Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City (M.-L.W., K.W., R.S., F.L., C.T.G.).
Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City (C.T.G.).
Arterioscler Thromb Vasc Biol. 2024 Aug;44(8):1784-1798. doi: 10.1161/ATVBAHA.124.320881. Epub 2024 Jun 13.
The chromatin-remodeling enzymes BRG1 (brahma-related gene 1) and CHD4 (chromodomain helicase DNA-binding protein 4) independently regulate the transcription of genes critical for vascular development, but their coordinated impact on vessels in late-stage embryos has not been explored.
In this study, we genetically deleted endothelial and in mixed background mice (), and littermates that were negative for Cre recombinase were used as controls. Tissues were analyzed by immunostaining, immunoblot, and flow cytometry. Quantitative reverse transcription polymerase chain reaction was used to determine gene expression, and chromatin immunoprecipitation revealed gene targets of BRG1 and CHD4 in cultured endothelial cells.
We found double mutants grew normally but died soon after birth with small and compact lungs. Despite having normal cellular composition, distal air sacs of the mutant lungs displayed diminished ECM (extracellular matrix) components and TGFβ (transforming growth factor-β) signaling, which typically promotes ECM synthesis. Transcripts for collagen- and elastin-related genes and the TGFβ ligand were decreased in mutant lung endothelial cells, but genetic deletion of endothelial failed to recapitulate the small lungs and ECM defects seen in mutants. We instead found several ECM genes to be direct targets of BRG1 and CHD4 in cultured endothelial cells.
Collectively, our data highlight essential roles for endothelial chromatin-remodeling enzymes in promoting ECM deposition in the distal lung tissue during the saccular stage of embryonic lung development.
染色质重塑酶 BRG1（Brahma 相关基因 1）和 CHD4（染色质解旋酶 DNA 结合蛋白 4）独立调控血管发育关键基因的转录，但它们在晚期胚胎血管中的协调作用尚未被探索。
在这项研究中，我们在混合背景的小鼠中（）内皮细胞特异性地缺失 和 ，并用未进行 Cre 重组酶表达的同窝仔鼠作为对照。通过免疫染色、免疫印迹和流式细胞术分析组织。采用定量反转录聚合酶链反应（qRT-PCR）确定基因表达情况，并用染色质免疫沉淀实验揭示 BRG1 和 CHD4 在培养的内皮细胞中的基因靶标。
我们发现 双突变体生长正常，但出生后不久即死亡，肺部小而紧凑。尽管细胞组成正常，但突变肺部的远端气囊显示出 ECM（细胞外基质）成分和 TGFβ（转化生长因子-β）信号的减少，而 TGFβ 通常可促进 ECM 合成。突变肺内皮细胞中的胶原蛋白和弹性蛋白相关基因以及 TGFβ 配体 的转录本减少，但内皮细胞特异性缺失 并不能重现 突变体中所见的小肺和 ECM 缺陷。相反，我们发现几种 ECM 基因是培养的内皮细胞中 BRG1 和 CHD4 的直接靶标。
综上所述，我们的数据强调了内皮染色质重塑酶在促进胚胎肺发育囊状阶段远端肺组织 ECM 沉积中的重要作用。
