Human Molecular Genetics Advance Access published online on October 19, 2005
Human Molecular Genetics, doi:10.1093/hmg/ddi388
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1 Institute of Human Genetics, University of Newcastle upon Tyne, International Centre for Life, Central Parkway, Newcastle upon Tyne, NE1 3BZ, UK
* To whom correspondence should be addressed. Missing teeth (hypodontia and oligodontia) are a common developmental abnormality in humans and heterozygous mutations of PAX9 have recently been shown to underlie a number of familial, non-syndromic cases. Whereas PAX9 haploinsufficiency has been suggested as the underlying genetic mechanism, it is not known how this affects tooth development. Here we describe a novel, hypomorphic Pax9 mutant allele (Pax9neo) producing decreased levels of Pax9 wild-type mRNA and show that this causes oligodontia in mice. Homozygous Pax9neo mutants (Pax9neo/neo) exhibit hypoplastic or missing lower incisors and third molars, and when combined with the null allele Pax9lacZ, the compound mutants (Pax9neo/lacZ) develop severe forms of oligodontia. The missing molars are arrested at different developmental stages and posterior molars are consistently arrested at an earlier stage, suggesting that a reduction of Pax9 gene dosage affects the dental field as a whole. In addition, hypomorphic Pax9 mutants show defects in enamel formation of the continuously growing incisors, whereas molars exhibit increased attrition and reparative dentin formation. Together, we conclude that changes of Pax9 expression levels have a direct consequence for mammalian dental patterning and that a minimal Pax9 gene dosage is required for normal morphogenesis and differentiation throughout tooth development.
Received August 24, 2005
Revised October 12, 2005
Accepted October 12, 2005
Article
Reduction of Pax9 gene dosage in an allelic series of mouse mutants causes hypodontia and oligodontia
2 Department of Oral Biology, School of Dental Sciences, University of Newcastle upon Tyne, Framlington Place, Newcastle upon Tyne NE2 4BW, UK
Heiko Peters, E-mail: heiko.peters{at}ncl.ac.uk
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