New research into how a retrovirus is spreading across populations of wild koalas in Queensland, Australia is leading to a better understanding of the evolution of the animal's genome. Published this month in the journal Cell by scientists at UMass Chan Medical School and the University of Queensland, the paper explains how the animals adapted genomic immunity to the koala retrovirus (KoRV-A), by shutting it down, or silencing it, as it becomes a component of the genome . This is important because most wild koalas are born with this pathogen as part of their genetic material.
KoRV-A is spreading between wild koalas by infecting germ cells that make eggs and sperm, suppressing the immune system and making the animals susceptible to cancer and secondary chlamydia infection. Scientists report that a copy of the virus is captured by a host gene, and the germ cells process the product of this modified gene into small pieces of "anti-KoRV-A" RNA, known as piRNAs. The virus sequences captured in piRNAs are used to find copies of the pathogen in the genome, turning them off.
"The virus first infected koalas in the northern part of Australia and is spreading to the south while infecting germ cells and becoming a component of the genome. The north to south spread allowed us to watch how germ cells learn to control a brand-new infection," said William E. Theurkauf, Ph.
D., professor of molecular medicine at UMass Chan. The UMass Chan team includes Zhiping Weng, Ph.
D., the Li Weibo Chair .
