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First life may have survived by cooperating
THIS WEEK
Young blood for a keener mind
Teamwork was key to success of first life IT BEGAN with cooperation. When life first arose, teams of small molecules got together to perform tasks none could manage alone – or that’s the theory. For the first time, networks like this have been built in the lab. The earliest life may have been a primordial soup of RNA molecules, but the first crude self-replicating molecules in this “RNA world” would 10 | NewScientist | 20 October 2012
Kerstin Schomburg/plainpicture
HUMANS are constantly searching for an elixir of youth – could it be that an infusion of young blood holds the key? This seems to be true for mice, at least. According to research presented this week at the Society for Neuroscience conference in New Orleans, Louisiana, giving young blood to old mice can reverse some of the effects of age-related cognitive decline. Last year, Saul Villeda, then at Stanford University in California, and colleagues showed they could boost the growth of new cells in the brains of old mice by giving them a blood infusion from young mice (Nature, doi.org/ c9jwvm). “We know that blood has this huge effect on brain cells, but we didn’t know if its effects extended beyond cell regeneration,” he says. Now the team has tested for changes in cognition by linking the circulatory systems of young and old mice. Once the blood of each conjoined mouse had fully mixed with the other, the researchers analysed their brains. Tissue from the hippocampus
of old mice given young blood showed changes in the expression of 200 to 300 genes, particularly in those involved in synaptic plasticity, which underpins learning and memory. They also found changes in some proteins involved in nerve growth.
effect produced by blood cells. The mice then took part in a standard memory task to locate a hidden platform in water. The old mice that had received young blood plasma remembered where to find the platform much quicker than the mice on the old plasma. To find out which brain area was involved in this reversal of cognitive decline, the team performed fear conditioning tests. Mice that had been given young blood were better at remembering fear associated with tasks that activated the hippocampus, suggesting that young blood has a specific effect on this area of the brain. But the mystery remains: what exactly is it about young blood that old blood doesn’t have? “We have not identified any individual factors responsible for the rejuvenating effects of young plasma yet,” says Tony Wyss-Coray, also at Stanford. His team is now trying to identify possible candidates such as lipids and hormones. Villeda is hopeful the results might one day translate to humans since the components of blood that change with age in mice mirror those in humans. While “it’s plausible that similar mechanisms operate in humans,” says Joseph Quinn at Oregon Health and Science University in Portland, there is no evidence –New blood for old– yet to support this. n
Helen Thomson, New Orleans
The infusion of young blood also boosted the number and strength of neuronal connections in an area of the brain where new cells do not grow. This didn’t happen when old mice received old blood. To find out whether these changes improved cognition, the team gave 12 old mice eight intravenous shots of blood plasma either from a young or an old mouse, over the course of one month. They used plasma rather than whole blood to exclude any
have faced a big problem. They had to grow to store more information, but that made copying errors more likely. Get big enough and these errors become almost certain, destroying the molecule’s information. In theory, the first replicators could have avoided this “error catastrophe” by splitting their information between several cooperating molecules. Then the network could function as long as copies of each molecule survived. To see if this strategy would work, Niles Lehman of Portland State University in Oregon and colleagues created three RNA molecules that
could repair each other – A did B, B did C, and C did A. When the team put these broken molecules together in a test tube, the collective network worked well. When they pitted the cooperative network against a selfish, self-repairing molecule, the cooperators won out (Nature, DOI: 10.1038/nature11549). Although earlier studies showed that pairs of molecules can
“The ‘error catastrophe’ could be avoided by splitting information between molecules”
cooperate, Lehman is the first to create a network of 3, opening the door to much larger networks. “If you can go from 2 to 3, you can go from 3 to infinity,” he says. Lehman repeated the study with 48 different fragments of an RNA molecule. Sure enough, they assembled into a network that eventually included all 48. Such cooperation may have arisen early in the RNA world and helped to build complexity, says Gerald Joyce of the Scripps Research Institute in San Diego. “It’s an experimental demonstration that real molecules can do this,” he says. Bob Holmes n
Young blood for a keener mind
Teamwork was key to success of first life IT BEGAN with cooperation. When life first arose, teams of small molecules got together to perform tasks none could manage alone – or that’s the theory. For the first time, networks like this have been built in the lab. The earliest life may have been a primordial soup of RNA molecules, but the first crude self-replicating molecules in this “RNA world” would 10 | NewScientist | 20 October 2012
Kerstin Schomburg/plainpicture
HUMANS are constantly searching for an elixir of youth – could it be that an infusion of young blood holds the key? This seems to be true for mice, at least. According to research presented this week at the Society for Neuroscience conference in New Orleans, Louisiana, giving young blood to old mice can reverse some of the effects of age-related cognitive decline. Last year, Saul Villeda, then at Stanford University in California, and colleagues showed they could boost the growth of new cells in the brains of old mice by giving them a blood infusion from young mice (Nature, doi.org/ c9jwvm). “We know that blood has this huge effect on brain cells, but we didn’t know if its effects extended beyond cell regeneration,” he says. Now the team has tested for changes in cognition by linking the circulatory systems of young and old mice. Once the blood of each conjoined mouse had fully mixed with the other, the researchers analysed their brains. Tissue from the hippocampus
of old mice given young blood showed changes in the expression of 200 to 300 genes, particularly in those involved in synaptic plasticity, which underpins learning and memory. They also found changes in some proteins involved in nerve growth.
effect produced by blood cells. The mice then took part in a standard memory task to locate a hidden platform in water. The old mice that had received young blood plasma remembered where to find the platform much quicker than the mice on the old plasma. To find out which brain area was involved in this reversal of cognitive decline, the team performed fear conditioning tests. Mice that had been given young blood were better at remembering fear associated with tasks that activated the hippocampus, suggesting that young blood has a specific effect on this area of the brain. But the mystery remains: what exactly is it about young blood that old blood doesn’t have? “We have not identified any individual factors responsible for the rejuvenating effects of young plasma yet,” says Tony Wyss-Coray, also at Stanford. His team is now trying to identify possible candidates such as lipids and hormones. Villeda is hopeful the results might one day translate to humans since the components of blood that change with age in mice mirror those in humans. While “it’s plausible that similar mechanisms operate in humans,” says Joseph Quinn at Oregon Health and Science University in Portland, there is no evidence –New blood for old– yet to support this. n
Helen Thomson, New Orleans
The infusion of young blood also boosted the number and strength of neuronal connections in an area of the brain where new cells do not grow. This didn’t happen when old mice received old blood. To find out whether these changes improved cognition, the team gave 12 old mice eight intravenous shots of blood plasma either from a young or an old mouse, over the course of one month. They used plasma rather than whole blood to exclude any
have faced a big problem. They had to grow to store more information, but that made copying errors more likely. Get big enough and these errors become almost certain, destroying the molecule’s information. In theory, the first replicators could have avoided this “error catastrophe” by splitting their information between several cooperating molecules. Then the network could function as long as copies of each molecule survived. To see if this strategy would work, Niles Lehman of Portland State University in Oregon and colleagues created three RNA molecules that
could repair each other – A did B, B did C, and C did A. When the team put these broken molecules together in a test tube, the collective network worked well. When they pitted the cooperative network against a selfish, self-repairing molecule, the cooperators won out (Nature, DOI: 10.1038/nature11549). Although earlier studies showed that pairs of molecules can
“The ‘error catastrophe’ could be avoided by splitting information between molecules”
cooperate, Lehman is the first to create a network of 3, opening the door to much larger networks. “If you can go from 2 to 3, you can go from 3 to infinity,” he says. Lehman repeated the study with 48 different fragments of an RNA molecule. Sure enough, they assembled into a network that eventually included all 48. Such cooperation may have arisen early in the RNA world and helped to build complexity, says Gerald Joyce of the Scripps Research Institute in San Diego. “It’s an experimental demonstration that real molecules can do this,” he says. Bob Holmes n