Research on autism spectrum disorder offers opportunities to study specific genetic mutations that could potentially reveal biological insights into the development of autism. Consistent with this, researchers have created lists of hundreds of studied risk genes for autism. The vast majority of autism cases are the result of multiple genetic and biological factors (Singer, n.d.).
New research has focused on the SCN2A gene, which encodes a neuronal sodium channel (aka NaV1.2). The gene is responsible for producing voltage-gated sodium channels (channels in the cell membrane that open and close as a result of alterations in voltage) in neurons to govern the excitability of the cells. Mutations in the gene are strongly associated to epilepsy. Excitable brain cells can trigger seizures and therefore the gene is strongly implicated to the disorder.
However, there is a connection to a mutation in the SCN2A gene and autism that is more direct rather than through epilepsy, sometimes a feature of autism in some individuals. Stephan Sanders and Kevin Bender, two scientists at the University of California San Francisco, developed a theory that there was one type of SCN2A mutation linked directly to autism through loss of function and another type of mutation linked to seizures through gain of function (Sanders et al., 2018; Wright, 2016). In mice, mutations in the SCN2A gene dampen the electrical neuron activity. The mice have fewer functioning sodium channels and mirrored social behaviors known of autistic people with SCN2A mutations (I will never be not fascinated that we can use animal models to model neurodevelopmental disorders). These results give insight into possible mechanisms underlying behavioral abnormalities in ASD.
One interesting connection between the gene mutation and autism could possibly explain a certain eye reflex in children. Bender developed an eye-tracking system to test the reflex in 5 children with SCN2A mutations and 11 neurotypical individuals who had to spin back and forth in a rotating chair. The reflex is known as the vestibulo-ocular reflex, or forced eye movements caused by head rotation (Voges et al., 2017). The mutation prevented changes in the synapse in neurons that would usually adjust to the reflex. The mutation is known to be implicated in autism and can explain the sensitivity to alterations in sensory stimuli that some individuals with autism suffer from (Choi, 2023).
References
Choi, C. (2023, July 7). Mutation in top autism-linked gene may alter eye reflex. Spectrum News.
Sanders, S., Campbell, A., Bender, K., Spiro, J., Chung, W., Taylor, C., Wagner, F., Lal, D., Cottrell, J., Pitt, G., Moller, R., Auldridge, A., & Bernier, R. (2018). Progress in Understanding and Treating SCN2A-Mediated Disorders. https://doi.org/10.1016/j.tins.2018.03.011
Singer, E. (n.d.). SCN2A: An Evolving Picture. SPARK. https://sparkforautism.org/discover_article/scn2a-an-evolving-picture/
Voges, K., Post, L., Wu, B., Schonewille, M., & De Zeeuew. (2017). Mechanisms underlying vestibulo-cerebellar motor learning in mice depend on movement direction. The Journal of Pyhsiology, 595.
Wright, J. (2016, November 16). Sodium channel gene takes diverging paths in autism, epilepsy. Spectrum News.