F. Lezot et al., Biomineralization, life-time of odontogenic cells and differential expression of the two homeobox genes MSX-1 and DLX-2 in transgenic mice, J BONE MIN, 15(3), 2000, pp. 430-441
Msx and Dlx homeobox genes encode for transcription factors that control ea
rly morphogenesis, More specifically, Msx-1, Msx-2, and Dlx-2 homeobox gene
s contribute to the initial patterning of the dentition, The present study
is devoted to the potential role of those homeobox genes during the late fo
rmation of mineralized tissues, using the rodent incisor as an experimental
system. The continuously erupting mandibular incisor allows (1) the coinve
stigation of the whole sequences of amelogenesis and dentinogenesis, aligne
d along the main dental axis in a single sample in situ and (2) the differe
ntial characterization of transcripts generated by epithelial and ectomesen
chymal odontogenic cells, Northern blot experiments on microdissected cells
showed the continuing expression of Msx-2 and Dlx-2 in the later stages of
dental biomineralization, differentially in epithelial and ectomesenchymal
compartments. Transgenic mice produced with LacZ reporter constructs for D
lx-2 and Msx-1 were used to detect different components of the gene express
ion patterns with the sensitive B-galactosidase histoenzymology, The result
s show a prominent epithelial involvement of Dlx-2, with stage-specific var
iations in the cells involved in enamel formation, Quantitative analyses id
entified specific modulations of Dlx-2 expression in ameloblasts depending
on the anatomical sites of the incisor, showing more specifically an invers
e linear relationship between the Dlx-2 promoter activity level and enamel
thickness. This investigation extends the role of homeoproteins to postmito
tic stages, which would control secretory cell activity, in a site-specific
manner as shown here for Dlx-2.