Gene fragments linked to brain development and autism
While the anti-vaccine movement enjoys the simple (and very wrong) answer to the cause of autism, there are people who want the actual truth. This drive had lead to a slew of causes (and risk factors) for autism in recent times. Now scientists have found that very small segments of genes called “microexons” influence how proteins interact with each other in the nervous system. In turn, this opens up a new line of research into the cause of autism.
The researchers found that microexons are used in neurons by alternative splicing, a process in which a single gene can produce many different proteins. Microexons are sort of pasted — or really spliced — into gene messengers (mRNAs) to generate forms of proteins that the nervous system needs to function properly. Misregulation of this process, the researchers found, can have major effects on how proteins function.
“We’re seeing a new landscape of splicing regulation that is highly specific to the nervous system, and which is very important for controlling how proteins interact with each other,” said Benjamin Blencowe.
“In addition, a large number of the microexons we detected show misregulation in people with autism.”
The team previously created algorithms to predict which exons are spliced in mRNAs to produce proteins. But these algorithms failed to capture microexons.
In their new study the group created a new computational tool that detects many more splicing combinations within a cell, including those that involve microexons. They used their tool to discover splicing of microexons in neurons.
“We were really surprised to find that some microexons encode just 1 or 2 amino acids—the basic building blocks of proteins,” said Manuel Irimia.
“And they modify proteins—changing their surface structures—in ways that longer exons cannot. Microexons perform a type of microsurgery on proteins to alter their function.”
The researchers also found that neuronal microexons are highly conserved during evolution, which strongly suggests they play conserved functional roles — a simpler way to put this is they serve a purpose, so they are kept around. They discovered the existence of similar microexons in many vertebrate species, including mice and humans.
Perhaps most importantly, the researchers also found that even though microexons make very small changes to proteins, the effects of those changes can be dramatic. For example, when they deleted microexons they found that in some cases proteins completely lost their ability to interact with partner proteins.
As well, the group found that many neuronal microexons are weakly spliced in the brains of some individuals with autism, and that this reduced splicing activity is linked to the under-expression of a splicing regulatory protein called nSR100. Blencowe is cautiously optimistic about the potential therapeutic value of this discovery.
“While a lot more work has to be done to understand the functions of microexons in the nervous system, we were amazed by the extent to which microexons are misregulated in people with autism, which suggests they are an important component of this neurological disorder.”
Blencowe and his colleagues are pursuing the role of nSR100 in autism as they map the function of microexons in more detail. By following this line of research, they hope to learn how the misregulation of microexons contributes to autism as well as other disorders of the nervous system.
“Microexons are an underappreciated class of splicing event that is highly conserved. They change the way proteins interact and clearly play an important role in development, so understanding their role in human neurological disorders represents a major avenue of future research,” said Blencowe.
It is sometimes hard to hear, “We don’t know why” when your child is the one who falls on the autistic spectrum. The anti-vaccination movement has latched onto this fear and frustration to give people a simple answer to a problem which there is no simple answer.
Vaccinate your children, while we don’t know all the causes for autism, we do know that vaccines are NOT the cause — we know this, it is not a question, it is not up for debate because there is some controversy with the science, we know this as a fact.
Not only do we know this, it has caused a loss of funding from actual autism research and prompted any actual autism research/awareness organization to place several statements explaining the same thing like autism speaks in the faq under Are Vaccines to Blame? So please, don’t give into the fear and support actual research.
Irimia, M., Weatheritt, R., Ellis, J., Parikshak, N., Gonatopoulos-Pournatzis, T., Babor, M., Quesnel-Vallières, M., Tapial, J., Raj, B., O’Hanlon, D., Barrios-Rodiles, M., Sternberg, M., Cordes, S., Roth, F., Wrana, J., Geschwind, D., & Blencowe, B. (2014). A Highly Conserved Program of Neuronal Microexons Is Misregulated in Autistic Brains Cell, 159 (7), 1511-1523 DOI: 10.1016/j.cell.2014.11.035