BALANCED GENE DOSAGE CONTROL RATHER THAN PARENTAL ORIGIN UNDERPINS GENOMIC IMPRINTING

Mammalian parental imprinting represents an exquisite form of epigenetic control regulating the parent-specific monoallelic expression of genes in clusters. While imprinting perturbations are widely associated with developmental abnormalities, the intricate regional interplay between imprinted genes makes interpreting the contribution of gene dosage effects to phenotypes a challenging task. Using mouse models with distinct deletions in an intergenic region controlling imprinting across the Dlk1-Dio3 domain, we link changes in genetic and epigenetic states to allelic-expression and phenotypic outcome in vivo. This determined how hierarchical interactions between regulatory elements orchestrate robust parent-specific expression, with implications for non-imprinted gene regulation. Strikingly, flipping imprinting on the parental chromosomes by crossing genotypes of complete and partial intergenic element deletions, rescues the lethality of each deletion on its own. Our work indicates that parental origin of an epigenetic state is irrelevant as long as appropriate balanced gene expression is established and maintained at imprinted loci. Overall design: Tail DNA was collected from E18.5 and E8.5 embryos. DNA was genotyped and embryos were divided into groups by genotype. WT littermates were used as controls. Each embryo was sequenced and analyzed separately. A total of 13 paternal deletion, 2 maternal deletion, 5 biallelic deletion and 3 WT controls were collected. We used the PBAT capture protocol combining PBAT and hybridization with an RNA probe library (capture), as described in detail in Meir Z. et al. Nature Genetics 2020. Final libraries were pooled and sequenced on an Illumina NextSeq system using the 150-bp high-output sequencing kit.