title: Subtractive hybridization identifies chick-cripto, a novel EGF-CFC ortholog expressed during gastrulation, neurulation and early cardiogenesis.
abstract: EGF-CFC genes encode a novel class of extracellular, membrane-associated proteins that notably play an important role during vertebrate gastrulation. Whereas the two cysteine-rich domains that characterize these proteins, namely the extracellular EGF-like and the CFC domain, are known to be encoded by two evolutionarily conserved exons, it is generally assumed, based on weak primary sequence identity, that the remaining parts of the protein differ among vertebrates, suggesting that known members of the EGF-CFC family do not represent true orthologs. Here, by characterizing the full cDNA and genomic sequences of a new EGF-CFC gene in chick, and by comparing them with their counterparts in human (CRIPTO), mouse (cripto and cryptic), Xenopus (FRL-1) and zebrafish (one-eyed pinhead), we show that all EGF-CFC genes share an identical genomic organization over the entire coding region. Not only are the central two exons (coding for the EGF-like and CFC motifs) conserved, but also conserved are the total number of exons, their size, their intron phase and their correlation with discrete protein modules, in particular those modules that allow the EGF-CFC motif to become membrane-associated. Therefore, despite apparent divergence between their 5' and 3'-terminal exons, all known CRIPTO-related genes are structurally orthologous. We named this novel ortholog in bird, chick-cripto. We report the mRNA distribution of chick-cripto, which begins in the epiblast of the gastrula, with a pattern similar to EGF-CFC genes of other vertebrates.
authors.affiliation: Department of Neurobiology and Anatomy, University of Utah School of Medicine, 50 North Medical Drive, Salt Lake City, UT 84132, USA.
authors.forename: J F
authors.initials: JF
authors.lastname: Colas
authors.forename: G C
authors.initials: GC
authors.lastname: Schoenwolf
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002642:Chick Embryo / Q000378:metabolism*; D002645:Chickens; D003001:Cloning, Molecular; D004247:DNA / Q000737:chemistry / Q000235:genetics; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D004815:Epidermal Growth Factor / Q000737:chemistry / Q000235:genetics*; D005091:Exons; D058851:GPI-Linked Proteins; D005775:Gastrula / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D005796:Genes / Q000235:genetics; D006321:Heart / Q000196:embryology; D018398:Homeodomain Proteins; D017403:In Situ Hybridization; D036341:Intercellular Signaling Peptides and Proteins; D007438:Introns; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D009206:Myocardium / Q000378:metabolism; D009363:Neoplasm Proteins / Q000737:chemistry / Q000235:genetics*; D009420:Nervous System / Q000196:embryology / Q000378:metabolism; D009693:Nucleic Acid Hybridization / Q000379:methods; D017433:Protein Structure, Secondary; D012313:RNA / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution; D014157:Transcription Factors; D014158:Transcription, Genetic; D029867:Xenopus Proteins; D029961:Zebrafish Proteins
chemical_list: D018076:DNA, Complementary; D058851:GPI-Linked Proteins; D018398:Homeodomain Proteins; D036341:Intercellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009363:Neoplasm Proteins; C489450:Tdgf1 protein, mouse; D014157:Transcription Factors; D029867:Xenopus Proteins; D029961:Zebrafish Proteins; C110484:tdgf1 protein, zebrafish; C096788:tdgf1.3 protein, Xenopus; D004815:Epidermal Growth Factor; D012313:RNA; D004247:DNA