A new word in gene therapy
Self-destructing vectors
NanoNewsNet based on UT Dallas: Team Creates New Approach to Gene TherapyBioengineers from The University of Texas at Dallas have created a new gene delivery system that avoids the risks associated with the permanent residence of a therapeutic gene in a cell.
On its basis, a new strategy of gene therapy for the treatment of diseases can be developed.
According to the author of the development, graduate student of the School of Engineering and Computer Science Eric Johnson (Erik Jonsson School of Engineering and Computer Science) Richard Taplin Moore (Richard Taplin Moore), in comparison with other currently developed methods of gene therapy, his approach has a number of clear advantages. The scientist and his colleagues published their article in the journal Nuclear Acids Research (Moore et al., CRISPR-based self-cleansing mechanism for controllable gene delivery in human cells).
"With other gene therapy approaches, the delivered therapeutic genetic information can be stored in the patient's body for a long time, potentially his entire life," explains Moore. "This irreversibility is one of the reasons why it is so difficult for gene therapy methods to obtain permission for use."
In their article, the researchers describe experiments conducted to prove the validity of their concept, in which a gene carrying instructions for the synthesis of a certain protein "receives an order" to begin self-destruction as soon as the cell reads its instructions and synthesizes a certain amount of the protein encoded by it. Working with isolated human kidney cells, the scientists successfully delivered and then destroyed a test gene encoding a red fluorescent protein.
To determine how well this system can work in a living organism (and whether it can at all), additional research is needed. But such a delivery system assumes more reliable control over the amount of protein synthesized by the cell. In addition, since there are no irreversible changes in the DNA of the cell, this method allows you to bypass the potential problems that may arise if the gene is delivered to the wrong region of the genome.
"Our goal was to create a self–destructing therapeutic gene delivery system that allows for more efficient control of delivered DNA by limiting the time it stays in cells," Moore continues.
The genes located in the nucleus of each cell and consisting of DNA contain instructions for protein synthesis. Special cellular mechanisms "read" these instructions and build proteins based on them, which then perform various functions necessary to maintain life. Damaged or mutated genes cause the appearance of proteins in the cell with impaired function or the absence of corresponding proteins, which leads to the development of various diseases.
The goal of gene therapy is to replace defective genes with their healthy versions. As a rule, healthy genes are "packaged" into a delivery mechanism called a vector that transports genetic material inside cells. When using traditional approaches, the gene delivered to the cell is integrated into its genome forever.
For all its promise, this method of gene therapy is fraught with serious risks. Embedding a therapeutic gene in the DNA of a cell in the "wrong" place, for example, too close to a gene associated with the development of cancer, can activate other genes, as a result of which the patient may have health problems that will persist throughout his life. To a large extent, this is why the US Food and Drug Administration has not yet approved the commercial use of any of these methods, although clinical trials of many gene therapy methods are being conducted around the world today.
Having adopted synthetic biology, scientists from UT Dallas approached the problem from scratch. They combined the genes of a cow, anemone, bacteria and a virus that infects insects, and created a delivery vector from these genes. In their native organism, each gene performs a specific function, but their new configuration allowed them to use these functions for new purposes.
For example, one of the bacterial genes included in the vector contains instructions for the synthesis of the protein caspase Cas9, which cuts and destroys other genes. In bacteria, Cas9 helps to fight the invasion of foreign genetic information, but in the synthetic vector it is modified in such a way that it serves as a self-destruction mechanism of the vector itself.
Diagram from an article in Nucleic Acids Research – VM
"When we first started our project, we treated it like a Mission Impossible TV series. This reflected both the initial difficulties in achieving our goal and the fate of the messages in this series, where instructions for a team of secret agents are promptly self–destructed after they have been read or listened to," comments the study's leader, Dr. Leonidas Bleris, associate professor of bioengineering at UT Dallas. "In our experiments, cellular mechanisms "read" instructions in the vector and create a fluorescent protein based on them, as well as a protein that destroys the vector itself."
According to Dr. Bleris, this method is promising not only in terms of the delivery of genes encoding therapeutic proteins, but also for the protection of intellectual property.
"With this method, pharmaceutical companies could deliver a therapeutic vector and then cut it. It cannot be restored by anyone who would like to redesign it," the scientist concludes.
Portal "Eternal youth" http://vechnayamolodost.ru19.02.2015