 Media
release 24 January 2004
Are prions shadoos of their former
selves?
Kangaroo genome casts light on mad cow disease
Besides being scary,
debilitating and poorly understood, mad cow disease (BSE), Creutzfeld Jacob
disease and kuru in humans and scrapie in sheep have something else in common.
They are all associated with prions—mysterious infectious protein particles
that can deform key proteins in the body.
The strange thing about
the prion protein is that we still don’t know its normal function in the body.
But an Australia research group may have found a home-grown way into the secret
world of prions.
“We’ve isolated the gene
that codes for the prion protein in kangaroos,” says Marko Premzl, a PhD student
at the ARC Centre for Kangaroo Genomics in Canberra and the John Curtin School
of Medical Research , who presented his findings at the Genome Conference in
Lorne, Victoria last week.
“The Australian Genome
Research Facility sequenced the gene and surrounding DNA for us so we could
identify five short gene sequences that act as switches or control points – and
these are all stretches of DNA known to bind to regulatory proteins that turn
genes on in the brain.
“This tells us something
about the normal function of prion protein - which obviously doesn’t exist just
to cause disease! It suggests that prion proteins play a role in brain
development or function,” says Jenny Graves, Director of the ARC Centre for
Kangaroo Genomics.
“Comparing prion-like gene
sequences with international databases, Marko has discovered a new human
prion-like gene that we think is more important. We named it Shadoo (Japanese
for shadow). This gene has changed little in the 450 million years of separation
between fish and humans – suggesting that it has a more important brain function
than the prion protein. So maybe the prion protein is a shadow (or more properly
a duplicate) of the shadoo protein, not the other way around,” says Jenny
Graves.
“This research
demonstrates the practical benefits that flow from gene sequencing,” says Sue
Forrest, Director of the Australian Genome Research Facility.
The marsupial genome can
offer key insights into the genetic programming of all mammals – including
humans. Because they are such distant relatives in the mammalian family tree,
they are sufficiently different from us to make useful comparisons which may
point the way to how we evolved.
“When you find a gene in
humans and kangaroos that has hardly changed in 180 million years of evolution
you know you are onto something important to human development,” says Sue
Forrest.
So, there’s international
interest in the marsupial genome—so much so that the US government is committing
$80 million to sequence the only marsupial native to North America, the
primitive opossum.
But Australia already has
a head start with the Tammar Wallaby according to Sue Forrest, “We plan to
sequence most of the wallaby genome in the next two years thanks to a generous
offer of $AU6 million worth of sequencing from US government – provided we can
match their contribution. We are currently working with State and Federal
agencies to secure this funding.”
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