Structural variation-induced changes of chromatin architecture and gene expression

Copy number variants (CNVs) influence the expression of genes that map not only within the rearrangement, but also to its flanks. To assess the possible mechanism(s) underlying this “neighboring effect”, we compared intrachromosomal interactions and histone modifications in cell lines of patients affected by genomic disorders and control individuals. Using chromosome conformation capture (4C-seq), we observed that a set of genes flanking the Williams-Beuren Syndrome critical region (WBSCR) were often looping together, possibly forming an interacting cluster with each other and the WBSCR. Deletion of the WBSCR disrupts the expression of this group of flanking genes, as well as long-range interactions between them and the rearranged interval. We also pinpointed concomitant changes in histone modifications between samples.We conclude that large genomic rearrangements can lead to chromatin conformation changes that extend far away from the structural variant, thereby possibly modulating expression globally and modifying the phenotype. For example, we determined that the chromatin conformation, histone marks and relative expression levels of the flanking AUTS2 gene, mutations of which are associated with autism and intellectual disabilities, are modified in cell lines from Williams-Beuren syndrome patients. Overall design: Examination of 4C-seq interaction profile of seven different genes (of which three in duplicate) in 2 different cell lines.