This article has been updated to reflect the fact that the PLoS Biology paper discussed the analysis of the opossum MHC, not the entire opossum genome.
NEW YORK, Feb. 1 (GenomeWeb News) - An international team led by researchers at the University of Sydney in Australia has used the draft sequence data for a South American opossum to map the marsupial major histocompatability complex and infer the MHC of ancestral mammals.
The work focused on the evolution of the cluster of immune genes, and was published this week in the journal PLoS Biology. According to a statement from Kathy Belov, who led the team, "mapping the opossum MHC has allowed us to deduce what the MHC of ancestral mammals looked like."
All results presented in the paper are based on the MHC-containing scaffold from the preliminary assembly of the Monodelphis domestica genome, MonDom2, released by the Broad Institute.
Describing the ancestral MHC, Belov said, "we think it contained several different types of immune genes in a single complex." The researchers have named this complex 'The Immune Supercomplex,' she said. These genes are no longer found in a single complex in any living animal but are scattered over various chromosomes.
Belov also said that marsupial genomes filled a gap for researchers comparing the evolution of immune systems because comparing "the genes of placental mammals, such as the human and the mouse, is not very efficient" because their genes are too similar. Belov added that comparing humans with more distant genomes, such as chicken, can be too difficult because the sequences are too different.
She said that marsupial genomes "
are easily aligned with placental mammal genomes, yet are different enough to pinpoint regions that have important functions and therefore have been conserved for long periods of time."