A team of researchers from Tufts School of Medicine in Boston have discovered evidence that offspring may benefit from their parents’ cognitive abilities at the time of conception. Led by Larry Feig, the team bred a group of mice, ‘knockout’ mice, lacking the ras-grf-2 gene which results in defective memory. Half of these knockout mice were exposed to an enriched environment (EE) - a cage with toys, increased social interaction and voluntary exercise - for two weeks before adolescence with the aim to overcome this memory defect.
Both groups of knockout mice were subjected to a fear conditioning memory exercise. This exercise involved placing the mice in a cage in which they soon receive a small electric shock to their feet. Normal mice quickly develop a fear association with the cage and learn to freeze in fear when placed inside. In contrast, knockout mice are unable to form this association and consequently fail to freeze. Carrying out this fear exercise with enriched knockout mice, it was found that they froze when placed in the cage, just as the normal mice. From this it was concluded that the two weeks spent in an EE was sufficient to compensate for their defective memory.
With this information in mind, the research team bred the enriched knockout mice to investigate whether these cognitive benefits could be passed on to offspring. To achieve this, the offspring were raised by unenriched parents to prevent any direct learning from enriched parents and were not exposed to an EE. The offspring then underwent the fear conditioning memory exercise. Most remarkably, the offspring froze when reintroduced to the cage, indicating that they were able to form the normal fear association despite their memory defect and lack of enrichment. This same test was carried out with the offspring of unenriched knockout mice, however, like their parents, they were unable to form any fear association with the electric shock cage.
In addition to these findings, researchers found that it was not sufficient to have an unenriched mother and an enriched father to overcome the memory defect. Also, the cognitive effect was not passed on to a third generation and was only inherited if the offspring were conceived within three months of enrichment.
To explain these results, Feig suggests that the cognitive benefits the enriched mice enjoy is passed on during gestation through epigenetic chemical markers which attach themselves to the embryo’s genes, regulating their expression.
Written by student 42019431
Primary reference:
Motluk, Alison. Can experience before conception be passed on?. New Scientist, Feb 7, 2009, pp 12.
For original journal article:
The Journal of Neuroscience, February 4, 2009, 29(5):1496-1502; doi:10.1523/JNEUROSCI.5057-08.2009
