Expression Survey Of Shh Signalling Pathway In The Human Embryonic Tooth Germ

A lot of research work have been done to the expression patterns of SHH (Sonic Hedgehog) signaling pathway in the developing mouse tooth, and their significant roles have begun to be revealed. In this study, to unveil the possible molecular mechanisms of SHH signaling pathway in human, we firstly examine the expression patterns of SHH signaling pathway, including SHH, PTC1, SMO, GUI1,2,3, and compared them with that found in mice. We show that compared with that in mouse these genes exhibit basically similar expression patterns in human tooth germ at the bud stage and cap stage. However, it was also showed that slightly different expression patterns exist. For example, SHH was detected in the inner enamel epithelium in the human tooth germ, but Shh was only expressed at the tip of the invaginating cell at the bud stage and the enamel knot at the cap stage in the mouse tooth. Moreover, the downstream genes in human have broader expression domain at the same stage. The expression of SHH and PTC1 in the human tooth is the same with it in mouse at the bell stage, while the expression of SMO and GUI1,2,3 can not be detected in human. The results indicate that although SHH singalling pathway may patterns the growth of the human and mouse tooth development in the same way between bud and cap stage, some differences exist. In addition, other regulatory genes may direct the growth of the human tooth instead of SHH signaling, or SHH signaling may also intact with other regulatory genes and come into being new molecular networks.