A study published in the Journal of Neuroscience and supported by grants from the National Institutes of Health and Autism Speaks has found that the loss of a specific mutated gene in the auditory cortical neurons – the powerhouses of the sound-processing center – causes hypersensitive to sound.
While the functioning PTEN gene is known for it’s anti-cancer roll in powering down cell growth, proliferation, and survival, a mutated version of PTEN has the opposite effect and has been found in autistic individuals with macroencephaly, or an increase in brain volume. Previous work with the mutated form of PTEN in mice has resulted in boosted cell size and number of neurological connections in the brain.
For this study, Professor Tony Zador and his team distributed the mutated gene to just the neurons in the auditory cortex, leaving the functioning gene in neighboring neurons of the brain. As a result, a rapid and robust increase in the strength of both long-range and local inputs due to the increase in length and density of dentritic spines (tiny, knob-like structures that extend from the neuron and act as antennae for electrical or chemical signals.
This effect, however, can be prevented and blocked by chemical negation. Because the PTEN gene controls the intracellular enzyme called mTORC1, a cell growth promoter, when the gene is mutated, there is an abundance of the enzyme. Zadors team found that, by treating the affected mice for 10 days with the mTORC1-inhibitor rapamycin, the increase in dendritic spine number and signal strength was prevented.
While the study is promising in the treatment of hypersensitivity, it brings researchers one step closer to understanding a possible autism spectrum disorder genotype. An autism spectrum disorder phenotype could help researchers develop new methods of treatment and therapeutic strategies for those with autism.