CRISPR is a type of gene therapy that can be used to make changes in DNA.
Scientists target genetic mutations that are known to cause diseases and developmental disabilities, such as autism. So far, CRISPR technologies have been primarily studied in mice, with more recent studies taking place in monkeys.
Scientists have discovered promising applications of the technology for the effective treatment of diseases caused by specific genes. Studies have found that CRISPR changes to genes linked to autism in mice and primates reduce symptoms of autism.
Future research will be dedicated to safely developing CRISPR treatments for genetic conditions in humans.
What Is CRISPR?
Clustered regularly interspaced short palindromic repeat (CRISPR) is a genetic engineering technique used to make precise modifications in the DNA of humans, animals, and plants. It is easier and more expedient than previous methods of modifying DNA and provides a new way of thinking about addressing diseases and disorders.
The name references the unique structure of certain DNA sequences found in the genomes of bacteria and other microorganisms. These sequences play a vital role in the immune systems of these organisms.
The immune system maintains an organism’s health by demolishing the genomes of invading viruses. The CRISPR immune system guards healthy bacteria from continuing infection by destroying the viral genome.
CRISPR technology works through three primary steps.
- Adaptation: DNA from an attacking virus is managed as new spacers into a CRISPR DNA sequence.
- Production: The new spacers in the DNA are copied into RNA (ribonucleic acid), and the new RNA chains are divided into short pieces called CRISPR RNAs.
- Targeting: The new CRISPR RNAs guide bacterial molecules to destroy viral material.
Experts from Harvard University describe CRISPR gene editing as similar to using a word processor on your computer to delete words or correct spelling mistakes. The technology could one day be used to make specific genetic changes in humans in order to study and treat diseases.
Applications of CRISPR
The type of CRISPR-based immunity, as described above, can be applied for many different uses, explains Harvard University. It has been successfully applied to scientific research, medicine, and developments in the food industry.
Since scientists first became aware of the CRISPR technique, they have realized the powerful potential of the gene-altering method. Through CRISPR, genomes can be changed to almost anything you want. CRISPR offers the potential to treat genetic diseases by correcting genetic abnormalities at almost any spot in the genetic code of cells.
How CRISPR May Impact Autism
With the therapeutic potential of CRISPR being clear, many scientists have enthusiastically investigated the potential of using CRISPR to treat autism.
As of 2020, there have not been any applications of CRISPR therapy on humans, though studies on mice are promising. Studies of mice who have a form of fragile X syndrome, a genetic defect also found in humans that has been identified as a genetic cause of autism, have successfully used CRISPR technology to reduce repetitive behaviors.
CRISPR technologies are able to target specific genes that are known to cause autism. There are, however, over 100 genetic conditions that have been linked to autism.
A 2018 study developed a CRISPR gene editing strategy for 10 of the genes related to autism. In the study, a protein tag was inserted into premature termination sites on human DNA collected via blood samples and skin biopsies to block the expression of ASD-relevant genes. The use of CRISPR technologies in such a way may have a significant impact on the ability to treat autism caused by many different types of genetic mutations.
Challenges of Using CRISPR to Treat Autism
There are many promising applications of CRISPR for the treatment of autism, but there are also challenges. CRISPR is an effective approach for targeting and treating specific gene mutations. Autism has a clear genetic component to it, but many different genes have been linked to autism. For CRISPR to be effective for the treatment of autism, it will need to be tailored to each individual.
There is no one-size-fits-all CRISPR treatment, explains the CRISPR Report. The specific autism-related genes that have a mutation in each individual with autism must be targeted in order for the treatment to be effective.
Currently, researchers are working on developing specific CRISPR therapies for a variety of autism-related genes, such as the genes that cause Angelman syndrome and fragile X syndrome.
The Research on CRISPR
Again, the latest research on CRISPR has only been done on mice, but the results have been promising.
One mice study targeted the SCN2A gene, one of the top genes linked to autism. Researchers injected CRISPR into the brains of adolescent mice and found that it successfully counteracted the effects of the SCN2A mutation. The researchers noted that the intervention was successful in mice of varying ages, from infancy to adolescents. The strategy is not yet safe to be applied to people, but it does suggest promising future applications for autistic individuals of all ages.
In an effort to make CRISPR findings more translatable to humans, researchers working together from the Chinese Academy of Sciences and the Massachusetts Institute of Technology (MIT) used CRISPR technology to develop a primate genetic model to identify better medicines and gene therapies for autism.
The researchers targeted the Shank3 gene, which is responsible for about 1% of spontaneous forms of autism. In the study using macaque monkeys, the Shank3 mutation caused monkeys to exhibit behavioral patterns similar to those seen in humans with the same gene mutation. The next step is to develop CRISPR treatments for the autism-related symptoms in the monkeys that can be applied to humans in the future.
Is CRISPR a ‘Cure’ for Autism?
Autism is a complicated disorder that does not have a single known cause. Gene mutations of over 1,000 genes have been associated with autism spectrum disorder, though many have not been confirmed.
Experts also agree that a combination of genetics and environmental factors are responsible for causing autism. Scientists estimate that up to 40% of the risk of developing autism is due to non-genetic factors.
Because of the complex nature of autism, CRISPR is unlikely to be a cure for the condition, as it can only target genetic factors. As CRISPR technologies are developed, however, they may become highly effective at targeting specific autism-related gene mutations and thus reducing the symptoms associated with those specific genes.
CRISPR is a fast and affordable breakthrough in the technology of genetic therapy. It has changed the way researchers think about approaching the treatment of genetic diseases.
As the technology is studied further and methods of safely delivering the therapy to humans are established, CRISPR therapy will provide an affordable approach to gene therapy that makes it much more accessible to many more people.
Advancements in CRISPR provide hope to autistic individuals and their families in 2020. It is widely accepted that there is a strong genetic component to autism. As autism researchers are able to identify more specific autism-related genes, CRISPR researchers can develop specific interventions to target those genes, repair them, and reduce symptoms of autism.
A CRISPR Way to Fix Faulty Genes. (June 2014). National Public Radio.
Autism Spectrum Disorder. (July 2020). U.S. National Library of Medicine.
Complete Disruption of Autism-Susceptibility Genes by Gene Editing Predominantly Reduces Functional Connectivity of Isogenic Human Neurons. (November 2018). Stem Cell Reports.
CRISPR: A Game-Changing Genetic Engineering Technique. (July 2014). Harvard University.
CRISPR-Cas9 Gene Editing Used to Engineer Primate Model of Autism. (June 2019). Genetic Engineering & Biotechnology News.
CRISPR Therapy May Reverse Autism Mutation’s Effects Well Past Infancy. (October 2019). Spectrum.
How CRISPR Could Help Treat Autism. (April 2020). CRISPR Report.