title: Functionally conserved cis-regulatory elements of COL18A1 identified through zebrafish transgenesis.
abstract: Type XVIII collagen is a component of basement membranes, and expressed prominently in the eye, blood vessels, liver, and the central nervous system. Homozygous mutations in COL18A1 lead to Knobloch Syndrome, characterized by ocular defects and occipital encephalocele. However, relatively little has been described on the role of type XVIII collagen in development, and nothing is known about the regulation of its tissue-specific expression pattern. We have used zebrafish transgenesis to identify and characterize cis-regulatory sequences controlling expression of the human gene. Candidate enhancers were selected from non-coding sequence associated with COL18A1 based on sequence conservation among mammals. Although these displayed no overt conservation with orthologous zebrafish sequences, four regions nonetheless acted as tissue-specific transcriptional enhancers in the zebrafish embryo, and together recapitulated the major aspects of col18a1 expression. Additional post-hoc computational analysis on positive enhancer sequences revealed alignments between mammalian and teleost sequences, which we hypothesize predict the corresponding zebrafish enhancers; for one of these, we demonstrate functional overlap with the orthologous human enhancer sequence. Our results provide important insight into the biological function and regulation of COL18A1, and point to additional sequences that may contribute to complex diseases involving COL18A1. More generally, we show that combining functional data with targeted analyses for phylogenetic conservation can reveal conserved cis-regulatory elements in the large number of cases where computational alignment alone falls short.
authors.affiliation: Centro de Estudo do Genoma Humano, Department Genetica e Biologia Evolutiva, Instituto de Biociencias/Universidade de São Paulo, Brazil.
authors.forename: Erika
authors.initials: E
authors.lastname: Kague
authors.forename: Seneca L
authors.initials: SL
authors.lastname: Bessling
authors.forename: Josephine
authors.initials: J
authors.lastname: Lee
authors.forename: Gui
authors.initials: G
authors.lastname: Hu
authors.forename: Maria Rita
authors.initials: MR
authors.lastname: Passos-Bueno
authors.forename: Shannon
authors.initials: S
authors.lastname: Fisher
mesh_terms: D000818:Animals; D001483:Base Sequence; D019295:Computational Biology; D017124:Conserved Sequence; D021901:DNA, Intergenic / Q000235:genetics; D004622:Embryo, Mammalian / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018014:Gene Transfer Techniques; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D007438:Introns / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D009928:Organ Specificity / Q000235:genetics; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D015027:Zebrafish / Q000196:embryology / Q000235:genetics*; D029961:Zebrafish Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D021901:DNA, Intergenic; D029961:Zebrafish Proteins; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins