Genomic organization of zebra finch alpha and beta globin genes and their expression in primitive and definitive blood in comparison with globins in chicken

Abstract

How alpha and beta globin genes are organized and expressed in amniotes is of interest to researchers in a wide variety of fields. Data regarding this from avian species have been scarce. Using genomic and proteomic approaches, we present here our analysis of alpha and beta globins of zebra finch, a passerine bird. We show that finch alpha globin gene cluster has three genes (alphas 1-3), each orthologous to its chicken counterpart. Finch beta globin gene cluster has three genes (betas 1-3), with an additional pseudogene at the 3' end. Finch beta3 is orthologous to chicken betaA, but the orthology of beta1 and beta2 to chicken counterparts is less clear. All six finch globins are confirmed to encode functional proteins. Gene expression in both globin gene clusters is regulated developmentally. Adult finch blood has a globin profile similar to that of adult chicken, with high levels of beta3 and alpha3 and moderate levels of alpha2. Finch embryonic primitive blood exhibits a globin profile very different from that of equivalent stage chick embryos, with all six globins expressed at high levels. Overall, our data provide a valuable resource for future studies in avian globin gene evolution and globin switching during erythropoietic development.