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Hitoshi NIWA, M. D., Ph. D. 
Pluripotency
is a term used to describe the ability of certain types of stem cells
that are capable of giving rise to at least one type of cell from all
three germ layers – endoderm, mesoderm and ectoderm. Stem cells are
also characterized by their ability to produce copies of themselves with
similar differentiative potential as well as more specialized cells with
different properties through differentiation. Embryonic stem (ES) cells
are the best known example of a type of stem cell possessing these properties
of pluripotency and self-renewal. In our lab, we use ES cells as a model
system for studying the molecular mechanisms that determine and enable
the mysterious properties of pluripotent cells.
In
previous work, we identified a peptide hormone that works to maintain
the ability of ES cells to self-renew and developed an ES culture medium
using fully characterized components. These developments were made in
parallel with studies aimed at resolving the functions of genes involved
in the maintenance of stem cells in an undifferentiated state and the
induction of differentiation. We have also identified a transcriptional
factor that directs differentiation into placenta and yolk sac. Given
their ability to generate all of the body's cell types, ES cells
have come to stand as a symbol for the emerging fields of cell replacement
therapy and regenerative medicine, but they also represent an ideal system
for the study of many of the processes of early mammalian embryonic development.
The study of the basic biology of stem cells may one day bear fruit in
the development of culture methods suitable for ES cells intended for
clinical use or techniques for inducing differentiated cells to revert
to a pluripotent state, while at the same time providing fundamental new
insights into the differentiation of extra-embryonic tissues in the earliest
phases of mammalian development.
