KEY POINTS:
The humble possum, a pest in New Zealand, could help in the fight against a range of human health problems from skin cancer and high cholesterol to miscarriages and spinal paralysis.
Scientists have decoded the full genetic sequence of the possum genome and believe that the information could
be invaluable for studies into the genetics of human disorders.
Unlike other mammals, marsupials do not rear their young in an internal womb - but it is this and other differences that could help the advance of medical research, scientists said.
The South American possum is found in the wild in Brazil, Bolivia and Guyana and grows to about twice the size of a mouse. In recent years, captive-bred colonies have become important in medical research, said John VandeBerg of the Southwest Foundation for Biomedical Research in San Antonio, Texas.
"Since marsupials have very different characteristics from eutherian, or placental mammals, particularly in their early stages of birth, my thinking was that any marsupial that could be produced in large numbers in the laboratory would become extraordinarily valuable for research on early mammalian development."
With the publication of the full genome of the possum in the journal Nature, scientists believe that studies of the possum DNA could help to track down human genes as well as lead to a greater understanding of disorders such as skin cancer and high cholesterol, both of which are seen in the gray, short-tailed possum, Monodelphis domestica.
Dr VandeBerg said the possum genome, the first marsupial to have its DNA fully sequenced, would allow scientists to match possum genes to their human equivalents in a matter of hours so that scientists could begin useful experiments in a fraction of the time it would have otherwise taken.
The possum, a relative of the kangaroo and koala bear, packs all of its genes on to just nine pairs of chromosomes, whereas human genes are spread out over 23 pairs.
One of the first insights to emerge from the possum's genome is that genes positioned towards the tips of the chromosomes undergo evolutionary changes at a faster rate than those in the middle, said Professor Chris Ponting of the Medical Research Council (MRC) functional genetics unit at Oxford University in England.
"Evolution has been pretty good at getting rid of mutations when they're near the edges of chromosomes, but rather poor at doing so in their middles because genes in the middle are less likely to be shuffled before being passed on to the next generation," Professor Ponting said.
"It really is all about location. Where a gene lives matters. This discovery is important because it will help us to separate DNA changes in the human genome that lead to disease from those that don't."
The scientists found that the fastest evolving genes in the possum DNA were those involved in immunity to diseases, reproduction and adaptation to new diets.
"Immunity genes can't stay still even for a single moment," said Leo Goodstadt, an MRC researcher at Oxford. "The possum genome has shown us that it is genes involved in immunity that change most rapidly. This is important in giving us extra options in tackling human diseases that affect people."
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