Big Brain And High IQ - A One-Letter Change In Genetic Code

Brain 041612

In what is perhaps the world's largest brain study to date, researchers have uncovered specific genes that are linked to brain size and intelligence.

The study, conducted by a team of more than 200 scientists from 100 institutions worldwide, measured the size of the brain and its memory centers in thousands of MRI images from 21,151 healthy people while simultaneously screening their DNA. According to the researchers, a variant in a gene called HMGA2 affected the brain size, as well as a person's intelligence.

Remember that every gene contains a unique sequence of four bases namely, adenine (A), cytosine (C), guanine (G) and thymine (T). People whose HMGA2 gene held a letter "C" instead of a "T" at a specific location on the gene possessed larger brains and scored more highly on standardized IQ tests, noted the researchers.

According to the study, there was a consistent relationship between subtle shifts in the genetic code and diminished memory centers in people with smaller brains. Since reduced brain size is a biological marker for disorders like schizophrenia, bipolar disorder, depression, Alzheimer's disease and dementia, if we identify the gene variants that deplete brain tissue beyond normal in a healthy person, it can be targeted with a drug to reduce the risk of those diseases, said the researchers.

Commenting on the study findings, lead researcher Paul Thompson, a neurologist at the University of California, Los Angeles, School of Medicine, said, "This is a really exciting discovery, that a single letter change leads to a bigger brain. For the first time, we have watertight evidence of how these genes affect the brain.

The study was published April 15 in the advance online edition of the journal Nature Genetics.

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