title: prx-1 functions cooperatively with another paired-related homeobox gene, prx-2, to maintain cell fates within the craniofacial mesenchyme.
abstract: The paired-related homeobox gene, prx-1, is expressed in the postmigratory cranial mesenchyme of all facial prominences and is required for the formation of proximal first arch derivatives. We introduced lacZ into the prx-1 locus to study the developmental fate of cells destined to express prx-1 in the prx-1 mutant background. lacZ was normally expressed in prx-1(neo); prx-1(lacZ )mutant craniofacial mesenchyme up until 11.5 d.p.c. At later time points, lacZ expression was lost from structures that are defective in the prx-1(neo) mutant mice. A related gene, prx-2, demonstrated overlapping expression with prx-1. To test the idea that prx-1 and prx-2 perform redundant functions, we generated prx-1(neo;)prx-2 compound mutant mice. Double mutant mice had novel phenotypes in which the rostral aspect of the mandible was defective, the mandibular incisor arrested as a single, bud-stage tooth germ and Meckel's cartilage was absent. Expression of two markers for tooth development, pax9 and patched, were downregulated. Using a transgene that marks a subset of prx-1-expressing cells in the craniofacial mesenchyme, we showed that cells within the hyoid arch take on the properties of the first branchial arch. These data suggest that prx-1 and prx-2 coordinately regulate gene expression in cells that contribute to the distal aspects of the mandibular arch mesenchyme and that prx-1 and prx-2 play a role in the maintenance of cell fate within the craniofacial mesenchyme.
authors.affiliation: Alkek Institute of Biosciences and Technology, Center for Cancer Biology and Nutrition, Department of Medical Biochemistry and Genetics, Texas A&M University, Houston, TX 77030, USA.
authors.forename: M F
authors.initials: MF
authors.lastname: Lu
authors.forename: H T
authors.initials: HT
authors.lastname: Cheng
authors.forename: M J
authors.initials: MJ
authors.lastname: Kern
authors.forename: S S
authors.initials: SS
authors.lastname: Potter
authors.forename: B
authors.initials: B
authors.lastname: Tran
authors.forename: T G
authors.initials: TG
authors.lastname: Diekwisch
authors.forename: J F
authors.initials: JF
authors.lastname: Martin
mesh_terms: D000483:Alleles; D000818:Animals; D005147:Facial Bones / Q000196:embryology*; D005801:Genes, Homeobox; D005838:Genotype; D018398:Homeodomain Proteins / Q000235:genetics / Q000502:physiology*; D007763:Lac Operon; D008648:Mesoderm / Q000166:cytology*; D051379:Mice; D008822:Mice, Transgenic; D016296:Mutagenesis; D012886:Skull / Q000196:embryology*
chemical_list: D018398:Homeodomain Proteins; C489936:Prrx1 protein, mouse; C115469:Prrx2 protein, mouse