title: Multiple roles of Hoxa11 and Hoxd11 in the formation of the mammalian forelimb zeugopod.
abstract: Mutations in the 5' or posterior murine Hox genes (paralogous groups 9-13) markedly affect the formation of the stylopod, zeugopod and autopod of both forelimbs and hindlimbs. Targeted disruption of Hoxa11 and Hoxd11 or Hoxa10, Hoxc10 and Hoxd10 result in gross mispatterning of the radius and ulna or the femur, respectively. Similarly, in mice with disruptions of both Hoxa13 and Hoxd13, development of the forelimb and hindlimb autopod is severely curtailed. Although these examples clearly illustrate the major roles played by the posterior Hox genes, little is known regarding the stage or stages at which Hox transcription factors intersect with the limb development program to ensure proper patterning of the principle elements of the limb. Moreover, the cellular and/or molecular bases for the developmental defects observed in these mutant mice have not been described. In this study, we show that malformation of the forelimb zeugopod in Hoxa11/Hoxd11 double mutants is a consequence of interruption at multiple steps during the formation of the radius and ulna. In particular, reductions in the levels of Fgf8 and Fgf10 expression may be related to the observed delay in forelimb bud outgrowth that, in turn, leads to the formation of smaller mesenchymal condensations. However, the most significant defect appears to be the failure to form normal growth plates at the proximal and distal ends of the zeugopod bones. As a consequence, growth and maturation of these bones is highly disorganized, resulting in the creation of amorphous bony elements, rather than a normal radius and ulna.
authors.affiliation: Howard Hughes Medical Institute, Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, UT 84112, USA.
authors.forename: Anne M
authors.initials: AM
authors.lastname: Boulet
authors.forename: Mario R
authors.initials: MR
authors.lastname: Capecchi
mesh_terms: D000818:Animals; D017209:Apoptosis; D019521:Body Patterning / Q000235:genetics / Q000502:physiology; D019902:Chondrocytes / Q000166:cytology; D020219:Chondrogenesis / Q000235:genetics / Q000502:physiology; D005260:Female; D051526:Fibroblast Growth Factor 10; D051524:Fibroblast Growth Factor 8; D005346:Fibroblast Growth Factors / Q000235:genetics; D005552:Forelimb / Q000196:embryology*; D018507:Gene Expression Regulation, Developmental; D005801:Genes, Homeobox; D053823:Hedgehog Proteins; D018398:Homeodomain Proteins / Q000235:genetics / Q000502:physiology*; D008648:Mesoderm / Q000166:cytology; D051379:Mice; D018345:Mice, Knockout; D015513:Oncogene Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D011247:Pregnancy; D011884:Radius / Q000196:embryology / Q000254:growth & development; D015534:Trans-Activators / Q000235:genetics; D014457:Ulna / Q000196:embryology / Q000254:growth & development
chemical_list: C496464:Fgf10 protein, mouse; C496457:Fgf8 protein, mouse; D051526:Fibroblast Growth Factor 10; D053823:Hedgehog Proteins; D018398:Homeodomain Proteins; D015513:Oncogene Proteins; C487378:Tlx1 protein, mouse; D015534:Trans-Activators; D051524:Fibroblast Growth Factor 8; D005346:Fibroblast Growth Factors