Meeting Abstract
99.5 Wednesday, Jan. 7 How snakes and lizards replace their teeth: Molecular and embryological scrutiny of tooth cycling in squamates HANDRIGAN, GR*; BUCHTOVA, M; LEUNG, KJ; RICHMAN, JM; University of British Columbia, Vancouver, Canada; Academy of Sciences, Brno, Czech Republic; University of British Columbia, Vancouver, Canada; University of British Columbia, Vancouver, Canada gregory.handrigan@gmail.com
Tooth regenerative capacity varies widely among amniotes and is affected in many human congenital diseases. It is our objective to elucidate the molecular signaling network that directs tooth cycling in amniotes. For this work, we have turned to the Squamata, which generally replace teeth throughout life (polyphyodonty). We are surveying gene expression in squamate dentigenous tissues by radioactive in situ hybridization and testing gene function by in vitro jaw-explant culture. Model species used by our group include the snake Python regius, the leopard gecko Eublepharis macularius and the bearded dragon Pogona vitticeps. The two former species commence tooth cycling while still in ovo, whereas P. vitticeps has lost its ability to replace teeth. By comparing odontogenesis among these three species, we can then identify crucial repressive or inductive signals in tooth replacement. Recently, we have explored the role of Hedgehog (Hh) signaling in squamate odontogenesis (Buchtova et al, 2008; PMID: 18456251). Whereas Hh is necessary for dental epithelial ingrowth and polarity, the pathway does not function in replacement tooth initiation. Accordingly, transcripts for each of the Hh pathway ligand Shh, receptor Patched1, and transcription factor Gli2 are present in the dental lamina, but conspicuously absent from the generational lamina, the site of replacement tooth-budding. Here we discuss new data that instead implicate the transcription factor Runx2 and members of three odontogenic pathways, TNF, BMP, and canonical Wnt, in squamate tooth cycling. We propose an epithelial-mesenchymal signaling scheme that integrates all three pathways to mediate tooth succession in squamates and other amniotes.
