Globin gene structure in a reptile supports the transpositional model for amniote α- and β-globin gene evolution

• Published in: Chromosome research 2010-12, Vol.18 (8), p.897-907
• Main Authors: Patel, Vidushi S, Ezaz, Tariq, Deakin, Janine E, Marshall Graves, Jennifer A
• Format: Article
• Language: English
• Subjects: Agamidae; alpha-Globins - genetics; Amniota; Animal Genetics and Genomics; Animals; beta-Globins - genetics; Biomedical and Life Sciences; Cell Biology; Chromosome Mapping; Chromosomes - genetics; comparative mapping; evolution; Evolution, Molecular; Gene Library; Gene Order; Globins - genetics; hemoglobin; Human Genetics; Lacertilia; Life Sciences; lizards; Lizards - genetics; Models, Genetic; Multigene Family - genetics; Plant Genetics and Genomics; Pogona vitticeps
• ISSN: 0967-3849; 1573-6849
• DOI: 10.1007/s10577-010-9164-5

The haemoglobin protein, required for oxygen transportation in the body, is encoded by α- and β-globin genes that are arranged in clusters. The transpositional model for the evolution of distinct α-globin and β-globin clusters in amniotes is much simpler than the previously proposed whole genome duplication model. According to this model, all jawed vertebrates share one ancient region containing α- and β-globin genes and several flanking genes in the order MPG-C16orf35-(α-β)-GBY-LUC7L that has been conserved for more than 410 million years, whereas amniotes evolved a distinct β-globin cluster by insertion of a transposed β-globin gene from this ancient region into a cluster of olfactory receptors flanked by CCKBR and RRM1. It could not be determined whether this organisation is conserved in all amniotes because of the paucity of information from non-avian reptiles. To fill in this gap, we examined globin gene organisation in a squamate reptile, the Australian bearded dragon lizard, Pogona vitticeps (Agamidae). We report here that the α-globin cluster (HBK, HBA) is flanked by C16orf35 and GBY and is located on a pair of microchromosomes, whereas the β-globin cluster is flanked by RRM1 on the 3′ end and is located on the long arm of chromosome 3. However, the CCKBR gene that flanks the β-globin cluster on the 5′ end in other amniotes is located on the short arm of chromosome 5 in P. vitticeps, indicating that a chromosomal break between the β-globin cluster and CCKBR occurred at least in the agamid lineage. Our data from a reptile species provide further evidence to support the transpositional model for the evolution of β-globin gene cluster in amniotes.