TIP SHEET: Highlights from the opossum genome papers in Genome Research
EMBARGOED: Not for release until 1:00 p.m. EDT (US time) / 1800 (UK time) on Wednesday, May 9, 2007.
The opossum genome sequence casts light on evolution, immunity, and disease
Genome Research is publishing three papers related to the genome of the gray short-tailed opossum, Monodelphis domestica, a small, nocturnal
marsupial found in South America. The papers will appear online on May 10, concomitant with the publication of the opossum
genome sequence in the journal Nature.
1. A fresh start for immune-related genes
Like all marsupials, opossums are born without a functioning immune system; they develop immunological tissues, organs, and
the ability to produce antibodies outside the shelter of the mother’s body. The genome sequence of the opossum—the first
for any marsupial—provided Dr. Katherine Belov and her colleagues the opportunity to compare immune-related genes in opossums
with those in humans.
Belov’s team aligned 1528 human immune-related proteins to the opossum genome, and found that the genetic constituents of
the human and opossum “immunomes” were quite similar. “Given the similarities, opossums would make an ideal model organism
for developmental immunology studies in mammals, including humans,” says Belov.
Contact:
Katherine Belov, Ph.D.
University of Sydney, Australia
kbelov{at}vetsci.usyd.edu.au
+61-2-9351-3454
Reference:
Belov, K., Sanderson, C.E., Deakin, J.E., Wong, E.S.W., Assange, D., McColl, K.A., Gout, A., de Bono, B., Speed, T.P., Trowsdale,
J., and Papenfuss, A.T. 2007. Characterization of the opossum immune genome provides insights into the evolution of the mammalian
immune system. Genome Res. doi:10.1101/gr.6121807
2. New functions for ancient DNA
Transposable elements (TEs) are mobile, repetitive DNA sequences that can provide insight into evolutionary processes. “The
opossum genome has been bombarded by TEs,” explains Dr. Andrew Gentles, the first author on a paper that describes the first
comprehensive survey of TEs in any marsupial. “TEs cover around 52% of the opossum genome, which is higher than any other
amniotic lineage studied to date.”
Gentles and his colleagues also discovered ancient TEs that appear to have been recruited for specific biological activities.
For example, they identified MER131, a non-protein coding sequence that is highly conserved in the human, chicken, and opossum
genomes but absent from zebrafish and frogs. They suggest that MER131 acquired a new function—possibly in regulating gene
expression—about 300 million years ago, before the evolutionary divergence of birds and marsupials.
“MER131 is one of many non-coding DNA sequences that are conserved across an amazing variety of species, covering several
hundred million years of evolution,” says Gentles. “As more genomes are sequenced, we will find more pieces of these molecular
jigsaw puzzles that can help us trace the influence of TEs in the development and function of modern genomes.”
Contact:
Andrew J. Gentles, Ph.D.
Stanford University, Stanford, CA, USA
andrewg{at}highwire.org
+1-650-725-3121
Reference:
Gentles, A.J. Wakefield, M.J., Kohany, O., Gu, Wanjun, Batzer, M.A., Pollock, D.D., and Jurka, J. 2007. Evolutionary dynamics
of transposable elements in the short-tailed opossum Monodelphis domestica. Genome Res. doi:10.1101/gr.6070707
3. Colonizing colossal chromosomes
The opossum autosomes (non-sex chromosomes) are unusually large—up to three times longer than the largest human chromosome.
When Dr. Leo Goodstadt and his colleagues scrutinized these chromosomes, they discovered that genes situated near the edges
of the chromosomes were better at removing mutations that may lead to disease.
“Where a gene lives matters,” says Goodstadt. “Genes that lie in the middle of chromosomes are less likely to be shuffled
before being passed on to the next generation. So evolution has been pretty good at getting rid of mutations when they’re
near the ends of chromosomes, but rather poor at doing so in their middles.”
In addition, Goodstadt’s group identified 2,733 genes that have duplicated in the opossum lineage since its divergence from
humans ~170-190 million years ago. These genes contribute to unique physiological and behavioral characteristics in the opossum,
including nocturnal foraging, pheromonal communication, immunity, and adaptation to dietary changes.
Contact:
Leo Goodstadt, D.Phil.
University of Oxford, UK
leo.goodstadt{at}dpag.ox.ac.uk
+44-1865-285854
Reference:
Goodstadt, L., Heger, A., Webber, C., and Ponting, C.P. 2007. An analysis of the gene complement of a marsupial, Monodelphis
domestica: evolution of lineage-specific genes and giant chromosomes. Genome Res. doi:10.1101/gr.6093907
Please direct requests for pre-print copies of the manuscripts to Peggy Calicchia (calicchi{at}cshl.org; +1-516-422-4012), the
Editorial Secretary for Genome Research.
ABOUT GENOME RESEARCH:
Genome Research (www.genome.org) is an international, monthly, peer-reviewed journal published by Cold Spring Harbor Laboratory Press. Launched
in 1995, it is one of the five most highly cited primary research journals in genetics and genomics.
ABOUT COLD SPRING HARBOR LABORATORY PRESS:
Cold Spring Harbor Laboratory Press is an internationally renowned publisher of books, journals, and electronic media located
on Long Island, New York. It is a division of Cold Spring Harbor Laboratory, an innovator in life science research and the
education of scientists, students, and the public. For more information, visit www.cshlpress.com.
Genome Research issues press releases to highlight significant research studies that are published in the journal.
