title: Regulation of Dlx5 and Dlx6 gene expression by p63 is involved in EEC and SHFM congenital limb defects.
abstract: The congenital malformation Split Hand-Foot Malformation (SHFM, or ectrodactyly) is characterized by a medial cleft of hands and feet, and missing central fingers. Five genetically distinct forms are known in humans; the most common (type-I) is linked to deletions of DSS1 and the distalless-related homeogenes DLX5 and DLX6. As Dlx5;Dlx6 double-knockout mice show a SHFM-like phenotype, the human orthologs are believed to be the disease genes. SHFM-IV and Ectrodactyly-Ectodermal dysplasia-Cleft lip (EEC) are caused by mutations in p63, an ectoderm-specific p53-related transcription factor. The similarity in the limb phenotype of different forms of SHFM may underlie the existence of a regulatory cascade involving the disease genes. Here, we show that p63 and Dlx proteins colocalize in the nuclei of the apical ectodermal ridge (AER). In homozygous p63- (null) and p63EEC (R279H) mutant limbs, the AER fails to stratify and the expression of four Dlx genes is strongly reduced; interestingly, the p63+/EEC and p63+/- hindlimbs, which develop normally and have a normally stratified AER, show reduced Dlx gene expression. The p63+/EEC mutation combined with an incomplete loss of Dlx5 and Dlx6 alleles leads to severe limb phenotypes, which are not observed in mice with either mutation alone. In vitro, DeltaNp63alpha induces transcription from the Dlx5 and Dlx6 promoters, an activity abolished by EEC and SHFM-IV mutations, but not by Ankyloblepharon-Ectodermal defects-Cleft lip/palate (AEC) mutations. ChIP analysis shows that p63 is directly associated with the Dlx5 and Dlx6 promoters. Thus, our data strongly implicate p63 and the Dlx5-Dlx6 locus in a pathway relevant in the aetio-pathogenesis of SHFM.
authors.affiliation: Dulbecco Telethon Institute, Molecular Biotechnology Center, University of Torino, Via Nizza 52, Torino, 10126, Italy.
authors.forename: Nadia
authors.initials: N
authors.lastname: Lo Iacono
authors.forename: Stefano
authors.initials: S
authors.lastname: Mantero
authors.forename: Anna
authors.initials: A
authors.lastname: Chiarelli
authors.forename: Elvin
authors.initials: E
authors.lastname: Garcia
authors.forename: Alea A
authors.initials: AA
authors.lastname: Mills
authors.forename: Maria I
authors.initials: MI
authors.lastname: Morasso
authors.forename: Antonio
authors.initials: A
authors.lastname: Costanzo
authors.forename: Giovanni
authors.initials: G
authors.lastname: Levi
authors.forename: Luisa
authors.initials: L
authors.lastname: Guerrini
authors.forename: Giorgio R
authors.initials: GR
authors.lastname: Merlo
mesh_terms: D000818:Animals; D002971:Cleft Lip / Q000235:genetics*; D004476:Ectodermal Dysplasia / Q000235:genetics*; D005532:Foot Deformities, Congenital / Q000196:embryology / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D006228:Hand Deformities, Congenital / Q000196:embryology / Q000235:genetics; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D017880:Limb Deformities, Congenital / Q000145:classification / Q000196:embryology / Q000235:genetics*; D051379:Mice; D018345:Mice, Knockout; D009154:Mutation; D010750:Phosphoproteins / Q000235:genetics / Q000502:physiology*; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: C088334:Distal-less homeobox proteins; D018398:Homeodomain Proteins; D010750:Phosphoproteins; D015534:Trans-Activators; D014157:Transcription Factors; C486419:Trp63 protein, mouse