Scientists from Washington University and Emory University School of Medicine in Atlanta, GA, have published a study that suggests that more knowledge about fragile X syndrome have been obtained following an analysis conducted on a patient with a mutation in a specific gene exhibiting some of the disorder symptoms.
Fragile X syndrome is an inherited intellectual disability, and it results from the disabling of the fragile X mental retardation (FMR1) gene responsible for creating the fragile X mental retardation protein (FMRP). FMRP is largely used to regulate the electrical signals produced in the brain.
Patients with fragile X syndrome sometimes experience anxiety and seizures, and they may also have flat feet and enlarged heads; and then, one-third of people with fragile X syndrome exhibit symptoms that are characteristic of autism spectrum disorders.
Little was initially known about fragile X syndrome, but one particular patient has shown a particular error in the gene and exhibited two of the primary symptoms associated with the disorder.
“This individual case has allowed us to separate two independent functions of the fragile X protein in the brain,” says co-senior author Prof. Vitaly A. Klyachko, associate professor of cell biology and physiology at Washington University School of Medicine in St. Louis, MO.
“By finding the mutation, even in just one patient, and linking it to a partial set of traits, we have identified a distinct function that this gene is responsible for and that is likely impaired in all people with fragile X.”
The US Centers for Disease Control and Prevention (CDC) estimate about one in 5,000 males are born with this anomaly. Fragile X syndrome leads to intellectual disability and may include the inability to communicate. This condition affects males more because the FMR1 gene develops with the X chromosome.
The researchers had initially analyzed the genetic sequencing data of over 900 males with intellectual disabilities – but lacking the fragile X syndrome; and their main objective was to detect the FMR1 gene that mars FMR1 without really eliminating it.
However, the one patient found to have the abnormal FMRP that is the result of a slight mutation in the FMR1 gene’s DNA code. This patient had intellectual disabilities but never experienced the seizures or had the large head or flat feet or autism features associated with the abnormal gene.
“This patient presents a case of partial fragile X syndrome associated with mutated, rather than absent, FMRP,” says Prof. Klyachko. “As far as I know, this is the only known case of this. It’s a unique opportunity to parse out the functions of FMRP. What does this mutation impair to cause only two symptoms of fragile X?”
Ultimately, researchers found that while the factors associated with fragile X syndrome has to do with how and when signals are received in the brain – the receivers that are sensitized to allow for information processing. However, drugs used for this condition may have been ineffective because they target receivers in the brain and never address the higher levels of signal transmission.
“The mechanisms that researchers have long thought were the entirety of the problem with fragile X are obviously still very much in play,” Prof. Klyachko observes. “But this unique case has allowed us to see that something else is going on.”