CTCF demarcates chicken embryonic ?-globin gene autonomous silencing and contributes to adult stage-specific gene expression.

ABSTRACT: Genomic loci composed of more than one gene are frequently subjected to differential gene expression, with the chicken ?-globin domain being a clear example. In the present study we aim to understand the globin switching mechanisms responsible for the epigenetic silencing of the embryonic ? gene and the transcriptional activation of the adult ?(D) and ?(A) genes at the genomic domain level. In early stages, we describe a physical contact between the embryonic ? gene and the distal 3' enhancer that is lost later during development. We show that such a level of regulation is achieved through the establishment of a DNA hypermethylation sub-domain that includes the embryonic gene and the adjacent genomic sequences. The multifunctional CCCTCC-binding factor (CTCF), which is located upstream of the ?(D) gene promoter, delimits this sub-domain and creates a transition between the inactive sub-domain and the active sub-domain, which includes the adult ?(D) gene. In avian-transformed erythroblast HD3 cells that are induced to differentiate, we found active DNA demethylation of the adult ?(D) promoter, coincident with the incorporation of 5-hydroxymethylcytosine (5hmC) and concomitant with adult gene transcriptional activation. These results suggest that autonomous silencing of the embryonic ? gene is needed to facilitate an optimal topological conformation of the domain. This model proposes that CTCF is contributing to a specific chromatin configuration that is necessary for differential ?-globin gene expression during development.

SUBMITTER: Valdes-Quezada C 

PROVIDER: S-EPMC3883786 | biostudies-literature | 2013 Aug

REPOSITORIES: biostudies-literature