Ahuja Neha, Hiltabidle Max S, Rajasekhar Hariprem, Voss Sophie, Lu Steven Z, Barlow Haley R, Cowdin Mitzy A, Daniel Edward, Vaddaraju Vedha, Anandakumar Thejal, Black Ethan, Cleaver Ondine, Maynard Caitlin
Department of Molecular Biology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX, USA, 75390.
Department of Pediatrics, Rutgers Robert Wood Johnson Medical School, One Robert Wood Johnson Place, New Brunswick, NJ, USA, 08901.
Dev Biol. 2022 Jun;486:81-95. doi: 10.1016/j.ydbio.2022.03.003. Epub 2022 Mar 29.
Endothelial cells (ECs) are critical to proper heart valve development, directly contributing to the mesenchyme of the cardiac cushions, which progressively transform into mature valves. To date, investigators have lacked sufficient markers of valve ECs to evaluate their contributions during valve morphogenesis fully. As a result, it has been unclear whether the well-characterized regional differentiation of valves correlates with any endothelial domains in the heart. Furthermore, it has been difficult to ascertain whether endothelial heterogeneity in the heart influences underlying mesenchymal zones in an angiocrine manner. To identify regionally expressed EC genes in the heart valves, we screened publicly available databases and assembled a toolkit of endothelial-enriched genes. We identified Cyp26b1 as one of many endothelial enriched genes found to be expressed in the endocardium of the developing cushions and valves. Here, we show that Cyp26b1 is required for normal heart valve development. Genetic ablation of Cyp26b1 in mouse embryos leads to abnormally thickened aortic valve leaflets, which is due in part to increased endothelial and mesenchymal cell proliferation in the remodeling valves. In addition, Cyp26b1 mutant hearts display ventricular septal defects (VSDs) in a portion of null embryos. We show that loss of Cyp26b1 results in upregulation of retinoic acid (RA) target genes, supporting the observation that Cyp26b1 has RA-dependent roles. Together, this work identifies a novel role for Cyp26b1 in heart valve morphogenesis and points to a role of RA in this process. Understanding the spatiotemporal expression dynamics of cardiac EC genes will pave the way for investigation of both normal and dysfunctional heart valve development.
内皮细胞（ECs）对心脏瓣膜的正常发育至关重要，直接参与心脏垫间充质的形成，而心脏垫会逐渐转变为成熟的瓣膜。迄今为止，研究人员缺乏足够的瓣膜内皮细胞标志物来全面评估它们在瓣膜形态发生过程中的作用。因此，目前尚不清楚已明确的瓣膜区域分化是否与心脏中的任何内皮区域相关。此外，很难确定心脏中的内皮细胞异质性是否以血管分泌的方式影响潜在的间充质区域。为了鉴定心脏瓣膜中区域表达的内皮细胞基因，我们筛选了公开可用的数据库，并组装了一套富含内皮细胞基因的工具包。我们将Cyp26b1鉴定为在发育中的心脏垫和瓣膜的心内膜中表达的众多富含内皮细胞基因之一。在此，我们表明Cyp26b1是正常心脏瓣膜发育所必需的。在小鼠胚胎中对Cyp26b1进行基因敲除会导致主动脉瓣小叶异常增厚，这部分归因于重塑瓣膜中内皮细胞和间充质细胞增殖增加。此外，一部分Cyp26b1突变体心脏显示出室间隔缺损（VSDs）。我们表明Cyp26b1的缺失导致视黄酸（RA）靶基因上调，支持了Cyp26b1具有RA依赖性作用的观察结果。总之，这项工作确定了Cyp26b1在心脏瓣膜形态发生中的新作用，并指出了RA在此过程中的作用。了解心脏内皮细胞基因的时空表达动态将为研究正常和功能失调的心脏瓣膜发育铺平道路。
