Living Life To The Extreme
Having extra copies of certain genes helps fish live in AntarcticaI've always loved weird creatures. Bacteria that can live in boiling mudpots. Weird tubeworms huddled around deep sea hydrothermal vents. Fish that live in below freezing water.
What I like is learning how these beasts have adapted to their incredibly harsh environment. More specifically, what changes have happened in their DNA that allow them to live where no other animal could.
In this blog I'll focus on those poor fish living in the waters off Antarctica. These waters are icy cold and the fish aren't warm blooded. Which means their body temperature is the same as the water around them.
Most biological processes do terribly under these conditions. Proteins don't fold right, enzymes work incredibly slowly, fats glob up. It is astonishing that these fish survive at all.
Scientists figured out back in the 70's that these fish evolved a special antifreeze protein to keep their blood from freezing. Since then they've done other experiments that show other adaptations to the cold too.
In a new study, scientists from the University of Illinois and the Chinese Academy of Sciences decided to take a look at as many genes and as much of the DNA of these fish as they could. What they found was that lots of genes are turned up in these fish compared to relatives that live in warmer waters. And that many of these genes are turned on higher because the Antarctic fish have extra copies of them.
The genes they found that were different made sense. For example, there are a bunch of genes that make proteins called chaperones. Chaperones help other proteins fold up right. In this cold, proteins need all the help they can get!
Also they found that there were more of the proteins that scavenge reactive oxygen species (ROS) in these fish. This makes sense because colder water has more oxygen.
O2 is a pretty nasty molecule that tends to create even nastier chemicals (ROS) that beat up on DNA and proteins. We all have proteins whose job it is to defuse these chemicals. These fish make more of these proteins.
A few years ago it would have been surprising to find that the way these genes made more proteins was by duplicating themselves. Not anymore.
As we look closely at the DNA of various creatures, we are finding that gene duplications (and deletions) happen a lot. Even in people.
For example, people from cultures that eat a lot of starch have extra amylase genes. (This gene makes amylase, a protein that helps breakdown starch.) Some people are resistant to HIV (the virus that causes AIDS) because they have extra copies of the CCL3L1 gene. And so on.
Our DNA is much less stable than we thought. Which is one way we can better adapt to our surroundings. I can't wait to see what they learn about those tubeworms!