"Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors," by Kazutoshi Takahashi and Shinya Yamanaka, Cell, 126[4]: 663-76, 25 August 2006.

[Authors' affiliation: Kyoto University, Japan; CREST, Kawaguchi, Japan]

Abstract: "Differentiated cells can be reprogrammed to an embryonic-like state by transfer of nuclear contents into oocytes or by fusion with embryonic stem (ES) cells. Little is known about factors that induce this reprogramming. Here, we demonstrate induction of pluripotent stem cells from mouse embryonic or adult fibroblasts by introducing four factors, Oct3/4, Sox2, c-Myc, and Klf4, under ES cell culture conditions. Unexpectedly, Nanog was dispensable. These cells, which we designated PS (induced pluripotent stem) cells, exhibit the morphology and growth properties of ES cells and express ES cell marker genes. Subcutaneous transplantation of PS cells into nude mice resulted in tumors containing a variety of tissues from all three germ layers. Following injection into blastocysts, i1PS cells contributed to mouse embryonic development. These data demonstrate that pluripotent stem cells can be directly generated from fibroblast cultures by the addition of only a few defined factors."

This 2006 report from Cell was cited 76 times in current journal articles indexed by Thomson Reuters during July-August 2008. With that bimonthly total, this report currently ranks as the second-most-cited biology paper, aside from reviews, published in the last two years. The current #1 biology paper, in fact, also features authors Takahashi and Yamanaka and is a more-recent report (from 2007) on the induction of pluripotent stem cells from adult human fibroblasts (K. Takahasi, et al., Cell, 131[5]: 861-72, 30 November 2007; featured in the previous "What Hot in Biology" slot). Clearly, the current flurry of activity on induced pluripotent stem cells has jump-started interest in this earlier paper, as the latest tally attests. Prior to the most recent bimonthly count, citations to the paper have accrued as follows:

May-June 2008: 12 citations
September-October 2006: 1

Total citations to date: 89

SOURCE: Hot Papers Database (Included with a subscription to the print newsletter Science Watch^®, available from the Research Services Group of Thomson Reuters. Packaged on a CD that is mailed with each Science Watch issue, the Hot Papers Database contains data on hundreds of highly cited papers published during the last two years. User interface permits searching by author, organization, journal, field, and more. Total citations, as well as citations accrued during successive bimonthly periods, can be assessed and graphed. An updated CD containing the most recent bimonthly data is mailed with every new issue of Science Watch, six times a year. The CD also includes an electronic version of the Science Watch issue in HTML format, for personal desktop access.