In therapeutic cloning, limited cell division is induced in an unfertilized egg cell to produce embryonic stem cells. In reproductive cloning, an egg cell with a donor nucleus is implanted into a living surrogate female in an attempt to make a successful pregnancy.
"The chromosomes do not split properly," said Dr. Schatten, who also is professor and vice chairman of the departments of obstetrics, gynecology and reproductive sciences and of cell biology at the University of Pittsburgh School of Medicine. "From the very first cell division, development is inappropriate in vital ways."
In the current study, Dr. Schatten and his colleagues used known methods of nuclear transfer on 724 eggs retrieved from female rhesus macaques. Although 33 embryos were transferred into surrogates after initial cell division, no pregnancies were established. Imaging of DNA and basic cell structure revealed that while cell division continued in a superficially normal manner, chromosomal problems existed within each individual cell.
"We used antibodies to tag the cell proteins and DNA so that we could track progress," said Calvin Simerly, Ph.D., associate professor of obstetrics, gynecology and reproductive sciences at Pitt and the paper's first author. "When cells divide, there are very basic things that are supposed to happen, and they just didn't happen."
Contact: Michele Baum
University of Pittsburgh Medical Center