Blood-forming adult stem cells labled with BrdU showed the process to be random rather than nonrandom as previously believed.

Contrary to the belief that adult stem cells segregate their DNA in a nonrandom manner during cell division, University of Michigan (U-M) researchers discovered that blood-forming adult stem cells carry out DNA segregation in a random way.

To test the nonrandom segration theory, or the immortal strand hypothesis, the U-M team administered a DNA-labeling substance called BrdU to mice for several days. Then they extracted the blood-forming stem cells to see how many of them retained BrdU.

“What we found is that not many stem cells retained it,” says Sean Morrison, Ph.D., director of the Center for Stem Cell Biology at the U-M Life Sciences Institute. “In fact, what happened with the label was completely consistent with what you’d expect by random chromosome segregation and was completely inconsistent, in every context we looked, with the immortal strand model.”

The experiments also revealed that BrdU is not the general-purpose stem-cell marker many researchers thought it was. By measuring stem cell purity among BrdU-retaining cells, they found it to be “a very insensitive and nonspecific marker,” they report.

The paper will be published online August 29 in Nature.

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