Hayashi Shinichi, Ochi Haruki, Ogino Hajime, Kawasumi Aiko, Kamei Yasuhiro, Tamura Koji, Yokoyama Hitoshi
Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Aramaki-Aza-Aoba 6-3, Aoba-ku, Sendai 980-8578, Miyagi, Japan.
Yamagata University, Faculty of Medicine, 2-2-2 Iida-Nishi, Yamagata 990-9585, Yamagata, Japan.
Dev Biol. 2014 Dec 1;396(1):31-41. doi: 10.1016/j.ydbio.2014.09.018. Epub 2014 Oct 2.
The size and shape of tissues are tightly controlled by synchronized processes among cells and tissues to produce an integrated organ. The Hippo signaling pathway controls both cell proliferation and apoptosis by dual signal-transduction states regulated through a repressive kinase cascade. Yap1 and Tead, transcriptional regulators that act downstream of the Hippo signaling kinase cascade, have essential roles in regulating cell proliferation. In amphibian limb or tail regeneration, the local tissue outgrowth terminates when the correct size is reached, suggesting that organ size is strictly controlled during epimorphic organ-level regeneration. We recently demonstrated that Yap1 is required for the regeneration of Xenopus tadpole limb buds (Hayashi et al., 2014, Dev. Biol. 388, 57-67), but the molecular link between the Hippo pathway and organ size control in vertebrate epimorphic regeneration is not fully understood. To examine the requirement of Hippo pathway transcriptional regulators in epimorphic regeneration, including organ size control, we inhibited these regulators during Xenopus tadpole tail regeneration by overexpressing a dominant-negative form of Yap (dnYap) or Tead4 (dnTead4) under a heat-shock promoter in transgenic animal lines. Each inhibition resulted in regeneration defects accompanied by reduced cell mitosis and increased apoptosis. Single-cell gene manipulation experiments indicated that Tead4 cell-autonomously regulates the survival of neural progenitor cells in the regenerating tail. In amphibians, amputation at the proximal level of the tail (deep amputation) results in faster regeneration than that at the distal level (shallow amputation), to restore the original-sized tail with similar timing. However, dnTead4 overexpression abolished the position-dependent differential growth rate of tail regeneration. These results suggest that the transcriptional regulators in the Hippo pathway, Tead4 and Yap1, are required for general vertebrate epimorphic regeneration as well as for organ size control in appendage regeneration. In regenerative medicine, these findings should contribute to the development of three-dimensional organs with the correct size for a patient's body.
组织的大小和形状通过细胞与组织间的同步过程受到严格控制，以形成一个完整的器官。河马信号通路通过由抑制性激酶级联调节的双信号转导状态来控制细胞增殖和凋亡。Yap1和Tead是在河马信号激酶级联下游起作用的转录调节因子，在调节细胞增殖中起重要作用。在两栖动物肢体或尾巴再生过程中，当达到正确大小时，局部组织生长就会终止，这表明在形态发生器官水平的再生过程中，器官大小受到严格控制。我们最近证明Yap1是非洲爪蟾蝌蚪肢体芽再生所必需的（Hayashi等人，2014年，《发育生物学》388卷，57 - 67页），但河马信号通路与脊椎动物形态发生再生中器官大小控制之间的分子联系尚未完全了解。为了研究河马信号通路转录调节因子在包括器官大小控制在内的形态发生再生中的需求，我们在转基因动物品系的热休克启动子控制下，通过过表达显性负性形式的Yap（dnYap）或Tead4（dnTead4），在非洲爪蟾蝌蚪尾巴再生过程中抑制这些调节因子。每次抑制都导致再生缺陷，伴有细胞有丝分裂减少和凋亡增加。单细胞基因操作实验表明，Tead4在再生尾巴中自主调节神经祖细胞的存活。在两栖动物中，尾巴近端水平截肢（深度截肢）比远端水平截肢（浅度截肢）再生速度更快，能在相似时间内恢复到原来大小的尾巴。然而，dnTead4过表达消除了尾巴再生中位置依赖性的差异生长速度。这些结果表明，河马信号通路中的转录调节因子Tead4和Yap1是一般脊椎动物形态发生再生以及附属肢体再生中器官大小控制所必需的。在再生医学中，这些发现应该有助于为患者身体开发出大小合适的三维器官。
