Globin gene structure in a reptile supports the transpositional model for amniote α- and β-globin gene evolution.
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.
Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia. vidushi.patel@anu.edu.au
Vidushi S
VS
Patel
Tariq
T
Ezaz
Janine E
JE
Deakin
Jennifer A Marshall
JA
Graves
D000818:Animals; D002874:Chromosome Mapping; D002875:Chromosomes / Q000235:genetics; D019143:Evolution, Molecular; D015723:Gene Library; D023061:Gene Order; D005914:Globins / Q000235:genetics*; D008116:Lizards / Q000235:genetics*; D008957:Models, Genetic; D005810:Multigene Family / Q000235:genetics; D055542:alpha-Globins / Q000235:genetics*; D055544:beta-Globins / Q000235:genetics*
D055542:alpha-Globins; D055544:beta-Globins; D005914:Globins