Congress Abstracts - Society for Developmental Biology

Program/Abstract # 290
Developmental genetics of evolved tooth gain in sticklebacks
Cleves, Phillip; Jimenez, Monica (UC Berkeley, USA); Nunez, Stephanie (Univ. of Michigan, USA); Schluter, Dolph (University of
British Columbia, Canada); Kingsley, David (Stanford U. and HHMI, USA)
Teeth are a classic model for studying organogenesis and morphological evolution. Despite the incredible phenotypic diversification
in dentition in vertebrates, our understanding of the molecular and developmental basis behind this variation is limited. A derived
benthic freshwater stickleback population has evolved a two-fold gain in ventral pharyngeal tooth number compared to their ancestral
marine counterparts. This evolved tooth gain provides an excellent system to study the molecular basis of evolved dental variation. To
ask when during development evolved tooth gain appears, we generated lab-reared developmental time courses of a low-toothed
marine population and this high-toothed freshwater population. Early in development, no differences in dental patterning are observed.
However, at late larval stages, differences in tooth number, an increase in tooth plate area, and a decrease in tooth spacing arise. We
identified genomic regions controlling these evolved patterning changes by mapping quantitative trait loci (QTL) controlling tooth
number, area, and spacing in a marine by freshwater F2 cross. One large effect QTL controlling tooth number fine-maps to a genomic
region containing an excellent candidate gene, Bone morphogenetic protein 6 (Bmp6). Stickleback Bmp6 is expressed in developing
teeth, and no coding changes are found between the populations. However, by quantitatively comparing allele specific expression of
Bmp6, we find cis-regulatory changes have elevated the relative expression level of the freshwater Bmp6 allele at late, but not early,
stages of development. Ongoing genetic and transgenic approaches will functionally test Bmp6 as a candidate for underlying evolved
tooth gain in sticklebacks.
Program/Abstract # 291
The Roles of Canonical Wnt Signaling in Developing Teeth of Polyphyodont Lizards
Holmes, Scott N.; Richman, Joy (University of British Columbia, Canada)
Though most dentate vertebrates replace their teeth at least once in the course of their lives, the process of tooth replacement is poorly
understood. This is mainly because the major tooth development model is the mouse which only has one generation of teeth. Our
previous work suggested that tooth renewal in geckos might involve dental epithelial stem cells and that these putative stem cells
become transit amplifying cells when exposed to canonical Wnts. Here we further investigate this idea using adult leopard geckos
(Eublepharis macularius). First we mapped areas of high canonical WNT signaling using antibodies to activated beta-catenin. Nuclear
staining was principally found in the outer enamel epithelium and successional lamina. Ameloblasts were noticeably negative for beta
catenin. Injections of 1M LiCl over a 1 week period caused a significant increase in proliferation in the successional lamina (p