A molecular and evolutionary study of the beta-globin gene family of the Australian marsupial Sminthopsis crassicaudata.
Beta-globin gene families in eutherians (placental mammals) consist of a set of four or more developmentally regulated genes which are closely linked and, in general, arranged in the order 5'-embryonic/fetal genes-adult genes-3'. This cluster of genes is proposed to have arisen by tandem duplication of ancestral beta-globin genes, with the first duplication occurring 200 to 155 MYBP just prior to a period in mammalian evolution when eutherians and marsupials diverged from a common ancestor. In this paper we trace the evolutionary history of the beta-globin gene family back to the origins of these mammals by molecular characterization of the beta-globin gene family of the Australian marsupial Sminthopsis crassicaudata. Using Southern and restriction analysis of total genomic DNA and bacteriophage clones of beta-like globin genes, we provide evidence that just two functional beta-like globin genes exist in this marsupial, including one embryonic-expressed gene (S.c-epsilon) and one adult-expressed gene (S.c-beta), linked in the order 5'-epsilon-beta-3'. The entire DNA sequence of the adult beta-globin gene is reported and shown to be orthologous to the adult beta-globin genes of the North American marsupial Didelphis virginiana and eutherian mammals. These results, together with results from a phylogenetic analysis of mammalian beta-like globin genes, confirm the hypothesis that a two-gene cluster, containing an embryonic- and an adult-expressed beta-like globin gene, existed in the most recent common ancester of marsupials and eutherians. Northern analysis of total RNA isolated from embryos and neonatals indicates that a switch from embryonic to adult gene expression occurs at the time of birth, coinciding with the transfer of the marsupial from a uterus to a pouch environment.
Cooper
S J
SJ
Department of Genetics, University of Adelaide, Australia. scooper@genetics.adelaide.edu.au
Murphy
R
R
Dolman
G
G
Hussey
D
D
Hope
R M
RM
D000367:Age Factors; D000595:Amino Acid Sequence; D000818:Animals; D001315:Australia; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D003001:Cloning, Molecular; D015342:DNA Probes; D015245:Deoxyribonuclease BamHI / Q000378:metabolism; D019143:Evolution, Molecular; D018507:Gene Expression Regulation, Developmental; D008040:Genetic Linkage; D014644:Genetic Variation; D005914:Globins / Q000235:genetics* / Q000378:metabolism; D017403:In Situ Hybridization / Q000379:methods; D008394:Marsupialia / Q000196:embryology / Q000235:genetics* / Q000502:physiology; D008969:Molecular Sequence Data; D005810:Multigene Family; D010802:Phylogeny; D015183:Restriction Mapping; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific) / Q000378:metabolism
D015342:DNA Probes; D005914:Globins; C020098:DNA modification methylase EcoRI; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); D015245:Deoxyribonuclease BamHI