Howard Hughes Medical Institute and Department of Cell
and Developmental Biology, University of Pennsylvania School of Medicine,
Philadelphia, Pennsylvania 19104, USA.
bartolom@mail.med.upenn.edu and mel@hhmi.upenn.edu
The imprinting of a large cluster of paternally expressed genes
at the Prader-Willi syndrome locus is established by an imprinting centre
in human and mouse. Deletions carried by a member of a rare family and by
chimaeric mice demonstrate that the imprinting centre is additionally required
for postzygotic maintenance of paternal identity.
