DNA

Celebrating National DNA Day Together

/ Katie Sharify / Leave a comment

DNA provides the code of life for nearly all living organisms. So, it’s no wonder that scientists have been studying DNA and the human genome (complete set of DNA) for decades.

In April 1953, James Watson and Francis Crick, in collaboration with Rosalind Franklin, first described the structure of DNA as a double helix. In April 2003, exactly 50 years later, scientists completed the Human Genome Project- a massive research effort to sequence and map all the genes that comprise the human genome.

That same year, Congress approved the first National DNA Day to commemorate both the discovery of the double helix and the completion of the Human Genome Project. The goal of National DNA Day is to offer students, educators, and the public an opportunity to learn about the DNA molecule and genomic research.

You can celebrate National DNA Day this year by following scientists Lilly Lee and Tom Quinn at Takara Bio as they demonstrate how to extract DNA from strawberries. Their lesson plan guides mentors to teach about DNA and genomic research, starting with having students extract DNA on their own.

Laurel Barchas, one of the people behind the video has also played an important role at the California Institute for Regenerative Medicine (CIRM). She has collaborated with us on many projects over the years, including helping us build CIRM’s own education portal with lessons for high school students that meet Next Generation Science Standards.

Watch the video below and Click Here for the full lesson plan!

Scientists at USC untangle the mysteries of cellular reprogramming- a method that could be used to treat diseases

/ Yimy Villa / 1 Comment
Dr. Justin Ichida, Assistant Professor at USC and lead author of the study

Scientists have long tried to repurpose cells in order to potentially treat various types of conditions. This process, called reprogramming, involves changing one type of cell into another, such as a blood cell into a muscle cell or nerve cell. Although the technique has been around for decades, it has only been effective 1% of the time.

Fortunately, thanks in part to a CIRM grant, Dr. Justin Ichida and other researchers at USC have been able to untangle this complicated process to ensure reprogramming happens more efficiently. The researchers were able to figure out a process that reprograms cells much more reliably than previous methods.

USC scientists have found a solution to untangle twisty DNA, removing kinks so the molecules can be used to reprogram cells to advance regenerative medicine to treat disease.
Photo courtesy of Illustration/iStock

The technique the scientists developed uses an enzyme to untangle reprogramming DNA, similar to how a hairdresser conditions untangled hair. Since DNA molecules are twisty by nature, due to the double helix configuration, they do not respond well when manipulated to change itself. Therefore, reprogramming DNA requires uncoiling, yet when scientists begin to unravel the molecules, they knot up tighter.

“Think of it as a phone cord, which is coily to begin with, then gets more coils and knots when something is trying to harm it,” Dr. Ichida said in a press release by USC.

To smooth the kinks, the researchers treated cells with a chemical and genetic cocktail that activates enzymes that open up the DNA molecules. This process releases the coiled tension and lays out the DNA smoothly, leading to more efficient cellular reprogramming.

This new technique works almost 100% of the time and has been proven in human and mouse cells. The increased efficiency of this techniques opens the possibilities for studying disease development and drug treatments. New cells could be created to replace lost cells or acquire cells that can’t be extracted from people, a problem observed in Parkinson’s, ALS, and other neurological diseases.

Moreover, since these reprogrammed cells are the same age as the parent cell, they could be used to better understand age-related diseases. It is possible that the reprogrammed cells may be better at creating age-accurate models of human disease, which are useful to study a wide array of degenerative diseases and accelerated aging syndromes.

To summarize his work, Dr. Ichida states in the USC press release that,

“A modern approach for disease studies and regenerative medicine is to induce cells to switch their identity. This is called reprogramming, and it enables the attainment of inaccessible tissue types from diseased patients for examination, as well as the potential restoration of lost tissue. However, reprogramming is extremely inefficient, limiting its utility. In this study, we’ve identified the roadblock that prevents cells from switching their identity. It turns out to be tangles on the DNA within cells that form during the reprogramming process. By activating enzymes that untangle the DNA, we enable near 100% reprogramming efficiency.”

The full findings of this study can be found in Cell Stem Cell.

HIV eliminated from mice using CRISPR and LASER ART

/ Yimy Villa / Leave a comment
Dr. Kamel Khalili

In the United States alone, there are approximately 1.1 million people living with Human immunodeficiency virus (HIV), a virus that weakens the immune system by destroying important cells that fight off disease and infection. This number is much larger on a global scale, with 36.9 million people living with HIV as of 2017. If left untreated, the immune system becomes so weakened that the condition worsens into acquired immunodeficiency syndrome (AIDS), which is usually fatal.

Current treatment for HIV focuses on the use of antiretroviral therapy (ART). This treatment is able to suppress replication of the virus, but it does not eliminate it from the body entirely. In order to be sustainable, ART must be taken throughout the course of a lifetime, otherwise HIV rebounds and the replication of the virus renews, fueling the development of AIDS.

The ability of HIV to rebound is related to the fact that it is able to integrate its DNA into various cells inside the body and beyond the reach of ART. Here they are able to remain dormant and ready to replicate as soon as ART is not interfering. It is because of this that ART is not sufficient on its own to cure HIV, but a group of scientists have uncovered a promising breakthrough to change that.

In a major collaboration, researchers at the Lewis Katz School of Medicine at Temple University and the University of Nebraska Medical Center (UNMC) have for the first time eliminated HIV from the DNA of living mice. This study marks a critical step toward the development of a possible cure for human HIV infection.

The team of researchers was able to do this with the help of a new technology called long-acting slow-effective release (LASER) ART. LASER ART is able to target HIV sanctuaries and maintain replication at low levels for extended periods of time. Immediately after administering LASER ART, the team used a gene editing technology known as CRISPR to remove the final remnants of HIV DNA hidden inside cells.

In a press release, Dr. Kamel Khalili, senior investigator for this study, was quoted as saying,

“Our study shows that treatment to suppress HIV replication and gene editing therapy, when given sequentially, can eliminate HIV from cells and organs of infected animals…We now have a clear path to move ahead to trials in non-human primates and possibly clinical trials in human patients within the year.”

The full results of this study were published in Nature Communications.

To learn more about how CRISPR technology works, you can read more about it on a previous blog post.

“Junk” DNA is development gold for the dividing embryo

/ Pallavi Penumetcha / Leave a comment

Single-two-cell-mouse-embryos-with-nuclear-LINE1-RNA-labeled-magenta-Credit-Ramalho-Santos-lab_1

Single two-cell mouse embryos with nuclear LINE1 RNA labeled magenta – Credit Ramalho-Santos lab

The DNA in our cells provide the instructions to make proteins, the workhorses of our body. Yet less than 2% of the 3 billion base pairs (the structural units of DNA) in each of our cells are actually involved in protein production. The rest, termed non-coding DNA for not being involved in protein production, has roles in regulating genetic activity, but, largely, these genetic regions have remained a mystery causing some to mis-characterize it as “junk” DNA.

One of the largest components of these “junk” DNA regions are transposons, which make up 50% of the genome. Transposons are variable length DNA segments that are able to duplicate and re-insert themselves into different locations of the genome which is why they’re often called “jumping genes”.

Transposons have been implicated in diseases like cancer because of their ability to disrupt normal gene function depending on where the transposon inserts itself. Now, a CIRM-funded study in Miguel Ramalho-Santos’ laboratory at UCSF has found a developmental function for transposons in the dividing embryo. The report was published today in the Journal Cell.

Of the transposons identified in humans, LINE1 is the most common, composing 24% of the entire human genome. Many investigators in the field had observed that LINE1 is highly expressed in embryonic stem cells, which seemed paradoxical given that these pieces of DNA were previously thought to be either inert or harmful. Because this DNA was present at such high levels, the investigators decided to eliminate it from fertilized mouse embryos at the two-cell stage and observe how this affected development.

To their surprise, they found that the embryo was not able to progress beyond this stage. Further investigation revealed that LINE1, along with other proteins, is responsible for turning off the genetic program that maintains the two-cell state, thus allowing the embryo to further divide and develop.

Dr. Ramalho-Santos believes that this is a fine-tuned mechanism to ensure that the early stages of develop progress successfully. Because there are so many copies of LINE1 in the genome, even if one is not functional, it is likely that there will be functional back up, an important factor in ensuring early mistakes in embryo development do not occur.

In a press release, Dr. Ramalho-Santos states:

“We now think these early embryos are playing with fire but in a very calculated way. This could be a very robust mechanism for regulating development…I’m personally excited to continue exploring novel functions of these elements in development and disease.”

Stem Cell Roundup: New understanding of Huntington’s; how stem cells can double your DNA; and using “the Gary Oldman of cell types” to reverse aging

/ Kevin McCormack / Leave a comment

This week’s roundup highlights how we are constantly finding out new and exciting ways that stem cells could help change the way we treat disease.

Our Cool Stem Cell Image of the Week comes from our first story, about unlocking some of the secrets of Huntington’s disease. It comes from the Laboratory of Stem Cell Biology and Molecular Embryology at The Rockefeller University

Huntington's neurons

A new approach to studying and developing therapies for Huntington’s disease

Researchers at Rockefeller University report new findings that may upend the way scientists study and ultimately develop therapies for Huntington’s disease, a devastating, inherited neurodegenerative disorder that has no cure. Though mouse models of the disease are well-established, the team wanted to focus on human biology since our brains are more complex than those of mice. So, they used CRISPR gene editing technology in human embryonic stem cells to introduce the genetic mutations that cause HD.

Though symptoms typically do not appear until adulthood, the researchers were surprised to find that in their human cell-based model of HD, abnormalities in nerve cells occur at the earliest steps in brain development. These results suggest that HD therapies should focus on treatments much earlier in life.

The researchers observed another unexpected twist: cells that lack Huntingtin, the gene responsible for HD, are very similar to cells found in HD. This suggests that too little Huntingtin may be causing the disease. Up until now, the prevailing idea has been that Huntington’s symptoms are caused by the toxicity of too much mutant Huntingtin activity.

We’ll certainly be keeping an eye on how further studies using this new model affect our understanding of and therapy development for HD.

This study was published in Development and was picked by Science Daily.

How you can double your DNA

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As you can imagine we get lots of questions about stem cell research here at CIRM. Last week we got an email asking if a stem cell transplant could alter your DNA? The answer is, under certain circumstances, yes it could.

A fascinating article in the Herald Review explains how this can happen. In a bone marrow transplant bad blood stem cells are killed and replaced with healthy ones from a donor. As those cells multiply, creating a new blood supply, they also carry the DNA for the donor.

But that’s not the only way that people may end up with dual DNA. And the really fascinating part of the article is how this can cause all sorts of legal and criminal problems.

One researcher’s efforts to reverse aging

gary-oldman

Gary Oldman: Photo courtesy Variety

“Stem cells are the Gary Oldman of cell types.” As a fan of Gary Oldman (terrific as Winston Churchill in the movie “Darkest Hour”) that one line made me want to read on in a profile of Stanford University researcher Vittorio Sebastiano.

Sebastiano’s goal is, to say the least, rather ambitious. He wants to reverse aging in people. He believes that if you can induce a person’s stem cells to revert to a younger state, without changing their function, you can effectively turn back the clock.

Sebastiano says if you want to achieve big things you have to think big:

“Yes, the ambition is huge, the potential applications could be dramatic, but that doesn’t mean that we are going to become immortal in some problematic way. After all, one way or the other, we have to die. We will just understand aging in a better way, and develop better drugs, and keep people happier and healthier for a few more years.”

The profile is in the journal Nautilus.

Stem Cell Stories that Caught our Eye: finding the perfect match, imaging stem cells and understanding gene activity

/ Karen Ring / Leave a comment

Here are the stem cell stories that caught our eye this week. Enjoy!

LAPD officer in search of the perfect match.

LAPD Officer Matthew Medina with his wife, Angelee, and their daughters Sadie and Cassiah. (Family photo)

This week, the San Diego Union-Tribune featured a story that tugs at your heart strings about an LAPD officer in desperate need of a bone marrow transplant. Matthew Medina is a 40-year-old man who was diagnosed earlier this year with aplastic anemia, a rare disorder that prevents the bone marrow from producing enough blood cells and platelets. Patients with this disorder are prone to chronic fatigue and are at higher risk for infection and uncontrolled bleeding.

Matthew needs a bone marrow transplant to replace his diseased bone marrow with healthy marrow from a donor, but so far, he has yet to find a match. Part of the reason for this difficulty is the lack of diversity in the national bone marrow registry, which has over 25 million registered donors, the majority of which are white Americans of European decent. As a Filipino, Matthew has a 40% chance of finding a perfect match in the national registry compared to a 75% chance if he were white. An even more unsettling fact is that Filipinos make up less than 1% of donors on the national registry.

Matthew has a sister, but unfortunately, she wasn’t a match. For now, Matthew is being kept alive with blood transfusions at his home in Bellflower while he waits for good news. With the support of his family and friends, the hope is that he won’t have to wait for long. Already 1000 people in his local community have signed up to be bone marrow donors.

On a larger scale, organizations like A3M and Mixed Marrow are hoping to help patients like Matthew by increasing the diversity of the national bone marrow registry. A3M specifically recruits Asian donors while Mixed Match focuses on people with multi-ethnic backgrounds. Ayumi Nagata, a recruitment manager at A3M, said their main challenge is making healthy people realize the importance of being a bone marrow donor.

“They could be the cure for someone’s cancer or other disease and save their life. How often do we have that kind of opportunity?”

An algorithm that makes it easier to see stem cell development.

To understand how certain organs like the brain develop, scientists rely on advanced technologies that can track individual stem cells and monitor their fate as they mature into more specialized cells. Scientists can observe stem cell development with fluorescent proteins that light up when a stem cell expresses specific transcription factors that help decide the cell’s fate. Using a time-lapse microscope, these fluorescent stem cells can easily be identified and tracked throughout their lifetime.

But the pictures don’t always come out crystal clear. Just as a dirty camera lens makes for a dirty picture, images produced by time-lapse microscopy images can be plagued by shadows, artifacts and lighting inconsistencies, making it difficult to observe the orchestrated expression of transcription factors involved in a stem cell’s development.

This week in the journal Nature Communications, a team of scientists from Germany reported a solution that gives a clear view of stem cell development. The team developed a computer algorithm called BaSiC that acts like a filter and removes the background noise from time-lapse images of individual cells. Unlike previous algorithms, BaSiC requires fewer reference images to make its corrections.

The software BaSiC improves microscope images. (Credit: Tingying Peng / TUM/HMGU)

In coverage by Phys.org, author Dr. Tingying Peng explained the advantages of their algorithm,

“Contrary to other programs, BaSiC can correct changes in the background of time-lapse videos. This makes it a valuable tool for stem cell researchers who want to detect the appearance of specific transcription factors early on.”

The team proved that BaSiC is an effective image correcting tool by using it to study the development of hematopoietic or blood stem cells. They took time-lapse videos of blood stem cells over six days and observed that the stem cells chose between two developmental tracks that produced different types of mature blood cells. Using BaSiC, they found that blood stem cells that specialized into white blood cells expressed the transcription factor Pu.1 while the stem cells that specialized into red blood cells did not. Without the algorithm, they didn’t see this difference.

Senior author on the study, Dr. Nassir Navab, concluded by highlighting the importance of their technology and sharing his team’s vision for the future.

“Using BaSiC, we were able to make important decision factors visible that would otherwise have been drowned out by noise. The long-term goal of this research is to facilitate influencing the development of stem cells in a targeted manner, for example to cultivate new heart muscle cells for heat-attack patients. The novel possibilities for observation are bringing us a step closer to this goal.”

Silenced vs active genes: it’s like oil and water (Todd Dubicoff)

The DNA from just one of your cells would be an astounding six feet in length if stretched out end to end. To fit into a nucleus that is a mere 4/10,000th of an inch in diameter, DNA’s double helical structure is organized into intricate twists within twists with the help of proteins called histones.

Together the DNA and histones are called chromatin. And it turns out that chromatin isn’t just for stuffing all that genetic material into a tiny space. The amount of DNA folding also affects the regulation of genes. Areas of chromatin that are less densely packed are more accessible to DNA-binding proteins called transcription factors that activate gene activity. Other regions, called heterochromatin, are compacted which leads to silencing of genes because transcription factors are shut out.

But there’s a wrinkle in this story. More recently, scientists have shown that large proteins are able to wriggle their way into heterochromatin while smaller proteins cannot. So, there must be additional factors at play. This week, a CIRM-funded research project published in Nature provides a possible explanation.

Liquid-like fusion of heterochromatin protein 1a droplets is shown in the embryo of a fruit fly. (Credit: Amy Strom/Berkeley Lab)

Examining the nuclei of fruit fly embryos, a UC Berkeley research team report that various regions of heterochromatin coalesce into liquid droplets which physically separates them from regions where gene activity is high. This phenomenon, called phase-phase separation, is what causes oil droplets to fuse together when added to water. Lead author Dr. Amy Strom explained the novelty of this finding and its implications in a press release:

“We are excited about these findings because they explain a mystery that’s existed in the field for a decade. That is, if compaction [of chromatin] controls access to silenced [DNA] sequences, how are other large proteins still able to get in? Chromatin organization by phase separation means that proteins are targeted to one liquid or the other based not on size, but on other physical traits, like charge, flexibility, and interaction partners.”

Phase-phase separation can also affect other cell components, and problems with it have been linked to neurological disorders like dementia. In diseases like Alzheimer’s and Huntington’s, proteins aggregate causing them to become more solid than liquid over time. Strom is excited about how phase-phase separation insights could lead to novel therapeutic strategies:

“If we can better understand what causes aggregation, and how to keep things more liquid, we might have a chance to combat these types of disease.”

Stem Cell Stories That Caught Our Eye: Free Patient Advocate Event in San Diego, and new clues on how to fix muscular dystrophy and Huntington’s disease

/ Kevin McCormack / 1 Comment

UCSD Patient Advocate mtg instagram

Stem cell research is advancing so fast that it’s sometimes hard to keep up. That’s one of the reasons we have our Friday roundup, to let you know about some fascinating research that came across our desk during the week that you might otherwise have missed.

Of course, another way to keep up with the latest in stem cell research is to join us for our free Patient Advocate Event at UC San Diego next Thursday, April 20th from 12-1pm.  We are going to talk about the progress being made in stem cell research, the problems we still face and need help in overcoming, and the prospects for the future.

We have four great speakers:

  • Catriona Jamieson, Director of the CIRM UC San Diego Alpha Stem Cell Clinic and an expert on cancers of the blood
  • Jonathan Thomas, PhD, JD, Chair of CIRM’s Board
  • Jennifer Briggs Braswell, Executive Director of the Sanford Stem Cell Clinical Center
  • David Higgins, Patient Advocate for Parkinson’s on the CIRM Board

We will give updates on the exciting work taking place at UCSD and the work that CIRM is funding. We have also set aside some time to get your thoughts on how we can improve the way we work and, of course, answer your questions.

What: Stem Cell Therapies and You: A Special Patient Advocate Event

When: Thursday, April 20th 12-1pm

Where: The Sanford Consortium for Regenerative Medicine, 2880 Torrey Pines Scenic Drive, La Jolla, CA 92037

Why: Because the people of California have a right to know how their money is helping change the face of regenerative medicine

Who: This event is FREE and open to everyone.

We have set up an EventBrite page for you to RSVP and let us know if you are coming. And, of course, feel free to share this with anyone you think might be interested.

This is the first of a series of similar Patient Advocate Update meetings we plan on holding around California this year. We’ll have news on other locations and dates shortly.

 

Fixing a mutation that causes muscular dystrophy (Karen Ring)

It’s easy to take things for granted. Take your muscles for instance. How often do you think about them? (Don’t answer this if you’re a body builder). Daily? Monthly? I honestly don’t think much about my muscles unless I’ve injured them or if they’re sore from working out.

duchennes-cardiomyocytes-body

Heart muscle cells (green) that don’t have dystrophin protein (Photo; UT Southwestern)

But there are people in this world who think about their muscles or their lack of them every day. They are patients with a muscle wasting disease called Duchenne muscular dystrophy (DMD). It’s the most common type of muscular dystrophy, and it affects mainly young boys – causing their muscles to progressively weaken to the point where they cannot walk or breathe on their own.

DMD is caused by mutations in the dystrophin gene. These mutations prevent muscle cells from making dystrophin protein, which is essential for maintaining muscle structure. Scientists are using gene editing technologies to find and fix these mutations in hopes of curing patients of DMD.

Last year, we blogged about a few of these studies where different teams of scientists corrected dystrophin mutations using CRISPR/Cas9 gene editing technology in human cells and in mice with DMD. One of these teams has recently followed up with a new study that builds upon these earlier findings.

Scientists from UT Southwestern are using an alternative form of the CRISPR gene editing complex to fix dystrophin mutations in both human cells and mice. This alternative CRISPR complex makes use of a different cutting enzyme, Cpf1, in place of the more traditionally used Cas9 protein. It’s a smaller protein that the scientists say can get into muscle cells more easily. Cpf1 also differs from Cas9 in what DNA nucleotide sequences it recognizes and latches onto, making it a new tool in the gene editing toolbox for scientists targeting DMD mutations.

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Gene-edited heart muscle cells (green) that now express dystrophin protein (Photo: UT Southwestern)

Using CRISPR/Cpf1, the scientists corrected the most commonly found dystrophin mutation in human induced pluripotent stem cells derived from DMD patients. They matured these corrected stem cells into heart muscle cells in the lab and found that they expressed the dystrophin protein and functioned like normal heart cells in a dish. CRISPR/Cpf1 also corrected mutations in DMD mice, which rescued dystrophin expression in their muscle tissues and some of the muscle wasting symptoms caused by the disease.

Because the dystrophin gene is one of the longest genes in our genome, it has more locations where DMD-causing mutations could occur. The scientists behind this study believe that CRISPR/Cpf1 offers a more flexible tool for targeting different dystrophin mutations and could potentially be used to develop an effective gene therapy for DMD.

Senior author on the study, Dr. Eric Olson, provided this conclusion about their research in a news release by EurekAlert:

“CRISPR-Cpf1 gene-editing can be applied to a vast number of mutations in the dystrophin gene. Our goal is to permanently correct the underlying genetic causes of this terrible disease, and this research brings us closer to realizing that end.”

 

A cellular traffic jam is the culprit behind Huntington’s disease (Todd Dubnicoff)

Back in the 1983, the scientific community cheered the first ever mapping of a genetic disease to a specific area on a human chromosome which led to the isolation of the disease gene in 1993. That disease was Huntington’s, an inherited neurodegenerative disorder that typically strikes in a person’s thirties and leads to death about 10 to 15 years later. Because no effective therapy existed for the disease, this discovery of Huntingtin, as the gene was named, was seen as a critical step toward a better understand of Huntington’s and an eventual cure.

But flash forward to 2017 and researchers are still foggy on how mutations in the Huntingtin gene cause Huntington’s. New research, funded in part by CIRM, promises to clear some things up. The report, published this week in Neuron, establishes a connection between mutant Huntingtin and its impact on the transport of cell components between the nucleus and cytoplasm.

Roundup Picture1

The pores in the nuclear envelope allows proteins and molecules to pass between a cell’s nucleus and it’s cytoplasm. Image: Blausen.com staff (2014).

To function smoothly, a cell must be able to transport proteins and molecules in and out of the nucleus through holes called nuclear pores. The research team – a collaboration of scientists from Johns Hopkins University, the University of Florida and UC Irvine – found that in nerve cells, the mutant Huntingtin protein clumps up and plays havoc on the nuclear pore structure which leads to cell death. The study was performed in fly and mouse models of HD, in human HD brain samples as well as HD patient nerve cells derived with the induced pluripotent stem cell technique – all with this same finding.

Roundup Picture2

Huntington’s disease is caused by the loss of a nerve cells called medium spiny neurons. Image: Wikimedia commons

By artificially producing more of the proteins that make up the nuclear pores, the damaging effects caused by the mutant Huntingtin protein were reduced. Similar results were seen using drugs that help stabilize the nuclear pore structure. The implications of these results did not escape George Yohrling, a senior director at the Huntington’s Disease Society of America, who was not involved in the study. Yohrling told Baltimore Sun reporter Meredith Cohn:

“This is very exciting research because we didn’t know what mutant genes or proteins were doing in the body, and this points to new areas to target research. Scientists, biotech companies and pharmaceutical companies could capitalize on this and maybe develop therapies for this biological process”,

It’s important to temper that excitement with a reality check on how much work is still needed before the thought of clinical trials can begin. Researchers still don’t understand why the mutant protein only affects a specific type of nerve cells and it’s far from clear if these drugs would work or be safe to use in the context of the human brain.

Still, each new insight is one step in the march toward a cure.

Stem cell stories that caught our eye: How Zika may impact adult brains; Move over CRISPR there’s a new kid in town; How our bodies store fat

/ Kevin McCormack / 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.

zika

Zika mosquito

Zika virus could impact adult brains

It’s not just a baby’s developing brain that is vulnerable to the Zika virus, adult brains may be too. A new study shows that some stem cells that help repair damage in the adult brain can be impacted by Zika. This is the first time we’ve had any indication this could be a problem in a fully developed brain.

The study, in the journal Cell Stem Cell, looked at neural progenitors, a  stem cell that plays an important role in helping replace or repair damaged neurons, or nerve cells, in the brain. The researchers exposed the cells to the Zika virus and found that it infected the cells, causing some of the cells to die, and also limited the ability of the cells to proliferate.

In an interview in Healthday, Sujan Shresta, a researcher at the La Jolla Institute for Allergy and Immunology and one of the lead authors of the study, says although their work was done in adult mice, it may have implications for people:

“Zika can clearly enter the brains of adults and can wreak havoc. But it’s a complex disease, it’s catastrophic for early brain development, yet the majority of adults who are infected with Zika rarely show detectable symptoms. Its effect on the adult brain may be more subtle and now we know what to look for.”

Move over CRISPR, there’s a new gene-editing tool in town

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Jennifer Lopez: Photo courtesy MTV

For much of the last year the hottest topic in stem cell and gene editing research has been CRISPR and the ease with which it can be used to edit genes. It’s so hot that apparently it’s the title of an upcoming TV show starring Jeniffer Lopez.

But hold on J-Lo, a new study in Nature Communications says by the time the show is on the air it may be old hat. Researchers at Carnegie Mellon and Yale University have developed a new gene-editing system, one they claim is easier to use and more accurate than CRISPR. And to prove it, they say they have successfully cured a genetic blood disorder in mice, using a simple IV approach.

Tools like CRISPR use enzymes to cut open sections of DNA to edit a specific gene. It’s like using a pair of scissors to cut a piece of string that has a big knot in the middle; you cut out the knot then join the ends of the string together. The problem with CRISPR is that the enzymes it uses are quite large and hard to use in a living animal – let alone a human – so they have to remove the target cells from the body and do the editing in the lab. Another problem is that CRISPR sometimes cuts sections of DNA that the researchers don’t want cut and could lead to dangerous side effects.

Greater precision

The Carnegie Mellon/Yale team say their new method avoids both problems. They use nanoparticles that contain molecules made from peptide nucleic acid (PNA), a kind of artificial form of DNA. This PNA is engineered to be able to cut open DNA and bind to a specific target without cutting anything else.

The team used this approach to target the mutated gene in beta thalassemia, a blood disorder that can be fatal if left untreated. The therapy binds to the malfunctioning gene, enabling the body’s own DNA repair system to correct the problem.

In a news story in Science Daily Danith Ly, one of the lead authors on the study, says even though the technique was successful in editing the target genes just 7 percent of the time, that is way more than the 0.1 percent rate most other gene editing tools achieve.

“The effect may only be 7 percent, but that’s curative. In the case of this particular disease model, you don’t need a lot of correction. You don’t need 100 percent to see the phenotype return to normal.”

Hormone that controls if and when fat cells mature

Obesity is one of the fastest growing public health problems in the US and globally. Understanding the mechanisms behind how that happens could be key to finding ways to address it. Now researchers at Stanford University think they may have uncovered an important part of the answer.

Their findings, reported in Science Signaling, show that mature fat cells produce a hormone called Adamts1 which acts like a switch for surrounding stem cells, determining if they change into fat-storing cells.   People who eat a high-fat diet experience a change in their Adamst1 production, and that triggers the nearby stem cells to specialize and start storing fat.

There are still a lot of questions to be answered about Adamst1, including whether it acts alone or in conjunction with other as yet unknown hormones. But in an article in Health Canal, Brian Feldman, the senior author of the study, says they can now start looking at potential use of Adamst1 to fight obesity.

“That won’t be a simple answer. If you block fat formation, extra calories have to go somewhere in the body, and sending them somewhere else outside fat cells could be more detrimental to metabolism. We know from other researchers’ work that liver and muscle are both bad places to store fat, for example. We do think there are going to be opportunities for new treatments based on our discoveries, but not by simply blocking fat formation alone.”

 

Salk scientists explain why brain cells are genetically diverse

/ Karen Ring / Leave a comment

twin_boys

I’ve always wondered why some sets of genetically identical twins become not so identical later in life. Sometimes they differ in appearance. Other times, one twin is healthy while the other is plagued with a serious disease. These differences can be explained by exposure to different environmental factors over time, but there could also be a genetic explanation involving our brains.

The brain is composed of approximately 100 billion cells called neurons, each with a DNA blueprint that contains instructions that determine the function of these neurons in the brain. Originally it was thought that all cells, including neurons, have the same DNA. But more recently, scientists discovered that the brain is genetically diverse and that neurons within the same brain can have slightly different DNA blueprints, which could give them slightly different functions.

Jumping genes and genetic diversity

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Fred “Rusty” Gage: Photo courtesy Salk Institute

Why and how neurons have differences in their DNA are questions that Salk Institute professor Fred Gage has pursued for more than a decade. In 2005, his lab discovered a mechanism during neural development that causes differences in the DNA of neurons. As a brain stem cell develops into a neuron, long interspersed nuclear elements (L1s), which are small pieces of DNA, copy and paste themselves, seemingly at random, throughout a neuron’s genome.

These elements were originally dubbed “jumping genes” because of their ability to hop around and insert themselves into DNA. It turns out that L1s do more than copy and paste themselves to create changes in DNA, they also can delete chunks of DNA. In a CIRM-funded study published this week in the journal Nature Neuroscience, Gage and colleagues at the Salk Institute reported new insights into L1 activity and how it creates genetic diversity in the brain.

Copy, paste, delete

Gage and his team had clues that L1s can cause DNA deletions in neurons back in 2013. They used a technique called single-cell sequencing to record the sequence of individual neuronal genomes and saw that some of their genomes had large sections of DNA added or missing.

They thought that L1s could be the reason for these insertions and deletions, but didn’t have proof until their current study, which used an improved method to identify areas of the neuronal genome modified by L1s. This method, combined with a computer algorithm that can easily tell the difference between various types of L1 modifications, revealed that areas of the genome with L1s were susceptible to DNA cutting caused by enzymes that home in on the L1 sequences. These breaks in the DNA then cause the observed deletions.

Gage explained their findings in a news release:

“In 2013, we discovered that different neurons within the same brain have various complements of DNA, suggesting that they function slightly differently from each other even within the same person. This recent study reveals a new and surprising form of variation that will help us understand the role of L1s, not only in healthy brains but in those affected by schizophrenia and autism.”

Jennifer Erwin, first author on the study, further elaborated:

“The surprising part was that we thought all L1s could do was insert into new places. But the fact that they’re causing deletions means that they’re affecting the genome in a more significant way,” says Erwin, a staff scientist in Gage’s group.”

Insights into brain disorders

It’s now known that L1s are important for the brain’s genetic diversity, but Gage also believes that L1s could play a role in causing brain disorders like schizophrenia and autism where there is heightened L1 activity in the neurons of these patients. In future work, Gage and his team will study how L1s can cause changes in genes associated with schizophrenia and autism and how these changes can effect brain function and cause disease.

New study says stem cells derived from older people may have more problems than we thought.

/ Kevin McCormack / Leave a comment

heart muscle from iPS

iPS-generated heart muscle cells

Ever since 2006 when Japanese researcher Shinya Yamanaka showed that you could take an adult cell, such as those in your skin, and reprogram it to act like an embryonic stem cell, the scientific world has looked at these induced pluripotent stem (iPS) cells as a potential game changer. They had the ability to convert a person’s own cells into any other kind of cell in the body, potentially offering a way of creating personalized treatments for a wide variety of diseases.

Fears that this reprogramming method might create some cancer-causing genetic mutations seemed to have been eased when two recent studies suggested this approach is relatively safe and unlikely to lead to any tumors in patients. We funded one of those studies and blogged about it.

Reason for caution

But now a new study in the journal Cell Stem Cell  says “not so fast”. The study says the older the person is, the greater the chance that any iPS cells derived from their tissue could contain potentially harmful mutations, but not in the places you would normally think.

A team at Oregon Health and Science University, led by renowned scientist Shoukhrat Mitalipov, took skin and blood samples from a 72-year-old man. The scientists examined the DNA from those samples, then reprogrammed those cells into iPS cells, and examined the DNA from the new stem cells.

Mitalipov-2

Shoukhrat Mitalipov: photo courtesy Oregon Health and Science University

When they looked at the cells collectively the levels of mutations in the new iPS cells appeared to be quite low. But when they looked at individual cells, they noticed a wide variety of mutations in the mitochondria in those cells.

Now, mitochondria play an important role in the life of a cell. They act as a kind of battery, providing the power a cell needs to perform a variety of functions such as signaling and cell growth. But while they are part of the cell, mitochondria have their own genomes. It was here that the researchers found the mutations that raised questions.

Older cells have more problems

Next they repeated the experiment but this time took skin and blood samples from 14 people between the ages of 24 and 72. They found that  older people had more genetic mutations in their mitochondrial DNA that were then transferred to the iPS cells derived from those people. In some cases up to 80 percent of the iPS cell lines generated showed mitochondrial mutations. That’s really important because the greater the amount of mutated mitochondrial DNA in a cell, the more its ability to function is compromised.

In a news release, Mitalipov says this should cause people to pause before using iPS cells derived from an older person for therapeutic purposes:

“Pathogenic mutations in our mitochondrial DNA have long been thought to be a driving force in aging and age-related diseases, though clear evidence was missing. Now with that evidence at hand, we know that we must screen stem cells for mutations or collect them at younger age to ensure their mitochondrial genes are healthy. This foundational knowledge of how cells are damaged in the natural process of aging may help to illuminate the role of mutated mitochondria in degenerative disease.”

To be clear, the researchers are not saying these iPS cells from older people should never be used, only that they need to be carefully screened to ensure they are not seriously damaged before being transplanted into a patient.

A possible solution

Mitalipov suggests a simple way around the problem would be to identify the iPS cell with the best mitochondria, and then use that as the basis for a new cell line that could then be used to create a new therapy.

Taosheng Huang, a researcher at the Mitochondrial Disorders Program at Cincinnati Children’s Hospital Medical Center, is quoted in the news release saying the lesson is clear:

“If you want to use iPS cells in a human, you must check for mutations in the mitochondrial genome. Every single cell can be different. Two cells next to each other could have different mutations or different percentages of mutations.”