Fig. 6: The establishment of ES sslis from blastocvircE erases 
epigenetic memory of donor misiens 
Most cells of the inner cell mass turn oE Oct-4 like genes and die 
after explantation of blastocysts into tissue culture. Only one or a :ev7 
cells turn on the Oct-4 like genes and proliferate. The surviving cells 
will give rise to ES ceus. During this highly selective outgrowth of 
the sundving cells all epigenetic memory of the donor nucleus is 
erased. Therefore, regardless of donor nucleus (fertilized egg or 
somatic nucleus in cloned embryos), all ES cells have an equivalent 
potency to generate functional differentiated cells. 
Fig 6 
In vitro Selection of ES cells; 
Erasure of Epigenetic Memory 
Nuciear Donor 
Nenaa! 
Btas.tocyKt 
neuron 
Cloned 
Blastecy&t 
Strong selection for 
Surviving celte 
RoganSlessof 
nuc^ar donor. 
Similar pottntiaJ 
ofBSceBs 
“Normal” 
ES cell 
PRE -PUBLICATION VERSION 
