Ptk7 promotes non-canonical Wnt/PCP-mediated morphogenesis and inhibits Wnt/β-catenin-dependent cell fate decisions during vertebrate development
Ptk7 promotes non-canonical Wnt/PCP-mediated morphogenesis and inhibits Wnt/β-catenin-dependent cell fate decisions during vertebrate development
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DOI：
10.1242/dev.090183
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发表时间：
2013-04-15
期刊：
影响因子：
4.6
通讯作者：
Ciruna, Brian
中科院分区：
文献类型：
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作者：
Hayes, Madeline;Naito, Mizue;Ciruna, Brian
利用斑马鱼，我们已经确定了蛋白酪氨酸激酶7(Ptk7)的功能，它是一种跨膜假性激酶，与胚胎发育和癌症中的Wnt信号转导有关。Ptk7是一种已知的哺乳动物神经管关闭和非洲爪哇收敛伸展运动的调节因子。然而，相互矛盾的报道表明，Ptk7在规范的Wnt/β-catenin信号转导中既有积极的作用，也有消极的作用。为了阐明Ptk7在脊椎动物胚胎模式和形态发生中的作用，我们利用锌指核酸酶(ZFN)基因打靶的方法获得了母体合子(MZ)ptk7突变斑马鱼。斑马鱼Ptk7基因的早期缺失导致轴向会聚和伸展、神经管形态发生和平面细胞极性(PCP)丧失。此外，在原肠发育后期和节段阶段，我们观察到β-catenin靶基因表达显著上调，并证明了Ptk7在体内减弱典型的Wnt/β-catenin活性的明显作用。MZptk7突变体在尾芽中显示出近轴中胚层的扩大分化，这表明Ptk7在调节原肠形成后后部干细胞池中典型的Wnt依赖的命运规范方面发挥了重要作用。此外，我们证明了质膜拴系的Ptk7胞外片段足以修复MZptk7突变胚胎中PCP的形态发生和Wnt/β-catenin模式缺陷。我们的结果表明，Ptk7的胞外结构域在多种脊椎动物的发育过程中都是非典型的Wnt/PCP和典型的Wnt/β-catenin信号的重要调节因子，对人类癌症中观察到的PTK7表达上调具有重要意义。
Using zebrafish, we have characterised the function of Protein tyrosine kinase 7 (Ptk7), a transmembrane pseudokinase implicated in Wnt signal transduction during embryonic development and in cancer. Ptk7 is a known regulator of mammalian neural tube closure and Xenopus convergent extension movement. However, conflicting reports have indicated both positive and negative roles for Ptk7 in canonical Wnt/beta-catenin signalling. To clarify the function of Ptk7 in vertebrate embryonic patterning and morphogenesis, we generated maternal-zygotic (MZ) ptk7 mutant zebrafish using a zinc-finger nuclease (ZFN) gene targeting approach. Early loss of zebrafish Ptk7 leads to defects in axial convergence and extension, neural tube morphogenesis and loss of planar cell polarity (PCP). Furthermore, during late gastrula and segmentation stages, we observe significant upregulation of beta-catenin target gene expression and demonstrate a clear role for Ptk7 in attenuating canonical Wnt/beta-catenin activity in vivo. MZptk7 mutants display expanded differentiation of paraxial mesoderm within the tailbud, suggesting an important role for Ptk7 in regulating canonical Wnt-dependent fate specification within posterior stem cell pools post-gastrulation. Furthermore, we demonstrate that a plasma membrane-tethered Ptk7 extracellular fragment is sufficient to rescue both PCP morphogenesis and Wnt/beta-catenin patterning defects in MZptk7 mutant embryos. Our results indicate that the extracellular domain of Ptk7 acts as an important regulator of both non-canonical Wnt/PCP and canonical Wnt/beta-catenin signalling in multiple vertebrate developmental contexts, with important implications for the upregulated PTK7 expression observed in human cancers.