An improved method of nuclear transfer involving the transplantation of
differentiated donor cell nuclei into enucleated oocytes of a species
different from the donor cell is provided. The resultant nuclear transfer
units are useful for the production of isogenic embryonic stem cells, in
particular human isogenic embryonic or stem cells. These embryonic or
stem-like cells are useful for producing desired differentiated cells and
for introduction, removal or modification, of desired genes, e.g., at
specific sites of the genome of such cells by homologous recombination.
These cells, which may contain a heterologous gene, are especially useful
in cell transplantation therapies and for in vitro study of cell
differentiation. Also, methods for improving nuclear transfer efficiency
by genetically altering donor cells to inhibit apoptosis, select for a
specific cell cycle and/or enhance embryonic growth and development are
provided.