Viral invasion of the koala genome

Jul 06, 2006
koala

University of Queensland researchers have made a startling discovery that may explain why the koala, one of the world's most loved marsupials, is susceptible to certain infections and cancers.

Researchers found the koala genome is currently being invaded by a virus called koala retrovirus (KoRV). Their findings have been published in this week`s issue of Nature.

Rachael Tarlinton, a PhD student from UQ's School of Molecular and Microbial Sciences, and supervisors Associate Professor Paul Young and Dr Joanne Meers studied the presence of the virus in captive and wild koala populations throughout Australia.

Retroviruses are a group of RNA viruses that insert a DNA copy of their genome into the chromosomes of a host cell as part of their natural life cycle. Some retroviruses become permanently integrated into the host genome and are passed on from one generation to the next, being gradually inactivated over time such that they no longer produce harmful infections.

These are referred to as endogenous retroviruses and are widespread in the animal kingdom with most having invaded their hosts many thousands to millions of years ago.

Retroviral elements make up as much as eight percent of the human genome. KoRV is still an active virus that appears to have entered the koala genome relatively recently, perhaps within the past 100-200 years.

Dr Young said what surprised researchers was, unlike other endogenous retroviruses of other species which are fairly stable and ancient inserts in the host genome of all members of the species, they found some koala populations were either free of this virus or showed a mixed prevalence.

This finding, combined with high levels of viral activity and variability between individual koalas, suggested the virus was in transition between infectious and endogenous forms.

The work has important implications for the conservation of Australia`s koala populations as the research has also shown an association between this virus and a high incidence of cancer in both captive and wild koalas.

The discovery of this virus-host interaction in the wild has additional significance.

“While many endogenous retroviruses appear to simply be inactive passengers or constitute ‘junk' within their host genome, some can be disruptive, with several human cancers being linked to the activity of selected retroviral elements,” Dr Young said.

“On the other hand, some have turned out to be highly beneficial having been co-opted through evolution to be essential genetic partners in our own life cycle.”

“Coming to grips with how the koala handles this initial viral onslaught may give us insights into the dynamic events that occurred millions of years ago when retroviruses first invaded the human genome.”

Source: University of Queensland

Explore further: Study IDs risk factors for severe hidradenitis suppurativa

add to favorites email to friend print save as pdf

Related Stories

World-first research will save koalas

Apr 09, 2013

The "holy grail" for understanding how and why koalas respond to infectious diseases has been uncovered in an Australian-led, world-first genome mapping project.

Tracking koala disease: New findings from old DNA

Sep 26, 2012

(Phys.org)—DNA extracted from the skins of koalas displayed in European and North American museums shows that a retrovirus has been a problem for the animals for much longer than was thought, according ...

Viruses for a healthy pregnancy

Jan 29, 2008

Sequences of DNA in the human genome that originated from ancient viral infections have some surprising effects on our bodies and are even essential for a healthy pregnancy, according to an article in the February issue of ...

Recommended for you

Endogenous hormones improve breast cancer risk models

8 hours ago

(HealthDay)—Inclusion of endogenous hormones in prediction models improves prediction of invasive breast cancer risk in postmenopausal women, according to a study published online Aug. 18 in the Journal of ...

With kids in school, parents can work out

8 hours ago

(HealthDay)—Back-to-school time provides an opportunity for parents to develop an exercise plan that fits into the family schedules, an expert suggests.

Ebola death toll rises to 1,427: WHO

9 hours ago

The death toll from the Ebola outbreak sweeping through west African countries has risen to 1,427 out of more than 2,600 cases, the World Health Organization said Friday.

User comments : 0