The superpowers of imprinting control regions

Genomic imprinting is a specialized mechanism of transcriptional regulation whereby approximately 200 mammalian genes are expressed monoallelically according to their parental origin. This crucial developmental process is primarily controlled by discrete cis-regulatory elements known as imprinting control regions (ICRs), which play essential roles in directing allele-specific gene expression across large imprinted domains. In this review, we highlight the features that define ICRs as a distinct class of cis-regulatory regions, from their ability to maintain germline-inherited DNA methylation to their multifunctional roles in transcriptional control. For each imprinted domain, we examine the diverse mechanisms by which individual ICRs integrate multiple regulatory functions to coordinate both proximal and distal imprinted gene expression. By uncovering the multifaceted roles of ICRs, this review provides a compelling framework for understanding, more broadly, the molecular basis of finely controlled gene expression.