Murine Dishevelled 3 Functions in Redundant Pathways with Dishevelled 1 and 2 in Normal Cardiac Outflow Tract, Cochlea, and Neural Tube Development

Dishevelled (Dvl) proteins are important signaling components of both the canonical β-catenin/Wnt pathway, which controls cell proliferation and patterning, and the planar cell polarity (PCP) pathway, which coordinates cell polarity within a sheet of cells and also directs convergent extension cell (CE) movements that produce narrowing and elongation of the tissue. Three mammalian Dvl genes have been identified and the developmental roles of Dvl1 and Dvl2 were previously determined. Here, we identify the functions of Dvl3 in development and provide evidence of functional redundancy among the three murine Dvls. Dvl3−/− mice died perinatally with cardiac outflow tract abnormalities, including double outlet right ventricle and persistent truncus arteriosis. These mutants also displayed a misorientated stereocilia in the organ of Corti, a phenotype that was enhanced with the additional loss of a single allele of the PCP component Vangl2/Ltap (LtapLp/+). Although neurulation appeared normal in both Dvl3−/− and LtapLp/+ mutants, Dvl3+/−;LtapLp/+ combined mutants displayed incomplete neural tube closure. Importantly, we show that many of the roles of Dvl3 are also shared by Dvl1 and Dvl2. More severe phenotypes were observed in Dvl3 mutants with the deficiency of another Dvl, and increasing Dvl dosage genetically with Dvl transgenes demonstrated the ability of Dvls to compensate for each other to enable normal development. Interestingly, global canonical Wnt signaling appeared largely unaffected in the double Dvl mutants, suggesting that low Dvl levels are sufficient for functional canonical Wnt signals. In summary, we demonstrate that Dvl3 is required for cardiac outflow tract development and describe its importance in the PCP pathway during neurulation and cochlea development. Finally, we establish several developmental processes in which the three Dvls are functionally redundant.

散乱蛋白（Dishevelled，Dvl）是调控细胞增殖与模式形成的经典β-连环蛋白/Wnt信号通路（canonical β-catenin/Wnt pathway），以及调控细胞片内细胞极性协调、并指导驱动组织缩窄与伸长的趋同延伸细胞（convergent extension cell，CE）运动的平面细胞极性（planar cell polarity，PCP）通路的关键信号组分。目前已鉴定出3种哺乳动物Dvl基因，且此前已明确Dvl1与Dvl2的发育功能。本研究鉴定了Dvl3在发育过程中的功能，并为3种小鼠Dvl蛋白间存在功能冗余提供了实验证据。Dvl3基因敲除（Dvl3−/−）小鼠围产期致死，伴随心脏流出道异常，包括右心室双出口与永存动脉干。该突变体同时出现柯蒂氏器（organ of Corti）内静纤毛（stereocilia）定向紊乱的表型，且当额外缺失1个拷贝的PCP通路组分Vangl2/Ltap（LtapLp/+）时，该表型会进一步加重。尽管Dvl3−/−与LtapLp/+单突变体的神经管闭合过程均未见异常，但Dvl3+/−;LtapLp/+双突变体则出现神经管闭合不全。重要的是，本研究证实Dvl3的诸多功能同样可由Dvl1与Dvl2替代。当其他Dvl蛋白表达缺失时，Dvl3突变体的表型会更为严重；而通过Dvl转基因在遗传上提升Dvl蛋白剂量的实验则证明，Dvl家族蛋白可相互补偿以保障正常发育。有趣的是，双Dvl突变体中的经典Wnt信号通路整体基本不受影响，这提示低水平的Dvl蛋白即可满足经典Wnt信号通路的功能需求。综上，本研究证实Dvl3对于心脏流出道发育必不可少，并阐明了其在神经管闭合与耳蜗发育过程中平面细胞极性通路的重要作用。最终，本研究明确了3种Dvl蛋白存在功能冗余的多项发育生物学过程。