Guest speaker:
Allon Klein, PhD
Post-doctoral Fellow
Systems Biology, Harvard Medical School/Dept. of Physics, TCM Group, Cambridge University (UK)

Faculty host:  Ramesh Shivdasani, MD, PhD (DFCI)

Pizza and beverages will be provided.

Abstract:
Adult stem cells must precisely balance division and differentiation to maintain a stable cell population throughout adult life. It is widely thought that stem cells self-renew through asymmetric division, with only occasional stem cell turnover as a result of aging, injury or chance loss. But what distinguishes long-lived stem cells from shorter lived ones? By analysing clone size statistics [1], I will discuss principles by which the rate of stem cell turnover (i.e. loss and replacement) can be calculated. Clonal analysis identifies universal statistical signatures across all tissues, which correspond to only three patterns of self-renewal. This identification reveals the rates of stem cell turnover, and presents a unifying framework to interpret clonal fate data and mosaic-chimera studies. When benchmarked against several cycling mammalian tissues, the analysis shows that individual stem cells are frequently replaced. The analysis shows that symmetric stem cells divisions, and stem cell loss, are central to the maintenance of cycling mammalian tissues.

[1] Clayton et al., Nature 446 (2007); Klein et al., Cell Stem Cell 7 (2010); Garcia-Lopez et al., Science (2010); Snippert et al., Cell 143 (2010).