Blood Test can Reveal Fragile X
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08 June 2010
Research gives hope to those with emotional problems caused by defective gene in the X chromosome
The research offers new hope to those with autism, Learning Disability, attention deficit and other conditions caused by the inheritance of a Fragile X chromosome.
Dr Sumantra Chattarji, who heads the team of neuroscientists at the National Centre for Biological Sciences in Bangalore, said the researchers mapped the cellular basis of emotional problems associated with Fragile X, which is a genetic mutation in the X chromosome.
“We have identified novel synaptic defects in the amygdala–the emotional hub of the brain,” Chattarji said. Synaptic connections are those between two nerve cells. The team found cellular signalling deficient in cells in the amygdala.
Incidental ly, this is the second important finding by the NCBS team on Fragile X. In 2007, the same scientists identified a specific enzyme that caused Fragile X.
It established that inhibiting the enzyme, called P21-Activated Kinase (PAK), reversed the debilitating symptoms of Fragile X Syndrome in mice.
This time around, the NCBS scientists, along with their collaborators at New York University, studied the synapses in the amygdala. “Using electro-physiological recordings from cells in the amygdala, my student Aparna Suvrathan identified synaptic defects on both sides of the synapses. Not only is there a shortage of glutamate being released, the receptors available to bind glutamate are also below normal levels,” said Chattarji.
In other words, the amygdala neurons failed to communicate and code information. This could explain why most children with Fragile X–and autism–are known to have severe phobias and behavioural problems. Shalini Kedia, who heads the Fragile X Society of India, said, “The brain has many enzymes that act as traffic policemen, directing information in the right direction. But this doesn’t happen in children with Fragile X Syndrome as the genetic defect prevents the production of a protein that helps create synpases.”
Kedia is hopeful about the new findings. “These findings hold scientific hope for parents who get so desperate that they are willing to try any advice.” There is little awareness about Fragile X among parents. “People don’t even know that there is a screening blood test for Fragile X. There are families in which every child is born with Fragile X, even though the mother could well have got herself tested and prevented this problem,” she added.
The hope seems immense, more so because the team tested mice who were old. Chattarji and colleagues used fully grown mice wih Fragile X.
“Strikingly, even a brief one-hour treatment with a pharmacological blocker of mGluRs (a type of glutamate receptor) was capable of reversing the action of deficient transmitter releases. This raises the exciting possibility that synaptic defects could be corrected pharmacologically even after the disease has had time to leave its mark in the adult brain,” said Chattarji.
However, Dr Vrajesh Udani, a paediatric neurologist at Hinduja Hospital, who treats many patients with Fragile X, was not overly impressed. “The team has only established theoretical possibilities. If at all these findings can translate into treatment, it is still very far away from human use,” he said.
Incidentally, in a separate development in early May, the New York Times reported that a pharma giant had announced the results of a small clinical trial in which researchers found substantial improvements in behaviour associated with retardation and autism in people with Fragile X Syndrome. Chattarji, who was in the US attending a conference on Fragile X at that time, said, “We were unaware about the Novartis trial. But their findings also give hope that a therapeutic treatment could be possible in humans in the near future.”