Characterization of CXC-type chemokine molecules in early Xenopus laevis development TOSHIYASU GOTO 1 , TATSUO MICHIUE 2 , YUZURU ITO 3 and MAKOTO ASASHIMA* ,2,3 1 Department of Molecular Cell Biology, Medical Research Institute and School of Biomedical Science, Tokyo Medical and Dental University, Tokyo, 2 Department of Life Sciences (Biology), Graduate School of Arts and Sciences, The University of Tokyo, Tokyo and 3 Research Center for Stem Cell Engineering, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan ABSTRACT Chemokine molecules play important roles in the immune system. However, several chemokine molecules are expressed during early development before the immune system is es- tablished. Using reverse transcription–polymerase chain reaction (RT-PCR) and overexpression of chemokine molecules, we identified and characterized Xenopus laevis CXC-type chemokine ligands (XCXCL13L1, XCXCL13L2, XCXCLa, XCXCLb, XCXCLd, and XCXCLe) and receptors (XCXCR1/2, XCXCR3, XCXCR5, XCXCR6, and XCXCRa) during early development. The CXC-type ligands have low identity with genes for human CXC ligands (CXCL). With the exception of XCXCRa, the CXC receptors (CXCR) identified in the present study had high (~40%–65%) identity with human CXCR genes. Although the expression patterns for the CXCL and CXCR genes differed, transcript levels for all genes were very low during early embryogenesis. Overexpression of XCXCL13L1, XCXCL13L2, XCXCLa, XCXCR3, XCXCR6, and XCXCRa interfered with gastrulation and neural fold closure. The results of the present study suggest that several chemokine molecules are related to cell move- ments during early morphogenesis. KEY WORDS: chemokine, CXC receptor, CXC ligand, gastrulation, Xenopus laevis Introduction Chemokine ligands are considered cytokine molecules and, in mammals, have been investigated primarily in terms of their immunomodulatory role. Mammalian chemokines are divided into four families, namely CC-, CXC-, XC-, and CX3C-type chemokines, which contain 28, 17, 2, and 1 member, respectively (Laing and Secombes, 2004; Hiraoka et al., 2011). Chemokine receptors are members of the G-protein-coupled receptor (GPCR) family and have seven transmembrane structures. The chemokine receptors are also divided into four families according to ligand type: CC-, CXC-, XC-, and CX3C-type receptors, containing 10, 7, 1, and 1 member, respectively (Allen et al., 2007). Seventeen CXC-type chemokines have been identifed and characterized in mammals (Laing and Secombes, 2004). The CXC chemokines are further divided into two groups depending on the presence (+) or absence (–) of the tripeptide motif glutamic acid–leucine–arginine (ELR) at the N-terminus of the frst cysteine residue. The CXC ligands (CXCL) CXCL1, CXCL2, CXCL3, CXCL5, CXCL6, CXCL7, CXCL8, and CXCL15 belong to the ELR(+) group Int. J. Dev. Biol. 57: 41-47 (2013) doi: 10.1387/ijdb.120223ma www.intjdevbiol.com *Address correspondence to: Makoto Asashima. Department of Life Sciences (Biology), Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan. Tel: +81-3-5454-6632. Fax: +81-3-5454-6698. e-mail: asashi@bio.c.u-tokyo.ac.jp Accepted: 7 November 2012. Final, author-corrected PDF published online: 8th March 2013. Edited by: Makoto Asashima. ISSN: Online 1696-3547, Print 0214-6282 © 2013 UBC Press Printed in Spain Abbreviations used in this paper: CXCL, CXC ligand; CXCR, CXC receptor; PGC, primordial germ cell; RT-PCR, reverse transcription-polymerase chain reaction. (Romagnani et al., 2004; Wang et al., 2005). It has been reported that CXCL1–CXCL8 bind to the CXC receptor (CXCR) CXCR2, but a receptor for CXCL15 is yet to be unidentifed (Zlotnik and Yoshie, 2000; Wang et al., 2005). Specifcally, CXCR1 binds CXCL1, CXCL6, and CXCL8 (Zlotnik and Yoshie, 2000); CXCR3 and its alternatively splicing variant bind CXCL4, CXCL9, CXCL10, and CXCL11 (Zlotnik and Yoshie, 2000; Lasagni et al., 2003); CXCR4 binds CXCL12; CXCR5 binds CXCL13; CXCR6 binds CXCL16; and, CXCR7 binds CXCL11 and CXCL12 (Zlotnik and Yoshie, 2000; Naumann et al., 2010; Agostini et al., 2005). No receptors have been identifed as yet for CXCL14 and CXCL17 (Hara and Tanegashima, 2012; Hiraoka et al., 2011). Recent studies have revealed that several chemokine ligands and receptors have important roles in early embryogenesis in vertebrates before the immune system is established. For ex- ample, CXCL12/CXCR4 promotes directional movement of pri- mordial germ cell (PGC) migration in zebrafsh (Doitsidou et al.,