By Katie Campbell
It has been well documented in scientific literature that individuals with autism spectrum disorders are often affected by sensory disorders. For example, some people may injure themselves by pulling their hair or banging their head repeatedly. This was thought to occur because individuals with autism spectrum disorders were less susceptible to pain, but no one knew why. A new study, published on December 1 in Neuron may point to a mechanism behind this insensitivity.
The study, conducted by two teams from Duke University, examined the relationship between the pain receptor TRPV1 and the SHANK3 gene. This receptor is well understood, but had not previously been studied in the context of autism and brain development.
One of the authors of the study had demonstrated that approximately 1% of cases of autism-spectrum disorders are caused by a mutation in the SHANK3 gene. In this study, SHANK3 deficient mice were subjected to a battery of tests. These mice showed a higher tolerance for heat related pain (similar to the soreness felt after a mild sunburn.)
The teams were able to draw two interesting conclusions: first, SHANK3 proteins were found in pain-sensing dorsal root ganglion cells. This marks the first investigation into the presence and function of these cells in the peripheral nervous system. Interestingly, these cells were also found in cells donated by humans who did not have autism spectrum disorders.
Second, the scientists found that mice with the SHANK3 mutation also possessed low quantities of TRPV1 present at the surface of the ganglion cells. This lowers TRPV1’s ability to transmit pain signals, and suggests that SHANK3 is crucial for pain sensation.
Overall, SHANK3 was previously thought to only be present in the post-synaptic spaces in the brain. This study shows that it not only is present in the peripheral nervous system, but also plays a role in a critical feedback loop. Current pharmaceuticals that block TRPV1 possess unpleasant side effects, so researchers hope that better understanding its relationship with the SHANK3 gene may help treat patients with autism-spectrum disorders more effectively.
Duke University. (2016, December 1). Autism-linked protein crucial for feeling pain: Well-known autism and pain proteins are likely co-conspirators. ScienceDaily. Retrieved December 11, 2016 from www.sciencedaily.com/releases/2016/12/161201122017.htm