Featured Research

from universities, journals, and other organizations

Brain's stem cells 'eavesdrop' to find out when to act

Date:
August 6, 2012
Source:
Johns Hopkins Medicine
Summary:
Working with mice, researchers say they have figured out how stem cells found in a part of the brain responsible for learning, memory and mood regulation decide to remain dormant or create new brain cells. Apparently, the stem cells “listen in” on the chemical communication among nearby neurons to get an idea about what is stressing the system and when they need to act.

A single parvalbumin-expressing interneuron (red) surrounded by many adult neural stem cells (green) in the brain’s hippocampus.
Credit: Gerry Sun

Working with mice, Johns Hopkins researchers say they have figured out how stem cells found in a part of the brain responsible for learning, memory and mood regulation decide to remain dormant or create new brain cells. Apparently, the stem cells "listen in" on the chemical communication among nearby neurons to get an idea about what is stressing the system and when they need to act.

The researchers say understanding this process of chemical signaling may shed light on how the brain reacts to its environment and how current antidepressants work, because in animals these drugs have been shown to increase the number of brain cells. The findings are reported July 29 in the advance online publication of Nature.

"What we learned is that brain stem cells don't communicate in the official way that neurons do, through synapses or by directly signaling each other," says Hongjun Song, Ph.D., professor of neurology and director of Johns Hopkins Medicine's Institute for Cell Engineering's Stem Cell Program. "Synapses, like cell phones, allow nerve cells to talk with each other. Stem cells don't have synapses, but our experiments show they indirectly hear the neurons talking to each other; it's like listening to someone near you talking on a phone."

The "indirect talk" that the stem cells detect is composed of chemical messaging fueled by the output of neurotransmitters that leak from neuronal synapses, the structures at the ends of brain cells that facilitate communication. These neurotransmitters, released from one neuron and detected by a another one, trigger receiving neurons to change their electrical charges, which either causes the neuron to fire off an electrical pulse propagating communication or to settle down, squelching further messages.

To find out which neurotransmitter brain stem cells can detect, the researchers took mouse brain tissue, attached electrodes to the stem cells and measured any change in electrical charge after the addition of certain neurotransmitters. When they treated the stem cells with the neurotransmitter GABA -- a known signal-inhibiting product the stem cells' electrical charges changed, suggesting that the stem cells can detect GABA messages.

To find out what message GABA imparts to brain stem cells, the scientists used a genetic trick to remove the gene for the GABA receptor -- the protein on the surface of the cell that detects GABA -- only from the brain stem cells. Microscopic observation of brain stem cells lacking the GABA receptor over five days showed these cells replicated themselves, or produced glial cells -- support cells for the neurons in the brain. Brain stem cells with their GABA receptors intact appeared to stay the same, not making more cells.

Next, the team treated normal mice with valium, often used as an anti-anxiety drug and known to act like GABA by activating GABA receptors when it comes in contact with them. The scientists checked the mice on the second and seventh day of valium use and counted the number of brain stem cells in untreated mice and mice treated with the GABA activator. They found the treated mice had many more dormant stem cells than the untreated mice.

"Traditionally GABA tells neurons to shut down and not continue to propagate a message to other neurons," says Song. "In this case the neurotransmitter also shuts off the stem cells and keeps them dormant."

The brain stem cell population in mice (and other mammals, including humans) is surrounded by as many as 10 different kinds of intermingled neurons, says Song, and any number of these may be keeping stem cells dormant. To find out which neurons control the stem cells, the researchers inserted special light-activating proteins into the neurons that trigger the cells to send an electrical pulse, as well as to release neurotransmitter, when light shines on them. By shining light to activate a specific type of neuron and monitoring the stem cells with an electrode, Song's team showed that one of the three types of neurons tested transmitted a signal to the stem cells causing a change in electrical charge in the stem cells. The neurons messaging the stem cells are parvalbumin-expressing interneurons.

Finally, to see if this stem cell control mechanism aligns with what an animal may be experiencing, the scientists created stress for normal mice by socially isolating them, and did the same in mice lacking GABA receptors in their brain stem cells. After a week, socially isolated normal mice had an increase in the number of stem cells and glial cells. But the socially isolated mice without GABA receptors did not show increases.

"GABA communication clearly conveys information about what brain cells experience of the outside world, and, in this case, keeps the brain stem cells in reserve, so if we don't need them, we don't use them up," says Song.


Story Source:

The above story is based on materials provided by Johns Hopkins Medicine. Note: Materials may be edited for content and length.


Journal Reference:

  1. Juan Song, Chun Zhong, Michael A. Bonaguidi, Gerald J. Sun, Derek Hsu, Yan Gu, Konstantinos Meletis, Z. Josh Huang, Shaoyu Ge, Grigori Enikolopov, Karl Deisseroth, Bernhard Luscher, Kimberly M. Christian, Guo-li Ming, Hongjun Song. Neuronal circuitry mechanism regulating adult quiescent neural stem-cell fate decision. Nature, 2012; DOI: 10.1038/nature11306

Cite This Page:

Johns Hopkins Medicine. "Brain's stem cells 'eavesdrop' to find out when to act." ScienceDaily. ScienceDaily, 6 August 2012. <www.sciencedaily.com/releases/2012/08/120806093934.htm>.
Johns Hopkins Medicine. (2012, August 6). Brain's stem cells 'eavesdrop' to find out when to act. ScienceDaily. Retrieved September 18, 2014 from www.sciencedaily.com/releases/2012/08/120806093934.htm
Johns Hopkins Medicine. "Brain's stem cells 'eavesdrop' to find out when to act." ScienceDaily. www.sciencedaily.com/releases/2012/08/120806093934.htm (accessed September 18, 2014).

Share This



More Health & Medicine News

Thursday, September 18, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Artificial Sweetener Could Promote Diabetes

Artificial Sweetener Could Promote Diabetes

Newsy (Sep. 17, 2014) Doctors once thought artificial sweeteners lacked the health risks of sugar, but a new study says they can impact blood sugar levels the same way. Video provided by Newsy
Powered by NewsLook.com
Ebola Vaccine Trial Gets Underway at Oxford University

Ebola Vaccine Trial Gets Underway at Oxford University

AFP (Sep. 17, 2014) A healthy British volunteer is to become the first person to receive a new vaccine for the Ebola virus after US President Barack Obama called for action against the epidemic and warned it was "spiralling out of control." Duration: 01:02 Video provided by AFP
Powered by NewsLook.com
Obesity Rates Steady Even As Americans' Waistlines Expand

Obesity Rates Steady Even As Americans' Waistlines Expand

Newsy (Sep. 17, 2014) Researchers are puzzled as to why obesity rates remain relatively stable as average waistlines continue to expand. Video provided by Newsy
Powered by NewsLook.com
President To Send 3,000 Military Personnel To Fight Ebola

President To Send 3,000 Military Personnel To Fight Ebola

Newsy (Sep. 16, 2014) President Obama is expected to send 3,000 troops to West Africa as part of the effort to contain Ebola's spread. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins