Garside Victoria C, Cullum Rebecca, Alder Olivia, Lu Daphne Y, Vander Werff Ryan, Bilenky Mikhail, Zhao Yongjun, Jones Steven J M, Marra Marco A, Underhill T Michael, Hoodless Pamela A
Terry Fox Laboratory, BC Cancer Agency, Vancouver, Canada V5Z 1L3 Program in Cell and Developmental Biology, University of British Columbia, Vancouver, Canada V6T 1Z4.
Terry Fox Laboratory, BC Cancer Agency, Vancouver, Canada V5Z 1L3.
Development. 2015 Dec 15;142(24):4340-50. doi: 10.1242/dev.125252. Epub 2015 Nov 2.
Heart valve formation initiates when endothelial cells of the heart transform into mesenchyme and populate the cardiac cushions. The transcription factor SOX9 is highly expressed in the cardiac cushion mesenchyme, and is essential for heart valve development. Loss of Sox9 in mouse cardiac cushion mesenchyme alters cell proliferation, embryonic survival, and valve formation. Despite this important role, little is known about how SOX9 regulates heart valve formation or its transcriptional targets. Therefore, we mapped putative SOX9 binding sites by ChIP-Seq in E12.5 heart valves, a stage at which the valve mesenchyme is actively proliferating and initiating differentiation. Embryonic heart valves have been shown to express a high number of genes that are associated with chondrogenesis, including several extracellular matrix proteins and transcription factors that regulate chondrogenesis. Therefore, we compared regions of putative SOX9 DNA binding between E12.5 heart valves and E12.5 limb buds. We identified context-dependent and context-independent SOX9-interacting regions throughout the genome. Analysis of context-independent SOX9 binding suggests an extensive role for SOX9 across tissues in regulating proliferation-associated genes including key components of the AP-1 complex. Integrative analysis of tissue-specific SOX9-interacting regions and gene expression profiles on Sox9-deficient heart valves demonstrated that SOX9 controls the expression of several transcription factors with previously identified roles in heart valve development, including Twist1, Sox4, Mecom and Pitx2. Together, our data identify SOX9-coordinated transcriptional hierarchies that control cell proliferation and differentiation during valve formation.
心脏瓣膜形成始于心脏内皮细胞转变为间充质并填充心脏垫。转录因子SOX9在心脏垫间充质中高度表达，对心脏瓣膜发育至关重要。小鼠心脏垫间充质中Sox9缺失会改变细胞增殖、胚胎存活和瓣膜形成。尽管SOX9具有这一重要作用，但对于它如何调节心脏瓣膜形成或其转录靶点却知之甚少。因此，我们通过染色质免疫沉淀测序（ChIP-Seq）在E12.5心脏瓣膜中绘制了假定的SOX9结合位点，此时瓣膜间充质正在积极增殖并开始分化。胚胎心脏瓣膜已被证明表达大量与软骨形成相关的基因，包括几种细胞外基质蛋白和调节软骨形成的转录因子。因此，我们比较了E12.5心脏瓣膜和E12.5肢芽之间假定的SOX9 DNA结合区域。我们在整个基因组中鉴定出了上下文依赖和上下文独立的SOX9相互作用区域。对上下文独立的SOX9结合的分析表明，SOX9在跨组织调节与增殖相关的基因（包括AP-1复合体的关键成分）方面发挥着广泛作用。对Sox9缺陷心脏瓣膜上组织特异性SOX9相互作用区域和基因表达谱的综合分析表明，SOX9控制着几种先前已确定在心脏瓣膜发育中起作用的转录因子的表达，包括Twist1、Sox4、Mecom和Pitx2。总之，我们的数据确定了SOX9协调的转录层次结构，其在瓣膜形成过程中控制细胞增殖和分化。
