Mutation that stops people feeling pain found in Italian family

A newly identified genetic mutation makes members of an Italian family unable to feel pain and could lead to the development of new painkillers, research suggests.

The study, published in the journal Brain, identified a mutation in a gene called ZFHX2 which causes six members of the family across three generations to not feel some types of pain. 

'The members of this family can burn themselves or experience pain-free bone fractures,' said Dr James Cox of University College London, and the study's lead author. Despite this, the family had normal density of nerve fibres in the skin, the team found. 'Their nerves are all there, they're just not working how they should be.' 

Although seemingly impervious to fractures and burns, the family members still experienced headaches and pains within the body. Three of the six individuals had given birth, which they had found painful. Interestingly, all six were unable to fully sense temperature and were unable to sweat. They were also unable to feel a burning sensation from capsaicin, the chemical which gives chilli peppers their spice.

The international study sequenced all the coding DNA of each family member who was unable to feel pain. Close inspection of the sequence of the ZFNX2 gene, which binds to DNA in pain-sensing nerves to begin the process of transcription, found that a base, or letter, A had been changed to a letter G in all six pain-free individuals. 

This single letter change is thought to alter the chemistry of the ZFNX2 protein, affecting its ability to bind to DNA. The mutation is dominant, meaning that a person only needs to inherit one mutated version of ZFNX2 to be unable to feel pain and all six members of the family have one mutated ZFNX2 gene and one normal copy. 

Once the mutation had been identified, the researchers produced mice carrying the same mutation and found that they too were unable to sense painful levels of heat. Further genetic analysis showed that the mutant ZFNX2 protein was no longer able to control the expression of 16 other genes in nerve cells, some of which are known to be involved in pain signalling.

It is hoped that this work could provide vital knowledge that could be used to produce new painkillers.

'By identifying this mutation and clarifying that it contributes to the family's pain insensitivity, we have opened up a whole new route to drug discovery for pain relief,' said Professor Anna Maria Aloisi at the University of Siena in Italy, and study co-author. 'With more research to understand exactly how the mutation impacts pain sensitivity, and to see what other genes might be involved, we could identify novel targets for drug development.'