Graduate School of Frontier Sciences, The University of Tokyo Department of
Integrated Biosciences

We are studying interesting developmental phenomena in insects, such as mimicry and metamorphosis, adaptive evolution of legs, wings, antennae and body shape. In addition, we are also studying the transposition mechanisms and adaptive strategies of retrotransposons that transpose into only the specific sites such as telomeres. Focusing on a variety of novel phenomena from molecular and cellular to ontogenic levels, we are trying to elucidate how the gene network system has been adaptively innovated, with an evolutionary perspective.

We are currently studying the following topics:

LINEs are selfish genes that are present in most eukaryotes, but the details of their transposition mechanism are still elusive. By using LINEs that transpose only into specific chromosomal sites, we are trying to comprehensively elucidate the entire picture of the structure and function of LINEs required for their transposition, and to use them as novel site-specific gene therapy vectors.

Telomeres are usually produced by telomerase, but some insects do not have telomerase activity. We are pursuing the possibility that telomere-specific LINEs maintain telomeres and are exploring the evolution and origin of telomere function by analyzing molecular mechanisms by which the telomere-specific LINEs target telomeres. We are also designing new molecules that target telomeres and exploring their application to the study of cellular aging and tumor activity.

Various color patterns can be seen on the body surface of animals. Variation in color patterns has been incorporated into life histories and behavioral strategies during evolution, and especially in insects, they function as “mimicry”. The molecular background of color pattern formation, however, is largely unknown. We are studying the color pattern formation mechanisms by using swallowtail butterflies that switch from a "bird droppings" mimicry pattern to a "citrus leaves" mimicry pattern during larval stages and swallowtail butterflies showing Batesian mimicry on the adult female wings, in addition to silkworms that have various color pattern mutant strains. Through this research, we are trying to approach the molecular mechanism of mimicry.

Living organisms have evolved a great variety of shapes and forms to adapt to their surrounding environment. Insects, in particular, have evolved a variety of appendages, such as legs, antennae, and mouth parts, which are thought to have originally had the same shape. Through understanding the mechanism of adult leg formation in Drosopihla, we are trying to understand the molecular mechanism of organismal shaping, and also to elucidate how the mechanism changes to bring about differences in the morphology among appendages and among insect species. The final goal of our research is to reveal the mystery of organismal shaping and of evolution and diversity of shapes.

(2) Mechanism of body shape regulation by extracellular matrix

Insects are exoskeletal organisms, and their bodies are covered by an extracellular matrix called cuticle. The cuticle is composed of substances secreted by epidermal cells, such as chitin fibers and various cuticular proteins. The body shape of insects varies from rounded to elongated forms. Recent our studies have shown that the properties of the cuticle, which is determined by cuticular proteins, play an important role in determining the body shape of insects. Through such research, we will elucidate how the shape of an organism is controlled not by the cell itself, but by substances secreted outside the cell.

Insects molt in the process of growth. During molting, the old cuticle is shed, and the individual covered with the new cuticle come out. At this time, the old cuticle does not break randomly, but always at a specific place. In other words, cuticle has a “cut here line” for molting. We are trying to understand how this “cut here line” is formed, how its location is determined, and what the cuticle structure that functions as the “cut here line” is. Since the “cut here line” is one of the most basic and essential character of all insects, we are trying to deepen our understanding of the evolution of insects through the study of the “cut here line”.