Project description:To search for factors regulating paternally imprinted genes (PEGs), we performed a genome-wide CRISPR/Cas9 screen in haploid hpESCs, and further analyzed the molecular phenotype upon perturbation of candidate PEGs regulators.
Project description:To search for factors regulating paternally imprinted genes (PEGs), we performed a genome-wide CRISPR/Cas9 screen in haploid hpESCs, and further analyzed the molecular phenotype upon perturbation of candidate PEGs regulators.
Project description:Histones modulate gene expression by chromatin compaction, regulating numerous processes such as differentiation. However, the mechanisms underlying histone degradation remain elusive. When compared with their differentiated counterparts, immortal human embryonic stem cells (hESCs) have a unique chromatin architecture and low levels of trimethylated histone H3 at lysine 9 (H3K9me3), a heterochromatin-associated modification. Here we assess a link between the intrinsic epigenetic landscape and ubiquitin-proteasome system of hESCs. We find that hESCs exhibit high expression of UBE2K, a ubiquitin-conjugating enzyme. Loss of UBE2K increases the levels of H3K9 trimethyltransferase SETDB1, resulting in H3K9 trimethylation and repression of neurogenic genes during differentiation. Concomitantly, loss of UBE2K impairs the ability of hESCs to differentiate into neural progenitors with neurogenic properties. Besides H3K9 trimethylation, we find that UBE2K binds histone H3 to induce its polyubiquitination and degradation by the proteasome. Notably, ubc-20, the worm orthologue of UBE2K, also regulates both histone H3 levels and H3K9 trimethylation in C. elegans germline. Thus, our results indicate that UBE2K crosses evolutionary boundaries to promote histone H3 degradation and reduce H3K9me3 repressive marks in immortal cells.
Project description: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.
Project description:Single cell CRISPR screens such as Perturb-seq enable transcriptomic profiling of cellular perturbations at scale. However, the data produced by these screens are inherently noisy, limiting power to detect true effects with conventional differential expression analyses. Here, we introduce TRanscriptome-wide Analysis of Differential Expression (TRADE), a statistical framework which estimates the transcriptome-wide distribution of true differential expression effects from noisy gene-level measurements.