Mouse Otlx2/RIEG expression in the odontogenic epithelium precedes tooth initiation and requires mesenchyme-derived signals for its maintenance.
The mouse Otlx2 gene is a new member of the paired-like family of homeobox genes whose human homologue, RIEG, is involved in Rieger syndrome, an autosomal-dominant disorder. One of the cardinal features of Rieger syndrome is dental hypoplasia, indicating that Otlx2/RIEG activity is essential for normal tooth development. Here, we analyzed the expression of Otlx2 during mouse tooth development and studied its regulation in dental explants. Otlx2 expression distinguishes stomatodeal from other ectoderm as early as Embryonic Day 8.5, well before tooth initiation. Thereafter, its craniofacial expression becomes restricted to the tooth-forming areas and to the epithelial components of molar and incisor primordia. Although Otlx2 induction precedes the specification of odontogenic mesenchyme, tissue recombination experiments show that the maintenance of its expression requires signals from the mesenchyme and that dental mesenchyme has the capacity to induce ectopic expression of Otlx2 in nondental epithelium. Finally, we compare Otlx2 expression with that of the recently identified homeodomain transcription factor Barx1 expressed in molar mesenchyme. Their strictly complementary expression patterns in the epithelial and mesenchymal components suggest that both genes participate in the reciprocal tissue interactions which are a hallmark of odontogenesis.
Mucchielli
M L
ML
Laboratoire de Génétique et Physiologie du Développement, IBDM CNRS-INSERM-Université de la Méditerranée, Marseille Cedex 9, 13288, France.
Mitsiadis
T A
TA
Raffo
S
S
Brunet
J F
JF
Proust
J P
JP
Goridis
C
C
D000818:Animals; D002454:Cell Differentiation; D004847:Epithelial Cells; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D008648:Mesoderm / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009024:Morphogenesis; D009061:Mouth Mucosa / Q000196:embryology; D009687:Nuclear Proteins; D009805:Odontogenesis / Q000235:genetics* / Q000502:physiology; D051761:Paired Box Transcription Factors; D015398:Signal Transduction / Q000502:physiology*; D014070:Tooth / Q000196:embryology*; D014157:Transcription Factors / Q000235:genetics*; D000097577:Homeobox Protein PITX2
D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D051761:Paired Box Transcription Factors; D014157:Transcription Factors; D000097577:Homeobox Protein PITX2; C490667:BARX1 protein, human; C095587:Barx1 protein, mouse; C101485:homeobox protein PITX1; C433629:homeobox protein PITX3