Gene responsible for pain discovered
A boy naturally immune to pain holds the key to a new generation of smarter anaesthetics, according to researchers.
PARIS: A boy naturally immune to pain holds the key to a new generation of smarter anaesthetics, according to researchers.
In a paper published on Thursday in the British journal Nature, a team of scientists described the genetic mutation that inactivated the boy’s ability to sense pain.
The child was well known to local doctors in his native Pakistan because he took part in ‘street theatre’, pushing knives through his arms and walking on burning coals, sometimes suffering injuries but never feeling any pain.
The child, who is being kept anonymous, died on his 14th birthday after jumping off a house roof.
From this single case, the researchers tracked down three families in northern Pakistan related to the boy, hoping to find others with the same remarkable trait.
Six people within this group also had immunity to pain – a ‘cluster’ of people whose DNA the researchers were able to study. “All six individuals had never felt any pain, at any time, in any part of their body,” the authors said.
“None knew what pain felt like, although the older individuals realised what actions should elicit pain, including acting as if in pain after football tackles.” All had injuries to their lips and tongues from accidental bites – two of the six had bitten off the last one-third of their tongues – and all had suffered frequent bruises and cuts.
They also suffered from badly-mended fractures. A broken leg or arm would be spotted only in retrospect, due to painless limping or the lack of use of the limb.
Tests showed that the mutant form of SCN9A effectively left the switch in the ‘off’ position.
At the same time, the children were otherwise healthy. All could sense heat and cold, and could feel a painless sensation when pricked with a needle.
The team unraveled these individuals’ genome to find what caused their remarkable trait. They eventually zeroed in on a single mutation in a gene called SCN9A.
SCN9A encodes a key protein called a voltage-gated sodium channel – a sort of switch in a certain type of nerve cells, called nociceptors, that respond to pain.
These receptors are studded around the body’s periphery, connecting to the brain via the spinal pathway.
Tests showed that the mutant form of SCN9A effectively left the switch in the ‘off’ position, meaning their brain never received the electrical signal for pain.
“Because pain perception pathways are so numerous and complex, it was surprising that disruption of a single gene… would lead to a complete loss of nociceptive input,” the researchers admitted.
The investigators, led by Geoffrey Woods of the University of Cambridge, in England, speculated the SCN9A gene may have other variants that could explain why the threshold of pain varies so widely from person to person.
Especially intriguing is the possibility for new pharmaceuticals opened up the discovery.
Anaesthesia is essential for surgery but can have many side effects, ranging from drowsiness to nausea, and it can be life-threatening for people with respiratory or cardiac problems.
If all goes well, a safer form of painkillers may one day emerge by throwing the SCN9A switch – “a new generation of drugs that can effectively mute the megaphone of pain,” said U.S. neurologist Stephen Waxman, of Yale University, in a commentary.