29 April 2018

Epigenetic Memories Passed For 14 Generations

The most important set of genetic instructions we all get comes from our DNA, passed down through generations. But the environment we live in can make genetic changes, too. Last year, researchers discovered that these kinds of environmental genetic changes can be passed down for a whopping 14 generations in an animal – the largest span ever observed in a creature, in this case being a dynasty of C. elegans nematodes (roundworms). To study how long the environment can leave a mark on genetic expression, a team led by scientists from the European Molecular Biology Organisation (EMBO) in Spain took genetically engineered nematode worms that carry a transgene for a fluorescent protein. When activated, this gene made the worms glow under ultraviolet light. Then, they switched things up for the nematodes by changing the temperature of their containers. When the team kept nematodes at 20° Celsius (68° F), they measured low activity of the transgene - which meant the worms hardly glowed at all. 

But by moving the worms to a warmer climate of 25° C (77° F), they suddenly lit up like little wormy Christmas trees, which meant the fluorescence gene had become much more active. Their tropical vacation didn't last long, however. The worms were moved back to cooler temperatures to see what would happen to the activity of the fluorescence gene. Surprisingly, they continued to glow brightly, suggesting they were retaining an 'environmental memory' of the warmer climate – and that the transgene was still highly active. Furthermore, that memory was passed onto their offspring for seven brightly-glowing generations, none of whom had experienced the warmer temperatures. The baby worms inherited this epigenetic change through both eggs and sperm. The team pushed the results even further - when they kept five generations of nematodes at 25° C (77° F) and then banished their offspring to colder temperatures, the worms continued to have higher transgene activity for an unprecedented 14 generations.

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