A one-step somatic cell nuclear transfer procedure using a differentiated cell as a nuclear donor is reported for the first time in a paper in the November 2006 issue of Nature Genetics. The study demonstrates that fully differentiated granulocytes - a specialized type of white blood cell - yield cloned mice with greater efficiency than undifferentiated blood stem cells.
Somatic cell nuclear transfer - SCNT - is the procedure by which cloned animals are typically produced and involves the injection of a nucleus from a donor cell into an egg whose nucleus has been removed. Previous studies report that cloned mice could only be generated with differentiated cells as nuclear donors using a two-step procedure, in which the early embryos generated by SCNT are first used to generate embryonic stem cells that are subsequently injected into another recipient embryo. Other studies also report that the cloning efficiency for embryonic stem cells is much higher than for other kinds of cells.
Yang and colleagues injected nuclei from blood cells at different stages of differentiation into donor eggs and report that the nuclei of granulocytes allow for more efficient production of cloned embryos than blood stem cells. They report that two live pups were born using this procedure, although these died shortly after birth. The authors believe that their findings - that a non-dividing, fully differentiated cell from an adult animal can be used to generate a live-born cloned mouse in a one-step SCNT procedure - contradict current assumptions concerning the efficiency of adult stem cells as donors in cloning.
Xiangzhong Yang (University of Connecticut, Storrs, CT, USA)
Abstract available online.
(C) Nature Genetics press release.
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