EXPRESSION OF THE TRANSCRIPTION FACTORS OTLX2, BARX1 AND SOX9 DURING MOUSE ODONTOGENESIS

The molecular mechanisms governing the decision between molariform and incisiform patterns of rodent dentition are not yet known. Transcript ion factors are regulators of regionally specific morphogenesis and ke y co-ordinators of gene activity during developmental processes. Here, we analysed the expression of several transcription factors during mo use tooth development. Otlx2/Rieg is a homeobox gene involved in Riege r syndrome, a human disorder characterized by dental hypoplasia. Otlx2 /Rieg expression distinguishes stomatodeal epithelium well before toot h initiation, and thereafter its expression becomes restricted to the epithelia of both molar and incisor primordia. The recently identified homeodomain transcription factor Barx1 is first expressed in mesenchy me of the first branchial arch, but during advanced developmental stag es the gene is exclusively expressed is the mesenchyme of molar primor dia. Finally, the Sry-related transcription factor Sox9 is expressed i n epithelial components and to a lesser degree in condensed mesenchyme of the developing teeth. These results suggest that Otlx2/Rieg, Barx1 , and Sox9 participate in the hierarchical cascade of factors involved in the regulation of tooth morphogenesis.