Master switches found for adult blood stem cells

February 9, 2007

Johns Hopkins Kimmel Cancer Center scientists have found a set of "master switches" that keep adult blood-forming stem cells in their primitive state. Unlocking the switches' code may one day enable scientists to grow new blood cells for transplant into patients with cancer and other bone marrow disorders.

The scientists located the control switches not at the gene level, but farther down the protein production line in more recently discovered forms of ribonucleic acid, or RNA. MicroRNA molecules, once thought to be cellular junk, are now known to switch off activity of the larger RNA strands which allow assembly of the proteins that let cells grow and function.

"Stem cells are poised to make proteins essential for maturing into blood cells, but microRNAs keep them locked in their place," says cancer researcher Curt Civin, M.D., Ph.D., who led the study. The journal account will appear online the week of February 5 in the early edition of the Proceedings of the National Academy of Sciences.

To halt protein assembly, microRNAs pair up with matching full-length RNA, then fold and twist it, rendering the larger RNA useless. But the RNA pairings are not perfect, and one microRNA can latch on to several hundred RNA strands. "They act like a single circuit breaker to efficiently control hundreds of RNAs," says Civin, the Herman and Walter Samuelson Professor of Cancer Research.

"We're looking for ways to flip these microRNA switches, to control when stem cells grow into new blood cells," says Robert Georgantas, Ph.D., research associate at the Johns Hopkins Kimmel Cancer Center and first and corresponding author of the study.

To identify the key microRNAs, Georgantas sifted through thousands of RNA pieces with a custom-built, computer software program. Its algorithms let the software, fed data from samples of blood and bone marrow from healthy donors, match RNA pairs. The outcome was a core set of 33 microRNAs that match with more than 1,200 of the larger variety RNA already known to be important for stem-cell maturation.

Georgantas and Civin currently are testing whether these pair predictions are valid by using a non-reproducing virus to insert genetic instructions for each of the 33 microRNAs into adult stem cells. They'll then be cultured in Petri dishes. MicroRNA-155 -- the first microRNA tested -- was predicted to stop stem cells from developing into red and white blood cells. As expected, stem cells without microRNA-155 matured: they formed approximately 75 red and 150 white blood cell colonies per dish. Stem cells with microRNA-155 matured into far fewer red and white cell colonies -- about seven and 30 per dish, respectively.

"Using microRNAs to stall an adult blood stem cell in its early stage could help us grow new ones in test tubes, and perhaps give us more insight into stem-cell maturation for other tissue types," says Civin.

Source: Johns Hopkins Medical Institutions

Explore further: Revolutionary method to map the brain at single-neuron resolution is successfully demonstrated

Related Stories

Stem cells of worms and humans more similar than expected

August 9, 2016

The transient form of genetic information, the RNA, is processed in a similar manner in the cells of both organisms. These mechanisms seem to be at work throughout the whole animal kingdom. Scientists from the Max Delbrück ...

Neural stem cells control their own fate

August 18, 2016

To date, it has been assumed that the differentiation of stem cells depends on the environment they are embedded in. A research group at the University of Basel now describes for the first time a mechanism by which hippocampal ...

Recommended for you

How the finch changes its tune

August 3, 2015

Like top musicians, songbirds train from a young age to weed out errors and trim variability from their songs, ultimately becoming consistent and reliable performers. But as with human musicians, even the best are not machines. ...

Cow embryos reveal new type of chromosome chimera

May 27, 2016

I've often wondered what happens between the time an egg is fertilized and the time the ball of cells that it becomes nestles into the uterine lining. It's a period that we know very little about, a black box of developmental ...

Shaving time to test antidotes for nerve agents

February 29, 2016

Imagine you wanted to know how much energy it took to bike up a mountain, but couldn't finish the ride to the peak yourself. So, to get the total energy required, you and a team of friends strap energy meters to your bikes ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.