By analyzing and comparing DNA of a child with autism and DNA from the child’s parents (who do not have autism), Yi and his team were able to see abnormally high amounts of ubiquitin protein ligases, the enzymes produced by the UBE3A gene. Ubiquitin protein ligases use ubiquitin protein to tag proteins for degradation. Proteasomes recognize proteins tagged for degradation because of ubiquitin, and these complexes are then able to break down the tagged proteins. A normal amount of protein degradation is necessary to keep cells “clean” by removing any proteins that are not functioning properly or that are not needed. However, Yi found a “switch in the brain” that controls ubiquitin protein ligase release, and when this switch malfunctions, increased amounts of ubiquitin protein ligase cause more proteins to be deleted than is healthy for the body’s cells.
Whatever mutation is causing the switch malfunction could be causing autism, Yi believes.
The National Institutes of Health lists ubiquitin protein ligase as playing “a critical role in the normal development and function of the nervous system,” although exact details are still unknown. Yi and the team at UNC could be on the verge of a major breakthrough in understanding the action of ubiquitin protein ligase in autism cases.
UNC has a long history of success in autism research – in 2013 scientists made connections between autism and topoisomerase suppression. Just last year, UNC scientists analyzed the gene NrCAM and its connection to autism.
Autism is classified by the Centers for Disease Control and Prevention (CDC) as a spectrum disorder, meaning that different cases show different levels of severity in developmental disability. Increasing amounts of autism diagnoses are occurring each year, and this increase is attributed to both a “broader definition of Autism Spectrum Disorder (ASD)” and a “true increase in the number of people with ASD” (CDC).
Cases of autism exhibit a wide variety of symptoms, depending on severity and other factors. Some symptoms include trouble expressing needs, unusual reactions to different sensations, and sensitivity to physical contact. According to the World Health Organization, one child in 160 is diagnosed with some sort of autism.
In the video animation below, check out an illustration of the process of protein degradation through ubiquitin tagging.
Source: The Daily Tar Heel