Engineers devise ways to selectively turn on RNA therapy in human cells | MIT News

Researchers at MIT and Harvard University have designed a way to selectively enable gene therapy in target cells, including human cells. Their technique can detect specific messenger RNA sequences in cells, which trigger the production of specific proteins from transgenes or artificial genes.

Since transgenes can have negative and even dangerous effects when expressed in the wrong cells, researchers wanted to find a way to reduce the off-target effects of gene therapy. One way to distinguish between different types of cells is to read the intracellular RNA sequences that differ from tissue to tissue.

Researchers have developed a technology that can fine-tune gene therapy in applications ranging from regenerative medicine to cancer treatment by finding a way to generate a transgene only after “reading” a specific RNA sequence in the cell. Did. For example, researchers could create new treatments to destroy tumors by identifying cancer cells, producing toxic proteins just inside those cells, and designing a system that kills them in the process. There is sex.

“This opens up new control circuits in new areas of RNA therapies and opens up next-generation RNA therapies that can only be turned on in cell-specific or tissue-specific ways,” says Termeer. James Collins said. Senior Author of Biomedical Engineering and Science and Research at MIT’s Institute for Biomedical Engineering (IMES) and Department of Bioengineering.

This highly targeted approach, based on the genetic factors that the virus uses to control genetic translation in host cells, may help avoid some of the side effects of treatment that affect the whole body. The researchers say.

Evan Zhao, a researcher at the Wyss Institute for Biologically Inspired Engineering at Harvard University, and Angelo Mao, a MIT postdoc and technical fellow at the Wyss Institute, today Nature biotechnology..

RNA detection

A messenger RNA (mRNA) molecule is a sequence of RNA that encodes instructions for building a particular protein. A few years ago, Collins and his colleagues developed a method that uses RNA detection as a trigger to stimulate cells to produce specific proteins in bacterial cells. This system works by introducing an RNA molecule called a “toehold” that binds to the ribosome binding site of an mRNA molecule that encodes a particular protein. (The ribosome is where the protein is assembled according to the instructions of the mRNA.) This binding prevents the mRNA from being translated into the protein because it cannot attach to the ribosome.

The RNA scaffold also contains a sequence that can bind to another mRNA sequence that acts as a trigger. When this target mRNA sequence is detected, the toes release the grip and the blocked mRNA is translated into protein. This mRNA can encode any gene, such as a fluorescent reporter molecule. The fluorescent signal provides researchers with a way to visualize whether a target mRNA sequence has been detected.

In a new study, researchers attempted to create a similar system that could be used in eukaryotic (non-bacterial) cells, including human cells.

Due to the more complex translation of genes in eukaryotic cells, it was not possible to import the genetic components used in bacteria into human cells. Instead, researchers used the system that the virus uses to hijack eukaryotic cells and translate their viral genes. This system is composed of RNA molecules called internal ribosome entry sites (IRES), which can mobilize ribosomes to initiate the translation of RNA into proteins.

“These are complex RNA folds that the virus has developed to hijack the ribosome because it needs to find some way to express the protein,” says Zhao.

Researchers started with IRES, which naturally occurs from various types of viruses, and designed them to contain sequences that bind to trigger mRNA. When an engineered IRES is inserted into a human cell prior to the transgene, it blocks translation of that gene unless the trigger mRNA is detected intracellularly. The trigger restores the IRES and allows the gene to be translated into a protein.

Targeted treatment

Researchers have used this technique to develop scaffolds that can detect a variety of different triggers in human and yeast cells. First, they showed that they could detect mRNAs encoding viral genes from Zika virus and SARS-CoV-2 virus. Researchers say one possible application for this could be to design T cells that detect and respond to viral mRNA during infection.

They also designed scaffolding molecules that can detect mRNAs of naturally occurring proteins in human cells that may help reveal cellular conditions such as stress. As an example, they have shown that they can detect the expression of heat shock proteins that cells make when exposed to high temperatures.

Finally, researchers have shown that cancer cells can be identified by manipulating scaffolds that detect mRNA for tyrosinase, an enzyme that produces excess melanin in melanoma cells. This type of targeting allows researchers to develop treatments that induce the production of proteins that initiate cell death when cancerous proteins are detected intracellularly.

“The idea is that we can target our own RNA signatures to deliver therapeutics,” says Mao. “This may be a way to limit the expression of biomolecules to target cells or tissues.”

This new technology represents “a conceptual breakthrough in controlling and programming the behavior of mammalian cells,” said ETH Zurich’s professor of biotechnology and biotechnology, who was not involved in the study. Martin Hussenegger said. “This new technology sets new standards for processing human cells to sense and react to viruses such as Zika virus and SARS-CoV-2.”

All studies performed in this paper were performed on cells grown in the laboratory dish. Researchers are currently working on a delivery strategy that will allow the RNA components of the system to reach target cells in animal models.

This study was funded by BASF, the National Institutes of Health, the Takeda Pharmaceutical Company Award for Gastrointestinal Diseases, Inflammatory Bowel Disease, and the Schmidt Science Fellow Program.