title: Ectopic Hoxa2 induction after neural crest migration results in homeosis of jaw elements in Xenopus.
abstract: Hox genes are required to pattern neural crest (NC) derived craniofacial and visceral skeletal structures. However, the temporal requirement of Hox patterning activity is not known. Here, we use an inducible system to establish Hoxa2 activity at distinct NC migratory stages in Xenopus embryos. We uncover stage-specific effects of Hoxa2 gain-of-function suggesting a multistep patterning process for hindbrain NC. Most interestingly, we show that Hoxa2 induction at postmigratory stages results in mirror image homeotic transformation of a subset of jaw elements, normally devoid of Hox expression, towards hyoid morphology. This is the reverse phenotype to that observed in the Hoxa2 knockout. These data demonstrate that the skeletal pattern of rhombomeric mandibular crest is not committed before migration and further implicate Hoxa2 as a true selector of hyoid fate. Moreover, the demonstration that the expression of Hoxa2 alone is sufficient to transform the upper jaw and its joint selectively may have implications for the evolution of jaws.
authors.affiliation: Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM/ULP, Collège de France, BP 163 - 67404 Illkirch Cedex, C.U. de Strasbourg, France.
authors.forename: M
authors.initials: M
authors.lastname: Pasqualetti
authors.forename: M
authors.initials: M
authors.lastname: Ori
authors.forename: I
authors.initials: I
authors.lastname: Nardi
authors.forename: F M
authors.initials: FM
authors.lastname: Rijli
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D005801:Genes, Homeobox; D018398:Homeodomain Proteins / Q000235:genetics*; D007568:Jaw / Q000196:embryology / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000196:embryology / Q000378:metabolism; D009432:Neural Crest / Q000196:embryology* / Q000378:metabolism; D012249:Rhombencephalon / Q000196:embryology / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014162:Transfection; D014981:Xenopus / Q000196:embryology* / Q000235:genetics*; D029867:Xenopus Proteins; D015027:Zebrafish; D029961:Zebrafish Proteins
chemical_list: D017931:DNA Primers; D018076:DNA, Complementary; D018398:Homeodomain Proteins; C489830:Hoxa2 protein, Xenopus; C489833:Hoxa2 protein, mouse; C080331:Hoxa3 protein, mouse; D029867:Xenopus Proteins; D029961:Zebrafish Proteins; C489831:hoxa2b protein, zebrafish