我们发现CHD4可通过高位点特异性的方式强效抑制包括Ripk3在内的一组基因，且该调控过程不依赖NuRD或ChAHP复合物。综上，本研究数据揭示β1整合素通过CHD4的全新作用模式，将纤维化信号通路与RIPK3驱动的炎症过程实现了内在关联。整体实验设计：采用ATAC-seq技术对对照组（Control）、Chd4基因敲除组（Chd4KO）以及Gatad2a/b双敲除组（Gatad2a/b DKO）的染色质开放状态进行分析。