Zika is caused by a virus that is mainly transmitted by infected female Aedes aegypti mosquitoes but also through sexual intercourse. People infected by Zika virus usually have mild symptoms that normally last for two to seven days and can include fever, skin rashes, conjunctivitis, muscle and joint pain, or headaches.
Zika also causes devastating congenital neurodefective disorders, most notably microcephaly, where a child’s head is much smaller than expected, in children born to infected mothers as well as neurological problems in those infected like Guillain-Barré syndrome.
To date, no vaccines or other treatments have been approved for Zika virus. Nor have investigations into other ways of fighting the virus led to clearly effective countermeasures.
But there is good news. Researchers from the University of California, Los Angeles (UCLA) have developed a Zika vaccine technology that is both highly effective and safe in preclinical mouse models. The study—partially funded by the California Institute for Regenerative Medicine (CIRM)—found that in a pregnant mouse model, the vaccine prevented both the pregnant mothers and the developing fetuses from developing systemic infection.
Dr. Vaithilingaraja Arumugaswami, an associate professor of molecular and medical pharmacology at the University of California, Los Angeles (UCLA) is a co-senior author of the study.
In engineering the vaccine, researchers deleted the part of the Zika genome that codes for the viral shell, the protective shell that a virus forms to evade the immune system. “This modification both stimulates an immunogenic reaction and prevents the virus from replicating and spreading from cell to cell,” said Vaithilingaraja Arumugaswami, D.V.M., Ph.D., Associate Professor of Molecular and Medical Pharmacology at UCLA.
This is important progress because the average length of time between periods of extensive Zika viral spread is approximately 7 years. Given that the virus was last widespread in 2016, “it is only a matter of time before we start seeing the virus spread again,” said Kouki Morizono, M.D., Ph.D., Associate Professor of Medicine at UCLA and co-senior author of this study.
“The ongoing COVID-19 pandemic has shown us the power of a strong pandemic preparedness plan and clear communication about prevention methods – all culminating in the rapid rollout of safe and reliable vaccines. Our research is a crucial first step in developing an effective vaccination program that could curb the spread of Zika virus and prevent large-scale spread from occurring,” said Arumugaswami.
Dr. Tariq Rana (left) and Dr. Jeremy Rich (right) both lead independent teams at UC San Diego that identified a molecule, αvβ5 integrin, as the Zika virus’ key to getting into brain stem cells
Zika virus is caused by a virus transmitted by Aedes mosquitoes. People usually develop mild symptoms that include fever, rash, and muscle and joint pain. However, Zika virus infection during pregnancy can lead to much more serious problems. The virus causes infants to be born with microcephaly, a condition in which the brain does not develop properly, resulting in an abnormally small head. In 2015-2016, the rapid spread of the virus was observed in Latin America and the Caribbean, increasing the urgency of understanding how the virus affected brain development.
Working independently, Dr. Tariq Rana and Dr. Jeremy Rich from UC San Diego identified the same molecule, αvβ5 integrin, as the Zika virus’ key to entering brain stem cells. The two studies, with the aid of CIRM funding, discovered how to take advantage of the molecule in order to block the Zika virus from infecting cells. In addition to this, they were able to turn it into something useful: a way to destroy brain cancer stem cells.
In the first study, Dr. Rana and his team used CRISPR gene editing on brain cancer stem cells to delete individual genes, which was done to see which genes are required for the Zika virus to enter the cells. They discovered that the gene responsible for αvβ5 integrin also enabled the Zika virus.
In a press release by UC San Diego, Dr. Rana elaborates on the importance of his findings.
“…we found Zika uses αvβ5, which is unique. When we further examined αvβ5 expression in brain, it made perfect sense because αvβ5 is the only integrin member enriched in neural stem cells, which Zika preferentially infects. Therefore, we believe that αvβ5 is the key contributor to Zika’s ability to infect brain cells.”
In the second study, Dr. Rich and his team use an antibody to block αvβ5 integrin and found that it prevented the virus from infecting brain cancer stem cells and normal brain stem cells. The team then went on to block αvβ5 integrin in a mouse model for glioblastoma, an aggressive type of brain tumor, by using an antibody or deactivating the gene responsible for the molecule. Both approaches blocked Zika virus infection and allowed the treated mice to live longer than untreated mice.
Dr. Rich then partnered with Dr. Alysson Muotri at UC San Diego to transplant glioblastoma tumors into laboratory “mini-brains” that can be used for drug discovery. The researchers discovered that Zika virus selectively eliminates glioblastoma stem cells from the mini-brains. Additionally, blocking αvβ5 integrin reversed that anti-cancer activity, further demonstrating the molecule’s crucial role in Zika virus’ ability to destroy cells.
In the same UC San Diego press release, Dr. Rich talks about how understanding Zika virus could help in treating glioblastoma.
“While we would likely need to modify the normal Zika virus to make it safer to treat brain tumors, we may also be able to take advantage of the mechanisms the virus uses to destroy cells to improve the way we treat glioblastoma.”
Dr. Rana’s full study was published in Cell Reports and Dr. Rich’s full study was published in Cell Stem Cell.
An out of control flame can be very dangerous, even life-threatening. But when harnessed, that same flame sustains life in the form of warm air, a source of light, and a means to cook.
A similar duality holds true for viruses. Once it infects the body, a virus can replicate like wildfire and cause serious illness and sometimes death. But in the lab, researchers can manipulate viruses to provide an efficient, harmless method to deliver genetic material into cells, as well as to prime the immune system to protect against future infections.
In a Journal of Experimental Medicine study published this week, researchers from the University of Washington, St. Louis and UC San Diego also show evidence that a virus, in this case the Zika virus, could even be a possible therapy for a hard-to-treat brain cancer called glioblastoma.
Brain cancer stem cells (left) are killed by Zika virus infection (image at right shows cells after Zika treatment). Image: Zhe Zhu, Washington U., St. Louis.
Recent outbreaks of the Zika virus have caused microcephaly during fetal development. Babies born with microcephaly have a much smaller than average head size due to a lack of proper brain development. Children born with this condition suffer a wide range of devastating symptoms like seizures, difficulty learning, and movement problems just to name a few. In the race to understand the outbreak, scientists have learned that the Zika virus induces microcephaly by infecting and killing brain stem cells, called neural progenitors, that are critical for the growth of the developing fetal brain.
Now, glioblastoma tumors contain a small population of cells called glioblastoma stem cells (GSCs) that, like neural progenitors, can lay dormant but also make unlimited copies of themselves. It’s these properties of glioblastoma stem cells that are thought to allow the glioblastoma tumor to evade treatment and grow back. The research team in this study wondered if the Zika virus, which causes so much damage to neural progenitors in developing babies, could be used for good by infecting and killing cancer stem cells in glioblastoma tumors in adult patients.
To test this idea, the scientists infected glioblastoma brain tumor samples with Zika and showed that the virus spreads through the cells but primarily kills off the glioblastoma stem cells, leaving other cells in the tumor unscathed. Since radiation and chemotherapy are effective at killing most of the tumor but not the cancer stem cells, a combination of Zika and standard cancer therapies could provide a knockout punch to this aggressive brain cancer.
Even though Zika virus is much more destructive to the developing fetal brain than to adult brains, it’s hard to imagine the US Food and Drug Administration ever approving the injection of a dangerous virus into the site of a glioblastoma tumor. So, the scientists genetically modified the Zika virus to make it more sensitive to the immune system’s first line of defense called the innate immunity. With just the right balance of genetic alterations, it might be possible to retain the Zika virus’ ability to kill off cancer stem cells without causing a serious infection.
The results were encouraging though not a closed and shut case: when glioblastoma cancer stem cells were infected with these modified Zika virus strains, the virus’ cancer-killing abilities were weaker than the original Zika strains but still intact. Based on these results, co-senior author and WashU professor, Dr. Michael S. Diamond, plans to make more tweaks to the virus to harness it’s potential to treat the cancer without infecting the entire brain in the process.
“We’re going to introduce additional mutations to sensitize the virus even more to the innate immune response and prevent the infection from spreading,” said Diamond in a press release. “Once we add a few more changes, I think it’s going to be impossible for the virus to overcome them and cause disease.”
April is National Autism Awareness Month and people and organizations around the world are raising awareness about a disorder that affects more than 20 million people globally. Autism affects early brain development and causes a wide spectrum of social, mental, physical and emotional symptoms that appear during childhood. Because the symptoms and their severity can vary extremely between people, scientists now use the classification of autism spectrum disorder (ASM).
Alysson Muotri UC San Diego
In celebration of Autism Awareness Month, we’re featuring an interview with a CIRM-funded scientist who is on the forefront of autism and ASD research. Dr. Alysson Muotri is a professor at UC San Diego and his lab is interested in unlocking the secrets to brain development by using molecular tools and stem cell models.
One of his main research projects is on autism. Scientists in his lab are using induced pluripotent stem cells (iPSCs) derived from individuals with ASD to model the disease in a dish. From these stem cell models, his team is identifying genes that are associated with ASD and potential drugs that could be used to treat this disorder. Ultimately, Dr. Muotri’s goal is to pave a path for the development of personalized therapies for people with ASD.
I reached out to Dr. Muotri to ask for an update on his Autism research. His responses are below.
Q: Can you briefly summarize your lab’s work on Autism Spectrum Disorders?
AM: As a neuroscientist studying autism, I was frustrated with the lack of a good experimental model to understand autism. All the previous models (animal, postmortem brain tissues, etc.) have serious experimental limitations. The inaccessibility of the human brain has blocked the progress of research on ASD for a long time. Cellular reprogramming allows us to transform easy-access cell types (such as skin, blood, dental pulp, etc.) into brain cells or even “mini-brains” in the lab. Because we can capture the entire genome of the person, we can recapitulate early stages of neurodevelopment of that same individual. This is crucial to study neurodevelopment disorders, such as ASD, because of the strong genetic factor underlying the pathology [the cause of a disease]. By comparing “mini-brains” between an ASD and neurotypical [non-ASD] groups, we can find anatomical and functional differences that might explain the clinical symptoms.
Q: What types of tools and models are you using to study ASD?
AM: Most of my lab takes advantage of reprogramming stem cells and genome editing techniques to generate 3D organoid models of ASD. We use the stem cells to create brain organoids, also called “mini-brains” in the lab. These mini-brains will develop from single cells and grow and mature in the same way as the fetal brain. Thus, we can learn about their structure and connectivity over time.
A cross section of a cerebral organoid or mini-brain courtesy of Alysson Muotri.
This new model brings something novel to the table: the ability to experimentally test specific hypotheses in a human background. For example, we can ask if a specific genetic variant is causal for an autistic individual. Thus, we can edit the genome of that autistic individual, fixing target mutations in these mini-brains and check if now the fixed mini-brains will develop any abnormalities seen in ASD.
The ability to combine all these recent technologies to create a human experimental model of ASD in the lab is quite new and very exciting. As with any other model, there are limitations. For example, the mini-brains don’t have all the complexity and cell types seen in the developing human embryo/fetus. We also don’t know exactly if we are giving them the right and necessary environment (nutrients, growth factors, etc.) to mature. Nonetheless, the progress in this field is taking off quickly and it is all very promising.
Two mini-brains grown in a culture dish send out cellular extensions to connect with each other. Neurons are in green and astrocytes are in pink. Image courtesy of Dr. Muotri.
Q: We’ve previously written about your lab’s work on the Tooth Fairy Project and how you identified the TRPC6 gene. Can you share updates on this project and any new insights?
AM: The Tooth Fairy Project was designed to collect dental pulp cells from ASD and control individuals in a non-invasive fashion (no need for skin biopsy or to draw blood). We used social media to connect with families and engage them in our research. It was so successful we have now hundreds of cells in the lab. We use this material to reprogram into stem cells and to sequence their DNA.
One of the first ASD participants had a mutation in one copy of the TRPC6 gene, a novel ASD gene candidate. Everybody has two copies of this gene in the genome, but because of the mutation, this autistic kid has only one functional copy. Using stem cells, we re-created cortical neurons from that individual and confirmed that this mutation inhibits the formation of excitatory synapses (connections required to propagate information).
Interestingly, while studying TRPC6, we realized that a molecule found in Saint John’s Wort, hyperforin, could stimulate the functional TRPC6. Since the individual still has one functional TRPC6 gene copy, it seemed reasonable to test if hyperforin treatment could compensate the mutation on the other copy. It did. A treatment with hyperforin for only two weeks could revert the deficits on the neurons derived from that autistic boy. More exciting is the fact that the family agreed to incorporate St. John’s Wort on his diet. We have anecdotal evidence that this actually improved his social and emotional skills.
To me, this is the first example of personalized treatment for ASD, starting with genome sequencing, detecting potential causative genetic mutations, performing cellular modeling in the lab, and moving into clinic. I believe that there are many other autistic cases where this approach could be used to find better treatments, even with off the counter medications. To me, that is the greatest insight.
Watch Dr. Muotri’s Spotlight presentation about the Tooth Fairy Project and his work on autism.
Q: Is any of the research you are currently doing in autism moving towards clinical trials?
AM: IGF-1, or insulin growth factor-1, a drug we found promising for Rett syndrome and a subgroup of idiopathic [meaning its causes are spontaneous or unknown] ASD is now in clinical trials. Moreover, we just concluded a CIRM award on a large drug screening for ASD. The data is very promising, with several candidates. We have 14 drugs in the pipeline, some are repurposed drugs (initially designed for cancer, but might work for ASD). It will require additional pre-clinical studies before we start clinical trials.
Q: What do you think the future of diagnosis and treatment will be for patients with ASD?
AM: I am a big enthusiastic fan of personalized treatments for ASD. While we continue to search for a treatment that could help a large fraction of ASD people, we also recognized that some cases might be easier than others depending on their genetic profile. The idea of using stem cells to create “brain avatars” of ASD individuals in the lab is very exciting. We are also studying the possibility of using this approach as a future diagnostic tool for ASD. I can imagine every baby having their “brain avatar” analyses done in the lab, eventually pointing out “red flags” on the ones that failed to achieve neurodevelopment milestones. If we could capture these cases, way before the autism symptoms onset, we could initiate early treatments and therapies, increasing the chances for a better prognostic and clinical trajectory. None of these would be possible without stem cell research.
Q: What other types of research is your lab doing?
Mini-brains grown in a dish in Dr. Muotri’s lab.
AM: My lab is also using these human mini-brains to test the impact of environmental factors in neurodevelopment. By exposing the mini-brains to certain agents, such as pollution particles, household chemicals, cosmetics or agrotoxic products [pesticides], we can measure the concentration that is likely to induce brain abnormalities (defects in neuronal migration, synaptogenesis, etc.). This toxicological test can complement or substitute for other commonly used analyses, such as animal models, that are not very humane or predictive of human biology. A nice example from my lab was when we used this approach to confirm the detrimental effect of the Zika virus on brain development. Not only did we show causation between the circulating Brazilian Zika virus and microcephaly [a birth defect that causes an abnormally small head], but our data also pointed towards a potential mechanism (we showed that the virus kills neural progenitor cells, reducing the thickness of the cortical layers in the brain).
You can learn more about Dr. Muotri’s research on his lab’s website.
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.
Stem cell model identifies new culprit for anorexia.
Eating disorders like anorexia nervosa are often thought to be caused by psychological disturbances or societal pressure. However, research into the genes of anorexia patients suggests that what’s written in your DNA can be associated with an increased vulnerability to having this disorder. But identifying individual genes at fault for a disease this complex has remained mostly out of scientists’ reach, until now.
A CIRM-funded team from the UC San Diego (UCSD) School of Medicine reported this week that they’ve developed a stem cell-based model of anorexia and used it to identify a gene called TACR1, which they believe is associated with an increased likelihood of getting anorexia.
They took skin samples from female patients with anorexia and reprogrammed them into induced pluripotent stem cells (iPSCs). These stem cells contained the genetic information potentially responsible for causing their anorexia. The team matured these iPSCs into brain cells, called neurons, in a dish, and then studied what genes got activated. When they looked at the genes activated by anorexia neurons, they found that TACR1, a gene associated with psychiatric disorders, was switched on higher in anorexia neurons than in healthy neurons. These findings suggest that the TACR1 gene could be an identifier for this disease and a potential target for developing new treatments.
In a UCSD press release, Professor and author on the study, Alysson Muotri, said that they will follow up on their findings by studying stem cell lines derived from a larger group of patients.
Alysson Muotri UC San Diego
“But more to the point, this work helps make that possible. It’s a novel technological advance in the field of eating disorders, which impacts millions of people. These findings transform our ability to study how genetic variations alter brain molecular pathways and cellular networks to change risk of anorexia nervosa — and perhaps our ability to create new therapies.”
Anorexia is a disease that affects 1% of the global population and although therapy can be an effective treatment for some, many do not make a full recovery. Stem cell-based models could prove to be a new method for unlocking new clues into what causes anorexia and what can cure it.
Nature versus Zika, who will win?
Zika virus is no longer dominating the news headlines these days compared to 2015 when large outbreaks of the virus in the Southern hemisphere came to a head. However, the threat of Zika-induced birth defects, like microcephaly to pregnant women and their unborn children is no less real or serious two years later. There are still no effective vaccines or antiviral drugs that prevent Zika infection but scientists are working fast to meet this unmet need.
Speaking of which, scientists at UCLA think they might have a new weapon in the war against Zika. Back in 2013, they reported that a natural compound in the body called 25HC was effective at attacking viruses and prevented human cells from being infected by viruses like HIV, Ebola and Hepatitis C.
When the Zika outbreak hit, they thought that this compound could potentially be effective at preventing Zika infection as well. In their new study published in the journal Immunity, they tested a synthetic version of 25HC in animal and primate models, they found that it protected against infection. They also tested the compound on human brain organoids, or mini brains in a dish made from pluripotent stem cells. Brain organoids are typically susceptible to Zika infection, which causes substantial cell damage, but this was prevented by treatment with 25HC.
Left to right: (1) Zika virus (green) infects and destroys the formation of neurons (pink) in human stem cell-derived brain organoids. (2) 25HC blocks Zika infection and preserves neuron formation in the organoids. (3) Reduced brain size and structure in a Zika-infected mouse brain. (4) 25HC preserves mouse brain size and structure. Image courtesy of UCLA Stem Cell.
A UCLA news release summarized the impact that this research could have on the prevention of Zika infection,
“The new research highlights the potential use of 25HC to combat Zika virus infection and prevent its devastating outcomes, such as microcephaly. The research team will further study whether 25HC can be modified to be even more effective against Zika and other mosquito-borne viruses.”
Harnessing a naturally made weapon already found in the human body to fight Zika could be an alternative strategy to preventing Zika infection.
Gene therapy in stem cells gives hope to bubble-babies.
Last week, an inspiring and touching story was reported by Erin Allday in the San Francisco Chronicle. She featured Ja’Ceon Golden, a young baby not even 6 months old, who was born into a life of isolation because he lacked a properly functioning immune system. Ja’Ceon had a rare disease called severe combined immunodeficiency (SCID), also known as bubble-baby disease.
Ja’Ceon Golden is treated by patient care assistant Grace Deng (center) and pediatric oncology nurse Kat Wienskowski. Photo: Santiago Mejia, The Chronicle.
Babies with SCID lack the body’s immune defenses against infectious diseases and are forced to live in a sterile environment. Without early treatment, SCID babies often die within one year due to recurring infections. Bone marrow transplantation is the most common treatment for SCID, but it’s only effective if the patient has a donor that is a perfect genetic match, which is only possible for about one out of five babies with this disease.
Advances in gene therapy are giving SCID babies like Ja’Ceon hope for safer, more effective cures. The SF Chronicle piece highlights two CIRM-funded clinical trials for SCID run by UCLA in collaboration with UCSF and St. Jude Children’s Research Hospital. In these trials, scientists isolate the bone marrow stem cells from SCID babies, correct the genetic mutation causing SCID in their stem cells, and then transplant them back into the patient to give them a healthy new immune system.
The initial results from these clinical trials are promising and support other findings that gene therapy could be an effective treatment for certain genetic diseases. CIRM’s Senior Science Officer, Sohel Talib, was quoted in the Chronicle piece saying,
“Gene therapy has been shown to work, the efficacy has been shown. And it’s safe. The confidence has come. Now we have to follow it up.”
Ja’Ceon was the first baby treated at the UCSF Benioff Children’s Hospital and so far, he is responding well to the treatment. His great aunt Dannie Hawkins said that it was initially hard for her to enroll Ja’Ceon in this trial because she was a partial genetic match and had the option of donating her own bone-marrow to help save his life. In the end, she decided that his involvement in the trial would “open the door for other kids” to receive this treatment if it worked.
Ja’Ceon Golden plays with patient care assistant Grace Deng in a sterile play area at UCSF Benioff Children’s Hospital.Photo: Santiago Mejia, The Chronicle
It’s brave patients and family members like Ja’Ceon and Dannie that make it possible for research to advance from clinical trials into effective treatments for future patients. We at CIRM are eternally grateful for their strength and the sacrifices they make to participate in these trials.
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.
Glowing stem cells help scientists understand how cells work. (Karen Ring) It’s easy to notice when something is going wrong. It’s a lot harder to notice when something is going right. The same thing can be said for biology. Scientists dedicate their careers to studying unhealthy cells, trying to understand why people get certain diseases and what’s going wrong at the cellular level to cause these problems. But there is a lot to be said for doing scientific research on healthy cells so that we can better understand what’s happening when cells start to malfunction.
A group from the Allen Institute for Cell Science is doing just this. They used a popular gene-editing technology called CRISPR/Cas9 to genetically modify human stem cell lines so that certain parts inside the cell will glow different colors when observed under a fluorescent microscope. Specifically, the scientists inserted the genetic code to produce fluorescent proteins in both the nucleus and the mitochondria of the stem cells. The final result is a tool that allows scientists to study how stem cells specialize into mature cells in various tissues and organs.
Glowing human stem cells. The edges of the cells are shown in purple while the DNA in the cell’s nucleus is in blue. (Allen Institute for Cell Science).
The director of stem cells and gene editing at the Allen Institute, Ruwanthi Gunawardane, explained how their technology improves upon previous methods for getting cells to glow in an interview with Forbes:
“We’re trying to understand how the cell behaves, how it functions, but flooding it with some external protein can really mess it up. The CRISPR system allows us to go into the DNA—the blueprint—and insert a gene that allows the cell to express the protein in its normal environment. Then, through live imaging, we can watch the cell and understand how it works.”
The team has made five of these glowing stem cell lines available for use by the scientific community through the Coriell Institute for Medical Research (which also works closely with the CIRM iPSC Initiative). Each cell line is unique and has a different cellular structure that glows. You can learn more about these cell lines on the Coriell Allen Institute webpage and by watching this video:
Zika can take multiple routes to infect a child’s brain. (Kevin McCormack) One of the biggest health stories of 2016 has been the rapid, indeed alarming, spread of the Zika virus. It went from an obscure virus to a global epidemic found in more than 70 countries.
The major concern about the virus is its ability to cause brain defects in the developing brain. Now researchers at Harvard have found that it can do this in more ways than previously believed.
Up till now, it was believed that Zika does its damage by grabbing onto a protein called AXL on the surface of brain cells called neural progenitor cells (NPCs). However, the study, published in the journal Cell Stem Cell, showed that even when AXL was blocked, Zika still managed to infiltrate the brain.
Using induced pluripotent stem cell technology, the researchers were able to create NPCs and then modify them so they had no AXL expression. That should, in theory, have been able to block the Zika virus. But when they exposed those cells to the virus they found they were infected just as much as ordinary brain cells exposed to the virus were.
Caption: Zika virus (light blue) spreads through a three-dimensional model of a developing brain. Image by Max Salick and Nathaniel Kirkpatrick/Novartis
In a story in the Harvard Gazette, Kevin Eggan, one of the lead researchers, said this shows scientists need to re-think their approach to countering the virus:
“Our finding really recalibrates this field of research because it tells us we still have to go and find out how Zika is getting into these cells.”
Treatment for a severe form of bubble baby disease appears on the horizon. (Todd Dubnicoff) Without treatment, kids born with bubble baby disease typically die before reaching 12 months of age. Formally called severe combined immunodeficiency (SCID), this genetic blood disorder leaves infants without an effective immune system and unable to fight off even minor infections. A bone marrow stem cell transplant from a matched sibling can treat the disease but this is only available in less than 20 percent of cases and other types of donors carry severe risks.
In what is shaping up to be a life-changing medical breakthrough, a UCLA team has developed a stem cell/gene therapy treatment that corrects the SCID mutation. Over 40 patients have participated to date with a 100% survival rate and CIRM has just awarded the team $20 million to continue clinical trials.
There’s a catch though: other forms of SCID exist. The therapy described above treats SCID patients with a mutation in a gene responsible for producing a protein called ADA. But an inherited mutation in another gene called Artemis, leads to a more severe form of SCID. These Artemis-SCID infants have even less success with a standard bone marrow transplant compared to those with ADA-SCID. Artemis plays a role in DNA damage repair something that occurs during the chemo and radiation therapy sessions that are often necessary for blood marrow transplants. So Artemis-SCID patients are hyper-sensitive to the side of effects of standard treatments.
A recent study by UCSF scientists in Human Gene Therapy, funded in part by CIRM, brings a lot of hope to these Artemis-SCID patient. Using a similar stem cell/gene therapy method, this team collected blood stem cells from the bone marrow of mice with a form of Artemis-SCID. Then they added a good copy of the human Artemis gene to these cells. Transplanting the blood stem cells back to mice, restored their immune systems which paves the way for delivering this approach to clinic to also help the Artemis-SCID patients in desperate need of a treatment.
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 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
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.”
Did you hear that? It’s the sound of more than 15,000 people taking a collective breath. That’s because we are now at the halfway point of the 2016 BIO International Convention, the world’s largest biotechnology gathering with over 900 speakers, 180 company presentations, 19 education tracks, 6 super sessions, and 35,000 partnering meetings. Now that’s a lot of stuff!
While many at BIO are focused on partnering – establishing new and exciting relationships with other biotech and pharmaceutical companies to push their products forward – others come to BIO to learn about the latest in research, innovation, and healthcare in the biotechnology space.
With so much going on at once, it’s hard to choose where to spend your time. If you follow BIO on twitter using the hashtag #BIO2016, you’ll get a condensed version of the who, what, and how of BIO.
For those of you who are more partial to blogs, here’s a brief recap of the talks that we’ve attended so far:
Mitochondrial Disease Education Session
A panel of scientific experts and patient advocates gave an overview of mitochondrial diseases and the latest research efforts to develop therapies for mitochondrial disease patients. Phil Yeske of the United Mitochondrial Disease Foundation described his foundation as the largest funder of mitochondrial research next to the government. Their focus is on patient-centered therapeutic development and they’ve established a community registry of patients that makes patients the central stewards for research and clinical development.
The most moving part of this session was an impromptu speech by Liz Kennerley, a mitochondrial disease patient and advocate. She bravely spoke about the roller coaster of symptoms affecting all of the organs in her body and aptly described her daily experience by quoting Forest Gump, “Life is like a box of chocolates, you never know what you’re gonna get.” She ended with the powerful statement that patients are at the core of everything scientists do, and encouraged the panel to engage patients more often because they will tell you everything if you ask them the right questions.
Mitochondrial Disease Patient Liz Kennerley speaks at BIO 2016.
Moving out of Stealth Mode: Biotech journalists offer real-world advice on working with media to tell your story
One of my favorite panels of the conference so far featured three biotech journalists, Christina Farr of Fast Company, Jeff Cranmer of BioCentury, and Alex Lash of Xconomy. It was a dynamic conversation about how biotech companies coming out of stealth mode can best pitch their story to the media. Take home points include:
When pitching to a journalist, make sure that you are honest about what you can and can’t say. Have a “BS committee” that can address the validity of your work and your research claims.
When pitching, journalists want to know what the problem is you’re trying to solve and how you are trying to solve it better than anyone else.
On press releases: Unless it’s a press release from a big name, journalists won’t read it. The panel said they would prefer a personalized email detailing a company’s background and stage of work. They would also consider reading a press release that included a short personalized email from the company CEO.
Most hated words used to describe research: “Revolutionary” “Game-changing” “Disruptive”.
Moderator Carin Canale-Theakston with biotech journalists Jeff Cranmer, Alex Lash, and Christina Farr
Fireside Chat with University of California President Janet Napolitano
In an intimate Fireside chat, Janet Napolitano described her passion for higher education and making a difference in students’ lives. In her new role as the President of the UC system, her main focus is on aligning the policies and initiatives between the UC campuses and promoting research and innovation that can be commercialized around the world.
When asked about how she values basic research compared to applied research, Napolitano responded,
UC President Janet Napolitano
“We want an atmosphere where basic research is supported and one where innovation and entrepreneurship is fostered through incubators and public/private partnerships. We need to make these a tangible reality.”
Napolitano also mentioned that the UC system needs support from the private sector and gave PrimeUC – a collaboration with Johnson & Johnson Innovation that is part of her innovation and entrepreneurship initiative – as an example of a step in the right direction. You can read more about PrimeUC in this Event Recap.
From Ebola to Zika, how can we go faster in a global emergency?
I was only able to sit in on part of this expert panel, but here is the gist of their conversation. The global number of human infectious diseases is rapidly increasing every year due to hard-to-control factors like overpopulation, deforestation, and global climate change. As a result, we’ve had two global health emergencies in the past two years: Ebola and Zika. We were more prepared to deal with the Ebola epidemic because more treatments were already in development. Unfortunately, we weren’t as prepared for Zika as it wasn’t on the world’s radar as a serious disease until 2015.
Martin Friede of the World Health Organization (WHO) said we should take what we learned from the recent Ebola outbreak and apply it to the Zika threat. He said the WHO wants to plan ahead for future outbreaks and remove bottlenecks to health benefits. They want to predict what diseases might surface in the future and have products ready for approval by the time those diseases manifest.
That’s all for now, but be sure to read Part 2 of our BIO2016 coverage tomorrow on the Stem Cellar. We will give highlights from an entertaining and fascinating Keynote address with Dr. Bennet Omalu (the doctor who blew the whistle on concussion in the NFL) and Oscar-nominated actor Will Smith (who played Dr. Omalu in the movie “Concussion”) on “Knowledge precipitates Evolution”. I’ll also tell you about an eye-opening Fireside chat with the US Food and Drug Administration Commissioner Robert Califf, and much more!
In April of this year, the Centers for Disease Control and Prevention (CDC) announced their conclusion that Zika virus causes microcephaly, a birth defect that results in abnormal brain development and a smaller sized head in infants. Rather than a single study being responsible for their conclusion, the CDC argued that “mounting evidence” from multiple recent reports has made the link between Zika infection in pregnant women and microcephaly undeniable.
Now that the general consensus is that Zika virus impairs brain development, scientists are making fast progress to develop appropriate models of brain development to understand exactly how the virus causes microcephaly. We recently blogged about one study from UC San Francisco, which found a molecular link between Zika infection and the function of brain stem cells. They used a brain organoid model, derived from human stem cells, to identify a protein receptor called AXL that is expressed on the surface of brain stem cells and is a major entry point for Zika virus infection.
So called “mini-brains”, or 3D brain organoids, have proven to be a very useful model for brain development and Zika virus infection. With rapid advances in stem cell technologies, mini-brains now develop the appropriate cell types and brain structures representative of the first trimester of fetal brain development. They also can be derived from both embryonic stem cells and induced pluripotent stem cells, making them a versatile technology that can model patient specific diseases.
Speaking of mini-brains, a study was published just last week in the journal Cell Stem Cell from UC San Diego that used mini-brains to identify an immune system molecule that gets hijacked by the Zika virus. They found that Toll-like-Receptor 3 (TLR3) negatively impacts the ability of brain stem cells to differentiate or specialize into the mature cells of the brain.
When the organoids were exposed to a strain of the Zika virus, MR766, their size five days later was smaller than organoids that weren’t exposed to the virus. The growth rate for normal organoids in the time period was 22.6% while the rate for Zika-treated organoids was only 16%. Dissection of the Zika-treated organoids revealed that the virus was successful in infecting brain stem cells specifically and somehow impaired their ability to differentiate. They also noticed that a specific immune molecule called TLR3 was abnormally activated in the organoids after Zika infection.
TLR3: too much of a good thing
In an attempt to put the puzzle pieces together, the authors focused on TLR3 and its potential role in causing brain development defects caused by Zika virus. TLR3 is a sentinel of the innate immune system, the body’s first line defense against infection. It’s a receptor on the surface of cells that can recognize foreign viruses and mount an immune response by activating infection fighting genes.
Brain organoids were used to model Zika virus infection. (Cell Stem Cell)
TLR3 sounds like a good guy when it comes to defending the immune system, but there are cases where too much TLR3 is not a good thing. Activation of TLR3 in Zika-infected brain organoids turned on a group of 41 genes that blocked the differentiation of brain stem cells, causing brain organoid shrinkage, and also caused the stem cells to commit apoptosis, a cellular form of programmed suicide.
Logically, the authors tested whether blocking the activity of TLR3 in Zika-infected organoids alleviated these negative effects. A TLR3 inhibitor was effective at preventing brain stem cell apoptosis and also organoid shrinkage in Zika-treated organoids. However, the treatment wasn’t perfect, the Zika-infected organoids did not grow to the same size as untreated organoids after TLR3 inhibition and still experienced more cell death.
Senior author on the study Dr. Tariq Rana explained:
“We all have an innate immune system that evolved specifically to fight off viruses, but here the virus turns that very same defense mechanism against us. By activating TLR3, the Zika virus blocks genes that tell stem cells to develop into the various parts of the brain. The good news is that we have TLR3 inhibitors that can stop this from happening.”
The size of brain organoids is reduced with Zika infection but partly rescued with a TLR3 inhibitor. Normal (left), Zika infected (middle), Zika infected with TLR3 inhibitor treatment. (Cell Stem Cell)
Next Steps
In a UCSD press release, the authors admit that this work is still in its early stages. The experiments they conducted used both mouse and human cells and further work is needed to determine whether TLR3 is an appropriate target for blocking Zika infection in humans.
They also note that this study tests only one strain of the Zika virus, one that originated in Uganda, and that other strains prevalent in countries like Latin America and Asia should be tested as well. Other strains could have different mechanisms of infection and different effects on the function of brain stem cells.
Rana acknowledged this and commented:
Dr. Tariq Rana, UCSD
“We used this 3D model of early human brain development to help find one mechanism by which Zika virus causes microcephaly in developing fetuses, but we anticipate that other researchers will now also use this same scalable, reproducible system to study other aspects of the infection and test potential therapeutics.”
The Zika virus scare came to a head in 2015, prompting the World Health Organization to declare the outbreak a global health emergency earlier this year. From a research standpoint, much of the effort has centered on understanding whether the Zika infection is actually a cause of birth defects like microcephaly and how the virus infects mothers and their unborn children.
The Zika Virus is spread to humans by mosquitos.
What’s known so far is that the Zika virus can pass from the mother to the fetus through the placenta and it can infect the developing brain of the fetus. But how exactly the virus infects brain cells is less clear.
Brain stem cells are vulnerable to Zika
Scientists from UC San Francisco (UCSF) are tackling this question and have unraveled one more piece to the Zika infection puzzle. UCSF professor Dr. Arnold Kriegstein and his team reported yesterday in the journal Cell Stem Cell that they’ve identified a protein receptor on the surface of brain stem cells that could be the culprit for Zika virus infection.
Based on previous studies that showed that the Zika virus specifically infects brain stem cells, Kriegstein and his colleagues hypothesized that these cells expressed specific proteins that made them vulnerable to Zika infection. They looked to see which genes were turned on and off in brain stem cells derived from donated fetal tissue as well as other cell types in the developing brain to identify proteins that would mediate Zika virus entry.
AXL is to blame
They found a protein receptor called AXL that was heavily expressed in a type of brain stem cell called the radial glial cell, which gives rise to the outer layer of the brain called the cerebral cortex. AXL piqued their interest because it was identified in other studies as an entry point for Zika and other similar viruses like dengue in human skin cells. Furthermore, the team confirmed that radial glial cells produce a lot of AXL protein during development and it appears during a specific window of time – the second trimester of pregnancy.
A link between radial glial cells and Zika infection made sense to first author Tomasz Nowakowski who explained in a UCSF news release,
“In the rare cases of congenital microcephaly, these [radial glial cells] are the cells that die or differentiate prematurely, which is one of the reasons we became interested in the possible link.”
The team also found that AXL was expressed in mature brain cells including astrocytes and microglia and in retinal progenitor cells in the eye. They pointed out that the presence of AXL in the developing eye could help explain why many cases of Zika infection are associated with eye defects.
Modeling Zika infection using mini-brains
The bulk of the study used stem cells isolated from donated human fetal tissue, but the team also developed a different stem cell model to confirm their results. They generated brain organoids, also coined as “mini-brains”, in a dish from human induced pluripotent stem cells. These mini-brains contain structures and cell types that closely resemble parts of the developing brain. The team studied radial glial like cells in the mini-brains and found that they also expressed AXL on their surface.
Mini-brains grown in a dish have radial glia stem cells (red), neurons (blue) and the AXL receptor (green). Photo by Elizabeth DiLullo, UCSF
Kriegstein and his team believe they now have a working stem cell model for how viruses like Zika can infect the brain. Using their brain organoid model, they plan to collaborate with other UCSF researchers to learn more about how Zika infection occurs and whether it really causes birth defects.
“If we can understand how Zika may be causing birth defects,” Kriegstein said, “we can start looking for compounds to protect pregnant women who become infected.”
What’s next?
While the evidence points towards AXL as one of the major entry points for Zika infection in the developing brain, the UCSF team and other scientists still need to confirm that this receptor is to blame.
Kriegstein explained:
Arnold Kriegstein, UCSF
“While by no means a full explanation, we believe that the expression of AXL by these cell types is an important clue for how the Zika virus is able to produce such devastating cases of microcephaly, and it fits very nicely with the evidence that’s available. AXL isn’t the only receptor that’s been linked with Zika infection, so next we need to move from ‘guilt by association’ and demonstrate that blocking this specific receptor can prevent infection.”
If AXL turns out to be the culprit, scientists will have to be careful about testing drugs that block its function given that AXL is important for the proliferation of brain stem cells during development. There might be a way however that such treatments could be given to at risk women before they get pregnant.
The Stem Cellar 