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Brief Communications

Nature 407, 318-319 (21 September 2000) | doi:10.1038/35030301

Ageing: Cloning of mice to six generations

Teruhiko Wakayama1,7, Yoichi Shinkai2, Kellie L. K. Tamashiro1, Hiroyuki Niida3, D. Caroline Blanchard4, Robert J. Blanchard4, Atsuo Ogura5, Kentaro Tanemura5, Makoto Tachibana2, Anthony C. F. Perry6, Diana F. Colgan6, Peter Mombaerts6 & Ryuzo Yanagimachi1

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Mice have been cloned by nuclear transfer into enucleated oocytes1, 2, 3, and here we describe the reiterative cloning of mice to four and six generations in two independent lines. Successive generations showed no signs of prematureageing, as judged by gross behaviouralparameters, and there was no evidence of shortening of telomeres at the ends of chromosomes, normally an indicator of cellular senescence — in fact, these appeared to increase slightly in length. This increase is surprising, given that the number of mitotic divisions greatly exceeds that of sexually produced animals and that any deleterious effects of cloning might be expected to be amplified in sequentially cloned mice. Our results offer a new approach to the study of organismal ageing.