Genomic organization and developmental expression of globin genes in the teleost Oryzias latipes

Abstract

We isolated globin genes from a genomic DNA library of the drR strain of medaka Oryzias latipes, and walked on chromosome. The present study is the first demonstration of the full-length structure of globin gene locus in the teleosts. Two gene clusters were found. One cluster of 36 kbp consisted of nine globin genes and two pseudogenes. Based on structural and phylogenetic similarity of amino acid sequences, the cluster was named embryonic globin gene cluster (E1). The orientation of the genes was in 5′α0 3′- 3′β1 5′- 5′α1 3′- 5′β2 3′- 5′α2 3′- 3′α3 5′- 5′β3 3′- 3′β4 5′- 5′α4 3′- 3′ψα 5′- 5′ψβ 3′. The other cluster of 20 kbp contained three globin genes ( 3′ad.α1 5′- 5′ad.β1 3′- 3′ad.α2 5′), and was named adult globin gene cluster (A1). Genetic linkage analysis clarified that E1 and A1 were mapped on linkage groups 8 and 19, respectively. The E1 cluster included other genes homologous to human EST clone KIAA0172, Sushi-1 retrotransposon, and protein 14 gene-like gene, while the A1 cluster linked to aquaporin-8 gene-like gene. The expression patterns of the genes were classified into four types: embryo-specific expression (α3, β3, α4 and β4), expression in embryo to young fish (α0, β1, α1 and ad.α2), expression in young to adult fish (α2 and ad.α1) and successive expression in embryo to adult (ad.β1).