Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
Cardiovascular Center, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
Development. 2020 Aug 25;147(16):dev193581. doi: 10.1242/dev.193581.
The Hippo-Yap pathway regulates multiple cellular processes in response to mechanical and other stimuli. In , the polarity protein Lethal (2) giant larvae [L(2)gl], negatively regulates Hippo-mediated transcriptional output. However, in vertebrates, little is known about its homolog Llgl1. Here, we define a novel role for vertebrate Llgl1 in regulating Yap stability in cardiomyocytes, which impacts heart development. In contrast to the role of L(2)gl, Llgl1 depletion in cultured rat cardiomyocytes decreased Yap protein levels and blunted target gene transcription without affecting Yap transcript abundance. Llgl1 depletion in zebrafish resulted in larger and dysmorphic cardiomyocytes, pericardial effusion, impaired blood flow and aberrant valvulogenesis. Cardiomyocyte Yap protein levels were decreased in morphants, whereas Notch, which is regulated by hemodynamic forces and participates in valvulogenesis, was more broadly activated. Consistent with the role of Llgl1 in regulating Yap stability, cardiomyocyte-specific overexpression of Yap in Llgl1-depleted embryos ameliorated pericardial effusion and restored blood flow velocity. Altogether, our data reveal that vertebrate Llgl1 is crucial for Yap stability in cardiomyocytes and its absence impairs cardiac development.
Hippo-Yap 通路响应机械和其他刺激调节多种细胞过程。在果蝇中，极性蛋白致死（2）巨幼虫 [L(2)gl]负调控 Hippo 介导的转录输出。然而，在脊椎动物中，其同源物 Llgl1 的功能知之甚少。在这里，我们定义了脊椎动物 Llgl1 在调节心肌细胞中 Yap 稳定性方面的新作用，这会影响心脏发育。与 L(2)gl 的作用相反，培养的大鼠心肌细胞中 Llgl1 的耗竭降低了 yap 蛋白水平，并使靶基因转录减弱，而不影响 yap 转录物丰度。斑马鱼中 Llgl1 的耗竭导致心肌细胞增大和畸形，心包积液，血流受损和瓣膜形成异常。在 morphants 中，心肌细胞 yap 蛋白水平降低，而 Notch 受血流动力学调节并参与瓣膜形成，其激活更为广泛。与 Llgl1 在调节 yap 稳定性中的作用一致，在 Llgl1 耗竭胚胎中过表达心肌细胞特异性 yap 可减轻心包积液并恢复血流速度。总的来说，我们的数据表明，脊椎动物 Llgl1 对心肌细胞中 yap 的稳定性至关重要，其缺失会损害心脏发育。
