Research brief: Bat teeth illuminate the diversification of mammalian tooth classes

FINDINGS

In this paper, UCLA researchers used bats teeth to investigate the evolution of developmental rules governing the evolution of organs. This model system can be applied to other organs that develop like teeth, such as hair, nails, feathers, or scales that all develop in the same way. and allow us the better understand their diversification.

BACKGROUND

What can bats teach us about one of our most important tools of a mammal, teeth? As human, we have different kind of teeth called tooth classes: incisors, canines, premolar and molars. In primary school, we learn their slightly different functions (incisors allow us to cut food while molars are used to crush food) and our pets or many mammals around us used them for one of the most important things in mammal life: eating. In fact, they are so important that they are considered a key mammalian innovation that is responsible for their evolutionary success. While we can follow the evolution of tooth classes in the fossil record and despite their interest for human health, very little is known about the genetic and developmental mechanisms that have allowed them to diversify from the conical teeth of ancient vertebrates.

METHOD

In this paper led by Dr. Alexa Sadier, the team investigate these questions by looking at the dentition of an hyperdiverse group of bats, that are a unique model to study the evolution of mammalian dentition from a genetic, developmental, and morphological point of view. In only 25 million years, these bats have evolved multiple mammal diets such as sanguivory, insectivory or frugivory (some of them even eat fishes!) and exhibit a large variation of jaw length, tooth shape and size. By looking at bat teeth in the adult and during development using morphological and molecular tooth on many different species captured in the jungle, they show that two tooth classes, premolars and molars develop and evolved independently. In particular, they used two-photon excitation microscopy to investigate the variation in growth rate in the teeth region in multiple species. Then, by using molecular tool and a mathematical model, they show that this variation is triggered by a variation of the length of the jaw that perturbate the Turing mechanisms by which teeth emerge in these bats. More largely, this work shows how the number and size of teeth can rapidly vary during the colonization of new environments by mammals and provide new insights in how tooth classes evolve with potential consequences for human health and in vitro tooth engineering.

CNSI AUTHORS

Laurent Bentolila, Director of the Advanced Light Microscopy/Spectroscopy Laboratory (ALMS) at the California NanoSystems Institute at UCLA (CNSI) and Mike Lake, Technical Director of the BioPACIFIC MIP Living BioFoundry at CNSI.

JOURNAL

The study is published online in the journal Nature Communications.

FUNDING

The study was supported by the National Institutes of Health (NIH) and the National Science Foundation (NSF).