Ancient Viruses Lurk in Human DNA

Scientists have discovered 19 new pieces of non-human DNA – left by viruses that infected our ancestors hundreds of thousands of years ago – in the genomes of modern humans.

Scientists analyzed the genomes of some 2,500 people from around the world, and one stretch of new-found DNA, found in about 50 of the 2,500 people, contains a full genetic recipe for an entire virus. Whether or not it can replicate is not yet known, but other studies of ancient virus DNA have proved it can affect the humans who carry it.

The study investigated the entire span of DNA from people from around the world, including a large number from Africa, where our ancestors originated before migration.

Human endogenous retroviruses, or HERVs, are ancient viruses that succeeded in depositing DNA-based copies of their RNA genetic material into the genomes of early humans. Over generations, the virus-generated DNA kept getting copied and passed on when humans reproduced, which is how it ended up in our DNA today. In fact, about 8 percent of what we think of as our “human” DNA actually came from viruses. In some cases, HERV sequences have been adopted by the human body to serve a valuable purpose, such as one that helps pregnant women’s bodies build a cell layer around a developing fetus to protect it from toxins in the mother’s blood.

The new HERVs are part of the family called HERV-K. The intact whole viral genome, just found was on the X chromosome and it’s been dubbed Xq21. “This one looks like it is capable of making infectious virus, which would be very exciting if true, as it would allow us to study a viral epidemic that took place long ago,” said senior author of the study and virologist John Coffin, Ph.D. of the Tufts University School of Medicine.

“Many studies have tried to link these endogenous viral elements to cancer and other diseases, but a major difficulty has been that we haven’t actually found all of them yet,” said co-author Zachary H. Williams.

The new discovery will open up many doors to research, according to co-first author Julia Wildschutte. “What’s more, we have confirmed in this paper that we can use genomic data from multiple individuals compared to the reference human genome to detect new HERVs. But this has also shown us that some people carry insertions that we can’t map back to the reference.”

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Link Made Between Genetics and Aging

Scientists from the University of Georgia, Rob Pazdro and Yang Zhou, led a study that showed how genetics regulates aging and disease – a hormone that is essential in the aging process is apparently under genetic control.

Past studies have found that the blood levels of the hormone that is instrumental in the aging process – growth differentiation factor 11 (GDF11) – decrease over time. By restoring GDF11 in old mice, cardiovascular aging was reversed, as well as brain rejuvenation. This finding was listed as one of the top 10 breakthroughs in science in the year 2014.

The new study shows that the levels of the GDF11 are determined by genetics, offering another potential mechanism by which aging is encoded in the genome. The hope is to sustain the levels of this hormone in order to prevent various diseases.

“Finding that GDF11 levels are under genetic control is of significant interest. Since it is under genetic control, we can find the genes responsible for GDF11 levels and its changes with age,” said the study’s senior author, Rob Pazdro.

Pazdro and his colleagues confirmed the findings of the previous studies that showed that the GDF11 levels decrease over time and that the most of the depletion takes place by middle age.

The study examined the link between the GDF11 levels and markers of aging, such as lifespan in 22 genetically diverse inbred mice strains. As expected, the strains with the highest GDF11 levels lived longer than the others.

The team used gene mapping to identify seven candidate genes that may determine blood concentration levels of the GDF11 at middle age. For the first time, the study demonstrated that the GDF11 levels are strongly heritable.

“Essentially, we found a missing piece of the aging/genetics puzzle,” Pazdro said. “Very generally, we’ve made an important step toward learning about aging and why we age and what are the pathways that drive it. It’s the first step down a long road, but it’s an important step.”

Possibility for Amoeba to Cure Genetic Diseases

 

 

Immune system is one of the most important parts of our body that protects us from viruses and bacteria. There are two ways for our immune system to work. First is killing the foreign bodies inside the cell by using reactive oxygen species (ozone, hydrogen peroxide, bleach, etc), which are produced by enzyme NOX2, and the second is killing them outside the cell, using poisonous net composed by DNA called “neutrophil extracellular traps” (NETS).

People thought that the ways of how immune system works was only in human and other complex animals. However, the microbiologists from University of Geneva (UNIGE) discovered that the social amoeba, an unicellular organism, has a similar way of protecting its body from foreign bodies with human. Usually, these microorganisms survive by eating bacteria as a main source of food. When the food runs out, they gather together and make a slug-like mini animal with lots of pores and survive until the wind or other factors to move them to a new place. To make this slug, 20% of the cell sacrifice themselves in order to make the other 80% into pores. However, there is still 1% remaining keeps its phagocytic functions. “This last percentage is made up of cells called “sentinel” cells. They make up the primitive innate immune system of the slug and play the same role as immune cells in animals, “ explains Thierry Soldati, last author of the study.

As explained in the first paragraph, our immune system uses poisonous DNA nets to kill foreign bodies. According to the study of Soldati and his colleagues in Geneva and the Baylor College of Medicine in Houston, Texas, the social ameoba’s immune systems (sentinel cells) can also produce the DNA-based extracellular traps (ETS) to kill foreign bodies.

This study has great impact for the medical study of the diseases related to humman’s immune system, such as leukemia and chronic granulomatous disease (CGD). Patients with CGD are unable to produce normal enzyme NOX2 and therefore, they suffer lots of diseases even though they are easy to be cured because their immune systme cannot work properly. Now, by modifying and changing the DNA of this microrganism, scientists can do all kinds of experiments that can be adapted to human beings more easily. Thus, by using Dictyostelium discoideum (scientific name of the slug) to find the genetic disorder in immune systmem, scientist will be able to open a new way to find the treatment.

 

References:  http://www.sciencedaily.com/releases/2016/03/160301074240.htm

Monkeys Genetically Modified to Help Study Autism

A team of scientists from the Institute of Neuroscience at the Chinese Academy of Sciences in Shanghai, has genetically modified monkeys in order to create a better model for studying autism.

The team has introduced a human gene called MECP2, which people with autism symptoms have extra copies of, into the monkeys’ DNA. This caused the monkeys to display at least one symptom related to autism, like repetitive movements, decreased social interaction and anxiety. The monkeys have also been able to pass the gene and their autism-like behaviors to their offspring.

The creation of the first genetically modified monkeys occurred in 2010 when the MECP2 genes were attached to a dormant virus injected into the eggs of crab-eating macaque monkeys. Once the eggs were fertilized, they were implanted into female monkeys in order to develop – and they did – 8 modified monkeys with 1 to 7 copies of the MECP2 gene. A year later scientists found that the monkeys were showing at least one behavior linked to autism. However, this was not enough to say that the monkeys involved in the study were autism models.

The next breakthrough came with the next generation of genetically modified monkeys. They started showing asocial behavior when they were 11 months old, which proved that the MECP2 gene and autism symptoms were passed onto the second generation of macaques.

Zilong Qiu, a molecular biologist at the Institute of Neuroscience, and his team are now using brain-imaging technology on the monkeys to identify exactly where in the brain the MECP2 over expression happens. They plan to use CRISPR gene editing technique to remove extra copies of the gene to see if autism-like behaviors and symptoms will cease.

Genetically Modified Organisms

For a long time, people have been using the traditional breeding techniques such as Artificial selection to obtain the desired characters in the various organisms ranging from ornamental flowers to milk giving animals. In this technique, the organisms having the desired traits are selected and bred to obtain the progeny having the desired qualities of both the parents. But, the problem with this technique is that we have no control over the characters or variations appearing in the progeny. However, with the advancement in the field of biotechnology and genetic engineering, it has become possible to control the characters in an organism right from the gene level. Today, a gene from an organism can be isolated and inserted into an organism of completely different species through the techniques of genetic engineering. The organism resulting from such mechanism is termed as Genetically Modified Organism or GMO.

Cloning and Recombinant DNA technology are the two methods which are widely employed for the development of the GMOs

In the process of cloning, a nucleus is isolated from the cell of the organism to be cloned and is introduced into an enucleated cytoplasm of the host egg cell. This egg cell is then further grown up to 16-32 celled stage and each cell is then transferred into different surrogate mothers. This results in the development of the progeny which is genetically identical to the donor. The first animal to be cloned using this technique was in the year 1996 where a sheep named Dolly was cloned from an adult donor cell. Since that time, a lot of animals have been cloned using this technique such as dogs, horses, cows etc.

In the recombinant DNA technology one or more genes responsible for the specific character are isolated from the organism showing that character, using the restriction enzymes and is then introduced in the host genome using the suitable ligating enzymes. The host cell is then checked for successful transformation and if transformation is successful, multiple clones of the cell are made. BT cotton, golden rice, humulin are some examples which employed this technology for their development.

These techniques have been very useful in the field of agriculture and medicine as they various drought resistant, pest resistant, high nutrition genetically modified crops have been developed. Also many drugs, hormones and enzymes of human use have been manufactured using genetically modified organisms.

Although these techniques are very useful, there are few drawbacks associated with them. Also, the long term effects of GMOs on the naturally occurring organisms haven’t been fully studied yet. Due to these causes the use of GMOs is still controversial and is under debate.