UBC Theses and Dissertations
Longitudinal studies on tooth replacement in the leopard gecko Wong, Andrew Carlton Edward
The leopard gecko is an emerging reptilian model for the molecular basis of indefinite tooth replacement. Here we characterize the tooth replacement frequency and pattern of tooth loss in the normal adult gecko. We chose to perturb the system of tooth replacement by activating the Wingless signaling pathway (Wnt). Misregulation of Wnt leads to supernumerary teeth in mice and humans. We hypothesized by activating Wnt signaling with LiCl, tooth replacement frequency would increase. To measure the rate of tooth loss and replacement, weekly dental wax bites of 3 leopard geckos were taken over a 35-week period. The present/absent tooth positions were recorded. During the experimental period, the palate was injected bilaterally with NaCl (control) and then with LiCl. The geckos were to be biological replicates. Symmetry was analyzed with parametric tests (repeated measures ANOVA, Tukey’s post-hoc), while time for emergence and total absent teeth per week were analyzed with non-parametric tests (Kruskal-Wallis ANOVA, Mann-Whitney U post-hoc and Bonferroni Correction). The average replacement frequency was 6-7 weeks and posterior-to-anterior waves of replacement were formed. Right to left symmetry between individual tooth positions was high (>80%) when all teeth were included but dropped to 50% when only absent teeth were included. Two animals were followed for 14 weeks after NaCl injections and 14 weeks after LiCl injections. NaCl did not affect the replacement dentition but LiCl delayed and disrupted the pattern of replacement. The phenotypes were more severe for one animal including 1) increased time before emergence, 2) increased total number of absent teeth per week, 3) a greater effect on anterior teeth and 4) disruption of symmetry. The most affected period began 7 weeks post LiCl injection. At the end of the study, in vitro CT scans of both animals revealed normal patterns of unerupted teeth however there was bone loss in one animal. Gecko tooth replacement is rapid enough to be useful for longitudinal studies. Between-animal variation is high when studying individual teeth therefore each animal should be used as its own control. Future work includes increasing the biological replicates and detailed molecular studies to confirm the effect of LiCl.
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