Salk researchers have discovered, for the first time, how to place DNA in specific locations in non-dividing cells
Salk Institute researchers have discovered a holy grail of gene editing—the ability to, for the first time, insert DNA at a target location into the non-dividing cells that make up the majority of adult organs and tissues. The technique, which the team showed was able to partially restore visual responses in blind rodents, will open new avenues for basic research and a variety of treatments, such as for retinal, heart and neurological diseases.
“We are very excited by the technology we discovered because it’s something that could not be done before,” says Juan Carlos Izpisua Belmonte, a professor in Salk’s Gene Expression Laboratory and senior author of the paper published on November 16, 2016 in Nature. “For the first time, we can enter into cells that do not divide and modify the DNA at will. The possible applications of this discovery are vast.”
Until now, techniques that modify DNA—such as the CRISPR-Cas9 system—have been most effective in dividing cells, such as those in skin or the gut, using the cells’ normal copying mechanisms. The new Salk technology is ten times more efficient than other methods at incorporating new DNA into cultures of dividing cells, making it a promising tool for both research and medicine. But, more importantly, the Salk technique represents the first time scientists have managed to insert a new gene into a precise DNA location in adult cells that no longer divide, such as those of the eye, brain, pancreas or heart, offering new possibilities for therapeutic applications in these cells.
To achieve this, the Salk researchers targeted a DNA-repair cellular pathway called NHEJ (for “non-homologous end-joining”), which repairs routine DNA breaks by rejoining the original strand ends. They paired this process with existing gene-editing technology to successfully place new DNA into a precise location in non-dividing cells.
“Using this NHEJ pathway to insert entirely new DNA is revolutionary for editing the genome in live adult organisms,” says Keiichiro Suzuki, a senior research associate in the Izpisua Belmonte lab and one of the paper’s lead authors. “No one has done this before.”
First, the Salk team worked on optimizing the NHEJ machinery for use with the CRISPR-Cas9 system, which allows DNA to be inserted at very precise locations within the genome. The team created a custom insertion package made up of a nucleic acid cocktail, which they call HITI, or homology-independent targeted integration. Then they used an inert virus to deliver HITI’s package of genetic instructions to neurons derived from human embryonic stem cells.
“That was the first indication that HITI might work in non-dividing cells,” says Jun Wu, staff scientist and co-lead author. With that feat under their belts, the team then successfully delivered the construct to the brains of adult mice. Finally, to explore the possibility of using HITI for gene-replacement therapy, the team tested the technique on a rat model for retinitis pigmentosa, an inherited retinal degeneration condition that causes blindness in humans. This time, the team used HITI to deliver to the eyes of 3-week-old rats a functional copy of Mertk, one of the genes that is damaged in retinitis pigmentosa. Analysis performed when the rats were 8 weeks old showed that the animals were able to respond to light, and passed several tests indicating healing in their retinal cells.
“We were able to improve the vision of these blind rats,” says co-lead author Reyna Hernandez-Benitez, a Salk research associate. “This early success suggests that this technology is very promising.”
The team’s next steps will be to improve the delivery efficiency of the HITI construct. As with all genome editing technologies, getting enough cells to incorporate the new DNA is a challenge. The beauty of HITI technology is that it is adaptable to any targeted genome engineering system, not just CRISPR-Cas9. Thus, as the safety and efficiency of these systems improve, so too will the usefulness of HITI.
“We now have a technology that allows us to modify the DNA of non-dividing cells, to fix broken genes in the brain, heart and liver,” says Izpisua Belmonte. “It allows us for the first time to be able to dream of curing diseases that we couldn’t before, which is exciting.”
TSRI Study Points Way to Better Vaccines and New Autoimmune Therapies
A new international collaboration involving scientists at The Scripps Research Institute (TSRI) opens a door to influencing the immune system, which would be useful to boost the effectiveness of vaccines or to counter autoimmune diseases such as lupus and rheumatoid arthritis.
The research, published August 1, 2016, in The Journal of Experimental Medicine, focused on a molecule called microRNA-155 (miR-155), a key player in the immune system’s production of disease-fighting antibodies.
“It’s very exciting to see exactly how this molecule works in the body,” said TSRI Associate Professor Changchun Xiao, who co-led the study with Professor Wen-Hsien Liu of Xiamen University in Fuijan province, China.
An Immune System Tango
Our cells rely on molecules called microRNAs (miRNAs) as a sort of “dimmer switches” to carefully regulate protein levels and combat disease.
“People know miRNAs are involved in immune response, but they don’t know which miRNAs and how exactly,” explained TSRI Research Associate Zhe Huang, study co-first author with Liu and Seung Goo Kang of TSRI and Kangwon National University.
In the new study, the researchers focused on the roles of miRNAs during the critical period when the immune system first detects “invaders” such as viruses or bacteria. At this time, cells called T follicular helpers proliferate and migrate to a different area of the lymph organs to interact with B cells.
“They do a sort of tango,” said Xiao.
This interaction prompts B cells to mature and produce effective antibodies, eventually offering long-term protection against infection.
“The next time you encounter that virus, for example, the body can respond quickly,” said Xiao.
Identifying a Dancer
Using a technique called deep sequencing, the team identified miR-155 as a potential part of this process. Studies in mouse models suggested that miR-155 works by repressing a protein called Peli1. This leaves a molecule called c-Rel free to jump in and promote normal T cell proliferation.
This finding could help scientists improve current vaccines. While vaccines are life-saving, some vaccines wear off after a decade or only cover around 80 percent of those vaccinated.
“If you could increase T cell proliferation using a molecule that mimics miR-155, maybe you could boost that to 90 to 95 percent,” said Xiao. He also sees potential for using miR-155 to help in creating longer-lasting vaccines.
The research may also apply to treating autoimmune diseases, which occur when antibodies mistakenly attack the body’s own tissues. Xiao and his colleagues think an mRNA inhibitor could dial back miR-155’s response when T cell proliferation and antibody production is in overdrive.
For the next stage of this research, Xiao plans to collaborate with scientists on the Florida campus of TSRI to test possible miRNA inhibitors against autoimmune disease.
Researchers uncover molecular switch to make effective sugar-responsive, insulin-releasing cells in a dish, offering hope for diabetes therapy
Salk scientists have solved a longstanding problem in the effort to create replacement cells for diabetic patients. The team uncovered a hidden energy switch that, when flipped, powers up pancreatic cells to respond to glucose, a step that eluded previous research. The result is the production of hundreds of millions of lab-produced human beta cells—able to relieve diabetes in mice.
For more than a decade, scientists across the globe strived to replace failing pancreatic beta cells linked to immune destruction in children (type 1 diabetes) or obesity-associated diabetes in adults (type 2 diabetes). Although cells made in a dish were able to produce insulin, they were sluggish or simply unable to respond to glucose.
“We found the missing energy switch needed to produce robust and functional human beta cells, potentially turning this discovery into a viable treatment for human diabetes,” says Ronald Evans, co-senior author and director of the Gene Expression Laboratory at Salk. The new work was published in Cell Metabolism on April 12, 2016.
The Salk Institute for Biological Studies is an independent, non-profit, scientific research institute located in La Jolla, California.
It was founded in 1960 by Jonas Salk, the developer of the polio vaccine; among the founding consultants were Jacob Bronowski and Francis Crick. Building did not start until spring of 1962. The institute consistently ranks among the top institutions in the US in terms of research output and quality in the life sciences. In 2004, the Times Higher Education Supplement ranked Salk as the world’s top biomedicine research institute, and in 2009 it was ranked number one globally by ScienceWatch in the neuroscience and behavior areas.
The institute employs 850 researchers in 60 research groups and focuses its research in three areas: Molecular Biology and Genetics; Neurosciences; and Plant Biology. Research topics include cancer, diabetes, birth defects, Alzheimer’s disease, Parkinson’s disease, AIDS, and the neurobiology of American Sign Language. The March of Dimes provided the initial funding and continues to support the institute. Current research is funded by a variety of organizations, such as the NIH, the HHMI and private organizations such as Paris-based Ipsen and the Waitt Family Foundation. In addition, the internally administered Innovation Grants Program encourages cutting-edge high-risk research. The institute appointed genome biologist Eric Lander and stem cell biologist Irving Weissman as non-resident fellows in November 2009.
The campus was designed by Louis Kahn. Salk had sought to make a beautiful campus in order to draw the best researchers in the world. Salk and Kahn having both descended from Russian Jewish parents that had immigrated to the United States had a deeper connection than just mere partners on an architectural project. The results of their connection is seen in the design that resulted from their collaboration. The original buildings of the Salk Institute were designated as a historical landmark in 1991. The entire 27-acre (11 ha) site was deemed eligible by the California Historical Resources Commission in 2006 for listing on the National Register of Historic Places.
The Latest Updated Research News:
Salk Institute for Biological Studies research articles from Innovation Toronto
- Experimental drug J147 targeting Alzheimer’s disease shows anti-aging effects – November 14, 2015
- Salk scientists use sound waves to control brain cells – September 16, 2015
- Scientists discover key driver of human aging – May 1, 2015
- Breakthrough in ‘editing’ mitochondrial disease DNA – April 27, 2015
- Scientists discover an on/off switch for aging cells – September 22, 2014
- Simple Method Turns Human Skin Cells Into Immune-Fighting White Blood Cells – September 22, 2014
- Salk Scientists Uncover New Clues to Repairing an Injured Spinal Cord – August 5, 2014
- One injection stops diabetes in its tracks – July 17, 2014
- Salk scientists develop faster, safer method for producing stem cells – May 25, 2014
- Drug blocks light sensors in eye that may trigger migraine attacks
- Surviving Drought
- Neurons Derived from Cord Blood Cells May Represent New Therapeutic Option
- Study May Offer Drug-Free Intervention to Prevent Obesity and Diabetes
- Discovery May Lead to Safer Treatments for Asthma, Allergies and Arthritis
- Long-Lived Fruit Flies Offer Clues to Slowing Human Aging and Fighting Disease
- Studying Mental Illness in a Dish