Educational Activities

Graduate School: Molecular and Cellular Biology of Reproduction, Lessons in Wrighting of Scientific Papers in English, Practice in Oral Presentation in English

Research Activities

1. Investigation of the molecular mechanisms involved in fish fertilization.
Medaka has been used as a vertebrate fertilization model for longer than 50 years in Japan. To understand the machinery required to induce diversity in the fertilization mechanism, we are attempting to determine which genes are responsible for fertilization using genomic sequences and to investigate their actual physiological and biochemical functions in Medaka. Furthermore, the ortholog genes of numerous other marine/freshwater species will be also identified and their structures, functions will be investigated and compared with each other.

2. Investigation of DNA mutation/repair in germ cells.
Medaka has been used extensively in Japan to study radiation biology for more than 30 years. Recently, we have established a new mutant strain by ENU-mutagenesis, which has germ cells with a particularly high susceptibility to gamma-rays irradiation. Positional cloning of the responsible gene is currently underway. Gamma-ray irradiation also induces interesting responses in Medaka testis and we are currently studying the details and underlying molecular mechanisms.

3. Development of new techniques for studying in vivo physiology.
TILLING is the only practical approach of reverse genetics in Medaka. To understand the functions of genes in the individual level, we are employing TILLING, the wild-Medaka stocks, and transgenic Medaka production. The transparent embryonic body of Medaka enables us to monitor the promoter activities in living individual embryos, using fluorescent microscopic observation.

Literature

1) Oda S., Deguchi R., Mohri T., Shikano T., Nakanishi S., Miyazaki S. (1999) Developmental Biology 209: 172-185.
2) Kaji K., Oda S., Shikano T., Ohnuki T., Uematsu Y., Sakagami J., Tada N., Miyazaki S., Kudo A. (2000) Nature Genetics 24:279-282.
3) Kumakiri J., Oda S., Kinoshita K., Miyazaki S. (2003) Develpmental Biology 260:522-535.
4) Yoda A., Oda S., Shikano T., Kouchi Z., Awaji T., Shirakawa H., Kinoshita K., Miyazaki S. (2004) Developmental Biology 268: 245-257.
5) Mitani H., Kamei Y., Fukamachi S., Oda S., Sasaki T., Asakawa S., Todo T., Shimizu N. (2006) Genome Dynamics. 2: 165-182.

Other Activities

The Zoological Society of Japan,
Physiological Society of Japan,
The Molecular Biology Society of Japan,
The Japanese Society of Mammalian Ova Research,
The Japan Radiation Research Society

Future Plan

Recent investigations have revealed that the molecular mechanisms associated with animal fertilization consist of both highly conserved and highly diverse mechanisms . Diversification of fertilization mechanisms can result in reproductive isolation and lead to the development of distinct species. To understand the machinery responsible for the diversify of the fertilization mechanisms, we are investigating the DNA mutation/repair mechanisms in germ cells and are attempting to clarify how sperm/egg genomes can change and also how their phenotypes can change.
Medaka has become an excellent model organism not only for fertilization studies but also for the all fields in the life sciences. Its genome sequence is available on the web, it is relatively straightforward to establish transgenic lines, and the TILLING (Targeting Induced Local Lesions IN Genomes) approach means that Medaka is a powerful tool for functional genomic studies. Numerous attempts have been made to produce transgenic Medaka lines that express fluorescent proteins under the control of promoters. Furthermore, the transparent embryonic bodies of Medaka means that they are well suited to florescent microscopic imaging, and we are currently trying to develop new methods for in vivo physiology on Medaka.

Messages to Students

Dive into the woods.

URL

https://webpark1015.sakura.ne.jp/TOP.html