title: Chicken Pax-1 gene: structure and expression during embryonic somite development.
abstract: Recent mouse genetic studies have implicated Pax-1, a paired-box-containing gene, in sclerotomal differentiation and vertebral body formation. To investigate Pax-1 function in somitic sclerotomal differentiation in the chick embryo, we have cloned the chicken Pax-1 gene, and its full length cDNA, and characterized its temporal and spatial expression pattern during somite development. Sequence analysis shows that chicken Pax-1 is highly homologous to murine and human Pax-1 genes with respect to the putative DNA-binding paired-box domain and the octapeptide domain. Northern analysis using probes derived from the paired-box domain and a unique non-paired box sequence of chicken Pax-1 detected 2-kb mRNA transcript. The expression profiles of Pax-1 were examined by in situ hybridization and Northern analysis. The first detectable expression of Pax-1 is seen in the most caudal epithelial somite. As the somite matures, Pax-1 expression takes on a medial distribution, thus corresponding to but preceding the emergence of the sclerotome. In the more mature, rostral somites (stage V and older), Pax-1 expression is found to be progressively localized first to the ventral-medial regions, and then to the caudal-ventral-medial quadrant of the mature somite. This pattern strongly supports the notion that Pax-1 expression is involved in somitogenesis and sclerotomal differentiation, and that it is subsequently a characteristic of the caudal half of the sclerotome, the presumptive precursor of vertebral cartilage. Northern analysis substantiated this expression profile and further revealed that the level of somitic Pax-1 expression increases as a function of embryonic development. Finally, we subjected chicken embryos to controlled heat shock treatment to perturb somite formation and segmentation. The pattern of Pax-1 expression in the anomalous somitic structures generated by controlled heat shock further supports a functional role for Pax-1 in somite development.
authors.affiliation: Department of Orthopaedic Surgery, Thomas Jefferson University, Philadelphia, PA 19107, USA.
authors.forename: G L
authors.initials: GL
authors.lastname: Barnes
authors.forename: C W
authors.initials: CW
authors.lastname: Hsu
authors.forename: B D
authors.initials: BD
authors.lastname: Mariani
authors.forename: R S
authors.initials: RS
authors.lastname: Tuan
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002642:Chick Embryo / Q000002:abnormalities*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics*; D004627:Embryonic Induction / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D018869:Heat-Shock Response / Q000235:genetics; D006358:Hot Temperature; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D051761:Paired Box Transcription Factors; D017422:Sequence Analysis, DNA; D014157:Transcription Factors / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics*
chemical_list: D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D051761:Paired Box Transcription Factors; D014157:Transcription Factors; C070835:PAX1 transcription factor