title: Hox genes regulate the onset of Tbx5 expression in the forelimb.
abstract: Tbx4 and Tbx5 are two closely related T-box genes that encode transcription factors expressed in the prospective hindlimb and forelimb territories, respectively, of all jawed vertebrates. Despite their striking limb type-restricted expression pattern, we have shown that these genes do not participate in the acquisition of limb type-specific morphologies. Instead, Tbx4 and Tbx5 play similar roles in the initiation of hindlimb and forelimb outgrowth, respectively. We hypothesized that different combinations of Hox proteins expressed in different rostral and caudal domains of the lateral plate mesoderm, where limb induction occurs, might be involved in regulating the limb type-restricted expression of Tbx4 and Tbx5 and in the later determination of limb type-specific morphologies. Here, we identify the minimal regulatory element sufficient for the earliest forelimb-restricted expression of the mouse Tbx5 gene and show that this sequence is Hox responsive. Our results support a mechanism in which Hox genes act upstream of Tbx5 to control the axial position of forelimb formation.
authors.affiliation: Division of Developmental Biology, MRC National Institute for Medical Research, Mill Hill, London NW7 1AA, UK. cmgbmc@ibmb.csic.es
authors.forename: Carolina
authors.initials: C
authors.lastname: Minguillon
authors.forename: Satoko
authors.initials: S
authors.lastname: Nishimoto
authors.forename: Sophie
authors.initials: S
authors.lastname: Wood
authors.forename: Elisenda
authors.initials: E
authors.lastname: Vendrell
authors.forename: Jeremy J
authors.initials: JJ
authors.lastname: Gibson-Brown
authors.forename: Malcolm P O
authors.initials: MP
authors.lastname: Logan
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D019521:Body Patterning / Q000235:genetics*; D002642:Chick Embryo; D017931:DNA Primers / Q000235:genetics; D024202:Electrophoretic Mobility Shift Assay; D018274:Electroporation; D005552:Forelimb / Q000196:embryology* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D005801:Genes, Homeobox / Q000235:genetics*; D017403:In Situ Hybridization; D051379:Mice; D009024:Morphogenesis / Q000235:genetics*; D020825:T-Box Domain Proteins / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D020825:T-Box Domain Proteins; C103172:T-box transcription factor 5