title: Cloning and functional characterization of a novel connexin expressed in somites of Xenopus laevis.
abstract: Connexin-containing gap junctions play an essential role in vertebrate development. More than 20 connexin isoforms have been identified in mammals. However, the number identified in Xenopus trails with only six isoforms described. Here, identification of a new connexin isoform from Xenopus laevis is described. Connexin40.4 was found by screening expressed sequence tag databases and carrying out polymerase chain reaction on genomic DNA. This new connexin has limited amino acid identity with mammalian (<50%) connexins, but conservation is higher (approximately 62%) with fish. During Xenopus laevis development, connexin40.4 was first expressed after the mid-blastula transition. There was prominent expression in the presomitic paraxial mesoderm and later in the developing somites. In adult frogs, expression was detected in kidney and stomach as well as in brain, heart, and skeletal muscle. Ectopic expression of connexin40.4 in HEK293 cells, resulted in formation of gap junction like structures at the cell interfaces. Similar ectopic expression in neural N2A cells resulted in functional electrical coupling, displaying mild, asymmetric voltage dependence. We thus cloned a novel connexin from Xenopus laevis, strongly expressed in developing somites, with no apparent orthologue in mammals.
authors.affiliation: Department of Medical Physiology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Teun P
authors.initials: TP
authors.lastname: De Boer
authors.forename: Bart
authors.initials: B
authors.lastname: Kok
authors.forename: Kirsten I E
authors.initials: KI
authors.lastname: Neuteboom
authors.forename: Nicole
authors.initials: N
authors.lastname: Spieker
authors.forename: Jochum
authors.initials: J
authors.lastname: De Graaf
authors.forename: Olivier H J
authors.initials: OH
authors.lastname: Destrée
authors.forename: Martin B
authors.initials: MB
authors.lastname: Rook
authors.forename: Toon A B
authors.initials: TA
authors.lastname: Van Veen
authors.forename: Habo J
authors.initials: HJ
authors.lastname: Jongsma
authors.forename: Marc A
authors.initials: MA
authors.lastname: Vos
authors.forename: Jacques M T
authors.initials: JM
authors.lastname: De Bakker
authors.forename: Marcel A G
authors.initials: MA
authors.lastname: Van Der Heyden
mesh_terms: D000375:Aging / Q000502:physiology; D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D019295:Computational Biology; D017630:Connexins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004594:Electrophysiology; D018507:Gene Expression Regulation, Developmental; D008969:Molecular Sequence Data; D018408:Patch-Clamp Techniques; D010802:Phylogeny; D016415:Sequence Alignment; D019170:Somites / Q000737:chemistry / Q000378:metabolism*; D029867:Xenopus Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis / Q000196:embryology* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*
chemical_list: D017630:Connexins; D029867:Xenopus Proteins; C504912:connexin 40.4 protein, Xenopus