title: Analyses of fugu hoxa2 genes provide evidence for subfunctionalization of neural crest cell and rhombomere cis-regulatory modules during vertebrate evolution.
abstract: Hoxa2 gene is a primary player in regulation of craniofacial programs of head development in vertebrates. Here we investigate the evolution of a Hoxa2 neural crest enhancer identified originally in mouse by comparing and contrasting the fugu hoxa2a and hoxa2b genes with their orthologous teleost and mammalian sequences. Using sequence analyses in combination with transgenic regulatory assays in zebrafish and mouse embryos we demonstrate subfunctionalization of regulatory activity for expression in hindbrain segments and neural crest cells between these two fugu co-orthologs. hoxa2a regulatory sequences have retained the ability to mediate expression in neural crest cells while those of hoxa2b include cis-elements that direct expression in rhombomeres. Functional dissection of the neural crest regulatory potential of the fugu hoxa2a and hoxa2b genes identify the previously unknown cis-element NC5, which is implicated in generating the differential activity of the enhancers from these genes. The NC5 region plays a similar role in the ability of this enhancer to mediate reporter expression in mice, suggesting it is a conserved component involved in control of neural crest expression of Hoxa2 in vertebrate craniofacial development.
authors.affiliation: Stowers Institute for Medical Research, Kansas City, MO 64110, USA.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: McEllin
authors.affiliation: Stowers Institute for Medical Research, Kansas City, MO 64110, USA.
authors.forename: Tara B
authors.initials: TB
authors.lastname: Alexander
authors.affiliation: Stowers Institute for Medical Research, Kansas City, MO 64110, USA. Electronic address: tuempel@fli-leibniz.de.
authors.forename: Stefan
authors.initials: S
authors.lastname: Tümpel
authors.affiliation: Stowers Institute for Medical Research, Kansas City, MO 64110, USA; Department of Pathology and Laboratory Medicine, Kansas University Medical Center, Kansas City, KS 66160, USA.
authors.forename: Leanne M
authors.initials: LM
authors.lastname: Wiedemann
authors.affiliation: Stowers Institute for Medical Research, Kansas City, MO 64110, USA; Department of Anatomy and Cell Biology, Kansas University Medical Center, Kansas City, KS 66160, USA. Electronic address: rek@stowers.org.
authors.forename: Robb
authors.initials: R
authors.lastname: Krumlauf
mesh_terms: D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D017124:Conserved Sequence / Q000235:genetics; D004625:Embryo, Nonmammalian / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009432:Neural Crest / Q000166:cytology*; D012249:Rhombencephalon / Q000166:cytology / Q000196:embryology*; D016415:Sequence Alignment; D023741:Takifugu / Q000196:embryology / Q000235:genetics*; D015027:Zebrafish / Q000235:genetics
chemical_list: D018398:Homeodomain Proteins
keywords: Enhancers; Evolution of cis-elements; Gene regulation; Hindbrain; Hox genes; Neural crest