By comparing the gene's sequence in a range of primates, including humans, as well as non-primate mammals, the scientists found evidence that the pressure of natural selection accelerated changes in the gene, particularly in the primate lineage leading to humans.

The researchers, led by Howard Hughes Medical Institute (HHMI) investigator Bruce Lahn at the University of Chicago, reported their findings in an advance access article published on January 13, 2004, in the journal Human Molecular Genetics. Patrick Evans and Jeffrey Anderson in Lahn's laboratory were joint lead authors of the article.

"People have studied the evolution of the brain for a long time, but they have traditionally focused on the comparative anatomy and physiology of brain evolution," said Lahn. "I would venture, however, that there really hasn't been any convincing evidence until now of any gene whose changes might have contributed to the evolution of the brain."

In this study, the researchers focused on a gene called the Abnormal Spindle-Like Microcephaly Associated (ASPM) gene. Loss of function of the ASPM gene is linked to human microcephaly a severe reduction in the size of the cerebral cortex, the part of the brain responsible for planning, abstract reasoning and other higher brain function. The discovery of this association by HHMI investigator Christopher A. Walsh and colleagues at Beth Israel Deaconess Medical Center is what prompted Lahn to launch an evolutionary study of the gene.

Lahn and his colleagues compared the sequence of the human ASPM gene to that from six other
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Contact: Jim Keeley
keeleyj@hhmi.org
301-215-8858
Howard Hughes Medical Institute
13-Jan-2004