title: Xenopus laevis Stromal cell-derived factor 1: conservation of structure and function during vertebrate development.
abstract: Transmembrane signaling of the CXC chemokine stromal cell-derived factor-1 (SDF-1) is mediated by CXCR4, a G protein-coupled receptor initially identified in leukocytes and shown to serve as a coreceptor for the entry of HIV into lymphocytes. Characterization of SDF-1- and CXCR4-deficient mice has revealed that SDF-1 and CXCR4 are of vital developmental importance. To study the role of the SDF-1/CXCR4-chemokine/receptor system as a regulator of vertebrate development, we isolated and characterized a cDNA encoding SDF-1 of the lower vertebrate Xenopus laevis (xSDF-1). Recombinant xSDF-1 was produced in insect cells, purified, and functionally characterized. Although xSDF-1 is only 64-66% identical with its mammalian counterparts, it is indistinguishable from human (h)SDF-1alpha in terms of activating both X. laevis CXCR4 and hCXCR4. Thus, both xSDF-1 and hSDF-1alpha promoted CXCR4-mediated activation of heterotrimeric G(i2) in a cell-free system and induced release of intracellular calcium ions in and chemotaxis of intact lymphoblastic cells. Analysis of the time course of xSDF-1 mRNA expression during Xenopus embryogenesis revealed a tightly coordinated regulation of xSDF-1 and X. laevis CXCR4. xSDF-1 mRNA was specifically detected in the developing CNS, incipient sensory organs, and the embryonic heart. In Xenopus, CXCR4 mRNA appears to be absent from the heart anlage, but present in neural crest cells. This observation suggests that xSDF-1 expressed in the heart anlage may attract cardiac neural crest cells expressing CXCR4 to migrate to the primordial heart to regulate both septation of the cardiac outflow tract and differentiation of the myocardium during early heart development.
authors.affiliation: Department of Pharmacology and Toxicology, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany.
authors.forename: Mike
authors.initials: M
authors.lastname: Braun
authors.forename: Markus
authors.initials: M
authors.lastname: Wunderlin
authors.forename: Kathrin
authors.initials: K
authors.lastname: Spieth
authors.forename: Walter
authors.initials: W
authors.lastname: Knöchel
authors.forename: Peter
authors.initials: P
authors.lastname: Gierschik
authors.forename: Barbara
authors.initials: B
authors.lastname: Moepps
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism; D054377:Chemokine CXCL12; D019743:Chemokines, CXC / Q000235:genetics* / Q000502:physiology*; D002633:Chemotaxis; D003001:Cloning, Molecular; D017124:Conserved Sequence; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism; D006801:Humans; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000096:biosynthesis; D019718:Receptors, CXCR4 / Q000502:physiology; D011994:Recombinant Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D018411:Spodoptera / Q000235:genetics; D014018:Tissue Distribution; D029867:Xenopus Proteins / Q000235:genetics / Q000502:physiology; D014982:Xenopus laevis / Q000196:embryology* / Q000235:genetics / Q000378:metabolism*
chemical_list: C449185:CXCL12 protein, Xenopus; C515255:CXCL12 protein, human; D054377:Chemokine CXCL12; D019743:Chemokines, CXC; D012333:RNA, Messenger; D019718:Receptors, CXCR4; D011994:Recombinant Proteins; D029867:Xenopus Proteins; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D002118:Calcium