Research on treating autism. Some symptoms can be inhibited
Using the CRISPR gene-editing method, researchers have managed to significantly attenuate some over-repetitive behaviors associated with autism in mice. Researchers developed a special technique for this using gold nanoparticles.
Researchers used gene editing techniqueóin CRISPR-Cas9 to alleviate some of theóre symptoms of autism in mice with a form of broken X chromosome syndrome, the most common known single cause of autism spectrum disorders. Syndromeó³³ broken X chromosome syndrome is characterized by a reduction in intellectual development. Someóre behavioral symptoms of the disease overlap with those characteristic of autism.
Technique developed at the University of California, Berkeley – UC Berkeley) uses gold nanoparticles to deliver a DNA-cutting enzyme to mózgu. The technique has been dubbed CRISPR-Gold. With it, scientists were able to edit the gene for the neurotransmitter receptor and reduce the repetitive behavior characteristic of fragile X syndrome (FXS).
CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) is a system used by bacteria to defend themselves against viruses. It is such a defense mechanism, a repeated sequence of fragmentsóin DNA. It was noticed by Yoshizumi Ishino in the late 1980s. Last century in the genome of the bacterium Escherichia coli. Theses mechanism contains information about the DNA of the virusóIn and in conjunction with DNA cutting enzyme – Cas9 endonuclease provides a defense system against viruses.
The CRISPR-Cas9 method itself works by recognizing foreign DNA through mRNA, whichóre is responsible for carrying genetic information. RNA is a guide to the DNA chain. Being able to find a precise location in the genome and bring the right enzyme there – Cas9. Cas9 protein acts like a pair of scissors – it cuts DNA at the exact spot indicated. At the next stage, some other precisely designed DNA fragment can be built into this selected DNA site.
Exaggerated repetitive behaviors are typical features of autism spectrum disorders. The successful reduction of these behaviors in mouse models of broken X chromosome syndrome demonstrates the potential application of this technique in other types of autism, for which theóhe genetic cause is known.
– In the case of autism, there are no effective therapies or cures yet, and many clinical trials for drugóin attacking proteins that cause autism have failed – said Hye Young Lee of the University of Texas at San Antonio. – This is the first case in whichórym we were able to edit the gene responsible for autism in mózg and demonstrate inhibition of symptomaticóin behavioral – she added.
– The really interesting thing is that Hye Young Lee was able to show that with CRISPR-Gold you can eliminate disease-causing genes and actually see quite significant behavioral changes in – noted Niren Murthy, professor of bioengineering at UC Berkeley.
Scientists still do not know the cause of autism spectrum disorder (ASD). About 30-35 percent. caseóin ASD is associated with rare genetic variants. In addition, environmental factors and róthat other mutations also play a role. People with ASD have problems interacting with other people. Often there are the aforementioned excessive repetitive behaviors, such as swaying or obsessively arranging toys in a straight line.
But the array of symptomsów is huge. These can include mild behavioral problems or debilitating compulsive behaviors, anxiety, cognitive disorders and many others. Because the symptoms of ASD are so zrósiblings, and the causes are not yet fully understood, diagnosis and treatment are very difficult.
While ASD appears to have rós multiple causes, including many genetic mutations, single gene disorders, as in the case of FXS, are a simpler way to investigate causes and develop potential therapies. ASD affects about one percent of. children, and cases of FXS occur in one in 4,000. boyców and one in 6,000. girls.
The new study is the first demonstration that the Cas9 protein can be transported into mózg to remove the gene and have a therapeutic effect. The introduction of Cas9 into the neuronóin the virus-mediatedów can create problems because the gene retains expression of the Cas9 enzyme, leading to random cutting of other genesów. CRISPR-Gold carries the Cas9 complex itself – purified Cas9 protein and guide RNA – directly into the cellórek, where it makes the cut and then disappears.
– If you use the virus in the CRISPR technique, you can’t control the amount of Cas9 protein and guide RNA, so virus injection could potentially lead to a problemów. With the CRISPR-Gold method, we can control the amount, którą we want to inject and która is likely to minimize the side effects of using CRISPR – explained Lee.
– The technique opens the door to treating róFGD conditionów – from opioid addictionów and bólu neuropathic to schizophrenia and epileptic seizures,” said Murthy.
In an experiment on FXS mice, researchers injected CRISPR-Gold carrying the Cas9 complex into the striatum, a region of the mózg known to mediate habit formationów, including those associated with repetitive behavior typical of ASD. Cas9 targeted the excitatory receptor, metabotropic glutamate receptor 5 (mGluR5), whichóry is involved in communication between neurons and is known to be dysregulated in FXS. By turning off the gene for mGluR5, researchers were able to suppress exaggerated signal transduction between cellsórkami and reduce repetitive behavior.
– Before this experiment, we did not know whether the mGluR5 receptor in the striatum was specificallyólently involved in exaggerated repetitive behavior; an important finding – emphasized Lee.
In FXS mice, repetitive behavior included obsessive digging and periodic jumping. After using CRISPR-Gold, digging was reduced by about 30 percent., a frequency of spikesóin decreased by 70 percent. In the experiment, about 50 percent of the geneómGluR5 in the striatum has been edited, reducing the number of receptor proteins by almost half.
In earlier studies, róThe technique uses gold nanoparticles covered with a dense network of chainsóbicians have been injecting nanoparticles carrying drugs into the bloodstream to block the same receptor. In these studies, some reductions in repetitive behavior were observed, but the mice became resistant to subsequent doses, as if their tolerance had increased.
Murthy is behind the development of the CRISPR-Gold method. His work focuses on ways to deliver drugsóIn and developing new antibioticsów. The technique uses gold nanoparticles coated with a dense network of chainsóIn DNA, które hold Cas9 molecules, whichóre in turn are a combination of enzyme to cut geneów and guide RNA. The whole is encapsulated in a polymer, whichóry helps it get into the right chambersórecords.
Last year, Murthy and his colleagues showed that CRISPR-Gold can transfer Cas9 into cellsórec muscle and replace the mutated gene with a normal gene to increase strength in mice with Duchenne muscular dystrophy'a. A new study shows that CRISPR-Gold can successfully introduce róCas9 to róof the comórek in mózgu.
– In the publication, we showed that we were able to edit not only neurons, but also microglia, które are part of the immune system mózgu and astrocytes, które support neurons – Murthy admitted, whichóry and his colleagues are developing and testing new CRISPR-Gold therapies for róof various diseasesób genetic. Edit comórek mózg gene opens the door to treating many disorders.