Functional and spatial segregation of embryo-larval and adult globin genes in Danio rerio major globin gene locus shows possible way of generation of structural-functional genomic domains in eukaryotic genome

To get insights into domain organization and functioning of the Danio rerio major a/ß-globin locus (Ma/ßGL), we have characterized profiles of histone H3 panacetylation across this locus in erythrocytes of adult fish and 18 dpf larvas. To identify enriched domains in our ChipSeq data we used our original protocol and peak caller MACS2. Histone acetylation profiles of Ma/ßGL for adult and embryo cells reveal a breaking point in upstream region of the first embryo-larval gene ße1.There are two sub-segments of acetylation: sub-segment to the left of ße1 harbors adult-specific globin genes and is acetylated only in adult cells. Embryo sub-segment contains embryo-larval globin genes and is located to the right of ße1 gene. Acetylation in this subsegment was detected only in 18 dpf larva. Acetylation profile in adult subs-egment possess largest acetylation domain which covers two pairs of adult-stage globins: aa1, and ßa1. High acetylation level in this domain well correlates with high expression level observed for these 4 genes in adult erythrocyte. Pattern of H3 panacetylation in 18 dpf larval erythrocytes differs strikingly from that for adult cells. Embryo-larval segment is fragmented in small domains co-located with gene bodies with gaps in intergenic regions. Adult subsegment in adult cells contains strong acetylation domain that cover 4 globin genes along with a part of intergenic regions and few smaller domains. Alternative stage-specific acetylation of subdomains and different pattern of embryonic-larval and adult domain acetylation strongly support the hypothesis of deep structural and functional segregation of stage-specific subdomains within Ma/ßGL locus in zebrafish. Overall design: Examination of histone H3panac in adult and larval erythrocyte of Danio rerio.