Surgery without anesthesia, life without anxiety, rare gene mutations inspire new medicine

The easiest pain to bear is someone else's.

—François de La Rochefoucauld

Written by | Jiawei

It was not until she was 65 that she realized she was a "superpower".

Jo Cameron, who lives in Scotland, is a retired Scottish teacher, a socially responsible vegetarian and a pillar of the local community - she seems to be just an ordinary, optimistic old lady.

By "superpowers," she doesn't mean she can read other people's minds, control the weather, or bend silver spoons with her mind alone. What's special about her is that she doesn't feel pain, never seems to experience anxiety or fear, and her wounds heal faster than most people.

A new gene mutation

Like all people who have lost their sense of pain, Joe was burned as a child but didn't feel it. However, unlike the known patients with congenital insensitivity to pain (CIP), Joe carries a gene mutation, which, according to the BBC, is only known to occur in two cases worldwide.

The mutation left her with no sense of pain, anxiety or fear. One of the costs was that she developed nausea and vomiting in response to morphine. So she had always resisted the use of anesthesia, even for major surgery - which frightened her doctors.

"They thought I was kidding. I said I really didn't need pain medication and they asked if I was taking anything magical."

During a hand surgery in 2013, doctors warned that it would literally be “slicing and slicing.” But when they saw Jo watching them slice and dig at her hand, they realized they had stumbled upon a medical miracle.

They sent her to pain geneticists at University College London and Oxford University for a battery of tests and examinations. They discovered a rare genetic mutation that prevented her nervous system from sensing any stimulation. That’s when Jo finally understood why she had always been “perfectly healthy.”

The amazing Ms. Jo Cameron | Source: Reference [1]

Joe is not a patient with the relatively common congenital insensitivity to pain (CIP). It is estimated that there are currently hundreds of people with CIP in the world. They can put their hands in boiling water or undergo surgery without anesthesia without feeling any pain. But CIP is more like a curse. Many patients lack the sense of pain in their childhood, and appear clumsy and slow in certain learning experiences that require physical sensations, so that their families think they have intellectual disabilities. Therefore, CIP patients often have psychological problems in adulthood.

But Joe is different. Although she also needs to be careful about the failure of danger warning caused by the lack of pain perception, she has never been depressed and can always maintain an optimistic and positive attitude - although this is essentially a "cheating" at the genetic level.

"I never thought I was any different. I just don't feel pain. I don't feel anxiety or fear. I feel like it's a gift from God."

Congenital insensitivity to pain is caused by some gene mutations that affect the molecular pathways of pain perception and transmission. Currently known gene mutations that can affect pain perception include:

Mutation of the Ntrk1 gene leads to functional loss or abnormality of the nerve growth factor receptor Trk-A, affecting the role of nerve growth factor (NGF) in pain perception and conduction.

The Prdm12 gene mutates. This gene is usually turned on during the development of pain-sensing neurons. People with homozygous mutations in the Prdm12 gene are congenitally incapable of feeling pain.

Mutations in the Zfhx2 gene lead to loss or abnormality of ZFHX2 protein function, affecting the transcriptional regulation of neurons.

But experts at University College London found that Joe's mutation was different from any of these. After six years of searching, they found a new gene they named Faah-out (the gene Faah was already known).

Joe's Faah-out contained a rare mutation, which, combined with another more common mutation in Faah, was the cause of Joe's unique "symptoms."

Molecular biological mechanism of "painless" mutation

Through Jo Cameron's "symptoms", we can know that the mutation she carries apparently has the function of eliminating anxiety and fear, and increasing the speed of wound healing.

For Jo, the greatest value of her rare mutation was the wonderful birthing experience it brought her: "It was a wonderful experience. I was just a little nervous, and then I saw my baby."

Jo doesn't want to change herself, but she also knows that pain has its meaning.

“Pain is your body’s way of telling you something is wrong, and without it, you might miss a lot of important signals. For example, my hip was completely broken due to arthritis. I didn’t even know it was wrong until I couldn’t walk anymore.”

Pain plays an important role in human survival and health. Pain is the body's warning mechanism that lets us know if we are injured or ill and take appropriate action. People who do not feel pain may not be able to detect and treat potential problems in time, leading to more serious consequences. Pain can also help us learn how to protect ourselves from danger and harm. People who do not feel pain are more likely to engage in risky or self-harming behaviors, such as walking barefoot on hot coals or stabbing themselves in the arm.

Pain can also make us sympathize with the suffering of others, enhancing interpersonal relationships and social cohesion. People who cannot feel pain may find it difficult to understand the feelings of others and thus lack compassion and empathy.

The spicy taste in the sweet, sour, bitter and spicy food is not a taste, but a pain. Joe once participated in a chili challenge with her husband and her anesthesiologist, Dr. Devjit Srivastava. The two men cried out in pain, but Joe smiled and remained calm.

But pain can also cause great suffering and affect quality of life. Chronic pain currently affects at least millions of people around the world, and the scientific community urgently needs to find new treatments. One path to identifying new analgesic strategies is to understand the biological dysfunction that leads to human genetic pain insensitivity.

By the end of May 2023, University College London finally revealed the molecular biological mechanism of Joe's rare gene mutation.

Expression levels and localization of Faah and Faah-out RNA in human brain tissue cells. Image source: Reference [2]

(A) Faah and Faah-out RNA expression levels and localization in human cerebral cortical cells. Fresh frozen cerebral cortex sections (7-10 μM thick) were analyzed by RNAscope assay, and the localization of Faah mRNA (green, AF488) was compared with the localization of Faah-out lncRNA (magenta, Opal650) and DAPI staining (blue) indicating the location of the nucleus. The scale bar is white. Representative areas (i) and magnified sub-areas indicated by white boxes show colocalization of green (Faah) and magenta signals (Faah-out) with the same cells (ii and iii). Magnified images of individual cells expressing Faah mRNA (green) and Faah-out lncRNA (magenta) are shown on the right.

(B) Faah and Faah-out RNA expression levels and localization in human cerebellar cells. Fresh frozen cortical sections (7–10 μM thick sections) were analyzed by RNAscope assay, and the localization of Faah mRNA (green, AF488) was compared with that of Faah-out lncRNA (magenta, Opal650) and DAPI staining (blue) indicating the location of the nucleus. Representative areas (i) and magnified sub-areas indicated by white boxes show that the green signal (Faah) and magenta signal (Faah-out) colocalize with the same large neuronal cells (Purkinje cells) located at the outer edge of the cerebellar lobe (ii and iii). Magnified images of individual cells expressing Faah mRNA (green) and Faah-out lncRNA (magenta) are shown on the right, demonstrating that Faah mRNA is mainly in the cytoplasm, while Faah-out lncRNA is enriched in the nucleus.

Earlier, scientists often referred to certain genes or genomic regions that do not encode proteins as "junk" genes because they seemed to have no direct function in gene expression. The genomic region containing Faah-out was previously considered a "junk" gene with no function, but now scientists have realized that in addition to directly directing the production of proteins, genes can also regulate the protein-making programs of other genomes (that is, in addition to expression, genes actually have regulatory functions), and Faah-out can regulate the expression of the Faah gene, which is a gene that regulates the endocrine system and is also involved in the regulation of pain, emotions and memory.

The study, published in Brain, reveals how the Faah-out gene mutation leads to decreased expression of the Faah gene and how this affects molecular pathways involved in wound healing and mood. The researchers hope that these findings will provide direction and targets for the development of new drugs and further research in this area.

Specifically, the Faah-out gene is a long noncoding RNA (lncRNA) gene that is located on human chromosome 1, adjacent to the gene Faah. The latter encodes an enzyme that can degrade endocannabinoids, which play an important role in nervous system functions such as pain and emotion. The latest research confirms that the Faah-out gene regulates the expression of the Faah gene in two ways: interruption of Faah-out lncRNA transcription leads to Dnmt1-dependent DNA methylation in the Faah promoter; Faah-out also contains a regulatory element Faah-amp, which is an enhancer of Faah expression. Enhancer is a DNA sequence that plays a key role in gene regulation and can affect the expression of nearby or distant genes.

Due to the mutation Joe Cameron carries, the function of the Faah-out gene is significantly weakened, resulting in a significant decrease in the level of FAAH enzyme activity.

In addition, they found that mutations in the Faah-out gene caused another 797 genes to be upregulated and 348 genes to be downregulated. Some of these genes are involved in the Wnt pathway associated with wound healing, especially the Wnt16 gene associated with bone regeneration. Other genes are related to mood regulation, such as Bdnf and Ackr3, the latter of which has also been shown to block endogenous opioid peptides and is believed to regulate their activity. In animal experiments, inhibition of Ackr3 can increase the activity of opioid peptides and produce analgesic and antidepressant effects.

Complex application prospects

Dr Andrei Okorokov, one of the senior authors of the study from UCL Medicine, said: "The Faah-out gene is just a small corner of a vast unknown that we have begun to explore with this study. We have not only discovered the molecular mechanism of painlessness, but also the impact of the Faah-out mutation on molecular pathways such as wound healing and mood regulation. As scientists, we have a responsibility to explore the unknown, and I believe these findings will have important implications for the treatment of problems such as wound healing and depression."

They determined that the Faah-out gene is a novel regulator of the endocannabinoid system, which provides new targets and strategies for treating neurological diseases such as pain, anxiety, and depression.

"Target" means to specifically target a specific part or molecule of a disease for treatment, just like we focus on hitting the target when shooting. This approach aims to affect the disease more precisely and reduce damage to normal tissues. Usually, doctors look for key molecules or biological processes in the disease, and then develop drugs or treatments to act on these key points to achieve better therapeutic effects. Compared with traditional broad-spectrum therapies, this approach can reduce side effects and improve the effectiveness of treatment.

Does this new research mean that in the future we will have a new type of painkiller and anti-anxiety drug that targets the Faah-out gene?

The situation here is a bit complicated. As mentioned above, the function of the Faah gene is something we have long known. Pharmaceutical research and development companies have tried to create a drug BIA 10-2474 that directly targets Faah, and the consequences are very famous. BIA 10-2474 was directly written into the textbooks: it caused the death of human experimenters in the first phase of clinical trials!

BIA 10-2474 is an experimental fatty amide hydrolase (FAAH) inhibitor that is considered to have the potential to treat pain and other diseases. In January 2016, this drug caused a disaster in the first phase of human clinical trials (FIH) in France. A healthy volunteer who received a 50 mg dose for 5 consecutive days died of severe cerebral microbleeding (consequences include deep hemorrhage and necrotic lesions), and four other volunteers who received the same dose for 6 consecutive days also showed symptoms of neurological damage. This is the first time in history that such a sudden and serious adverse event has occurred in a FIH trial.

In animal toxicity tests, BIA 10-2474 also caused a variety of adverse reactions, mainly including damage to the nervous system, digestive system, blood system, liver, kidney, lung and testicles. However, the damage mainly occurred after administration at higher doses (500 mg/kg body weight/day) or for a longer period of time (13 weeks or 26 weeks). However, the side effects seen in animal tests have no direct or obvious connection with the fatal events seen in human trials. In particular, no manifestations of severe neurological damage such as cerebral microbleeds or stroke were observed in animal tests.

By contrast, the tragedies in human trials are unpredictable and unexplainable, and there is no known mechanism that could reasonably account for the toxicity.

The unknown consequences of drugs targeting the Faah gene indicate that there are mechanisms that we have not yet figured out. It is not clear whether choosing not to directly target Faah but instead targeting the corresponding Faah-out gene is the right way to avoid tragedy or another detour leading to an unpredictable future.

References

[1] https://www.ucl.ac.uk/news/2023/may/study-reveals-unique-molecular-machinery-woman-who-cant-feel-pain

[2] https://academic.oup.com/brain/advance-article/doi/10.1093/brain/awad098/7169317

[3] Open letter on access to the BIA 10-2474 clinical trial data - The Lancet

[4] Full article: Non-clinical toxicology evaluation of BIA 10-2474 (tandfonline.com)

[5] Scientists in the dark after French clinical trial proves fatal | Nature

[6] https://www.bbc.com/future/article/20170426-the-people-who-never-feel-any-pain

This article is supported by the Science Popularization China Starry Sky Project

Produced by: China Association for Science and Technology Department of Science Popularization

Producer: China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd.

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