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Shigeo HAYASHI, Ph. D. 
A
range of vital developmental processes, including the abilities to build
complex structures through selective cell adhesion, to move through the
body, and to form epithelial tissues,rely on interactions between cells,
and between cells and the extracellular matrix. The means by which cells
are able to communicate, congregate and work together to build a body
are a central question in the study of morphogenesis, the focus of research
in our laboratory.
The
Drosophila tracheal system is a respiratory organ that delivers
air directly to tissues through a network of finely branched epithelial
tubes. Tracheal development begins by invagination of ectodermal epithelium
that subsequently forms branches with specific types of cells migrating
in stereotyped patterns. The branching patterns and cell fate are instructed
by external cues including FGF, WG and Dpp. We are studying the roles
of those signaling molecules in the specification and migration of tracheal
branches, as well as the mechanisms that coordinate cell movement and
cell adhesion. We additionally use 4D confocal imaging of GFP-labeled
embryos to study the dynamism of cell and organelle movement in living
organisms. Using combinations of GFP markers and transcriptional enhancers
of cell-specific expression, we have been able to capture movements of
tracheal cells at resolutions sufficient to image cytoskeletal organization
and cell adhesion structures in single cells.
The
development of appendages in Drosophila from primordial regions
called imaginal discs is a second area of interest. During this process,
subpopulations of cells in the imaginal discs segregate into distinct
domains by coupling cell growth and differentiation to cell sorting, which
provides us with an opportunity to study the regulation of cell affinity
by positional information. Each limb primordium also coordinates its specific
developmental pattern with other tissues, such as muscles, motor nerves
and trachea, that are specified independently in other parts of the embryo.
This understanding of mechanisms of limb specification and proximal-distal
axis formation gained from work on Drosophila , however, must
also be validated by comparative analyses in other species with simpler
appendage structures. We focus on three species for these comparative
studies: the bristletail, Pedetontus unimaculatus, the mayfly,
Ephemera japonica and the ragworm, Perinereis nuntia.
