embryo

Scientists fix heart disease mutation in human embryos using CRISPR

/ Karen Ring / Leave a comment

Last week the scientific community was buzzing with the news that US scientists had genetically modified human embryos using CRISPR gene editing technology. While the story broke before the research was published, many journalists and news outlets weighed in on the study’s findings and the ethical implications they raise. We covered this initial burst of news in last week’s stem cell stories that caught our eye.

Shoukhrat Mitalipov (Leah Nash, New York Times)

After a week of suspense, the highly-anticipated study was published yesterday in the journal Nature. The work was led by senior author Dr. Shoukhrat Mitalipov from Oregon Health and Sciences University (and a member of CIRM’s Grants Working Group, the panel of experts who review applications to us for funding) in collaboration with scientists from the Salk Institute and Korea’s Institute for Basic Science.

In brief, the study revealed that the teams’ CRISPR technology could correct a genetic mutation that causes a disease called hypertrophic cardiomyopathy (HCM) in 72% of human embryos without causing off-target effects, which are unwanted genome modifications caused by CRISPR. These findings are a big improvement over previous studies by other groups that had issues with off-target effects and mosaicism, where CRISPR only correctly modifies mutations in some but not all cells in an embryo.

Newly fertilized eggs before gene editing, left, and embryos after gene editing and a few rounds of cell division. (Image from Shoukrat Mitalipov in New York Times)

Mitalipov spoke to STATnews about a particularly interesting discovery that he and the other scientists made in the Nature study,

“The main finding is that the CRISPR’d embryos did not accept the “repair DNA” that the scientists expected them to use as a replacement for the mutated gene deleted by CRISPR, which the embryos inherited from their father. Instead, the embryos used the mother’s version of the gene, called the homologue.”

Sharon Begley, the author of the STATnews article, argued that this discovery means that “designer babies” aren’t just around the corner.

“If embryos resist taking up synthetic DNA after CRISPR has deleted an unwanted gene, then “designer babies,” created by inserting a gene for a desirable trait into an embryo, will likely be more difficult than expected.”

Ed Yong from the Atlantic also took a similar stance towards Mitalipov’s study in his article titled “The Designer Baby Era is Not Upon Us”. He wrote,

“The bigger worry is that gene-editing could be used to make people stronger, smarter, or taller, paving the way for a new eugenics, and widening the already substantial gaps between the wealthy and poor. But many geneticists believe that such a future is fundamentally unlikely because complex traits like height and intelligence are the work of hundreds or thousands of genes, each of which have a tiny effect. The prospect of editing them all is implausible. And since genes are so thoroughly interconnected, it may be impossible to edit one particular trait without also affecting many others.”

Dr. Juan Carlos Izpisua Belmonte, who’s a corresponding author on the paper and a former CIRM grantee from the Salk Institute, commented on the impact that this research could have on human health in a Salk news release.

Co-authors Juan Carlos Izpisua Belmonte and Jun Wu. (Salk Institute)

“Thanks to advances in stem cell technologies and gene editing, we are finally starting to address disease-causing mutations that impact potentially millions of people. Gene editing is still in its infancy so even though this preliminary effort was found to be safe and effective, it is crucial that we continue to proceed with the utmost caution, paying the highest attention to ethical considerations.”

Pam Belluck from The New York Times also suggested that this research could have a significant impact on how we prevent disease in newborns.

“This research marks a major milestone and, while a long way from clinical use, it raises the prospect that gene editing may one day protect babies from a variety of hereditary conditions.”

So when will the dawn of CRISPR babies arrive? Ed Yong took a stab at answering this million dollar question with help from experts in the field.

“Not for a while. The technique would need to be refined, tested on non-human primates, and shown to be safe. “The safety studies would likely take 10 to 15 years before FDA or other regulators would even consider allowing clinical trials,” wrote bioethicist Hank Greely in a piece for Scientific American. “The Mitalipov research could mean that moment is 9 years and 10 months away instead of 10 years, but it is not close.” In the meantime, Mitalipov’s colleague Sanjiv Kaul says, “We’ll get the method to perfection so that when it’s possible to use it in a clinical trial, we can.”

Stem Cell Stories that caught our eye: a womb with a view, reversing aging and stabilizing stem cells

/ Karen Ring / Leave a comment

Here are some stem cell stories that caught our eye this past week. Some are groundbreaking science, others are of personal interest to us, and still others are just fun.

Today we bring you a trifecta of stem cell stories that were partially funded by grants from CIRM.

A womb with a view: using 3D imaging to observe embryo implantation. Scientists have a good understanding of how the beginning stages of pregnancy happen. An egg cell from a woman is fertilized by a sperm cell from a man and the result is a single cell called a zygote. Over the next week, the zygote divides into multiple cells that form the developing embryo. At the end of that period, the embryo hatches out of its protective membrane and begins implanting itself into the lining of the mother’s uterus.

It’s possible to visualize the early stages of embryo development in culture dishes, which has helped scientists understand the biological steps required for an embryo to survive and develop into a healthy fetus. However, something that is not easy to observe is the implantation stage of the embryo in the uterus. This process is complex and involves a restructuring of the uterine wall to accommodate the developing embryo. As you can imagine, replicating these events would be extremely complicated and difficult to do in a culture dish, and current imaging techniques aren’t adequate either.

That’s where new CIRM-funded research from a team at UCSF comes to the rescue. They developed a 3D imaging technology and combined it with a previously developed “tissue clearing” method, which uses chemicals to turn tissues translucent, to provide clear images of the uterine wall during embryo implantation in mice. Their work was published this week in the journal Development.

According to a UCSF news release,

“Using their new approach, the team observed that the uterine lining becomes extensively folded as it approaches its window of receptivity for an embryo to implant. The geometry of the folds in which the incoming embryos dwell is important, the team found, as genetic mutants with defects in implantation have improper patterns of folding.”

Ultimately, the team aims to use their new imaging technology to get an inside scoop on how to prevent or treat pregnancy disorders and also how to improve the outcome of pregnancies by in vitro fertilization.

Senior author on the study, UCSF professor Diana Laird concluded:

“This new view of early pregnancy lets us ask fundamentally new questions about how the embryo finds its home within the uterus and what factors are needed for it to implant successfully. Once we can understand how these processes happen normally, we can also ask why certain genetic mutations cause pregnancies to fail, to study the potential dangers of environmental toxins such as the chemicals in common household products, and even why metabolic disease and obesity appears to compromise implantation.”

If you want to see this womb with a view, check out the video below.

Watch these two videos for more information:

Salk scientists reverse signs of aging in mice. For our next scintillating stem cell story, we’re turning back the clock – the aging clock that is. Scientists from the Salk Institute in La Jolla, reported an interesting method in the journal Cell  that reverses some signs of aging in mice. They found that periodic expression of embryonic stem cell genes in skin cells and mice could reverse some signs of aging.

The Salk team made use of cellular reprogramming tools developed by the Nobel Prize winning scientist Shinya Yamanaka. He found that four genes normally expressed in embryonic stem cells could revert adult cells back to a pluripotent stem cell state – a process called cellular reprogramming. Instead of turning adult cells back into stem cells, the Salk scientists asked whether the Yamanaka factors could instead turn back the clock on older, aging cells – making them healthier without turning them back into stem cells or cancer-forming cells.

The team found that they could rejuvenate skin cells from mice without turning them back into stem cells if they turned on the Yamanaka genes on for a short period of time. These skin cells were taken from mice that had progeria – a disease that causes them to age rapidly. Not only did their skin cells look and act younger after the treatment, but when the scientists used a similar technique to turn on the Yamanaka genes in progeria mice, they saw rejuvenating effects in the mice including a more rapid healing and regeneration of muscle and pancreas tissue.

(Left) impaired muscle repair in aged mice; (right) improved muscle regeneration in aged mice subjected to reprogramming. (Salk Institute)

(Left) impaired muscle repair in aged mice; (right) improved muscle regeneration in aged mice subjected to reprogramming. (Salk Institute)

The senior author on the study, Salk Professor Juan Carlos Izpisua Belmonte, acknowledged in a Salk news release that this is early stage work that focuses on animal models, not humans:

“Obviously, mice are not humans and we know it will be much more complex to rejuvenate a person. But this study shows that aging is a very dynamic and plastic process, and therefore will be more amenable to therapeutic interventions than what we previously thought.”

This story was very popular, which is not surprising as aging research is particularly fascinating to people who want to live longer lives. It was covered by many news outlets including STATnews, Scientific American and Science Magazine. I also recommend reading Paul Knoepfler’s journal club-style blog on the study for an objective take on the findings and implications of the study. Lastly, you can learn more about the science of this work by watching the movie below by the Salk.

Movie:

Stabilizing unstable stem cells. Our final stem cell story is brought to you by scientists from the UCLA Broad Stem Cell Research Center. They found that embryonic stem cells can harbor genetic instabilities that can be passed on to their offspring and cause complications, or even disease, later in life. Their work was published in two separate studies in Cell Stem Cell and Cell Reports.

The science behind the genetic instabilities is too complicated to explain in this blog, so I’ll refer you to the UCLA news release for more details. In brief, the UCLA team found a way to reverse the genetic instability in the stem cells such that the mature cells that they developed into turned out healthy.

As for the future impact of this research, “The research team, led by Kathrin Plath, found a way to correct the instability by resetting the stem cells from a later stage of development to an earlier stage of development. This fundamental discovery could have great impact on the creation of healthy tissues to cure disease.”

Confining Cells within Geometric Structures Key to Replicating Embryonic Development

/ cirmweb / Leave a comment

It’s like trying to capture, and then recreate, a moment in time: the exact instant after fertilization when a small group of dividing cells begin to organize themselves into the various cellular layers that will one day make up the skin, the heart, the liver and the brain. But for all the advances in our understanding of how an embryonic stem cell grows, matures and differentiates—scientists still can’t replicate that very important process in the lab.

Forty-two hours after they began to differentiate, embryonic cells are clearly segregating into the various layers that will one day become specific tissues and organs. Researchers say the key to achieving this patterning in culture is confining the colonies geometrically. [Credit: The Rockefeller University]

Forty-two hours after they began to differentiate, embryonic cells are clearly segregating into the various layers that will one day become specific tissues and organs. Researchers say the key to achieving this patterning in culture is confining the colonies geometrically. [Credit: The Rockefeller University]

But now, scientists at The Rockefeller University have tried something new, and in so doing have finally found a way to stimulate this organization, thus mimicking in a petri dish what happens in the human embryo. The missing ingredient, the researchers found, wasn’t a molecule or chemical compound. Rather, the team just had to use a bit of geometry.

Reporting in the June 29 issue of the journal Nature Methods, the Rockefeller team—led by Dr. Ali Brivanlou—describes how they constructed microscopic circular patterns on glass plates that confined embryonic stem cells inside, similar to a hedge maze.

To their amazement, the cells confined within these patterns soon began to go through gastrulation, the process by which embryonic stem cells begin to form highly organized layers that eventually mature into the body’s various organs and tissues. A second group of cells not confined within these patterns, however, did not.

The next question they had to figure out, according to the researchers, was why.

To solve this mystery, Brivanlou and his team next monitored specific chemical signals between the cells as they matured. In so doing they uncovered a delicate arrangement of chemical cues—molecular ‘on-and-off-switches’—that guided each cell down one developmental path as opposed to another. What were crucial to these cues going off without a hitch, the researchers found, were the geometric patterns.

As Dr. Aryeh Warmflash, one of the paper’s lead authors, stated in this week’s news release:

“At the fundamental level, what we have developed is a new model to explore how human embryonic stem cells first differentiate into separate populations with a very reproducible spatial order just as in an embryo. We can now follow individual cells in real time in order to find out what makes them specialize, and we can begin to ask questions about the underlying genetics of the process.”

Added Brivanlou:

“Understanding what happens in this moment, when individual members of this mass of embryonic stem cells begin to specialize for the very first time and organize themselves into layers, will be key to harnessing the promise of regenerative medicine.”

Confining Cells within Geometric Structures Key to Replicating Embryonic Development

/ cirmweb / Leave a comment

It’s like trying to capture, and then recreate, a moment in time: the exact instant after fertilization when a small group of dividing cells begin to organize themselves into the various cellular layers that will one day make up the skin, the heart, the liver and the brain. But for all the advances in our understanding of how an embryonic stem cell grows, matures and differentiates—scientists still can’t replicate that very important process in the lab.

Forty-two hours after they began to differentiate, embryonic cells are clearly segregating into the various layers that will one day become specific tissues and organs. Researchers say the key to achieving this patterning in culture is confining the colonies geometrically. [Credit: The Rockefeller University]

Forty-two hours after they began to differentiate, embryonic cells are clearly segregating into the various layers that will one day become specific tissues and organs. Researchers say the key to achieving this patterning in culture is confining the colonies geometrically. [Credit: The Rockefeller University]

But now, scientists at The Rockefeller University have tried something new, and in so doing have finally found a way to stimulate this organization, thus mimicking in a petri dish what happens in the human embryo. The missing ingredient, the researchers found, wasn’t a molecule or chemical compound. Rather, the team just had to use a bit of geometry.

Reporting in the June 29 issue of the journal Nature Methods, the Rockefeller team—led by Dr. Ali Brivanlou—describes how they constructed microscopic circular patterns on glass plates that confined embryonic stem cells inside, similar to a hedge maze.

To their amazement, the cells confined within these patterns soon began to go through gastrulation, the process by which embryonic stem cells begin to form highly organized layers that eventually mature into the body’s various organs and tissues. A second group of cells not confined within these patterns, however, did not.

The next question they had to figure out, according to the researchers, was why.

To solve this mystery, Brivanlou and his team next monitored specific chemical signals between the cells as they matured. In so doing they uncovered a delicate arrangement of chemical cues—molecular ‘on-and-off-switches’—that guided each cell down one developmental path as opposed to another. What were crucial to these cues going off without a hitch, the researchers found, were the geometric patterns.

As Dr. Aryeh Warmflash, one of the paper’s lead authors, stated in this week’s news release:

“At the fundamental level, what we have developed is a new model to explore how human embryonic stem cells first differentiate into separate populations with a very reproducible spatial order just as in an embryo. We can now follow individual cells in real time in order to find out what makes them specialize, and we can begin to ask questions about the underlying genetics of the process.”

Added Brivanlou:

“Understanding what happens in this moment, when individual members of this mass of embryonic stem cells begin to specialize for the very first time and organize themselves into layers, will be key to harnessing the promise of regenerative medicine.”