title: prep1.2 and aldh1a2 participate to a positive loop required for branchial arches development in zebrafish.
abstract: Segmentation is a key step in embryonic development. Acting in all germ layers, it is responsible for the generation of antero-posterior asymmetries. Hox genes, with their diverse expression in individual segments, are fundamental players in the determination of different segmental fates. In vertebrates, Hox gene products gain specificity for DNA sequences by interacting with Pbx, Prep and Meis homeodomain transcription factors. In this work we cloned and analysed prep1.2 in zebrafish. In-situ hybridization experiments show that prep1.2 is maternally and ubiquitously expressed up to early somitogenesis when its expression pattern becomes more restricted to the head and trunk mesenchyme. Experiments of loss of function with prep1.2 morpholinos change the shape of the hyoid and third pharyngeal cartilages while arches 4-7 and pectoral fins are absent, a phenotype strikingly similar to that caused by loss of retinoic acid (RA). In fact, we show that prep1.2 is positively regulated by RA and required for the normal expression of aldh1a2 at later stages, particularly in tissues involved in the development of the branchial arches and pectoral fins. Thus, prep1.2 and aldh1a2 are members of an indirect positive feedback loop required for pharyngeal endoderm and posterior branchial arches development. As the paralogue gene prep1.1 is more important in hindbrain patterning and neural crest chondrogenesis, we provide evidence of a functional specialization of prep genes in zebrafish head segmentation and morphogenesis.
authors.affiliation: Dipartimento di Biologia, Università degli Studi di Padova, Via Bassi 58B, Padova, Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Vaccari
authors.forename: Gianluca
authors.initials: G
authors.lastname: Deflorian
authors.forename: Elisa
authors.initials: E
authors.lastname: Bernardi
authors.forename: Stefan
authors.initials: S
authors.lastname: Pauls
authors.forename: Natascia
authors.initials: N
authors.lastname: Tiso
authors.forename: Marino
authors.initials: M
authors.lastname: Bortolussi
authors.forename: Francesco
authors.initials: F
authors.lastname: Argenton
mesh_terms: D000818:Animals; D019521:Body Patterning; D001934:Branchial Region / Q000196:embryology*; D004625:Embryo, Nonmammalian / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D050697:Retinal Dehydrogenase / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D015027:Zebrafish / Q000196:embryology* / Q000378:metabolism; D029961:Zebrafish Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D014157:Transcription Factors; D029961:Zebrafish Proteins; C551176:pknox1.2 protein, zebrafish; D050697:Retinal Dehydrogenase