Scientists create big-brained mice

Discussion in 'Biology & Genetics' started by Pine_net, Jul 19, 2002.

  1. Pine_net Chaos Product Registered Senior Member

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    Altering a single gene gives mice human-like brains

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    The image shows a normal mouse brain with a smooth surface. Mice with the altered gene developed large, folded brains, right, that looked like human brains.

    WASHINGTON, July 18 — Adding an extra version of a single gene makes mice grow big brains — brains so large they have to fold up, much as human brains do, to fit inside the skull, researchers said Thursday.

    IT IS NOT yet clear whether the mice are smarter — they were all killed soon after birth — but the scientists said they were surprised that one gene had such a strong effect and said they would do further experiments.
    “I know the most interesting question was whether they learned to play Mozart but we don’t know,” Dr. Christopher Walsh of Brigham and Women’s Hospital and Harvard Medical School in Boston, who led the study, said in a telephone interview.
    “A bigger brain is not always good,” he added, pointing out that a condition called megacephaly, in which the cerebral cortex grows too large, can cause mental retardation.
    Walsh and colleague Anjen Chenn started with a protein called beta-catenin, which helps control cell division.
    “It is expressed in the brain in such a way that made us think it could be a regulatory switch that makes cells stop dividing ... and become a neuron,” Walsh said. “Because neurons don’t divide, that has to happen for a cell to become a neuron.”
    Unlike cells in other tissues of the body, neurons stop dividing and become fully formed before birth.
    So Walsh and Chenn genetically engineered mice, adding extra beta-catenin that would become overactive specifically in brain tissue.

    SIMILAR TO HUMANS
    To their surprise, they report in Friday’s issue of the journal Science, the mice developed large, folded brains that looked like human brains.
    “We didn’t expect to see the folds. We sort of expected the cerebral cortex would be big. We didn’t expect it to be so big,” Walsh said.
    Mouse brains normally have a smooth surface. Human brains are all wrinkled and folded, because they are squashed into the skull.
    Humans have disproportionately large brains for their size. Especially large is the cerebral cortex, the surface layer made up of gray matter — the stuff involved in thought, as opposed to control of basic body functions.

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