title: The apical ectodermal ridge of the mouse model of ectrodactyly Dlx5;Dlx6-/- shows altered stratification and cell polarity, which are restored by exogenous Wnt5a ligand.
abstract: The congenital malformation split hand/foot (SHFM) is characterized by missing central fingers and dysmorphology or fusion of the remaining ones. Type-1 SHFM is linked to deletions/rearrangements of the DLX5-DLX6 locus and point mutations in the DLX5 gene. The ectrodactyly phenotype is reproduced in mice by the double knockout (DKO) of Dlx5 and Dlx6. During limb development, the apical ectodermal ridge (AER) is a key-signaling center responsible for early proximal-distal growth and patterning. In Dlx5;6 DKO hindlimbs, the central wedge of the AER loses multilayered organization and shows down-regulation of FGF8 and Dlx2. In search for the mechanism, we examined the non-canonical Wnt signaling, considering that Dwnt-5 is a target of distalless in Drosophila and the knockout of Wnt5, Ryk, Ror2 and Vangl2 in the mouse causes severe limb malformations. We found that in Dlx5;6 DKO limbs, the AER expresses lower levels of Wnt5a, shows scattered β-catenin responsive cells and altered basolateral and planar cell polarity (PCP). The addition of Wnt5a to cultured embryonic limbs restored the expression of AER markers and its stratification. Conversely, the inhibition of the PCP molecule c-jun N-terminal kinase caused a loss of AER marker expression. In vitro, the addition of Wnt5a on mixed primary cultures of embryonic ectoderm and mesenchyme was able to confer re-polarization. We conclude that the Dlx-related ectrodactyly defect is associated with the loss of basoapical and PCP, due to reduced Wnt5a expression and that the restoration of the Wnt5a level is sufficient to partially reverts AER misorganization and dysmorphology.
authors.affiliation: Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy.
authors.forename: Daniele
authors.initials: D
authors.lastname: Conte
authors.affiliation: Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Garaffo
authors.affiliation: Human Genome Department, Istituto Tecnologie Biomediche, CNR Milano, Italy.
authors.forename: Nadia
authors.initials: N
authors.lastname: Lo Iacono
authors.affiliation: Human Genome Department, Istituto Tecnologie Biomediche, CNR Milano, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Mantero
authors.affiliation: Department of Molecular Medicine, University of Padova, Padova, Italy and.
authors.forename: Stefano
authors.initials: S
authors.lastname: Piccolo
authors.affiliation: Department of Molecular Medicine, University of Padova, Padova, Italy and.
authors.forename: Michelangelo
authors.initials: M
authors.lastname: Cordenonsi
authors.affiliation: Laboratoire de Parasitologie Moléculaire, IBMM-DBM, Université Libre de Bruxelles, B-6041 Gosselies, Belgium.
authors.forename: David
authors.initials: D
authors.lastname: Perez-Morga
authors.affiliation: Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy.
authors.forename: Valeria
authors.initials: V
authors.lastname: Orecchia
authors.affiliation: Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy.
authors.forename: Valeria
authors.initials: V
authors.lastname: Poli
authors.affiliation: Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy, giorgioroberto.merlo@unito.it.
authors.forename: Giorgio R
authors.initials: GR
authors.lastname: Merlo
mesh_terms: D000818:Animals; D016764:Cell Polarity / Q000187:drug effects / Q000502:physiology; D004195:Disease Models, Animal; D015536:Down-Regulation; D004475:Ectoderm / Q000378:metabolism / Q000473:pathology; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D017880:Limb Deformities, Congenital / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D008648:Mesoderm / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D015534:Trans-Activators / Q000235:genetics; D060449:Wnt Signaling Pathway; D000071818:Wnt-5a Protein / Q000096:biosynthesis / Q000172:deficiency / Q000235:genetics / Q000494:pharmacology*; D051176:beta Catenin / Q000378:metabolism
chemical_list: C501120:Dlx5 protein, mouse; C100597:Dlx6 protein, mouse; D018398:Homeodomain Proteins; D015534:Trans-Activators; D000071818:Wnt-5a Protein; C438615:Wnt5a protein, mouse; D051176:beta Catenin; D048031:JNK Mitogen-Activated Protein Kinases