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

Living organisms adapt to their environment by evolving their shapes and forms in a wide variety of ways. In the Laboratory of Innovational Biology, we are pursuing our goal to understand “the mechanisms underlying the formation of various ‘shapes’ of life, ”such as “how ‘shapes’ are formed,” “how differences in ‘shapes’ are generated,” and “how ‘shapes’ evolve”.

Based on a tremendous number of studies to date, considerable progress in understanding the mechanisms by which the properties of each cell are determined during the developmental process has been made. However, how the final “shape” is achieved after the cell properties are determined is still largely unknown.

Insects boast more than one million species, and the diversity of their “shapes” is outstanding, making them suitable organisms for studying the mechanism of “shape-making.” Among these, a fruit fly Drosophila melanogaster is one of the most ideal organisms because you can change the activity of any gene at any time in any cell as you like, and there are tools to visualize the expression and localization of various genes and proteins in real-time while they are alive. In our laboratory, we are mainly studying the following subjects using Drosophila with an evolutionary perspective.

Insects have evolved a variety of appendages, such as legs, antennae, and mouth parts, which are thought to have originally had the same shape. Adult legs usually consist of several segments along the proximodistal axis, and the number and shape of the segments vary greatly among insect species. We are studying the “shaping” mechanism of the adult leg of Drosophila by using live imaging to continuously observe the formation of the leg. 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”.