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Genetic interactions between Pax9 and Msx1 regulate lip development and several stages of tooth morphogenesis

Lookup NU author(s): Dr Mitsushiro Nakatomi, Dr Darren Key, Dr Ralf KistORCiD, Andrew Aw, Dr Heiko Peters


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Developmental abnormalities of craniofacial structures and teeth often occur sporadically and the underlying genetic defects are not well understood, in part due to unknown gene-gene interactions. Pax9 and Msx1 are co-expressed during craniofacial development, and mice that are single homozygous mutant for either gene exhibit cleft palate and an early arrest of tooth formation. Whereas in vitro assays have demonstrated that protein-protein interactions between Pax9 and Msx1 can occur, it is unclear if Pax9 and Msx1 interact genetically in vivo during development. To address this question, we compounded the Pax9 and Msx1 mutations and observed that double homozygous mutants exhibit an incompletely penetrant cleft lip phenotype. Moreover, in double heterozygous mutants, the lower incisors were consistently missing and we find that transgenic BMP4 expression partly rescues this phenotype. Reduced expression of Shh and Bmp2 indicates that a smaller "incisor field" forms in Pax9(+/-);Msx1(+/-) mutants, and dental epithelial growth is substantially reduced after the bud to cap stage transition. This defect is preceded by drastically reduced mesenchymal expression of Fgf3 and Fgf10, two genes that encode known stimulators of epithelial growth during odontogenesis. Consistent with this result, cell proliferation is reduced in both the dental epithelium and mesenchyme of double heterozygous mutants. Furthermore, the developing incisors lack mesenchymal Notch1 expression at the bud stage and exhibit abnormal ameloblast differentiation on both labial and lingual surfaces. Thus, Msx1 and Pax9 interact synergistically throughout lower incisor development and affect multiple signaling pathways that influence incisor size and symmetry. The data also suggest that a combined reduction of PAX9 and MSX1 gene dosage in humans may increase the risk for orofacial clefting and oligodontia. (C) 2010 Elsevier Inc. All rights reserved.

Publication metadata

Author(s): Nakatomi M, Wang XP, Key D, Lund JJ, Turbe-Doan A, Kist R, Aw A, Chen YP, Maas RL, Peters H

Publication type: Article

Publication status: Published

Journal: Developmental Biology

Year: 2010

Volume: 340

Issue: 2

Pages: 438-449

Print publication date: 01/02/2010

ISSN (print): 0012-1606

ISSN (electronic): 1095-564X

Publisher: Academic Press


DOI: 10.1016/j.ydbio.2010.01.031


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Funder referenceFunder name
Wellcome Trust (UK)
K99DE019871Harvard School of Dental Medicine