July 15, 2013
New Retrovirus Discovered In Dead Polar Bear At Berlin Zoo
Lee Rannals for redOrbit.com - Your Universe Online
Knut died unexpectedly in 2011 at the age of four while in his enclosure. Caretakers at the zoo were shocked to find their superstar polar bear had died, especially since polar bears can live in captivity for 35 years.
Researchers analyzed the genetic material of the polar bear and were able to discover and characterize new sequences of endogenous retroviruses (ERVs). The retroviruses were also shown to have infected a giant panda at the same zoo named Bao Bao.
ERVs are viruses that at some point in the past inserted themselves into the nuclear genome of a host's germ cell. Once this takes place, the virus is passed on from one generation to the next and the endogenous retroviral genome would be inherited to new species that evolve from the original host.
"ERV sequences and fragments make up about eight percent of the human genome," said Professor Jens Mayer from the Department of Human Genetics at Saarland University.
The researchers characterized endogenous retroviral sequences in both bear species and found a strong similarity between the two, indicating that these two virus species are closely related. They also identified ERV sequences in other bear species such as the brown bear, the black bear and the spectacled bear.
"Using molecular dating methods we have now been able to show that the retrovirus became integrated into the genetic material of an ancestor of today's bear species around 45 million years ago," said Professor Alex D Greenwood from the Leibniz Institute for Zoo and Wildlife Research in Berlin.
The team showed that the original retrovirus was closely related to those found in the genomes of bats and cattle. Moreover, the viruses found in bears exhibit strong similarity with those found in the human genome.
"Some of these sequences are suspected of playing a role in the occurrence of cancer, neurodegenerative or autoimmune diseases," says Mayer.
Scientists can use this research to gain insight into the evolution of retroviruses by learning which ones infected which groups of animals millions of years ago. The data can provide valuable information on the evolutionary development of mammals.