title: The zebrafish homeobox gene irxl1 is required for brain and pharyngeal arch morphogenesis.
abstract: Iroquois homeobox-like 1 (irxl1) is a novel member of the TALE superfamily of homeobox genes that is most closely related to the Iroquois class. We have identified the zebrafish irxl1 gene and characterized its structure. The protein contains a homeodomain that shares 100% sequence identity with other vertebrate orthologs. During embryogenesis, irxl1 is expressed from 18 hours postfertilization onward and prominent expression is detected in the pharyngeal arches. Knockdown of irxl1 by morpholinos results in malformed brain and arch structures, which can be partially rescued by cRNA injection. The heads of the morphants become small and flat, and extensions along the anterior-posterior/dorso-ventral axes are reduced without affecting regional specification. Loss of irxl1 function also causes deficit in neural crest cells which consequently results in partial loss of craniofacial muscles and severe deformation of arch cartilages. These observations suggest that irxl1 may regulate factors involved in brain and pharyngeal arch development.
authors.affiliation: Department of Biomedical Sciences, Chung Shan Medical University, Taichung, Taiwan.
authors.forename: Han-Ni
authors.initials: HN
authors.lastname: Chuang
authors.forename: Hsiao-Yun
authors.initials: HY
authors.lastname: Cheng
authors.forename: Kuang-Ming
authors.initials: KM
authors.lastname: Hsiao
authors.forename: Chieh-Wen
authors.initials: CW
authors.lastname: Lin
authors.forename: Mei-Ling
authors.initials: ML
authors.lastname: Lin
authors.forename: Huichin
authors.initials: H
authors.lastname: Pan
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000196:embryology*; D001934:Branchial Region / Q000196:embryology*; D002454:Cell Differentiation; D002465:Cell Movement; D019902:Chondrocytes / Q000166:cytology; D003001:Cloning, Molecular; D047108:Embryonic Development; D029941:Fish Proteins / Q000235:genetics; D020869:Gene Expression Profiling; D055785:Gene Knockdown Techniques; D005801:Genes, Homeobox / Q000235:genetics*; D018398:Homeodomain Proteins / Q000235:genetics*; D007267:Injections; D008969:Molecular Sequence Data; D009432:Neural Crest / Q000166:cytology; D018075:RNA, Complementary; D015027:Zebrafish
chemical_list: D029941:Fish Proteins; D018398:Homeodomain Proteins; D018075:RNA, Complementary