1 Center for Cancer Research, Massachusetts Institute
of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 USA
2 The McGovern Institute for Brain Research and Department
of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue,
Cambridge, MA 02139 USA
* Correspondence: Phillip A. Sharp:
617-253-6421 (phone); 617-253-3867 (fax)
e-mail: sharppa@mit.edu
We have identified microRNAs (miRNAs) in undifferentiated and differentiated
mouse embryonic stem (ES)
cells. Some of these appear to be ES cell specific, have related
sequences, and are encoded by genomic loci
clustered within 2.2 kb of each other. Their expression is repressed
as ES cells differentiate into embryoid
bodies and is undetectable in adult mouse organs. In contrast, the
levels of many previously described miRNAs remain constant or increase
upon differentiation. Our results suggest that miRNAs may have a role in
the maintenance of the pluripotent cell state and in the regulation of
early mammalian development.
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