Researchers from Rudolf Jaenischs lab at the Whitehead Institute for Biomedical Research have taken a significant step toward answering a half century old questiondo clones, like Dolly, derived from adult cells develop from a fully mature adult cell or do they develop from rare stem cells found in adult tissues? The researchers have proved for the first time that fully differentiated adult cells can form clones, but they found the process is extremely inefficient. It is more likely that elusive adult stem cells, which exist in tiny numbers along with the mature adult cells, are actually the ones to form clones, says Jaenisch. The study was conducted by Konrad Hochedlinger, a student in the Jaenisch lab, and will appear in Nature online February 10, 2002.

"This finding tells us something about the nature of the genome of adult cellsthese cells are not very labile and difficult to clone. This is important to know, if adult cells are going to be cloned for personalized cell therapy," says Jaenisch. Therapeutic cloning involves removing the nucleus, or the genetic command center, of an egg and replacing it with the nucleus from an adult donor cell. Ideally, the egg resets the developmental clock of the nucleus back to a state compatible with early embryonic growth. This ball of cells growing in culture gives rise to embryonic stem (ES) cells that genetically match the donor and have the potential to become any tissue in the body. In theory, these ES cells may be used to treat diseases, such as diabetes or spinal cord injury, without the complications of organ rejection.

Using Immune Cells to Clone Mice

Scientists have known for sometime that cloning using ES cells is much more efficient than using adult cells, probably 10 fold more efficient. This makes sense because ES cells are at the earliest developmental stage and have the potential to become all the cells that make up an organism. But researchers didnt know if cloning could set the cloc
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Contact: Nadia Halim
halim@wi.mit.edu
617-258-9183
Whitehead Institute for Biomedical Research
10-Feb-2002