Sensory genetics, ecology and evolution

`Vision and chemical sense in humans, wild primates and fish`

It is crucial to understand humans within an evolutionary framework. By using (primarily) non-model organisms to explore genetic variation and its ecological correlates in wild populations, it is now possible to reevaluate the evolutionary significance of human genetic variation. The evolutionary diversity of sensory systems-the visual system in particular-is an excellent model case for addressing these questions because recent technical developments have enabled functional evaluation of the relevant genes.

Bearing these issues in mind, we pursue the following ongoing and prospective research projects using an interdisciplinary approach that spans molecular biology (population DNA sequencing, gene expression analysis, in vitro functional assays), biochemistry, population/evolutionary genetics, and behavioral ecology.

The evolutionary origin and driving force of variation in human color vision.
Catarrhine primates (humans, apes, and Old World monkeys) have the L and M opsin genes, the photo-sensor genes for long and middle wavelength light, respectively, arrayed in tandem on the X chromosome, with the S (short wave) opsin gene on an autosome. This arrangement enables uniformly trichromatic color vision. Yet, only humans are known to have a high incidence of deletion or fusion of the L/M opsin genes, causing a high incidence of vision polymorphism, known as color vision "deficiency". By using DNA sequence analysis of opsin gene regions from public population genome data, as well as our own sequencing data from diverse human populations, we reconsider the evolutionary origins and driving forces underlying human color vision polymorphism.

New World monkeys as models for understanding the evolutionary significance of primate trichromatic color vision.
The L/M opsin gene of the primates living in Central and South America is a single-locus, poly-allelic gene on the X chromosome that produces extensive di/tri-chromatic color vision polymorphism. We conduct field research in Costa Rica of
capuchin, spider, and howler monkeys because these species are excellent model organisms in which to reconsider the evolutionary significance of primate trichromacy and human vision variation.

Fish as a model to study the evolutionary flexibility of color vision.
Fish have the most diverse visual system among vertebrates, reflecting their adaptation to the diverse light environments in water. We study
guppy, stickleback, medaka, tetra and zebrafish, with particular focus on their visual opsin gene repertoires, expression patterns and absorption spectra. With zebrafish, we use a transgenic approach to study the regulatory mechanism of opsin gene expression.

Tsujimura et al. 2011 PLoS Genet.

Coevolution of chemical sense and vision in primates.
We study the evolutionary diversity of taste, olfactory, and pheromone receptors of primates, especially of New World monkeys with diverse color vision modes. We also examine chemicals from fruits that are responsible for their odors and tastes.

We conduct several other related projects as well. Feel free to contact us on any enquiry.