Research Interests

Molecular Evolution, Comparative Genomics, Bioinformatics

1. Molecular Evolution of Olfactory Receptor Gene Family

    Olfaction is the sense of smell. Olfactory receptors are the proteins that detect odor molecules in the environment. Recently, it revealed that mammals have only <25,000 genes in thier genome. Surprisingly, about 1,000 out of the 25,000 genes (4%) are olfactory receptor genes (see below), which comprise the largest multigene family ever known. To know how such a large multigene family has evolved, I conduct molecular evolutionary analyses by using the whole genome sequences of the human, chimpanzee, mouse, rat, dog, chicken, frog, zebrafish, and pufferefish. Olfactory receptors were first identified by Richard Axel and Linda Buck, who were awarded 2004 Nobel Prize in Physiology or Medicine.

    Note -  The number of olfactory receptor genes is quite variable among mammalian species. I identified olfactory receptor genes from the whole genome sequences of humans and mice (Table 1). As this table shows, more than half of the human olfactory receptor genes are actually pseudogenes. This reflects that humans are dependent on vision rather than olfaction.

Table 1. Numbers of olfactory receptor genes in humans and mice

No. of functionl genes
No. of pseudogenes
Fraction of pseudogenes

2. Identification of the sequnces determining the efficiency of gene translation
(in collaboration with Dr. Kin-ichiro Miura in Chiba Institute of Technology)

    Gene expression is controlled not only at the level of tanscription, but also at the level of translation. For example, the second codon, the codon immediately after the initiation codon, is highly biased in its frequency for many eukaryotes and prokaryotes, and is thought to be involved in the efficiency of translation. I examine this kind of sequences determining the translational efficiency by using whole genome seqeunces of various species.

Last updated: Nov. 11, 2004