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Gene manipulation influences mammalian brain development
In the Genetics section of the online edition of Discover Magazine is a presentation of the findings and implications of the “Inhibition of p21-Activated Kinase Rescues Symptoms of Fragile X Syndrome in Mice.” By Mansuo L. Hayashi et al. published in the July 3, 2007, issue of Proceedings of the National Academy of Sciences.
If a gene mutation hinders brain development, the resulting mental retardation is usually considered irreversible. Symptoms can be treated, but the broken wiring cannot be fixed. Or can it? A startling new study of fragile X syndrome-the most common cause of inherited mental retardation as well as a leading genetic cause of autism-indicates that not only can malformed nerves be repaired but that behavior can be restored to normal, or nearly so. The research was done with two strains of mutant mice, but the neuroscientists involved say the results point to a target for drugs that could potentially repair analogous damage in humans.
Nobel Prize winner Susumu Tonegawa and postdoc Mansuo Hayashi did not set out to fix fragile X. As researchers at the Picower Institute for Learning and Memory at MIT, they were simply interested in learning how mice acquire memories. But then Hayashi created a mouse with a mutation in a gene called PAK, which codes for an enzyme called p21-activated kinase that helps build nerve connections in the brain. When Hayashi injected a mutant gene for PAK into mouse embryos and later killed the adult mice and dissected and examined their brains, she discovered that the animals’ dendritic spines-branched stalks that receive input from neighboring neurons-were short, fat, and sparse. When she attached two electrodes to the neurons-one to stimulate the nerve, the other to record the response-she discovered that the neurons’ firing rate was abnormally high.
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Discover Magazine The Goldilocks Method for Curing Autism. Combining two bad mutant genes produces neurons that're just right. Josie Glausiusz
Synopsis edited by Dr Jim Vause, Blenheim, New Zealand. Posted on Global Family Doctor 27 August 2007
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