Researchers from seven interrelated and collaborative projects all focusing on fragile X syndrome, the most frequent cause of inherited mental retardation in humans, have received a program project grant from the National Institutes of Health (NIH) totaling approximately $3.7 million. The research group, assembled by Stephen Warren, Ph.D., W. T. Timmie Professor of Biochemistry in the Emory University School of Medicine, and a Howard Hughes Medical Institute Investigator (see sidebar), will try to further clarify the molecular basis of fragile X syndrome and expand the scope of contemporary fragile X syndrome research.

In recent years there has been a spectacular increase in the understanding of the fragile X syndrome, with many of the major discoveries originating in Dr. Warren's laboratory. Dr. Warren and his colleagues discovered in 1991 the gene responsible for fragile X syndrome, FMR1, and were among the first to develop genetic tests to diagnose the disease. In 1993 they discovered FMRP, the protein expressed by the normal FMR1 gene and learned that fragile X syndrome occurs when the FMR1 gene does not produce the FMRP protein. That protein suppression is responsible for the symptoms of the disease, namely mental retardation, attention deficit disorder and connective tissue disorders.

The scientists also learned that most affected patients share a common genetic mutation called triplet repeats. All genes are made of combinations of four chemicals, abbreviated A, C, G and T. Within the FMR1 gene, the triple combination of CGG, CGG, etc., is usually repeated only 30 times in unaffected persons, but between 230 to 1,000 times in those affected by fragile X syndrome.

With this knowledge, genetic counselors have been able to help carriers of FMR1 predict the probability of giving birth to a child affected by the syndrome, and pediatricians a
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Contact: Holly Korschun
hkorsch@emory.edu
404/727-3990
Emory University Health Sciences Center
26-Jan-1998