In the experiment reported in the July 23 Nature, the scientists used adult mouse cells to create new mice that are genetically identical to the parent mouse. Teruhiko Wakayama, Ph.D., a postdoctoral researcher working in Dr. Yanagimachi's laboratory, pioneered the Honolulu cloning technique.

Using a special pipette, the donor nucleus is microinjected into an egg whose nucleus was previously removed. The researchers cultured the resulting cell, placed it in a surrogate mouse and allowed the clone to develop. By repeating the procedure, the team created second and third generations of cloned mice that genetically match their sister/parent, sister/grandparents and sister/great grandparent.

"We succeeded both in using a new method and new cell type to clone mice from adult cells and in repeating it to produce clones of clones of clones -- essentially identical mice born a generation or more apart," said Dr. Wakayama, the study's lead author.

The donor nuclei came from cumulus cells, which surround developing eggs within the ovaries of female mice. Each nucleus contains all of the genetic instructions needed to create an adult. However, specialized adult cells do not need, or use, all of the instructions to exist. In contrast, embryonic cells have not yet specialized into their adult fates and, therefore, are still using many of their genetic instructions.

"We had to turn back the clock of an adult cell so that it behaves like a newly fertilized embryo, which would develop into a normal adult," says co-author Anthony Perry, Ph.D., a postdoctoral researcher in Dr. Yanagimachi's laboratory.

Within five minutes of the donor nucleus removal, the researchers inserted it into the developing egg cell, called an oocyte, using the special injection pipette. The oocytes removed from adult female mice had already undergone the first part of their two-step maturation process. The sec
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Contact: Ernie Knewitz
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Noonan/Russo Communications
22-Jul-1998