@misc{oai:ir.soken.ac.jp:00001378,
 author = {竹内, 雅貴 and タケウチ, マサキ and TAKEUCHI, Masaki},
 month = {2016-02-17, 2016-02-17},
 note = {Gastrulation is one of the most important processes during morphogenesis of early embryo, involving dynamic and coordinated cell movements that cause drastic changes in embryo shape. Although gastrulation proceeds by various types of cell movements, in Xenopus mesodermal cells, two cell movements known as convergence and extension in which polarized axial mesodermal cells intercalate in radial and mediolateral directions, thus elongating the dorsal marginal zone along the anterior-posterior axis<SUP>1,2</SUP>, have been mainly studied. Recently, it was reported that a non-canonical Wnt signalling pathway, which is known to regulate planar cell polarity (PCP) in Drosophila<SUP>3,4</SUP>, participates in the regulatuon of convergent extensnon movements in Xenopus as well as in the zebrafish embryo<SUP>5-8</SUP> . The Wnt5a/Wnt11 identified as ligands of PCP signalling are mediated by members of the seven-transmembrane receptor Frizzled (Fz) and the signal transducer Dishevelled (Dsh), through the Dsh domains that are selectively required for the PCP signal<SUP>6-8</SUP>. It has also been shown that the relocalization of Dsh to the cell membrane is required for convergent extension movements in Xenopus gastrulae. Although it appears that signalling via these components leads to the activation of JNK<SUP>9,10</SUP> and rearrangement of microfilaments, the precise interplay among these intercellular components is largely unknown.<br />　　In chapter 1, he shows that Xenopus prickle (Xpk), a Xenopus homologue of a Drosophila PCP gene<SUP>11-13</SUP> , is an essential component for gastrulation cell movement. Xpk encodes a protein that includes conserved PET and triple LIM domains in its N-terminal half. In gastrula, Xpk transcription are restricted to the marginal zone with a steep gradient from dorsal to ventral side, suggesting that Xpk plays a role during gastrulation. Both gain-of-function and loss-of-function of Xpk severely perturbed gastrulation and caused spina bifida embryos without affecting mesodermal differentiation. Loss-of-function of zebrafish prickle (Zpk) also disrupted the dorsal convergence, caused a phenotype similar to PCP mutants knypeck and trilobite, which have recently been found to encode a glypican and strabismus, respectively. The structure-activity relationship of XPK was examined by overexpression of some deletion constructs. As a result, triple LIM domain-deleted XPK mutants could act as the dominant-negative way to wild-type XPK, whereas XPK mutants containing the domain were still able to transmit signals similar to that of wild type.  Although XPK alone showed no effect on the JNK activation as output of PCP signaling, XPK could  enhanced the JNK activation mediated by Dsh. Importantly, he also demonstrated that XPK physically binds to Xenopus Dsh as well as to JNK. This suggests that XPK plays a pivotal role in connecting Dsh function to JNK activation.<br />　　In chapter 2, he discusses about the identification of Xenopus Ste20-like kinase as a XPK interacting protein. It has been identified by the yeast two hybrid screening with XPK as a bait, and named as Xenopus Prickle Interacting Kinase; XPIK. XPIK is expressed in dorsal side of early gastrula embryo overlapping with the expression domain of XPK during gastrulation, suggesting that XPIK play a role in Wnt/PCP signaling like XPK. In fact, he has found that XPIK could activate JNK via its kinase domain.  Both gain-of-function and loss-of-function of XPIK interfered　gastrulation movements, phenocopying XPK-disrupted embryos. In the overexpression analysis of some deletion mutants of XPIK, degree of gastrulation defects caused by each mutant was well-correlated with its activity level of JNK activation. he also designed a dominant negatively acting version of XPIK (XPIK-DN; Dl65A), XPIK-DN which is able to inhibit the JNK activation mediated by wild type XPIK and found that not only it could restore the gastrulation defective phenotype of dorsally overexpressed XPIK but also it alone perturbed gastrulation suggesting that DN-XPIK inhibited the endogenous XPIK activity of JNK activation. DN-XPIK also inhibited the JNK activation mediated by Dsh. Taken these observations together, he propose that XPIK is an essential components of the Wnt/PCP signaling linking Dsh function to JNK activation, thereby regulating gastrulation cell movements.<br />　　In conclusion, the analysis of Prickle function in this study confirmed that the mechanism of cell polarity establishment by PCP signaling in Drosophila is commonly utilized beyond animal species and adopted to the correct gastrulation cell movements in vertebrates. The action mechanism of Prickle was identified as a modulator protein of Dsh-JNK pathway. In addition, XPK Interacting Kinase (XPIK) was found to be required for activation of JNK mediated by Dsh. Accordingly, our results strongly suggest that non-canonical Wnt (PCP) pathway regulates gastrulation cell movements in vertebrate through activation of JNK mediated or modulated by Dsh, XPK and XPIK. To further understand the pathway, how Dsh, XPK and XPIK regulate each other remains to be explored., application/pdf, 総研大甲第726号},
 title = {The Planar Cell Polarity Gene Prickle in  Vertebrates Regulates Gastrulation Cell  Movements},
 year = {}
}