Submitted to: DNA and Cell Biology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/29/2004
Publication Date: 5/1/2004
Citation: Vidal, G., Scheffler, B.E., Michel, A., D'Surney, S.J. 2004. Genomic and phylogenic comparisons of the alpha globin and beta globin intergenic sequences between zebra fish (danio rerio) and six closely related cyprinindae species. DNA and Cell Biology. V. 23. P. 325-334. Interpretive Summary: Globins are produced by a large and ancient multigene family and their common function is the binding of oxygen (such as in hemoglobin). Two major gene types are alpha and beta globin. It is believed that they evolved through a duplication event from a common globin ancestral gene. In mammalians, subsequent evolutionary events have placed these two types on different chromosomes. In comparison, these two types are next to each in the African clawed frog and zebrafish. The alpha and beta genes are regulated by DNA between both of them, but in the frog the genes are in the same orientation to each other while in zebrafish they are in opposite orientation. In order to determine if this is a unique configuration and its evolutionary implications, this region from a number of species related to zebrafish (in the Cyprinindae) were cloned, sequenced and compared.
Technical Abstract: The a globin and b globin genes of the zebrafish are tightly linked on the same chromosome in a 3'-5' and 5'-3' configuration respectively (Chan et al., 1997). Although the location of the controlling sequences has been mapped to the intergenic region, analysis determining the uniqueness of this unusual arrangement to zebrafish has not been undertaken. To explore this, we isolated, sequenced, and phylogenetically analyzed the intergenic region between globin gene families of 7 cyprinindae species including zebrafish. These species were grouped into an in group (immediate relatives, not so distant relatives), and an out group (distant relative). Cellulose acetate electrophoresis of hemoglobin (Hb) detected multiple variants in each species, but a band with electrophoretic mobility (EM) of 6.7 x 10-5 cm2.volt-1.sec-1 was shared between species. Polymerase chain reaction (PCR) amplification of the intergenic globin gene region also detected a 1.0 kb fragment that was repeated in the in group and a 1.2 kb fragment in the out group. Sequence comparison confirmed that the genetic orientation and controlling sequences location were conserved throughout this region in all 7 species. This phylogenic footprinting indicated that the configuration was not exclusive to zebrafish. To confirm sequence alignment, maximum parsimony phylogenic analysis was performed. Only one member of that group, the giant danio, was not closely clustered being located almost equidistance between the immediate relative and the species of the other clusters. This may represent an ancestral configuration prior to transposition of the a globin and b globin genes families to non-synteny.