‘Prime editing’ is what researchers are calling the proof-of-concept research that promises improved diagnostics and more effective treatments for patients with genetic defects
Known as Prime Editing, the scientists developed this technique as a more accurate way to edit Deoxyribonucleic acid (DNA). In a paper published in Nature, the authors claim prime editing has the potential to correct up to 89% of disease-causing genetic variations. They also claim prime editing is more powerful, precise, and flexible than CRISPR.
The research paper describes prime editing as a “versatile and precise genome editing method that directly writes new genetic information into a specified DNA site using a catalytically impaired Cas9endonuclease fused to an engineered reverse transcriptase, programmed with a prime editing guide RNA (pegRNA) that both specifies the target site and encodes the desired edit.”
And a Harvard Gazette article states, “Prime editing differs from previous genome-editing systems in that it uses RNA to direct the insertion of new DNA sequences in human cells.”
Assuming further research and clinical studies confirm the
viability of this technology, clinical laboratories would have a new diagnostic
service line that could become a significant proportion of a lab’s specimen
volume and test mix.
In that e-briefing we wrote that Liu “has led a team of scientists in the development of a gene-editing protein delivery system that uses cationic lipids and works on animal and human cells. The new delivery method is as effective as protein delivery via DNA and has significantly higher specificity. If developed, this technology could open the door to routine use of genome analysis, worked up by the clinical laboratory, as one element in therapeutic decision-making.”
Now, Liu has taken that development even further.
“A major aspiration in the molecular life sciences is the ability to precisely make any change to the genome in any location. We think prime editing brings us closer to that goal,” David Liu, PhD (above), Director of the Merkin Institute of Transformative Technologies in Healthcare at the Broad Institute, told The Harvard Gazette. “We’re not aware of another editing technology in mammalian cells that offers this level of versatility and precision with so few byproducts.” (Photo copyright: Broad Institute.)
Cell Division Not Necessary
CRISPR stands for Clustered Regularly Interspaced Short Palindromic Repeats. It is considered the most advanced gene editing technology available. However, it has one drawback not found in Prime Editing—CRISPR relies on a cell’s ability to divide to generate desired alterations in DNA—prime editing does not.
This means prime editing could be used to repair genetic mutations in cells that do not always divide, such as cells in the human nervous system. Another advantage of prime editing is that it does not cut both strands of the DNA double helix. This lowers the risk of making unintended, potentially dangerous changes to a patient’s DNA.
The researchers claim prime editing can eradicate long lengths of disease-causing DNA and insert curative DNA to repair dangerous mutations. These feats, they say, can be accomplished without triggering genome responses introduced by other forms of CRISPR that may be potentially harmful.
“Prime editors are more like word processors capable of
searching for targeted DNA sequences and precisely replacing them with edited
DNA strands,” Liu told NPR.
The scientists involved in the study have used prime editing to perform over 175 edits in human cells. In the test lab, they have succeeded in repairing genetic mutations that cause both Sickle Cell Anemia (SCA) and Tay-Sachs disease, NPR reported.
“Prime editing is really a step—and potentially a significant step—towards this long-term aspiration of the field in which we are trying to be able to make just about any kind of DNA change that anyone wants at just about any site in the human genome,” Liu told News Medical.
Additional Research Required, but Results are Promising
Prime editing is very new and warrants further
investigation. The researchers plan to continue their work on the technology by
performing additional testing and exploring delivery mechanisms that could lead
to human therapeutic applications.
“Prime editing should be tested and optimized in as many cell types as researchers are interested in editing. Our initial study showed prime editing in four human cancer cell lines, as well as in post-mitotic primary mouse cortical neurons,” Liu told STAT. “The efficiency of prime editing varied quite a bit across these cell types, so illuminating the cell-type and cell-state determinants of prime editing outcomes is one focus of our current efforts.”
Although further research and clinical studies are needed to
confirm the viability of prime editing, clinical laboratories could benefit
from this technology. It’s worth watching.
Using animal blood, the researchers hope to improve the accuracy of AI driven diagnostic technology
What does a cheetah, a tortoise, and a Humboldt penguin have
in common? They are zoo animals helping scientists at Saarland University in
Saarbrücken, Germany, find biomarkers that can help computer-assisted diagnoses
of diseases in humans at early stages. And they are not the only animals
lending a paw or claw.
In their initial research, the scientists used blood samples
that had been collected during routine examinations of 21 zoo animals between
2016 and 2018, said a news
release. The team of bioinformatics
and human genetics experts
worked with German zoos Saarbrücken and Neunkircher for the study. The project
progresses, and thus far, they’ve studied the blood of 40 zoo animals, the
release states.
This research work may eventually add useful biomarkers and
assays that clinical
laboratories can use to support physicians as they diagnose patients,
select appropriate therapies, and monitor the progress of their patients. As medical
laboratory scientists know, for many decades, the animal kingdom has been
the source of useful insights and biological materials that have been
incorporated into laboratory assays.
“Measuring the molecular blood profiles of animals has never
been done before this way,” said Andreas
Keller, PhD, Saarland University Bioinformatics Professor and Chair for
Clinical Bioinformatics, in the news release. The Saarland researchers published
their findings in Nucleic Acids
Research, an Oxford
Academic journal.
“Studies on sncRNAs [small non-coding RNAs] are often largely based on homology-based information, relying on genomic sequence similarity and excluding actual expression data. To obtain information on sncRNA expression (including miRNAs, snoRNAs, YRNAs and tRNAs), we performed low-input-volume next-generation sequencing of 500 pg of RNA from 21 animals at two German zoological gardens,” the article states.
Can Animals Improve the Accuracy of AI to Detect Disease
in Humans?
However, the researchers perceived an inability for AI and machine learning to
discern real biomarker patterns from those that just seemed to fit.
“The machine learning methods recognize the typical
patterns, for example for a lung tumor or Alzheimer’s disease. However, it is
difficult for artificial intelligence to learn which biomarker patterns are
real and which only seem to fit the respective clinical picture. This is where
the blood samples of the animals come into play,” Keller states in the news
release.
“If a biomarker is evolutionarily conserved, i.e. also
occurs in other species in similar form and function, it is much more likely
that it is a resilient biomarker,” Keller explained. “The new findings are now
being incorporated into our computer models and will help us to identify the
correct biomarkers even more precisely in the future.”
Andreas Keller, PhD (left), and zoo director Richard Francke (right), hold a pair of radiated tortoises that participated in the Saarland University study. (Photo copyright: Oliver Dietze/Saarland University.)
“Because blood can be obtained in a standardized manner and
miRNA expression patterns are technically very stable, it is easy to accurately
compare expression between different animal species. In particular, dried blood
spots or microsampling devices appear to be well suited as containers for
miRNAs,” the researchers wrote in Nucleic Acids Research.
Animal species that participated in the study include:
Additionally, human volunteers contributed blood specimens
for a total of 19 species studied. The scientists reported success in capturing
data from all of the species. They are integrating the information into their
computer models and have developed a public database of their
findings for future research.
“With our study, we provide a large collection of small RNA
NGS expression data of species that have not been analyzed before in great
detail. We created a comprehensive publicly available online resource for
researchers in the field to facilitate the assessment of evolutionarily
conserved small RNA sequences,” the researchers wrote in their paper.
Clinical Laboratory Research and Zoos: A Future
Partnership?
This novel involvement of zoo animals in research aimed at improving
the ability of AI driven diagnostics to isolate and identify human disease is
notable and worth watching. It is obviously pioneering work and needs much
additional research. At the same time, these findings give evidence that there
is useful information to be extracted from a wide range of unlikely sources—in
this case, zoo animals.
Also, the use of artificial intelligence to search for
useful patterns in the data is a notable part of what these researchers
discovered. It is also notable that this research is focused on sequencing DNA
and RNA of the animals involved with the goal of identifying sequences that are
common across several species, thus demonstrating the common, important
functions they serve.
In coming years, those clinical laboratories doing genetic
testing in support of patient care may be incorporating some of this research
group’s findings into their interpretation of certain gene sequences.
According to the researchers, the finding could reveal athletes who removed their blood, took out the red blood cells, and transfused the cells into their bodies before competition. When conducted by medical laboratory professionals, such autologous blood therapies can enhance oxygen intake and increase performance during sports. However, these “self-transfusions” have been difficult to detect using current methods and that highlights the importance of ensuring these procedures are carried out by authorized healthcare facilities.
The World Anti-Doping Agency (WADA), an international organization aimed at research and education for doping-free sport, funded the Duke University research. WADA currently uses the Athlete Biological Passport to assess, over time, competitors’ body chemistries.
As the Duke researchers explored nucleic acids in red blood cells, they found that the cells actually do have a nucleus, contrary to popular belief. From there, they honed in on RNA.
Short RNA pieces, called microRNA (miRNA), control production of proteins in a cell, according to the researchers.
“While once thought to lack nucleic acids, red blood cells actually contain diverse and abundant RNA species,” the scientists noted in their paper. “In addition, proteomic analyses of red blood cells have identified the presence of Argonaute 2 (AGO2), supporting the regulatory function of miRNAs.”
The methodology Duke researchers followed involved these steps, among others:
Three units of blood were drawn from volunteers;
The researchers removed the white blood cells and about 80% of the plasma;
The remaining red blood cells were pure, just as they would need to be by someone doing autologous transfusion;
The researchers analyzed cell RNA samples at specific daily intervals: 1, 3, 7, 10, 14, 28, 36, and, 42 days;
They then compared samples to day 1 and recorded changes in RNA due to storage.
The researchers found:
Two types of miRNA increased during storage and two declined; and,
miR-720 had the most dramatic and consistent changes.
They concluded that finding increased miR-720 in athletes’ blood could be used as a biomarker for detecting stored red blood cells, which could indicate blood doping had taken place.
“The difficulty has been that the tests [WADA] have couldn’t tell the difference between a young blood cell and an old one,” Jen-Tsan Ashley Chi, MD, PhD, lead researcher on the study and Duke’s Associate Professor in Molecular Genetics and Microbiology, noted in the news release. “This increase in miR-720 is significant enough and consistent enough that it could be used as a biomarker for detecting stored red blood cells.” Chi is affiliated with Duke’s Center for Genomic and Computational Biology. (Photo copyright: Duke University.)
Implications for Detecting Blood Doping
How does this help clinical laboratories detect blood doping in athletes?
The researchers explained that RNA changes were, indeed, tell-tale signs of old blood cells circulating with normal cells. Those old blood cells could identify an athlete who did a self-transfusion of their blood before a competition.
However, before the test is used in sports more research is needed. Activity by the enzyme angiogenin in stored cells also is worthy of more exploration, as is its role in breaking apart larger RNA, the researchers noted.
“While autologous blood transfusions in athletes is very difficult to identify using conventional tests, it may be detectable based on the presence of red blood cells with levels of miR-720 significantly higher than the normal circulating cells. Further investigations will be necessary to identify the signals during red blood cell storage that stimulate angiogenin activation,” the study paper concluded.
Clinical Laboratories Involved in Sports Testing
In its 2017 Anti-Doping Testing Figures Report, WADA reported 322,050 samples were analyzed, a 7.1% increase from 300,565 samples in 2016. WADA accredits medical laboratories worldwide for conducting such analyses according to the organization’s code. This presents opportunities in sports medicine for medical laboratories to increase revenue through a new line of diagnostic tests.
The Duke study exemplifies how clinical laboratories can extend their services beyond patient care and enter a new realm of leveling playing fields worldwide.
CRISPR-Cas9 connection to cancer prompts research to investigate different approaches to gene editing
Dark Daily has covered CRISPR-Cas9 many times in previous e-briefings. Since its discovery, CRISPR, or Clustered Regularly Interspaced Short Palindromic Repeats, has been at the root of astonishing breakthroughs in genetic research. It appears to fulfill precision medicine goals for patients with conditions caused by genetic mutations and has anatomic pathologists, along with the entire scientific world, abuzz with the possibilities such a tool could bring to diagnostic medicine.
All of this research has contributed to a deeper understanding of how cells function. However, as is often the case with new technologies, unforeseen and problematic questions also have arisen.
“Here we report significant on-target mutagenesis, such as large deletions and more complex genomic rearrangements at the targeted sites in mouse embryonic stem cells, mouse hematopoietic progenitors, and a human differentiated cell line,” wrote the authors in their introduction.
Another study, this one conducted by biomedical researches at Cambridge, Mass., and published in Nature, describes possible toxicity caused by Cas9.
“Our results indicate that Cas9 toxicity creates an obstacle to the high-throughput use of CRISPR-Cas9 for genome engineering and screening in hPSCs [human pluripotent stem cells]. Moreover, as hPSCs can acquire P53 mutations, cell replacement therapies using CRISPR-Cas9-enginereed hPSCs should proceed with caution, and such engineered hPSCs should be monitored for P53 function.”
Essentially what both groups of researchers found is that CRISPR-Cas9 cuts through the double helix of DNA, which the cell responds to as it would any injury. A gene called p53 then directs a cellular “first-aid kit” to the “injury” site that either initiates self-destruction of the cell or repairs the DNA.
Therefore, in some instances, CRISPR-Cas9 is inefficient because the repaired cells continue to function. And, the repair process involves the p53 gene. P53 mutations have been implicated in ovarian, colorectal, lung, pancreatic, stomach, liver, and breast cancers.
Though important, some experts are downplaying the significance of the findings.
Erik Sontheimer, PhD (above), Professor, RNA Therapeutics Institute, at the University of Massachusetts Medical School, told Scientific American that the two studies are important, but not show-stoppers. “This is something that bears paying attention to, but I don’t think it’s a deal-breaker,” he said. (Photo copyright: University of Massachusetts.)
“It’s something we need to pay attention to, especially as CRISPR expands to more diseases. We need to do the work and make sure edited cells returned to patients don’t become cancerous,” Sam Kulkarni, PhD, CEO of CRISPR Therapeutics, told Scientific American.
Both studies are preliminary. The implications, however, is in how genes that have become corrupted are used.
A team from the Salk Institute may have found a solution. They are investigating a different enzyme—Cas13d—which, in conjunction with CRISPR would target RNA rather than DNA. “DNA is constant, but what’s always changing are the RNA messages that are copied from the DNA. Being able to modulate those messages by directly controlling the RNA has important implications for influencing a cell’s fate,” Silvana Konermann, PhD, a Howard Hughes Medical Institute (HHMI) Hanna Gray Fellow and member of the research team at Salk, said in a news release.
The Salk team published their findings in the journal Cell. The paper describes how “scientists from the Salk Institute are reporting for the first time the detailed molecular structure of CRISPR-Cas13d, a promising enzyme for emerging RNA-editing technology. They were able to visualize the enzyme thanks to cryo-electron microscopy (cryo-EM), a cutting-edge technology that enables researchers to capture the structure of complex molecules in unprecedented detail.”
The researchers think that CRISPR-Cas13d may be a way to make the process of gene editing more effective and allow for new strategies to emerge. Much like how CRISPR-Cas9 led to research into recording a cell’s history and to tools like SHERLOCK (Specific High-sensitivity Enzymatic Reporter unLOCKing), a new diagnostic tool that works with CRISPR and changed clinical laboratory diagnostics in a foundational way.
Each discovery will lead to more branches of inquiry and, hopefully, someday it will be possible to cure conditions like sickle cell anemia, dementia, and cystic fibrosis. Given the high expectations that CRISPR and related technologies can eventually be used to treat patients, pathologists and medical laboratory professionals will want to stay informed about future developments.
Identifying patients who will likely develop prolonged concussion symptoms could lead to new clinical laboratory tests and personalized medicine treatments
Researchers are homing in on a new diagnostic assay for concussion that could potentially generate significant numbers of test referrals to the nation’s clinical laboratories. This innovative work is targeting how concussions are diagnosed and treated.
Each year, thousands of children receive sports-related injuries, including concussions. There are ways for anatomic pathologists and hospital medical laboratories to diagnose concussions; however, testing can be invasive and doesn’t always reveal a complete picture of the injury state.
Additionally, about one third of children with concussions develop prolonged symptoms. However, when prescribing treatment plans, physicians have been unable to predict which patients are likely to recover quickly versus those who will have a longer recovery.
Now, researchers at Penn State College of Medicine (Penn State) believe they have discovered five microRNAs in saliva that could be used to identify patients who will likely experience prolonged concussion symptoms even one month after the initial injury.
The study also found that certain materials in saliva can help diagnose the severity of concussions and could hold the key to more effective clinical laboratory tests and personalized medicine treatments.
The Penn State researchers published their study results in JAMA Pediatrics, a publication of the Journal of the American Medical Association (JAMA).
Concussion Leading Sports-related Brain Injury
There are approximately 3.8 million sports and recreation-related traumatic brain injuries in the United States each year and the majority of those cases are concussions, according to The Concussion Place. Most concussions treated in emergency rooms are due to falls, motor-vehicle related injuries, being struck by an object, assaults, or playing sports.
Also known as mild traumatic brain injuries (mTBI), concussions are caused by blows or jolts to the head or body that cause the brain to move with excessive force inside the skull. The sudden impact damages brain cells and causes chemical changes within the brain that alter normal functioning. Though usually not life threatening, the damage can be serious and linger for months.
Symptoms of concussion include: headaches, fatigue, nausea, vomiting, dizziness, balance problems, confusion, memory problems, sleep disturbances, and double or blurry vision. Symptoms usually occur immediately, but could take days or even weeks to appear.
Identifying Severity/Predicting Prolonged Symptoms of Traumatic Brain Injuries
After a concussion occurs, brain cells release small fragments of genetic material known as microRNAs while they attempt to repair themselves. A portion of these microRNAs appear in the injured person’s blood and saliva.
In order to determine whether these microRNAs could be used to determine the severity of a traumatic brain injury and predict whether prolonged symptoms would occur, the prospective cohort study researchers gathered saliva samples from 52 concussion patients between the ages of seven and 21:
The average age of the subjects was 14;
Twenty-two of the participants were female;
They were all athletes; and,
The majority of the samples were collected one to two weeks after the initial injury.
The researchers examined distinct microRNAs in the samples and identified some that enabled them to predict how long a patient’s concussion symptoms might last. In addition, they found one microRNA in children and young adults that accurately predicted which subjects would experience memory and problem-solving difficulties as part of their symptomatology.
The researchers also evaluated the concussion patients using the Sport Concussion Assessment Tool (SCAT-3), Third Edition. Physicians use this questionnaire to assess the symptoms and severity of concussions. The researchers also asked the parents of the concussed patients for observations about their children’s symptoms.
During follow up visits, which occurred at four- and eight-week increments following the original assessment, the Penn State researchers collected additional saliva samples and re-evaluated the patients using SCAT-3.
New Biomarkers Based on MicroRNAs Instead of Protein
“There’s been a big push recently to find more objective markers that a concussion has occurred, instead of relying simply on patient surveys,” Steven Hicks, MD, PhD, Assistant Professor of Pediatrics, Penn State College of Medicine, Hershey, Pa., one of the study researchers, told Penn State News.
“Previous research has focused on proteins, but this approach is limited because proteins have a hard time crossing the blood-brain barrier. What’s novel about this study is we looked at microRNAs instead of proteins, and we decided to look in saliva rather than blood,” he noted.
According to Steven Hicks, MD, PhD (above), who worked on the Penn State College of Medicine study, microRNAs could be more accurate than the traditional questionnaire when diagnosing and forecasting the effects of concussions. “The microRNAs were able to predict whether symptoms would last beyond four weeks with about 85% accuracy,” he told Penn State News. “In comparison, using the SCAT-3 report of symptoms alone is about 64% accurate. If you just go off the parent’s report of symptoms, it goes down to the mid-50s. In this pilot study, these molecular signatures are outperforming survey tools.” (Photo copyright: MD Magazine.)
The goal of this research was to develop a way to definitively ascertain that a concussion had occurred, predict the length and type of symptoms, and then use that data to improve and personalize care for children and young adults who have had a concussion.
“With that knowledge physicians could make more informed decisions about how long to hold a child out of sports, whether starting more aggressive medication regimens might be warranted, or whether involving a concussion specialist might be appropriate,” Hicks told MD Magazine. “Anytime we can use accurate, objective measures to guide medical care, I think that represents an opportunity to improve concussion treatment.”
Further research and clinical trials will be needed to solidify the effectiveness and accuracy of these new biomarkers. However, a rapid, non-invasive saliva test that can determine the severity of a concussion, and predicted whether prolonged symptoms will likely occur, would be widely used and could be an important assay for clinical laboratories. Particularly those associated with hospital medical laboratories and emergency rooms.
