Linkage mapping, QTL detection, and identification of candidate genes for sharpe variation in the four tooth classes of mammals.

Morita W., Mekada K., Fukazawa S., Danjo K., Fusegawa M., Yamanaka A

15th Tooth Morphogenesis and Differentiation

Mammals have evolved a suite of features to adapt to diverse diets and ecological niches, including relatively large brains, hair or fur, homeothermy, mammary glands, a diaphragm, and middle ear bones. Among these adaptations, the differentiation of four tooth classes—incisors, canines, premolars, and molars—is particularly notable.
 
While many extant mammalian taxa have lost some teeth or entire tooth classes, the ancestral dental formula of 44 teeth (3.1.4.3 per quadrant in both upper and lower jaws) has undergone significant modification throughout the evolutionary history of placental mammals. This morphological variation is likely influenced by multiple genetic factors.
 
Understanding the genetic basis of diversity and variation in dental morphology across the dentition is crucial for a comprehensive understanding of mammalian evolution.
 
This study aims to elucidate the genetic architecture underlying shape variation within each tooth class by using the house shrew (Suncus murinus), an insectivorous species with a primitive placental mammal dental condition that retains all four tooth classes. By analyzing F2 samples derived from a larger continental standard strain and a smaller insular strain, we quantify tooth shape using morphometric mapping and construct a high-density genetic map to identify QTL regions and candidate genes.
 
Furthermore, we explore differences in shape variation and associated genes between single-cusped (unicuspid) and multi-cusped teeth, highlighting key factors involved in tooth shape differentiation.Mammals have evolved a suite of features to adapt to their diverse diets and ecological niches, including relatively large brains, hair or fur, homeothermy, mammary glands, a diaphragm, and middle ear bones, among others. One key feature is the differentiation of their four tooth classes: incisors, canines, premolars, and molars.
Although many extant mammalian taxa have lost some teeth or even entire tooth classes, the ancestral dental formula of 44 teeth (3.1.4.3 for each tooth class in both the upper and lower jaws) has been modified throughout mammalian evolutionary history. This morphological variation is likely influenced by multiple genetic factors.
Understanding the genetic basis of diversity and variation in dental morphology across the dentition is crucial for a comprehensive understanding of mammalian evolution.
 
This study aims to elucidate the genetic architecture underlying shape variation within each tooth class, using the house shrew (Suncus murinus), which retains all four tooth classes. By analyzing F2 samples derived from a larger continental standard strain and a smaller insular strain, we quantify tooth shape through morphometric mapping and construct a high-density genetic map to identify QTL regions and candidate genes.
Additionally, we aim to explore differences in shape variation and associated genes between unicuspid and multicuspid teeth, discussing key factors involved in the process of tooth shape differentiation.