via Harvard Medical School
Study in mice implicates changes to way DNA is organized, regulated rather than changes to genetic code itself
An international study 13 years in the making demonstrates for the first time that degradation in the way DNA is organized and regulated — known as epigenetics — can drive aging in an organism, independently of changes to the genetic code itself.
The work shows that a breakdown in epigenetic information causes mice to age and that restoring the integrity of the epigenome reverses those signs of aging.
“We believe ours is the first study to show epigenetic change as a primary driver of aging in mammals,” said the paper’s senior author, David Sinclair, professor of genetics in the Blavatnik Institute at Harvard Medical School and co-director of the Paul F. Glenn Center for Biology of Aging Research.
The team’s extensive series of experiments provide long-awaited confirmation that DNA changes are not the only, or even the main, cause of aging. Rather, the findings show, chemical and structural changes to chromatin — the complex of DNA and proteins that forms chromosomes — fuel aging without altering the genetic code itself.
“We expect the findings will transform the way we view the process of aging and the way we approach the treatment of diseases associated with aging,” said co-first author Jae-Hyun Yang, research fellow in genetics in the Sinclair lab.
The authors say that because it’s easier to manipulate the molecules that control epigenetic processes than to reverse DNA mutations, the work points to new avenues that focus on epigenetics rather than genetics to prevent or treat age-related damage.
First, the results need to be replicated in larger mammals and in humans. Studies in nonhuman primates are currently underway.
“We hope these results are seen as a turning point in our ability to control aging,” said Sinclair. “This is the first study showing that we can have precise control of the biological age of a complex animal; that we can drive it forwards and backwards at will.”
Perhaps the most burning question for those who study aging is what causes it.
For decades, a reigning theory in the field was that aging arises from an accumulation of changes to DNA, primarily genetic mutations, which over time prevent more and more genes from functioning properly. These malfunctions, in turn, cause cells to lose their identity, so that tissues and organs break down, leading to disease and, ultimately, death.
In recent years, however, studies have increasingly hinted that there’s more to the story.
For instance, some researchers found that some people and mice with high mutation rates don’t show signs of premature aging. Others observed that many types of aged cells have few or no mutations.
Researchers started wondering what else works with or instead of DNA changes to cause aging. A list of possible culprits grew. Among them were epigenetic changes.
A component of epigenetics is the physical structures such as histones that bundle DNA into tightly compacted chromatin and unspool portions of that DNA when needed. Genes are inaccessible when they’re bundled up but available to be copied and used to produce proteins when they’re unspooled. Thus, epigenetic factors regulate which genes are active or inactive in any given cell at any given time.
By acting as a toggle for gene activity, these epigenetic molecules help define cell type and function. Since each cell in an organism has basically the same DNA, it’s the on-off switching of particular genes that differentiates a nerve cell from a muscle cell from a lung cell.
“Epigenetics is like a cell’s operating system, telling it how to use the same genetic material differently,” said Yang, who is co-first author with Motoshi Hayano, a former postdoctoral fellow in the Sinclair lab who is now at Keio University School of Medicine in Tokyo.
In the late 1990s and early 2000s, Sinclair’s lab and others showed in yeast and mammals that epigenetic changes accompany aging. Yet they couldn’t tell whether these changes drove aging or were a consequence of it.
It wasn’t until the current study that Sinclair’s team was able to disentangle epigenetic from genetic changes and confirm that a breakdown in epigenetic information does, in fact, contribute to aging in mice.
The team’s main experiment involved creating temporary, fast-healing cuts in the DNA of lab mice.
These breaks mimicked the low-grade, ongoing breaks in chromosomes that mammalian cells experience every day in response to things like breathing, exposure to sunlight and cosmic rays, and contact with certain chemicals.
In the study, to test whether aging results from this process, the researchers sped the number of breaks to simulate life on fast-forward.
The team also ensured that most of the breaks were not made within the coding regions of the mice’s DNA — the segments that make up genes. This prevented the animals’ genes from developing mutations. Instead, the breaks altered the way DNA is folded.
Sinclair and colleagues called their system ICE, short for inducible changes to the epigenome.
At first, epigenetic factors paused their normal job of regulating genes and moved to the DNA breaks to coordinate repairs. Afterward, the factors returned to their original locations.
But as time passed, things changed. The researchers noticed that these factors got “distracted” and did not return home after repairing breaks. The epigenome grew disorganized and began to lose its original information. Chromatin got condensed and unspooled in the wrong patterns, a hallmark of epigenetic malfunction.
As the mice lost their youthful epigenetic function, they began to look and act old. The researchers saw a rise in biomarkers that indicate aging. Cells lost their identities as, for example, muscle or skin cells. Tissue function faltered. Organs failed.
The team used a recent tool developed by Sinclair’s lab to measure how old the mice were, not chronologically, in days or months, but “biologically,” based on how many sites across the genome lost the methyl groups normally attached to them. Compared to untreated mice born at the same time, the ICE mice had aged significantly more.
Next, the researchers gave the mice a gene therapy that reversed the epigenetic changes they’d caused.
“It’s like rebooting a malfunctioning computer,” said Sinclair.
The therapy delivered a trio of genes — Oct4, Sox2, and Klf4, together named OSK — that are active in stem cells and can help rewind mature cells to an earlier state. (Sinclair’s lab used this cocktail to restore sight in blind mice in 2020.)
The ICE mice’s organs and tissues resumed a youthful state.
The therapy “set in motion an epigenetic program that led cells to restore the epigenetic information they had when they were young,” said Sinclair. “It’s a permanent reset.”
How exactly OSK treatment achieved that remains unclear.
At this stage, Sinclair says the discovery supports the hypothesis that mammalian cells maintain a kind of backup copy of epigenetic software that, when accessed, can allow an aged, epigenetically scrambled cell to reboot into a youthful, healthy state.
For now, the extensive experiments led the team to conclude that “by manipulating the epigenome, aging can be driven forwards and backwards,” said Yang.
The ICE method offers researchers a new way to explore the role of epigenetics in aging and other biological processes.
Because signs of aging developed in the ICE mice after only six months rather than toward the end of the average mouse life span of two and a half years, the approach also saves time and money for researchers studying aging.
Researchers can also look beyond OSK gene therapy in exploring how lost epigenetic information might be restored in aged organisms.
“There are other ways to manipulate the epigenome, like drugs and small molecule chemicals that induce gentle stress,” said Yang. “This work opens a door for applying those other methods to rejuvenate cells and tissues.”
Sinclair hopes the work inspires other scientists to study how to control aging to prevent and eliminate age-related diseases and conditions in humans, such as cardiovascular disease, type 2 diabetes, neurodegeneration, and frailty.
“These are all manifestations of aging that we’ve been trying to treat with medicines when they arise, which is almost too late,” he said.
The goal would be to address the root causes of aging to extend human health span: the number of years that a person remains not just alive but well.
Medical applications are a long way off and will take extensive experiments in multiple cell and animal models. But, Sinclair said, scientists should think big and keep trying in order to achieve such dreams.
“We’re talking about taking someone who’s old or sick and making their whole body or a specific organ young again, so the disease goes away,” he said. “It’s a big idea. It’s not how we typically do medicine.”
Long time coming
The study marks the culmination of 10 years of Yang’s career as a postdoctoral researcher. But there were moments along the way when he thought he’d never see the work completed.
As the scope expanded year after year, with colleagues and critics urging Yang to add more experiments and incorporate new technologies, the project often felt overwhelming. Yang sometimes listened to those who asked whether it was all worth it. At one point he drafted an email to Sinclair saying he wanted to quit the project.
“Luckily,” said Sinclair, “he didn’t send it.”
The problem wasn’t Yang’s skills or dedication. Rather, the work was the most ambitious ever attempted in the lab. Sinclair thinks it may represent one of the hardest projects undertaken in science in recent years.
“You don’t get many chances in life to do a project like this,” he said. “It took an incredible amount of mental and physical labor to get to this point. Jae and the team demonstrated so much resilience as we got rejected and re-reviewed and did six more years of experiments until we ended up with a body of work that answers one of the most important questions in biology. I’m really proud of the team.”
Seeing the findings published at long last not only offers professional satisfaction but also feels poignant on a personal level, Sinclair said.
“This project began when I was 39. I’m now 53,” he said. “A lot has happened in those years. We’re older. Our families and friends have changed. People on the project have died. It’s more than just a paper for us; it’s a major part of our lives.”
“There’s a lot of emotion in this,” he continued. “I feel like some of my soul is in there.”
For his part, Yang hopes to now become a principal investigator in Korea, where he grew up.
“I’m very happy to have answered one of the long-standing questions in the field,” he said. “I’m really looking forward to seeing the impact.”
Original Article: Loss of Epigenetic Information Can Drive Aging, Restoration Can Reverse It
More from: Harvard Medical School
The Latest Updates from Bing News
Go deeper with Bing News on:
- Danforth Center researchers turn to epigenome editing to protect cash crop cassava from blight
Researchers recently demonstrated that epigenome editing can reduce blight symptoms in cassava plants without impacting plant growth or yield.
- Using a long-read approach to gain better understanding of DNA mutations in cancer genomes
Looking to learn more from genomics sequencing about DNA mutations and cancer, researchers applied a long-read approach to get a broader genomic view.
- Epigenome reprogramming after SARS-CoV-2 infection
The study aimed at improving the understanding of coronavirus disease 2019 (COVID-19)-related perturbations in the genome and epigenome of a host cell. The 3D folding of chromatin in mammals, ...
- Researchers apply a long-read approach to learn more about DNA mutations and cancer
Just as a flashlight casts a broader beam than the brightest candle when walking along a darkened trail, so too does long-read genomic sequencing seem to clarify a broader genomic picture of DNA ...
- 2023-2029 Epigenome Sequencing Market Size and Market Share Analysis | Latest Report by Absolute Reports
Mar 23, 2023 (The Expresswire) -- "Final Report will add the analysis of the impact of COVID-19 on this industry." Global "Epigenome Sequencing Market" research report [95 Pages] examines the market's ...
Go deeper with Bing News on:
- Welcome to the anti-aging era: How reversing your 'biological age' has become healthcare's hottest trend
Scientists say we have achieved anti-aging with other organisms, but it's not clear yet that we have done this in humans. The buzzy term "biological age" suggests there may be a more complex and ...
- Human Aging Is the End-Product of Our Developmental Program
A new study reports aging may not be a result of accumulative damage to the body, but instead is the result of "design" flaws in our DNA that orchestrates the development of single cells into an adult ...
- Researchers suggest that human aging is the end-product of our developmental program
A new study published in Genome Biology has challenged the traditional view that aging is a result of the accumulation of damage to the body's hardware, such as the molecular damage to cells caused by ...
- Loss of Menin helps drive the aging process, and dietary supplement can reverse it in mice
Could reversing age-related Menin loss reverse signs of physiological aging? To test that, the authors delivered the gene for Menin into the hypothalamus of elderly (20-month-old) mice.
- Previously Unknown Driver of Aging Discovered – Simple Supplement May Reverse It
Loss of Menin helps drive the aging process, and dietary supplement can reverse it in mice. Cognition, bone mass, skin thickness, and lifespan are all affected by Menin’s decline. According to a new ...