Thursday, August 30, 2007

Another blow to the stem cell hypothesis

You know the immortal strand hypothesis, which says that stem cells keep the "template" DNA when they replicate asymmetrically and send off the new and therefore mutation ridden strand to the daughter cell. Well it turns out to be wrong, thus undermining the use of BrdU as a way to isolate stem cells. These findings were published in the latest Nature: "Sequential administration of 5-chloro-2-deoxyuridine and 5-iodo-2-deoxyuridine indicated that all HSCs segregate their chromosomes randomly. Division of individual HSCs in culture revealed no asymmetric segregation of the label. Thus, HSCs cannot be identified on the basis of BrdU-label retention and do not retain older DNA strands during division, indicating that these are not general properties of stem cells."

In fact this article quotes the researchers as saying:

[BrdU is] ... "a very insensitive and nonspecific marker."


"This study suggests that researchers should test BrdU label retention as a marker before assuming it can be used to identify stem cells in other tissues"