title: Divergence of Hoxc8 early enhancer parallels diverged axial morphologies between mammals and fishes.
abstract: There is considerable interest in understanding how cis-regulatory modifications drive morphological changes across species. Because developmental regulatory genes, including Hox genes, are remarkably conserved, their noncoding regulatory regions are likely sources for variations. Modifications of Hox cis-regulatory elements have potential to alter Hox gene expression and, hence, axial morphologies. In vertebrates, differences in the axial levels of Hox gene expression correlate with differences in the number and relative position of thoracic vertebrae. Variation in cis-regulatory elements of Hox genes can be identified by comparative sequence and reporter gene analyses in transgenic mouse embryos. Using these approaches, we show a remarkable divergence of the Hoxc8 early enhancers between mammals and fishes representing diverse axial morphologies. Extensive restructuring of the Hoxc8 early enhancer including nucleotide substitutions, inversion, and divergence result in distinct patterns of reporter gene expression along the embryonic axis. Our results provide an evolutionary perspective on how the enhancer elements are engineered and support the hypothesis that remodeling of Hox regulatory elements in different species has played a significant role in generating morphological diversity.
authors.affiliation: Department of Dairy and Animal Science, College of Agricultural Sciences, Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Sanjay
authors.initials: S
authors.lastname: Anand
authors.forename: Wayne C H
authors.initials: WC
authors.lastname: Wang
authors.forename: Dennis R
authors.initials: DR
authors.lastname: Powell
authors.forename: Stacey A
authors.initials: SA
authors.lastname: Bolanowski
authors.forename: Jian
authors.initials: J
authors.lastname: Zhang
authors.forename: Christina
authors.initials: C
authors.lastname: Ledje
authors.forename: Aruna B
authors.initials: AB
authors.lastname: Pawashe
authors.forename: Chris T
authors.initials: CT
authors.lastname: Amemiya
authors.forename: Cooduvalli S
authors.initials: CS
authors.lastname: Shashikant
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D004742:Enhancer Elements, Genetic; D005399:Fishes; D018398:Homeodomain Proteins / Q000737:chemistry / Q000235:genetics*; D007668:Kidney / Q000196:embryology; D008322:Mammals; D051379:Mice / Q000235:genetics; D008969:Molecular Sequence Data; D009024:Morphogenesis; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D023741:Takifugu / Q000235:genetics; D015027:Zebrafish / Q000235:genetics; D029961:Zebrafish Proteins
chemical_list: D018398:Homeodomain Proteins; C489816:Hoxc8 protein, mouse; D029961:Zebrafish Proteins; C489818:hoxc8a protein, zebrafish