The relationship between the genotype and the phenotype, or the genotype–phenotype map, is generally approached with the tools of multivariate quantitative genetics and morphometrics1, 2, 3, 4. Whereas studies of development5, 6, 7 and mathematical models of development4, 8, 9, 10, 11, 12 may offer new insights into the genotype–phenotype map, the challenge is to make them useful at the level of microevolution. Here we report a computational model of mammalian tooth development that combines parameters of genetic and cellular interactions to produce a three-dimensional tooth from a simple tooth primordia. We systematically tinkered with each of the model parameters to generate phenotypic variation and used geometric morphometric analyses to identify, or developmentally ordinate, parameters best explaining population-level variation of real teeth. To model the full range of developmentally possible morphologies, we used a population sample of ringed seals (Phoca hispida ladogensis)13. Seal dentitions show a high degree of variation, typically linked to the lack of exact occlusion13, 14, 15, 16. Our model suggests that despite the complexity of development and teeth, there may be a simple basis for dental variation. Changes in single parameters regulating signalling during cusp development may explain shape variation among individuals, whereas a parameter regulating epithelial growth may explain serial, tooth-to-tooth variation along the jaw. Our study provides a step towards integrating the genotype, development and the phenotype.
This file contains Supplementary Figures 1-6 with legends, and Supplementary Tables 1-6.
The connection between genes (genotype) and the adult form of an organism (phenotype) is not a simple matter of one-to-one mapping. The nonlinear process of development intervenes, dependent on various genetic inputs and interactions between cells. Using a well studied system, the mammalian tooth, Isaac Salazar-Ciudad and Jukka Jernvall have developed a computational model to bridge the gap between genotype and phenotype. Based on data from seal teeth, which show extensive morphological variation, they find that a much of the dental variation can be explained by changes in single model parameters. This work could be a step towards understanding the contribution of genes and development to variation and, therefore, to evolution.