Measuring intellectual disability

Davis, CA — Researchers from the University of California, Davis have developed a specific and quantitative means of measuring levels of the fragile X mental retardation 1 (FMR1) protein (FMRP), which is mutated in fragile X syndrome. The related report by Iwahashi et al, "A quantitative ELISA assay for the fragile X mental retardation 1 protein," appears in the July 2009 issue of the Journal of Molecular Diagnostics.

Fragile X syndrome is the most common form of inherited intellectual impairment. Nearly one third of patients diagnosed with fragile X syndrome also have some degree of autism, and the mutation underlying fragile X syndrome is the most commonly known single gene cause of autism.

Fragile X syndrome is caused by low levels of the FMRP protein, which is thought to play a role in communication between nerve cells. In patients with fragile X syndrome, a sequence in the FMR1 gene that is repeated 10-40 times in normal individuals may be repeated from 200 to more than 1,000 times, decreasing levels of the FMRP protein.

Current tests for fragile X syndrome determine the presence of the mutation by measuring the number of repeats at the DNA and mRNA level; however, the lack of a quantifiable test to determine FMRP protein levels has prevented direct correlation between FMRP protein levels and clinical severity of disease. Therefore, a group led by Dr. Paul Hagerman at the University of California, Davis developed a sensitive and highly specific test for FMRP protein. The method used is able to detect protein throughout the biologically-relevant range of protein concentrations and is readily adaptable for large-scale use.