Identification of candidate genes for tooth loss in mammals

Morita W, Mekada K, Kawada SI, Nagata N, Yamanaka A

The 14th Tooth Morphogenesis and Differentiation

Through the long timescale of adaptation to their respective diets and ecological environments, mammals have evolved distinct patterns of dentition. The ancestor of placental mammals is thought to have 44 teeth (3.1.4.3 for both upper and lower jaw). However, most major extant mammalian taxa have lost several numbers of teeth or even a certain tooth class as a whole from the ancestral state, which would be involved in multiple genes. This study aims to determine the genetic basis of tooth loss using Suncus murinus, a taxon that preserves many characteristics of the ancestral mammals with a large variation in the number of teeth. The F2 population was generated by a cross experiment between a continental lineage with large body size and little tooth loss and an island lineage with small body size and high frequency of loss of upper third incisors (UI3) and third premolars (UP3). The preliminary genome-wide association analysis showed significant correlations with key signaling pathways essential for tooth morphogenesis and genes associated with somatic growth. The candidate genes related to UI3 and UP3 loss are not necessarily overlapped, and the number of genes related to UI3 loss was higher than that of UP3. As a future analysis, we plan to compare the sequences of candidate genes associated with tooth loss across mammals to explore the genetic underpinning of evolutionary changes in the dental formula.