Professor

Hiroshi Akashi

• Ph.D University of Chicago, 1996
• B.A. Harvard College, 1990

Assistant Professor

Naoki Osada

• Ph.D University of Tokyo, 2002
• B.A. University of Tokyo, 1997

Research interests

Research in our laboratory focuses on identifying adaptation at the molecular level. We study mechanisms of molecular evolution through a combination of laboratory work to sequence DNA from within and between closely related species, computational analyses of DNA sequence data available from public databases, and theoretical studies of population genetic predictions for molecular evolution. In particular, we are interested in detecting molecular variation with subtle fitness effects. Natural selection can have an important impact on the long-term evolution of such mutations but cannot be measured directly in the laboratory, or in natural populations. 

Current interests in the lab include :

• Identifying global forces governing protein evolution. We are particularly interested in investigating relationships between gene expression and patterns of both silent and protein evolution. Our findings suggest that selection acts on the amino acid usage of microbial proteomes to optimize the efficiency of the synthesis of proteins as well as their particular functions. We are expanding these analyses to multicellular eukaryotes.
  
• Studying lineage-specific patterns of silent and protein evolution among closely related species. If weak selection operates on a large fraction of mutations, then departures from steady-state should be common in molecular evolution. We have developed an efficient method to sequence orthologous genes from even distantly related species using vectorette PCR and are currently expanding the dataset of genes sequenced among all species in the D. melanogaster subgroup. Our findings suggest frequent non-equilibrium evolution of both silent and amino-acid altering mutations.
  
• Developing and testing models of the evolutionary process under a balance among weak forces that fluctuate over time. We employ computer simulations to model weak selection in the context of genetic linkage and fitness interactions among mutations to determine the appropriate data and statistical methods to detect subtle forces in evolution. In addition, ancestral state reconstructions can be valuable for testing causes of molecular evolution and we are studying the reliability of such inferences among closely related species.