title: Genomic, cDNA and embryonic expression analysis of zebrafish IRF6, the gene mutated in the human oral clefting disorders Van der Woude and popliteal pterygium syndromes.
abstract: Van der Woude syndrome (VWS) and popliteal pterygium syndrome (PPS) are autosomal dominant clefting disorders recently discovered to be caused by mutations in the IRF6 (Interferon Regulatory Factor 6) gene. The IRF gene family consists of nine members encoding transcription factors that share a highly conserved helix-turn-helix DNA-binding domain and a less conserved protein-binding domain. Most IRFs regulate the expression of interferon-alpha and -beta after viral infection, but the function of IRF6 remains unknown. We have isolated a full-length zebrafish irf6 cDNA, which encodes a 492 amino acid protein that contains a Smad-IRF interaction motif and a DNA-binding domain. The zebrafish irf6 gene consists of eight exons and maps to linkage group 22 closest to marker unp1375. By in situ hybridization analysis of embryo whole-mounts and cryosections, we demonstrate that irf6 is first expressed as a maternal transcript. During gastrulation, irf6 expression was concentrated in the forerunner cells. From the bud stage to the 3-somite stage, irf6 expression was observed in the Kupffer's vesicle. No expression could be detected at the 6-somite and 10-somite stages. At the 14-somite stage, expression was detected in the otic placode. At the 17-somite stage, strong expression was also observed in the cloaca. During the pharyngula, hatch and larva periods up to 5 days post-fertilization, irf6 was expressed in the pharyngeal arches, olfactory and otic placodes, and in the epithelial cells of endoderm derived tissues. The latter tissues include the mouth, pharynx, esophagus, endodermal lining of swim bladder, liver, exocrine pancreas, and associated ducts. Overall, the zebrafish expression data are consistent with the observations of lip pits in VWS patients, as well as more recent reports of alae nasi, otitis media and sensorineural hearing loss documented in some patients.
authors.affiliation: Department of Pediatrics, National University of Singapore, Level 4, Main Building, National University Hospital, Singapore.
authors.forename: Jin
authors.initials: J
authors.lastname: Ben
authors.forename: Ethylin Wang
authors.initials: EW
authors.lastname: Jabs
authors.forename: Samuel S
authors.initials: SS
authors.lastname: Chong
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002874:Chromosome Mapping; D002971:Cleft Lip / Q000235:genetics*; D002972:Cleft Palate / Q000235:genetics*; D003001:Cloning, Molecular; D004247:DNA / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics*; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D005775:Gastrula / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D008040:Genetic Linkage; D006801:Humans; D017403:In Situ Hybridization; D050835:Interferon Regulatory Factors; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D016366:Open Reading Frames; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013577:Syndrome; D013997:Time Factors; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics*; D015027:Zebrafish; D029961:Zebrafish Proteins / Q000096:biosynthesis* / Q000235:genetics*
chemical_list: D018076:DNA, Complementary; D004268:DNA-Binding Proteins; C109803:IRF6 protein, human; C504917:IRF6 protein, zebrafish; D050835:Interferon Regulatory Factors; D014157:Transcription Factors; D029961:Zebrafish Proteins; D004247:DNA