Article

Journal of Molecular Evolution

, Volume 58, Issue 6, pp 642-652

First online:

Linkage of the β-Like ω-Globin Gene to α-Like Globin Genes in an Australian Marsupial Supports the Chromosome Duplication Model for Separation of Globin Gene Clusters

  • David WheelerAffiliated withDepartment of Molecular Biosciences, The University of AdelaideCentre for Evolutionary Biology and Biodiversity, The University of Adelaide
  • , Rory M. HopeAffiliated withDepartment of Molecular Biosciences, The University of AdelaideCentre for Evolutionary Biology and Biodiversity, The University of AdelaideAustralian and New Zeland Council for the Care of Animals in Teaching and Research, University of Adelaide Email author 
  • , Steven J. B. CooperAffiliated withEvolutionary Biology Unit, South Australian MuseumCentre for Evolutionary Biology and Biodiversity, The University of Adelaide
  • , Andrew A. GooleyAffiliated withProteome Systems Ltd.
  • , Robert A. B. HollandAffiliated withSchool of Physiology and Pharmacology, University of New South Wales

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Abstract

The structure, function, and evolutionary history of globin genes have been the subject of extensive investigation over a period of more than 40 years, yet new globin genes with highly specialized functions are still being discovered and much remains uncertain about their evolutionary history. Here we investigate the molecular evolution of the β-globin gene family in a marsupial species, the tammar wallaby, Macropus eugenii. We report the complete DNA sequences of two β-like globin genes and show by phylogenetic analyses that one of these genes is orthologous to embryonically expressed ε-globin genes of marsupials and eutherians and the other is orthologous to adult expressed β-globin genes of marsupials and eutherians. We show that the tammar wallaby contains a third functional β-like globin gene, ω-globin, which forms part of the α-globin gene cluster. The position of ω-globin on the 3′ side of the α-globin cluster and its ancient phylogenetic history fit the criteria, originally proposed by Jeffreys et al. (1980), of a “fossil” β-globin gene and suggest that an ancient chromosome or genome duplication preceded the evolution of unlinked clusters of α- and β-globin genes in mammals and avians. In eutherian mammals, such as humans and mice, ω-globin has been silenced or translocated away from the α-globin locus, while in marsupials ω-globin is coordinately expressed with the adult α-globin gene just prior to birth to produce a functional hemoglobin (α2 ω2).

Keywords

Globin gene evolution α-globin β-globin ε-globin ω-globin Tammar wallaby Macropus eugenii Marsupial Molecular evolution