title: Ectopic Meis1 expression in the mouse limb bud alters P-D patterning in a Pbx1-independent manner.
abstract: During limb development, expression of the TALE homeobox transcription factor Meis1 is activated by retinoic acid in the proximal-most limb bud regions, which give rise to the upper forelimb and hindlimb. Early subdivision of the limb bud into proximal Meis-positive and distal Meis-negative domains is necessary for correct proximo-distal (P-D) limb development in the chick, since ectopic Meis1 overexpression abolishes distal limb structures, produces a proximal shift of limb identities along the P-D axis, and proximalizes distal limb cell affinity properties. To determine whether Meis activity is also required for P-D limb specification in mammals, we generated transgenic mice ectopically expressing Meis1 in the distal limb mesenchyme under the control of the Msx2 promoter. Msx2:Meis1 transgenic mice display altered P-D patterning and shifted P-D Hox gene expression domains, similar to those previously described for the chicken. Meis proteins function in cooperation with PBX factors, another TALE homeodomain subfamily. Meis-Pbx interaction is required for nuclear localization of both proteins in cell culture, and is important for their DNA-binding and transactivation efficiency. During limb development, Pbx1 nuclear expression correlates with the Meis expression domain, and Pbx1 has been proposed as the main Meis partner in this context; however, we found that Pbx1 deficiency did not modify the limb phenotype of Msx2:Meis1 mice. Our results indicate a conserved role of Meis activity in P-D specification of the tetrapod limb and suggest that Pbx function in this context is either not required or is provided by partners other than Pbx1.
authors.affiliation: Centro Nacional de Investigaciones Cardiovasculares, Melchor Fernandez Almagro 3, 28029 Madrid, Spain.
authors.forename: Nadia
authors.initials: N
authors.lastname: Mercader
authors.forename: Licia
authors.initials: L
authors.lastname: Selleri
authors.forename: Luis Miguel
authors.initials: LM
authors.lastname: Criado
authors.forename: Pilar
authors.initials: P
authors.lastname: Pallares
authors.forename: Carlos
authors.initials: C
authors.lastname: Parras
authors.forename: Michael L
authors.initials: ML
authors.lastname: Cleary
authors.forename: Miguel
authors.initials: M
authors.lastname: Torres
mesh_terms: D000818:Animals; D019521:Body Patterning / Q000235:genetics / Q000502:physiology*; D004622:Embryo, Mammalian / Q000196:embryology / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D018878:Limb Buds / Q000196:embryology* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D000075062:Pre-B-Cell Leukemia Transcription Factor 1; D013997:Time Factors; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D018398:Homeodomain Proteins; C094041:Hoxa11 protein, mouse; C000616392:Meis1 protein, mouse; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; D009363:Neoplasm Proteins; C481797:Pbx1 protein, mouse; D000075062:Pre-B-Cell Leukemia Transcription Factor 1; D014157:Transcription Factors; C099959:homeobox protein HOXA13