Laboratory of Developmental Biology


Associate Professor
Assistant Professor
Takeshi ONUMA

Animal Science


Graduate School of Science



Research Theme

We all have developed from fertilized eggs 100 ┬Ám in diameter. Have you thought about how it can be possible? Our laboratory is working on mechanisms how eggs develop into a well organized adult body using micromanipulative and molecular approaches.

Embryogenesis of ascidians

In animal development, embryonic cells not only proliferate, but also generate various types of cells such as epidermis, muscle, neuron, and blood cells. All of these cells are originally derived from a fertilized egg. What kinds of mechanisms are involved in these processes in which some cells are fated to become muscle and other cells to become neuron? Namely, cellular and molecular mechanisms of cell fate determination during embryogenesis are the theme of our laboratory. We use embryos of ascidian (sea squirt, Halocynthia roretzi) as an experimental material. Ascidian has been regarded as a primitive chordate that evolved to basic vertebrates. Fertilized eggs develop into tadpole larvae within 35 hours of development (Figure). Its embryogenesis has been intensively described in details so that we can predict which cells of the early embryo give rise to which cells of the tadpole larva (Figure, bottom). Ascidian embryos provide us the unique possibility of understanding various mechanisms of fate determination in every cell type, because the tadpole consists of a small number of cells, and of a few types of tissue. Understanding fate determination mechanisms using this simple model organism with the basic body plan of Chordates would contribute to our knowledge in Developmental Biology.

Development of larvacian

The appendicularian, Oikopleura dioika is also belongs to the phylum Chordata, but it develop into tadpole and maintain the tail during entire life. The life cycle is extreamly short (Figure). We are going to analyze developmental provesses of this organism by genetic approaches.

0(Top) 4-cell stage embryos. 3 hours after fertilization. (Middle) Tadpole larvae just before hatching. 35 hours. (Bottom) Fate map of the 110-cell stage blastula and tissue organization of the tadpole. For example red blastomeres give rise to tail muscle cells.

1Development of the Appendicularian, Oikopleura dioica. The life cycle is very short and just 5 days.


Nishida, H Specification of embryonic axis and mosaic development in ascidians Developmental Dynamics 233 , 1177 - 1193 (2005)

Nishida, H. Development of the appendicularian Oikopleura dioica: culture, genome, and cell lineages. Dev. Growth Differ. 50 , S239 - S256 (2008)

Nishida, H. and Sawada, K. macho-1 encodes localized mRNA in ascidian eggs that specifies muscle fate during embryogenesis. Nature 490 , 724 - 729 (2001)


Department of Biological Sciences
Graduate School of Science
Osaka University
1-1 Machikaneyama-cho
Toyonaka, Osaka 560-0043
Tel: +81-6-6850-5472