Understanding why some mutations impair normal bodily functions and contribute to cancer may lead to new clinical laboratory diagnostics
New insight into the human genome may help explain the ageing process and provide clues to improving human longevity that can be useful to clinical laboratories and researchers developing cancer diagnostics. A recent study conducted at the Wellcome Sanger Institute in Cambridge, United Kingdom, suggests that the speed of DNA errors in genetic mutations may play a critical role in the lifespan and survival of a species.
To perform their research, the scientists analyzed genomes from the intestines of 16 mammalian species looking for genetic changes. Known as somatic mutations, these mutations are a natural process that occur in all cells during the life of an organism and are typically harmless. However, some somatic mutations can impair the normal function of a cell and even play a role in causing cancer.
“Aging is a complex process, the result of multiple forms of molecular damage in our cells and tissues. Somatic mutations have been speculated to contribute to ageing since the 1950s, but studying them had remained difficult,” said Inigo Martincorena, PhD (above), Group Leader, Sanger Institute and one of the authors of the study. Greater understanding of the role DNA mutations play in cancer could lead to new clinical laboratory tools and diagnostics. (Photo copyright: Wellcome Sanger Institute.)
Lifespans versus Body Mass
The mammalian subjects examined in the study incorporated a wide range of lifespans and body masses and included humans, giraffes, tigers, mice, and the highly cancer-resistant naked mole-rat. The average number of somatic mutations at the end of a lifespan was around 3,200 for all the species studied, despite vast differences in age and body mass. It appears that species with longer lifespans can slow down their rate of genetic mutations.
The average lifespan of the humans used for the study was 83.6 years and they had a somatic mutation rate of 47 per year. Mice examined for the research endured 796 of the mutations annually and only lived for 3.7 years.
Species with similar amounts of the mutations had comparable lifespans. For example, the small, naked mole-rats analyzed experienced 93 mutations per year and lived to be 25 years of age. On the other hand, much larger giraffes encountered 99 mutations each year and had a lifespan of 24 years.
“With the recent advances in DNA sequencing technologies, we can finally investigate the roles that somatic mutations play in ageing and in multiple diseases,” said Inigo Martincorena, PhD, Group Leader, Sanger Institute, one of the authors of the study in a press release. He added, “That this diverse range of mammals end their lives with a similar number of mutations in their cells is an exciting and intriguing discovery.”
The scientists analyzed the patterns of the mutations and found that the somatic mutations accumulated linearly over time. They also discovered that the mutations were caused by similar mechanisms and the number acquired were relatively similar across all the species, despite a difference in diet and life histories. For example, a giraffe is typically 40,000 times larger than a mouse, but both species accumulate a similar number of somatic mutations during their lifetimes.
“The fact that differences in somatic mutation rate seem to be explained by differences in lifespan, rather than body size, suggests that although adjusting the mutation rate sounds like an elegant way of controlling the incidence of cancer across species, evolution has not actually chosen this path,” said Adrian Baez-Ortega, PhD, postdoctoral researcher at the Sanger Institute and one of the paper’s authors, in the press release.
“It is quite possible that every time a species evolves a larger size than its ancestors—as in giraffes, elephants, and whales—evolution might come up with a different solution to this problem. We will need to study these species in greater detail to find out,” he speculated.
Why Some Species Live Longer than Others
The researchers also found that the rate of somatic mutations decreased as the lifespan of each species increased which suggests the mutations have a likely role in ageing. It appears that humans and animals perish after accumulating a similar number of these genetic mutations which implies that the speed of the mutations is vital in ascertaining lifespan and could explain why some species live substantially longer than others.
“To find a similar pattern of genetic changes in animals as different from one another as a mouse and a tiger was surprising. But the most exciting aspect of the study has to be finding that lifespan is inversely proportional to the somatic mutation rate,” said Alex Cagan, PhD, Postdoctoral Fellow at the Sanger Institute and one of the authors of the study in the press release.
“This suggests that somatic mutations may play a role in ageing, although alternative explanations may be possible. Over the next few years, it will be fascinating to extend these studies into even more diverse species, such as insects or plants,” he noted.
Benefit of Understanding Ageing and Death
The scientists believe this study may provide insight to understanding the ageing process and the inevitability and timing of death. They surmise that ageing is likely to be caused by the aggregation of multiple types of damage to the cells and tissues suffered throughout a lifetime, including somatic mutations.
Some companies that offer genetic tests claim their products can predict longevity, despite the lack of widely accepted evidence that such tests are accurate within an acceptable range. Further research is needed to confirm that the findings of the Wellcome Sanger Institute study are relevant to understand the ageing process.
If the results are validated, though, it is probable that new direct-to-consumer (DTC) genetic tests will be developed, which could be a new revenue source for clinical laboratories.
DNA analysis of early plague victims pinpoints Black Death’s start on Silk Road trading communities in mountain region of what is now modern-day Kyrgyzstan in Central Asia
Microbiologists and clinical laboratory scientists will likely find it fascinating that an international team of scientists may have solved one of history’s greatest mysteries—the origin of the bubonic plague that ravaged Afro-Eurasia in the mid fourteenth century. Also known as the Black Death, the plague killed 60% of the population of Europe, Asia, and North Africa between 1346-1353 and, until now, the original source of this disease has largely gone unsolved.
In their study published in the journal Nature, titled, “The Source of the Black Death in Fourteenth-Century Central Eurasia,” the authors outlined their investigation of cemeteries in the Chüy Valley of modern-day Kyrgyzstan. The tombstone inscriptions showed a disproportionally high number of burials dating between 1338 and 1339 with inscriptions stating “pestilence” as the cause of death.
Archeological evidence combined with ancient DNA analysis of early plague victims enabled scientists to pinpoint the Black Death’s origins in Kyrgyzstan. “We have basically located the origin in time and space, which is really remarkable,” geneticist Johannes Krause, PhD (above), Professor at the Max Planck Institute for Evolutionary Anthropology, who co-led the study, told The Guardian. “We found not only the ancestor of the Black Death, but the ancestor of the majority of the plague strains that are circulating in the world today.” These new research findings may help microbiologists and clinical pathologists gain new insights into how current strains of Yersinia pestis can be better diagnosed. (Photo copyright: Max Planck Institute.)
Big Bang of Plague
Using 30 skeletons that were excavated from these cemeteries in the late 1880s and moved to St. Petersburg, Russia, the scientists analyzed the DNA of ancient pathogens recovered from the remains of seven people. They discovered Yersinia pestis (Y. pestis) DNA in three burials from Kara-Djigach, which lies in the foothills of the Tian Shan mountains.
According to another article in Nature, the scientists showed that a pair of full Y. pestis genomes from their data were direct ancestors of strains linked to the Black Death, and that the Kara-Djigach strain was an ancestor of the vast majority of Y. pestis lineages circulating today.
“It was like a big bang of plague,” Krause stated at a press briefing, Nature reported.
The research team concluded that the Tian Shan region was the location where Y. pestis first spread from rodents to people, and that the local marmot colonies likely the prevalent rodent carriers of plague.
“We found that modern strains [of the plague] most closely related to the ancient strain are today found in plague reservoirs around the Tian Shan mountains, so very close to where the ancient strain was found. This points to an origin of Black Death’s ancestor in Central Asia,” Krause explained in a Max Planck Institute news release.
He told Nature that fleas likely passed the marmot-based infection on to humans, sparking a local Kyrgyzstan epidemic. The disease then spread along the Silk Road trade routes, eventually reaching Europe, where rats (and the fleas that they carried) spread the disease.
Understanding Context of Plague
Writing in The Conversation, Associate Professor of Medieval and Environmental History Philip Slavin, PhD, University of Stirling, who co-authored the study, explained that Kara-Djigach is unlikely to be “the specific source of the pandemic,” but rather that the “disaster started somewhere in the wider Tian Shan area, perhaps not too far from that site,” where marmot colonies were likely the source of the 1338-1339 outbreak.
Making a modern-day comparison, Krause told Nature, “It is like finding the place where all the strains come together, like with coronavirus where we have Alpha, Delta, Omicron all coming from this strain in Wuhan.”
Slavin maintains that understanding the “big evolutionary picture” is key when studying the phenomenon of emerging epidemic diseases.
“It is important to see how these diseases develop evolutionary and historically, and avoid treating different strains as isolated phenomena,” he wrote in The Conversation. “To understand how the diseases develop and get transmitted, it is also crucial to consider the environmental and socioeconomic contexts.”
Scientists have spent centuries debating the source of the Black Death that devastated the medieval world. The multidisciplinary process used by the Slavin/Krause-led team provides a lesson to clinical laboratory managers and pathologists on the important role they play when collaborating with colleagues from different fields on scientific investigations.
By analyzing ancient poop, researchers have discovered how much the human microbiome has changed over the past millennium, what may have brought about the change, and how those changes formed today’s human microbiome
Two thousand year-old human poop has yielded new insights into the evolution of the microbial cells (microbiota) inhabiting today’s human gut—collectively known as the human microbiome—that could help pathologists and clinical laboratories better understand diseases that may be linked to gut bacteria.
A recent study conducted by an international team of scientists reveals that the gut bacteria of today’s humans may have been altered by the onset of modern processed foods, sanitation, and the use of antibiotics.
In “Reconstruction of Ancient Microbial Genomes from the Human Gut,” published in the journal Nature, the researchers wrote, “In this study, we establish that palaeofaeces [Paleofeces in the US] with well-preserved DNA are abundant sources of microbial genomes, including previously undescribed microbial species, that may elucidate the evolutionary histories of human microbiomes. Similar future studies tapping into the richness of palaeofaeces will not only expand our knowledge of the human microbiome but may also lead to the development of approaches to restore present-day gut microbiomes to their ancestral state.”
Ancient Poop Is a ‘Time Machine’ into the Human Microbiome
To perform the research for this study, scientists analyzed Deoxyribonucleic acid (DNA) from eight preserved, fossilized feces (coprolites) to gain insight into the gut bacteria of ancient communities. The samples used in the research were originally found in rock formations in Utah and Mexico and were preserved by dryness and stable temperatures. The coprolites were between 1,000 and 2,000 years old.
“These paleofeces are the equivalent of a time machine,” Justin Sonnenburg, PhD, Associate Professor, Microbiology and Immunology at Stanford University and co-author of the study, told Science. Tiny bits of food found in the coprolites indicated that the diet of the ancient people included:
The dried-out poop samples were first radiocarbon dated. Then, tiny fragments of the coprolites were rehydrated which allowed researchers to recover longer DNA strands than those found in previous, similar studies. This study compared the microbiome of the ancient populations to that of present-day individuals. The authors of the study suggest that during the past millennium, the human microbiome has lost dozens of bacterial species and has become less diverse.
Other research studies have linked lower diversity among gut bacteria to higher rates of modern diseases, such as diabetes, obesity, and allergies, Science noted.
“We really wanted to be able to go back in time and see when those changes [in the modern gut microbiome] came about, and what’s causing them,” Archeological Geneticist Christina Warinner, PhD, Assistant Professor of Anthropology at Harvard University and one of the authors of the study, told Science. “Is it food itself? Is it processing, is it antibiotics, is it sanitation?” Warinner is the Sally Starling Seaver Assistant Professor at the Radcliffe Institute, and a group leader in the Department of Archaeogenetics at the Max Planck Institute for Evolutionary Anthropology and affiliated with the faculty of biological sciences at the Friedrich Schiller University in Jena, Germany. (Photo copyright: The Game Changers.)
Ancient versus Modern Microbiome
The ancient microbiomes lacked markers for antibiotic resistance and included dozens of bacterial species that were previously unknown. According to the study, “a total of 181 of the 498 reconstructed microbial genomes were classified as gut derived and had extensive DNA damage, consistent with an ancient origin, and 39% of the ancient genomes offered evidence of being newly discovered species.”
The scientists also discovered that the gut bacteria of present-day people living in non-industrialized societies is more like that of the ancient people when compared to present-day humans living in industrialized societies. But there are still vast differences between the ancient and the modern microbiome.
For example, a bacteria known as Treponema is virtually unknown in the microbiome of current humans, even those living in non-industrialized societies. However, according to Kostic, “They’re present in every single one of the paleofeces, across all the geographic sites. That suggests it’s not purely diet that’s shaping things,” he told Science.
What Can Clinical Laboratories Learn from Ancient Poop?
The ancient poop study scientists hope that future research on coprolites from the past will reveal more information regarding when shifts in the microbiome occurred and what events or human activities prompted those changes.
Research on the human microbiome has been responsible for many discoveries that have greatly impacted clinical pathology and diagnostics development.
Microbiologists and other medical laboratory scientists may soon have more useful biomarkers that aid in earlier, more accurate detection of disease, as well as guiding physicians to select the most effective therapies for specific patients, a key component of Precision Medicine.
The findings of this study are another step forward in understanding the composition and functions of gut bacteria. The study of the microbiome could prove to be a growth area for clinical laboratories and microbiology labs as well. It is probable that soon, labs will be performing more microbiome testing to help with the diagnosis, and treatment selection and monitoring of patients.
The researchers also found that certain molecules, when added to cancer drugs, can prevent chromosome shattering from occurring in a discovery that may be useful to pathologists and oncologists
Anatomic pathologists who diagnose tissue and closely monitor advances in cancer diagnostics and therapy will be interested in a recent study into how a mutational process known as chromothripsis (chromosome shattering) can promote cancer cell growth in humans and increase resistance to cancer drug therapies.
The study, which was published in the journal Nature, titled, “Chromothripsis Drives the Evolution of Gene Amplification in Cancer,” provides insights into how cancer cells can adapt to different environments and also may suggest potential solutions to drug resistance among cancer patients.
Led by researchers from the University of California San Diego School of Medicine and the UC San Diego branch of the Ludwig Institute for Cancer Research, the discovery could open up a new field in cancer diagnostic testing, where the pathology laboratory analyzes a cancer patient’s tumor cells to determine where chromosomal damage exists. This knowledge could then inform efforts to repair damaged chromosomes or to identify which therapeutic drugs would be most effective in treating the patient, a key element of precision medicine.
“Drug resistance is the most problematic part of cancer therapy. If not for drug resistance, many cancer patients would survive,” said Ofer Shoshani, PhD (above right) postdoctoral fellow at the Cleveland Lab at UC San Diego School of Medicine and the study’s first author, in a news release. He’s shown with Don Cleveland, PhD (above left), head of the Cleveland Laboratory of Cell Biology at the Ludwig Institute for Cancer Research, another author of the study. Cleveland is also Chair of the Department of Cellular and Molecular Medicine, and Distinguished Professor of Cellular and Molecular Medicine, Medicine, and Neurosciences at UC San Diego School of Medicine. (Photo copyright: Ludwig Institute for Cancer Research.)
Shattered Chromosomes
Chromosomes that undergo chromothripsis shatter or fragment into several pieces and then are stitched back together by a DNA repair processes. However, not all of the fragments make it back into the repaired chromosome, and this can be a problem.
“During chromothripsis, a chromosome in a cell is shattered into many pieces, hundreds in some cases, followed by reassembly in a shuffled order,” Shoshani told Genetic Engineering and Biotechnology News (GEN News). “Some pieces get lost while others persist as extra-chromosomal DNA (ecDNA). Some of these ecDNA elements promote cancer cell growth and form minute-sized chromosomes called double minutes.”
Studies have shown that up to half of all cancer cells contain cancer-promoting ecDNA chromosome fragments.
Some Cancer Drugs Could be Fueling Drug Resistance
To perform their study, the UC San Diego/Ludwig scientists sequenced entire genomes of cancer cells that had developed drug resistance. Their research revealed that chromothripsis prompts and drives the formation of ecDNA and that the process can also be induced by some chemotherapeutic drugs. The researchers also discovered that the particular type of damage these drugs may cause can provide an opening for ecDNA to reintegrate back into chromosomes.
“We show that when we break a chromosome, these ecDNAs have a tendency to jump into the break and seal them, serving almost like a DNA glue,” Shoshani said in the news release. “Thus, some of the very drugs used to treat cancers might also be driving drug resistance by generating double-stranded DNA breaks.”
Preventing DNA Shattering and Reducing Drug Resistance
The scientists also discovered that ecDNA formation could be halted by pairing certain cancer drugs with molecules that prevent DNA shattering from occurring in the first place, thus reducing drug resistance.
“This means that an approach in which we combine DNA repair inhibitors with drugs such as methotrexate or vemurafenib could potentially prevent the initiation of drug resistance in cancer patients and improve clinical outcomes,” Shoshani said.
“Our identifications of repetitive DNA shattering as a driver of anticancer drug resistance and of DNA repair pathways necessary for reassembling the shattered chromosomal pieces has enabled rational design of combination drug therapies to prevent development of drug resistance in cancer patients, thereby improving their outcome,” Don Cleveland, PhD, Head of the Cleveland Laboratory of Cell Biology at the Ludwig Institute for Cancer Research and one of the authors of the paper, told GEN News.
This research from the University of California San Diego School of Medicine and the UC San Diego branch of the Ludwig Institute for Cancer Research is the latest example of how scientists have gained useful insights into how human genomes operate. More research and clinical studies are needed to solidify the advantages of this study, but the preliminary results are promising and could lead to new cancer diagnostics and therapies.
The St. Louis-based in vitro diagnostics (IVD) developer is making PrecivityAD available to physicians while awaiting FDA clearance for the non-invasive test
Clinical laboratories have long awaited a test for Alzheimer’s disease and the wait may soon be over. The first blood test to aid physicians and clinical laboratories in the diagnosis of patients with memory and cognitive issues has been released by C₂N Diagnostics of St. Louis. The test measures biomarkers associated with amyloid plaques in the brain—the pathological hallmark of Alzheimer’s.
In a news release, PrecivityAD describes the laboratory-developed test (LDT) as “a highly sensitive blood test using mass spectrometry and is performed in C₂N’s CLIA-certified laboratory. While the test by itself cannot diagnose Alzheimer’s disease … the test is an important new tool for physicians to aid in the evaluation process.”
PrecivityAD provides physicians with an Amyloid Probability Score (APS) for each patient. For example:
A low APS (0-36) is consistent with a negative amyloid PET scan result and, thus, has a low likelihood of amyloid plaques, an indication other causes of cognitive symptoms should be investigated.
An intermediate APS (37-57) does not distinguish between the presence or absence of amyloid plaques and indicates further diagnostic evaluation may be needed to assess the underlying cause(s) for the patient’s cognitive symptoms.
A high APS (58-100) is consistent with a positive amyloid positron-emission tomography (PET) scan result and, thus, a high likelihood of amyloid plaques. Presence of amyloid plaques is consistent with an Alzheimer’s disease diagnosis in someone who has cognitive decline, but alone is insufficient for a final diagnosis.
The $1,250 test is not currently covered by health insurance or Medicare. However, C₂N Diagnostics has pledged to offer discounts to patients based on income levels.
Jeff Cummings, MD, ScD (above) Research Professor, Department of Brain Health, University of Nevada, Las Vegas, said in a C₂N Diagnostics press release, “A blood test for Alzheimer’s is a game changer.” While there is no cure for Alzheimer’s, a non-invasive blood test can help providers diagnose patients when their symptoms are mild and often misdiagnosed. “Advances in Alzheimer’s diagnostics are key to more effective identification, diagnosis, and clinical trial recruitment,” he added. Currently, brain changes caused by the disease are most commonly identified through PET scans. (Photo copyright: University of Nevada Las Vegas.)
Additional Research Requested
While C₂N’s PrecivityAD is the first test of its kind to reach the commercial market, it has not received US Food and Drug Administration (FDA) clearance, nor has the company published detailed data on the test’s accuracy. However, the PrecivityAD website says the laboratory-developed test “correctly identified brain amyloid plaque status (as determined by quantitative PET scans) in 86%” of 686 patients, all of whom were older than 60 years of age with subjective cognitive impairment or dementia.
But some Alzheimer’s advocacy groups are tempering their enthusiasm about the breakthrough. Eliezer Masliah, MD, Director of the Division of Neuroscience, National Institute on Aging, told the Associated Press (AP), “I would be cautious about interpreting any of these things,” he said of the company’s claims. “We’re encouraged, we’re interested, we’re funding this work, but we want to see results.”
Heather Snyder, PhD, Vice President, Medical and Scientific Relations at the Alzheimer’s Association told the AP her organization will not endorse a test without FDA clearance. The Alzheimer’s Association also would like to see the test studied in larger and diverse populations. “It’s not quite clear how accurate or generalizable the results are,” she said.
Braunstein defended the decision to make the test for Alzheimer’s immediately available to physicians, asking in the AP article, “Should we be holding that technology back when it could have a big impact on patient care?”
Howard Fillit, MD, Founding Executive Director and Chief Science Officer of the Alzheimer’s Drug Discovery Foundation (ADDF), maintains the first-of-its-kind blood test is an important milestone in Alzheimer’s research. ADDF invested in C₂N’s development of the test.
“Investing in biomarker research has been a core goal for the ADDF because having reliable, accessible, and affordable biomarkers for Alzheimer’s diagnosis is step one in finding drugs to prevent, slow, and even cure the disease,” Fillit said in an ADDF news release.
C₂N is also developing a Brain Health Panel to detect multiple blood-based markers for Alzheimer’s disease that will aid in better disease staging, treatment monitoring, and differential diagnosis.
Second Alzheimer’s Test in Development
Soon medical laboratories may have two different in vitro diagnostic tests for Alzheimer’s disease. On December 2, Fujirebio Diagnostics filed for FDA 510(k) premarket clearance for its Lumipulse G β-Amyloid Ratio (1-42/1-40) test, which looks for biomarkers found in cerebral spinal fluid.
“Accurate and earlier intervention will also facilitate the development of new drug therapies, which are urgently needed as the prevalence of Alzheimer’s disease increases with a rapidly aging population globally,” Fujirebio Diagnostics President and CEO Monte Wiltse said in a news release.
The Lumipulse G β-Amyloid test, which is intended for use in patients aged 50 and over presenting with cognitive impairment, has received CE-marking for use in the European Union.
Clinical laboratory managers will want to keep a close eye on rapidly evolving developments in testing for Alzheimer’s disease. It is the sixth leading cause of death in the United States and any clinical laboratory test that could produce an early and accurate diagnosis of Alzheimer’s Disease would become a valuable tool for physicians who treat patients with the symptoms of Alzheimer’s.
