Expression of Set-alpha during morphogenesis of mouse lower first molar.

The detailed in situ expression pattern of the Set-alpha gene has been studied. Previously we showed that Set-alpha is a differentially expressed gene in the embryonic mouse mandible at day 10.5 (E10.5) gestational age. Cells expressing Set-alpha were widely distributed in both the epithelial and underlying ectomesenchymal cells at E10.5. At E12, they were slightly aggregated in an area where tooth germ of the lower first molar is estimated to be formed. At E13.5, Set-alpha was strongly expressed in the tooth germ. At the cap stage, Set-alpha was expressed in the enamel organ and dental papilla. At the bell stage, Set-alpha was distinctly expressed in the inner enamel epithelial and dental papilla cells facing the inner enamel epithelial layer, which were intended to differentiate into ameloblasts and odontoblasts, respectively. Interestingly, Set-alpha was also expressed in several embryonic craniofacial tissues derived from the ectoderm. This study is the first report that Set-alpha is distinctly expressed in the developing tooth germ, and suggests that Set-alpha plays an important role in both the initiation and the growth of the tooth germ, as well as in the differentiation of ameloblasts and odontoblasts.