Dr. Warren led the research that discovered how the gene mutation responsible for Fragile X Syndrome (FXS) alters the way brain cells communicate. FXS is the most commonly inherited form of mental retardation, with nearly a third of FXS patients also having autism, making FXS the single best understood cause of autism and a model for autism research.
FXS is caused by a mutation in the FMR1 gene on the X chromosome. Dr. Warren and his colleagues led an international team that discovered the FMR1 gene in 1991.They found that in patients with FXS, the expanded CGG triplet repeats can be repeated from 55 to over 200 times—whereas in healthy individuals the repeats range from 40 to fewer than 10. As a result of the hyper-CGG repeats, the expression of the FMR1 gene is repressed, which leads to the absence of FMR1 protein and subsequent mental retardation.
Dr. Warren and his team have since developed diagnostic tests for FXS. Clinical trials are now under way for FXS, taking advantage of the fundamental basic science research on FXS carried out over the past two decades. FXS is now used as a model of how fundamental research on autism could lead the way for future therapeutic interventions in autistic disorders.