( rchers compared the efficiency for clon...)Cloned mice created from fully differentiated cells, a milestone in cloning research

rchers compared the efficiency for cloning mice using a fully differentiated blood cell called a granulocyte with its ancestor cells at different stages: hematopoietic stem cells, which are found in bone marrow and give rise to all red and white blood cells, and progenitor cells. Granulocytes are well characterized white blood cells unique for their segmented nuclei and the numerous granules in the cells' cytoplasm.

Surprisingly, the granulocytes were the most efficient donor cells for nuclear transfer among the different lineage cells, with 35 to 39 percent becoming a blastocyst, an early embryo consisting of about 100 to 150 cells, compared to 11 percent for the progenitor cells and only 4 percent for the stem cells. Only the granulocytes were able to produce two live cloned pups, although both died within a few hours of birth. As a control, the researchers performed nuclear transfer using embryonic stem cells; 49 percent developed to the blastocyst stage and 18 cloned pups were born.

"Our results clearly demonstrate that there is no apparent advantage in using either adult stem cells or progenitor cells over fully differentiated cells as nuclear donors. To the contrary, we found that cloned pups can be produced from adult, fully differentiated somatic cells, a conclusion that goes against popular opinion and current hypotheses," says Dr. Yang, animal science professor, director of the University of Connecticut's Center for Regenerative Biology and co-corresponding author of the study.

"Even we were surprised to find fully differentiated cells were more efficient for cloning, because granulocytes are not capable of dividing. In fact, we repeated our experiments six times just to be sure. Now we can say with near certainty that a fully differentiated cell such as a granulocyte retains the genetic capacity for becoming like a seed that can give rise to all cell types necessary for the development of an entire organism," adds co-correspondin
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Source:University of Pittsburgh Medical Center

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