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Gene linked to mental retardation and cognitive function


A gene known as AGTR2, which has been shown in mice to play a role in the central nervous system, has now been associated with mental retardation in human patients.

Researchers have found that diminished mental capacity appears to be correlated with mutations in the gene or physical changes in its location on the X-chromosome. The new data, published in Science, suggest that AGTR2 is part of an important learning and memory pathway in the brain.

Image showing chromosomal translocations in female patient with mental retardation.

Virginie S. Vervoort, of the J. C. Self Research Institute of Human Genetics in Greenwood, South Carolina, and colleagues were studying a female patient who suffered from mental retardation. The scientists knew she had a genetic translocation—part of her X-chromosome was in the wrong location. By mapping this chromosome, they discovered three genes—AGTR2 among them—that had been shut down or silenced by the chromosomal abnormality.

Apparently, when the AGTR2 gene is physically located in the wrong place, it fails to function because it is separated from important regulatory genes. AGTR2 codes for a receptor that is present throughout the brain as part of a system that regulates blood pressure and electrolyte balance using the transmitter angiotensin.

The researchers also studied the AGTR2 gene in 590 male patients whose cognitive deficiencies were thought to be associated with the X-chromosome. X-linked mental retardation is the most common inherited type among males, who have only one copy of this chromosome. Eight of the 590 men had various AGTR2 mutations—a sufficient number to suggest that the gene can cause the disorder.

Additional research may reveal a role for the AGTR2 gene in forming and maintaining connections in the brain that permit normal development of learning and memory, according to the researchers.

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Vervoort, V.S. et al. AGTR2 mutations in X-linked mental retardation. Science 296, 2401-2403 (June 28, 2002).

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