|
|
|
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
First published online March 7, 2008
doi: 10.1242/10.1242/dev.011759
1 Dulbecco Telethon Institute, Molecular Biotechnology Center, University of
Torino, Via Nizza 52, Torino, 10126, Italy.
2 Department of Biomolecular Science and Biotechnology, University of Milan, Via
Celoria 26, 20133 Milan, Italy.
3 CNR Istituto Tecnologie Biomediche, Segrate Milano, Italy.
4 Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, USA.
5 Developmental Skin Biology Unit, NIAMS, NIH, Bethesda, MD, USA.
6 Department of Dermatology, University of Rome, TorVergata, Italy.
7 Evolution des Régulations Endocriniennes CNRS, UMR5166, Muséum
National d'Histoire Naturelle, Paris, France.
Authors for correspondence (e-mails:
luisa.guerrini{at}unimi.it;
gmerlo{at}dti.telethon.it)
Accepted 31 January 2008
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, 
Np63
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.
Key words: Dlx, p63, Ectrodactyly, Limb development, Transcription regulation
