Monthly Archives: February 2017

CRISPR-Cas9 can be delivered directly into the eyes of mice and treat age-related macular degeneration efficiently and safely.

Asian Scientist Newsroom | February 22, 2017 | In the Lab

AsianScientist (Feb. 22, 2017) - South Korean researchers have used CRISPR-Cas9 gene editing to treat symptoms of age-related macular degeneration (AMD) in mice. Their findings have been published in Genome Research.

It is estimated that almost one in every ten people over 65 has some signs of AMD, and its prevalence is likely to increase as a consequence of the aging population. AMD is a form of blindness which causes distorted vision and blind spots.

AMD in older adults and retinopathy of prematurity in newborns are the leading cause of blindness in those respective age groups. In both diseases, abnormally high levels of vascular endothelial growth factor (VEGF) are secreted. In AMD, VEGF causes the formation of new blood vessels in the eyes but also leads to leakages of blood and fluid into the eye, damaging an area at the center of the retina called macula.

Injections of anti-VEGF drugs are the most common treatment for AMD, but at least seven injections per year are required because VEGF is continuously overexpressed by the cells of the diseased retinal pigment epithelium. Instead of such invasive treatments, scientists at the Institute for Basic Science (IBS) believe that gene therapy with the third generation gene editing tool CRISPR-Cas9 could improve the situation.

The injections tackle the effects, but not the main cause of the problem. By editing the VEGF gene, we can achieve a longer-term cure, explained Professor Kim Jin-Soo, Director of the Center for Genome Engineering at IBS.

CRISPR-Cas9 can precisely cut and correct DNA at the desired site in the genome. The CRISPR-Cas9 system works by cutting DNA at a target site, in this case, inside the VEGF gene. Two year ago, IBS scientists proved that a pre-assembled version of CRISPR-Cas9 called Cas9 ribonucleoprotein (RNP) can be delivered to cells and stem cells to modify target genes.

The pre-assembled complex works rapidly and degrades before the body has time to build up an immune response against it. Despite these advantages and previous successes, the difficulty in delivering pre-assembled CRISPR-Cas9 has limited its use in therapeutic applications.

In this study, the research team successfully injected CRISPR-Cas9 into the eyes of a mouse model with wet AMD and locally modified the VEGF gene. Initially, they found that the delivery of the pre-assembled CRISPR-Cas9 complex is more efficient that the delivery of the same components in a plasmid form.

Secondly, the complex disappeared after just 72 hours. Scientists assessed the whole genome of the animals and found the CRISPR-Cas9 complex modified only the VEGF gene and did not affect other genes. The progression of the eye disease was monitored by looking at choroidal neovascularization (CNV), the creation of new blood vessels between the retina and the sclera, a common problem of wet macular degeneration.

The researchers found that the CRISPR-Cas9 complex reduced the CNV area by 58 percent. Moreover, cone dysfunction, a likely side effect that takes only that days to show in mice, did not occur a week after the treatment.

We have developed a treatment to suppress CNV by inactivating the VEGF gene, one of the causes of AMD. We envision that, in the future, surgeons will be able to cut and paste disease-causing genetic elements in patients, explained Kim.

While CRISPR-Cas9 is conventionally used to correct mutations causing hereditary diseases or cancer, this study suggests a new therapy for non-hereditary degenerative disease.

We believe that this is a new therapeutic modality for the treatment of non-hereditary degenerative diseases, said study co-author Professor Kim Jeong Hun from Seoul National University. We confirmed the effect on the animal models of the disease and now we wish to continue with preclinical trials.

The article can be found at: Kim et al. (2017) Genome Surgery Using Cas9 Ribonucleoproteins for the Treatment of Age-related Macular Degeneration.

Source: Institute for Basic Science. Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

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Editing Away AMD With CRISPR - Asian Scientist Magazine

For decades, some unluckydog lovers have welcomeda bundle of barking joy into their homes, only to see them perish from a mysterious disease mere weeks after their birth. The pups seemingly healthy muscles had literally wasted away in front of their owners eyes until they could no longer stand and breathe.

It wasnt until 2010 that a French research team isolated the genetic cause of this specific muscle-wasting disease in a group of Labrador Retrievers; these dogs were suffering from a single mutation that left them unable to produce an essential protein known asmyotubularin.Whats more, it was the exact kind of mutation and disease also long found in male human babies, too. That made the researchers wonder if these unfortunate puppiescould help us study the disease and even someday find a way to saveboth pets and people.

Now, years down the road, it appearsthey were right, thanks to a cutting-edgegene therapy treatment.

An international group of researchers, including some from the original French team, gathered together 10-week-old puppies with the mutation to take part in a randomized controlled trial. The dogs who were given a treatment that repaired their defectivemyotubularingene avoided the crippling muscle degeneration that killed the placebo-treated dogs by week 17. And by the ninth month of study, the saved puppies muscle and neurological function continued to match readings from healthy dogs, particularly forthose that got the highest doses.

The findings, building on an earlier proof-of-concept study of dogs and mice by the researchers, signal that a scaled-up treatment could save the lives of boys with the same sort of genetic flaw.

I believe that the dog study will be about as close as we will ever get to a human study, senior author Dr. Martin Childers of the University of Washington told Vocativ in an email. Because we found evidence that the gene therapy product spread throughout the entire skeletal musculature of adult dogs after a single infusion, it seems reasonable to expect a similar result in human patients.

Gene therapy has received plenty of attention for its potential to treat otherwise irreparable DNA defects, but according to the researchers, theres been little focus on bone- and muscle-relatedgenetic disorders. The condition treated in the current study, called x-linked myotubular myopathy, affects around one in every 50,000 boys, with most sufferers living no more than a few years. And though theres no true tally of how often it affects dogs, case reports of similar-sounding diseases have been published stretching back decades.

There will undoubtedly be hurdles to climb before the treatment Childers and his team developed, or a similar one, can be tested in people, Childers said. It is always possible that humans might respond differently, thus, clinical trials will be conducted with extraordinary care and oversight, he explained. And though the dogs suffered little adverse effects from the therapy delivered via a harmless virus researchers will still have to watch out for any possible toxicity in people.

That said, the treatment offers hope for both man and mutts. The changes seen after a single treatment have lasted for several years in the small sample of dogs the team has raised. So its possible that people wont need repeated doses or they would be infrequent, Childers said a big positive, given how expensive gene therapy is today.

And its also likely that these treatments, within the larger field of regenerative medicine, will find a place for dogs and other animals sooner than it will for people.

Veterinary medicine is ahead of human medicine in some cases with respect to regenerative technologies, Childers said. Stem cell infusions, for example, have been given to pets and horses for more than a decade.

But people may not have to wait so long for the promise of gene therapy either. Childers is hopeful that Audentes Therapeutics, a San Francisco biomedical company hes collaborating with (and which partially funded the current study), will begin their first human trials of a gene therapy treatment for x-linked myotubular myopathy, based on his teams research, later this year.

The teams findings were published earlier this February in Molecular Therapy.

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Gene Therapy Saves Puppies From A Fatal DiseaseAnd Maybe Us Next - Vocativ

Personalized medicine, which involves tailoring health care to each persons unique genetic makeup, has the potential to transform how we diagnose, prevent and treat disease. After all, no two people are alike. Mapping a persons unique susceptibility to disease and targeting the right treatment has deservedly been welcomed as a new power to heal.

The human genome, a complete set of human DNA, was identified and mapped a decade ago. But genomic science remains in its infancy. According to Francis Collins, the director of the National Institutes of Health, It is fair to say that the Human Genome Project has not yet directly affected the health care of most individuals.

Its not that there havent been tremendous breakthroughs. Its just that the gap between science and its ability to benefit most patients remains wide. This is mainly because we dont yet fully understand the complex pathways involved in common chronic diseases.

I am part of a research team that has taken on the ambitious goal of narrowing this gap. New technologies are allowing us to probe DNA, RNA, proteins and gut bacteria in a way that will change our understanding of health and disease. Our hope is to discover novel biological markers that can be used to diagnose and treat common chronic conditions, including Alzheimers disease, heart disease, diabetes and cancer.

But when it comes to preventing the leading causes of death which include chronic diseases, genomics and precision medicine may not do as much as we hope.

Many diseases arent due only to genetics

Chronic diseases are only partially heritable. This means that the genes you inherit from your parents arent entirely responsible for your risk of getting most chronic diseases.

The estimated heritability of heart disease is about 50 percent. Its 64 percent for Type 2 diabetes mellitus, and 58 percent for Alzheimers disease. Our environment and lifestyle choice are also major factors; they can change or influence how the information coded in our genes is translated.

Chronic diseases are also complex. Rather than being controlled by a few genes that are easy to find, they are weakly influenced by hundreds if not thousands of genes, the majority of which still elude scientists. Unlocking the infinite combinations in which these genes interact with each other and with the environment is a daunting task that will take decades, if ever, to achieve.

While unraveling the genomic complexity of chronic disease is important, it shouldnt detract from existing simple solutions. Many of our deadliest chronic diseases are preventable. For instance, among U.S. adults, more than 90 percent of Type 2 diabetes, 80 percent of coronary arterial disease, 70 percent of stroke and 70 percent of colon cancer are potentially avoidable.

Smoking, weight gain, lack of exercise, poor diet and alcohol consumption are all risk factors for these conditions. Based on their profound impact on gene expression, or how instructions within a gene are manifested, addressing these factors will likely remain fundamental in preventing these illnesses.

Will more knowledge be more power?

A major premise behind personalized medicine is that empowering patients and doctors with more knowledge will lead to better decision-making. With some major advances, this has indeed been the case. For instance, variants in genes that control an enzyme that metabolizes drugs can identify individuals who metabolize some drugs too rapidly (not giving them a chance to work), or too slowly (leading to toxicity). This can lead to changes in medication dosing.

When applied to prevention, however, identifying our susceptibility at an earlier stage has not aided in avoiding chronic diseases. Research challenges the assumption that we will use genetic markers to change our behavior. More knowledge may nudge intent, but that doesnt translate to motivating changes to our lifestyle.

A recent review found that even when people knew their personal genetic risk of disease, they were no more likely to quit smoking, change their diet or exercise. Expectations that communicating DNA-based risk estimates changes behavior is not supported by existing evidence, the authors conclude.

Increased knowledge may even have the unintended consequence of shifting the focus to personal responsibility while detracting from our joint responsibility for improving public health. Reducing the prevalence of chronic diseases will require changing the political, social and economic environment within which we make choices as well as individual effort.

What about treating chronic diseases?

Perhaps the most awaited hope of the genomic era is that we will be able to develop targeted treatments based on detailed molecular profiling. The implication is that we will be able to subdivide disease into new classifications. Rather than viewing Type 2 diabetes as one disease, for example, we may discover many unique subtypes of diabetes.

This already is happening with some cancers. Patients with melanoma, leukemia or metastatic lung, breast or brain cancers can, in some cases, be offered a molecular diagnosis to tailor their treatment and improve their chance of survival.

We have been able to make progress in cancer therapy and drug safety and efficacy because specific gene mutations control a persons response to these treatments. But for complex, chronic diseases, relatively few personalized targeted treatments exist.

Customizing treatments based on our uniqueness will be a breakthrough, but it also poses a challenge: Without the ability to test targeted treatments on large populations, it will make it infinitely harder to discover and predict their response.

The very reason we group people with the same signs and symptoms into diagnoses is to help predict the average response to treatment. There may be a time when we have one-person trials that custom tailor treatment. However, the anticipation is that the timeline to getting to such trials will be long, the failure rate high and the cost exorbitant.

Research that takes genetic risk of diabetes into account has found greater benefit in targeting prevention efforts to all people with obesity rather than targeting efforts based on genetic risk.

We also have to consider decades of research on chronic diseases that suggest there are inherent limitations to preventing the global prevalence of these diseases with genomic solutions. For most of us, personalized medicine will likely complement rather than replace one-size-fits-all medicine.

Where does that leave us? Despite the inherent limitations to the ability of genomic medicine to transform health care, medicine in the future should unquestionably aspire to be personal. Genomics and molecular biosciences will need to be used holistically in the context of a persons health, beliefs and attitudes to fulfill their power to greatly enhance medicine.

Sharon Horesh Bergquist, Physician, teacher, researcher in preventive medicine and healthy aging, Emory University

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Personalized medicine may do more to treat rather than prevent chronic diseases - Salon