Thursday, December 20, 2007

Study on Fragile X Syndrome

Fragile X syndrome is the most common form of inherited mental impairment. It is a sex-linked genetic disease and is more prevalent and severe in males. It is estimated that approximately 1 in 4000 males have fragile X (and 1 in 6000-8000 females). The condition is caused by a mutation in a gene on the X chromosome.

The National Fragile X Foundation describes the impact this inherited condition has on males:

The majority of males with fragile X syndrome will have a significant intellectual disability. The spectrum ranges from learning disabilities to severe mental retardation and autism.

In addition, males have a variety of physical and behavioral characteristics. However, no male has all of these characteristics.

Physical features such as enlarged ears, long face with prominent chin, and large testicles (in post pubertal males) are common. Connective tissue problems may include ear infections, mitral valve prolapse, flat feet, double-jointed fingers, hyperflexible joints and a variety of skeletal problems.

Behavioral characteristics in males include attention deficit disorders, speech disturbances, hand biting, hand flapping, autistic behaviors, poor eye contact, and unusual responses to various touch, auditory or visual stimuli.

At present there is no cure for fragile X. But the latest issue of Neuron has a promising report entitled "Correction of Fragile X Syndrome in Mice" by Gül Dölen et. al. Here is the abstract:

Fragile X syndrome (FXS) is the most common form of heritable mental retardation and the leading identified cause of autism. FXS is caused by transcriptional silencing of the FMR1 gene that encodes the fragile X mental retardation protein (FMRP), but the pathogenesis of the disease is unknown. According to one proposal, many psychiatric and neurological symptoms of FXS result from unchecked activation of mGluR5, a metabotropic glutamate receptor. To test this idea we generated Fmr1 mutant mice with a 50% reduction in mGluR5 expression and studied a range of phenotypes with relevance to the human disorder. Our results demonstrate that mGluR5 contributes significantly to the pathogenesis of the disease, a finding that has significant therapeutic implications for fragile X and related developmental disorders.

The BBC also has the scoop here.