Julia Reid

Transcription

Right now, at this very moment you have a virus controlling your brain. No just kidding, well sort of. Hello again, Julia here for Dnews. Fun fact: Our DNA contains a lot of virus DNA. Over one hundred thousand pieces of it! Over 8% of our DNA is made up of so-called En-dodge-e-nus retroviruses. And a recent study by Lund University in Sweden indicates that just such a virus might be responsible for our super powered homosapien brains. This study found that when these virus DNA bits are activated, they also activate nearby genes. Meaning, old viruses control our brains, well, that there are some old viruses in our DNA that control when certain genes get switched on and off. The researchers say this suggests that retroviruses have played an important role in the development of a complex brain. Perhaps they are one of the reasons brain cells are so complicated and versatile, giving humans the evolutionary advantage of intelligence. So how did viruses get in our DNA? Well, you can think of them like fossils. Once upon a time, millions of years ago, one of our ancestors got a virus. Maybe a cold, maybe something else. Back then, the virus was just a normal retrovirus, hanging out in a host cell. What makes retroviruses unique, is how they reproduce. Retrovirus carry their genetic material in RNA. To make more copies of itself, it makes a DNA copy of its genes and inserts it into a host’s DNA. The host cell then reads the DNA with the viral insert and is tricked into making more copies of the virus. But by a stroke of luck, this particular virus happened to infect a sperm or egg cell, then when the baby developed from that cell, it carried that virus DNA in every cell in its body, and when it in turn reproduced, passed that bit of DNA on to its baby. and so and so forth for millions of years. These bits of viral DNA become so well integrated into the host’s DNA, they become almost harmless. The viruses mutate to the point they can’t function. They lose their ability to break out of a cell and infect a new one, eventually, they can only make copies of themselves which get inserted back into the host cell. Multiple copies of the virus gene can wind up strewn throughout our genome. Since this has been going on for quite a while, humans and other mammals have defenses against these DNA intruders, proteins that keep the virus from replicating. It’s thought that most of the time this bit of virus DNA in our genome doesn’t do anything. So they become what scientists consider “junk DNA” While most of these viral fossils are just DNA duds, sometimes they are harmful. They’ve been linked to some brain disorders, like schizophrenia and even might cause certain cancers. Sometimes, they are kind of good. Some domesticated viral DNA functions like a gene regulator, they can tell which genes to turn on and off. On occasion the virus DNA is hijacked and put to good use. We owe a lot of our success to virus DNA - and when I saw “our” I mean mammals. On at least 6 different occasions, virus DNA led to the development of placenta in various mammalian species, a huge evolutionary step. This viral protein, called syncytin, used to help host cells bind together so a virus could spread more easily. Now this protein is responsible for the lining in the placenta that helps aid nutrient exchange between the mother and developing fetus and protects the fetus from the mom’s immune system. Studies show that when these viral genes matter a whole lot, when they are turned off in mice, embryos don’t survive. So we’re a little bit viral.. That’s kind of cool, and researchers think this latest study could lead to more research on genetic links in certain diseases of the brain. Most of the research on genetic factors for diseases focus on just two percent of the human genome. Adding the possibility of a viral related genetic link opens a whole new range of possibilities for scientists. so what do you think of our viral inheritance? Cool? Weird? Both? Sound off in the comments below. and for more cool and weird science, check out DNews everyday.