New Whitehead scientist uncovers
the regenerative secrets of flatworms
CAMBRIDGE, Mass. (July 20, 2005) — Chop a planarian
flatworm in half and you end up with two healthy, wiggly
worms. Unfortunately, not so with a lab mouse or fruit
fly. Peter Reddien, who joins the Whitehead faculty
as Associate Member this August after completing a postdoctoral
fellowship at the University of Utah, is determined
to find out why.
Identifying the molecular mechanisms that give planarians
such remarkable abilities will shed light on the little-understood
world of organ and tissue regeneration, as well as aid
a more general understanding of adult stem cells.
The planarian Schmidtea mediterranea challenges
common perceptions about the capabilities of biological
systems. When severed, both head and tail fragments
re-grow into complete animals. New tissues and organs
are created by neoblasts—adult stem cells that
share certain characteristics with embryonic stem cells
and can differentiate into essentially all cells found
in adult animals. A similar process occurs in normal
intact adults, in which neoblast progeny cells continually
replace aged cells. Additionally, if nutrition is limited,
planarians can exhibit “de-growth”—eliminating
cells while maintaining the form and function of the
various organ systems of the animals. The genetic and
molecular mechanisms that make such processes possible
are almost completely unknown.
At Whitehead, Reddien will continue to create a body
of knowledge and research tools that will establish
the planarian as a model organism to study the molecular
genetics of regeneration. (The classic invertebrate
model organisms, the Drosophila fruit fly and
the C. elegans worm, cannot efficiently regenerate
tissues as adults.) He and his colleagues at the University
of Utah’s Department of Neurobiology and Anatomy
developed methods for high-throughput RNA interference
(RNAi), which uses customized RNAs to silence production
of proteins from a given gene. Exploiting these methods,
Reddien led the first large-scale study of gene function
in planarians, discovering multiple genes needed for
regeneration.
He also is one of three members of a consortium to
sequence the S. mediterranea genome, working
in collaboration with the Genome Center at Washington
University in St. Louis.
“We’re very excited to be welcoming such
a bold, creative young scientist to the Whitehead faculty,”
says Whitehead Member and Interim Director David Page.
“I have no doubt that Peter will put the planarian
flatworm on the map as a model organism to study regeneration.”
Reddien obtained his PhD in biology from Massachusetts
Institute of Technology. As a graduate student, he discovered
that engulfment of dying cells by other cells helps
to ensure programmed cell death in C. elegans,
identified an engulfment signaling pathway, and found
new regulators of cell death in a genetic screen, among
other accomplishments. He carried out his undergraduate
studies in molecular biology at the University of Texas
at Austin where he graduated magna cum laude. In addition,
Reddien received a National Science Foundation graduate
fellowship (2000), a Howard Hughes Medical Institute
postdoctoral fellowship at MIT (2002), and a Helen Hay
Whitney Foundation postdoctoral fellowship (2003).
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