WASHINGTON, Sept 17: US scientists have discovered how the gene mutation responsible for fragile X syndrome — the most common inherited form of mental retardation — alters the way brain cells communicate, a published report said on Monday.

In neurons cultured from laboratory rats, the scientists also were able to reverse the effects of the mutation using a drug targeted to the specific site in an upstream pathway of the defect.

The finding could lead to the development of human therapies for this previously untreatable condition, the study said.

The research was led by Stephen Warren, PhD, chair of human genetics in Emory University School of Medicine, and Gary Bassell, Emory professor of cell biology. It is being reported in the Proceedings of the National Academy of Sciences this week.

“We have now explained the fundamental defect in the brain in fragile X syndrome and, most importantly, found that we can correct this problem in the laboratory,” says Warren.

“This is quite exciting, progressing from the identification of the gene in 1991 to now believing we will be able to treat a previously untreatable condition.” He added that the next steps will be to continue screening and identifying the best drugs likely to correct the deficiencies that result from fragile X syndrome.

Fragile X syndrome is caused by a mutation in the FMR1 gene on the X chromosome, the report said.

A region of the mutated gene repeats a trinucleotide sequence of DNA bases between 200 and 1,000 times, rather than the normal six to 55 repeats in normal individuals.

The abnormal trinucleotide repeats cause the absence of the FMR protein normally produced by the gene, according to the study.

—AFP