Project description:A genome-wide CRISPR screen was combined with a tdTomato reporter-based epigenetic memory assay to identify factors that erase epigenetic memory in ESC. After introducing genome wide perturbation and dCas9::KRAB-mediated epigenetic editing of the Esg1-tdTomato reporter, the trigger was released and cells that maintained the silencing sorted at FACS. Samples were collected out of sorted tdTomato negative (TOMminus) and positive (TOMplus) cells after 6 days of DOX treatment (epigenetic editing) and 3 or 7 days of DOX washout (release of the trigger), using a gating strategy to separate the bottom 2.5% negative cells (2.5%gate) and cells ranging from mildly to fully repressed (widegate).
Project description:To search for factors regulating neuronal differentiation, we performed a genome-wide loss-of-function CRISPR/Cas9 screen in haploid human ESCs. The regulators were identified by the quantification of depletion of their mutant clones within a pooled loss-of-function library upon neuronal differentiation.
Project description:Proinsulin is the precursor of insulin in pancreatic beta cells. Altered proinsulin and proinsulin to insulin ratio mark beta cell dysfunction, predictuing disease progression into type 1 and type 2 diabetes. Of essential role for beta cell function, knowledge about proinsulin production and its role in disease are currently very limited. Using genome wide CRISPR screen, we identified 84 proinsulin regulators including classical protein convertases Pcsk1 and Cpe, and novel factors like Pdia6. Among the list 29 proinsulin regulators were trajectory genes involved in disease progression in obesity and type 2 diabetes in humans. In vivo mouse genetics study revealed unique genetic architecture and quantitative trait loci (QTLs) modulating plasma proinsulin levels. Integrative analyzing and mapping of the QTL signals directly pinpointed to proinsulin regulators identified from the CRISPR screen, which in return greatly improved resolution of the mouse genetic study. 4 out of 5 overlapped genes can be individually validated. Knocking down the leading hits Pdia6 leads to decreased proinsulin content and remarkable loss of proinsulin granules in beta cells. Consequently, proinsulin secretion was greatly decreased. Mechanistically, protein translation rate was greatly impaired after knocking down Pdia6. Our study demonstrated the power of combining in vitro functional genomics with in vivo mouse genetics study to identify proinsulin regulatory network in pancreatic beta cells.
Project description:Proinsulin is the precursor of insulin in pancreatic beta cells. Altered proinsulin and proinsulin to insulin ratio mark beta cell dysfunction, predictuing disease progression into type 1 and type 2 diabetes. Of essential role for beta cell function, knowledge about proinsulin production and its role in disease are currently very limited. Using genome wide CRISPR screen, we identified 84 proinsulin regulators including classical protein convertases Pcsk1 and Cpe, and novel factors like Pdia6. Among the list 29 proinsulin regulators were trajectory genes involved in disease progression in obesity and type 2 diabetes in humans. In vivo mouse genetics study revealed unique genetic architecture and quantitative trait loci (QTLs) modulating plasma proinsulin levels. Integrative analyzing and mapping of the QTL signals directly pinpointed to proinsulin regulators identified from the CRISPR screen, which in return greatly improved resolution of the mouse genetic study. 4 out of 5 overlapped genes can be individually validated. Knocking down the leading hits Pdia6 leads to decreased proinsulin content and remarkable loss of proinsulin granules in beta cells. Consequently, proinsulin secretion was greatly decreased. Mechanistically, protein translation rate was greatly impaired after knocking down Pdia6. Our study demonstrated the power of combining in vitro functional genomics with in vivo mouse genetics study to identify proinsulin regulatory network in pancreatic beta cells.
Project description:We performed a FACS-based genome-wide CRISPR knockout screen in primary murine macrophages to identify regulators of efferocytosis, the phagocytic clearance of dying cells. The screen identified known and novel regulators of macrophage efferocytosis. More broadly, the screen approach can be applied to interrogate complex functional phenotypes in primary macrophages.
Project description:Nonsense-mediated decay (NMD) is a pathway that degrades messenger RNAs containing premature termination codons. Here, a genome-wide screen for NMD factors uncovered an unexpected mechanism that broadly governs 3ʹ untranslated region (UTR)-directed regulation. The screen revealed that NMD requires lysosomal acidification, which allows transferrin-mediated iron uptake, which in turn is necessary for iron-sulfur (Fe-S) cluster biogenesis. This pathway converges on the Fe-S cluster-containing ribosome recycling factor ABCE1, whose impaired function results in the movement of ribosomes into 3ʹ UTRs where they displace exon junction complexes, thereby abrogating NMD. Importantly, these effects extend beyond NMD substrates, with ABCE1 activity required to maintain the accessibility of 3ʹ UTRs to diverse regulators, including microRNAs and RNA binding proteins. Due to the sensitivity of the Fe-S cluster of ABCE1 to iron availability and reactive oxygen species, these findings reveal an unanticipated vulnerability of 3ʹ UTR-directed regulation to lysosomal dysfunction, iron deficiency, and oxidative stress.
Project description:Enhanced expression of the cold-shock protein RNA binding motif 3 (RBM3) is highly neuroprotective both in vitro and in vivo. Whilst upstream signalling pathways leading to RBM3 expression have been described, the precise molecular mechanism of RBM3 induction during cooling remains elusive. To identify temperature-dependent modulators of RBM3, we performed a genome-wide CRISPR-Cas9 knockout screen using RBM3-reporter human iPSC-derived neurons. We found that RBM3 mRNA and protein levels are robustly regulated by several splicing factors, with heterogeneous nuclear ribonucleoprotein H1 (HNRNPH1) being the strongest positive regulator.
Project description:The differentiation of B cells into antibody-secreting cells depends on cell division-coupled, epigenetic and other cellular processes that are incompletely understood. We have developed a CRISPR/Cas9-based screen that models an early stage of T cell-dependent plasma cell differentiation and measures B cell survival or proliferation versus the formation of CD138+ plasmablasts. Here, we refined and extended this screen to more than 500 candidate genes that are highly expressed in plasma cells. Among known genes whose deletion preferentially affected plasmablast formation were the transcriptional regulators Prdm1, Irf4 and Pou2af1, and the Ern1 gene encoding the ER stress sensor IRE1a. Moreover, we newly identified several genes involved in NF-kB or p38 signaling (Pim2, Nfkbia, Mapk14), vesicle trafficking (Arf4, Preb) and epigenetic regulators that form part of the NuRD complexes (Hdac1, Mta2, Mbd2). Defective plasmablast formation caused by Ern1 deletion could not be rescued by spliced XBP1 (XBP1s), a transcription factor dependent on and downstream of IRE1a, suggesting that in early plasma cell differentiation IRE1a acts independently of XBP1s. The deletion of ARF4, a small GTPase required for ER-to-Golgi transport, impaired plasmablast formation by blocking antibody secretion. Plasmablast formation after Hdac1 deletion was consistently reduced by about 50%, while deletion of the closely related Hdac2 gene had no effect. Hdac1 knock-out led to strongly perturbed protein expression of antagonistic transcription factors that specify plasma cell versus B cell identity (by decreasing IRF4 and BLIMP1 and increasing BACH2 and PAX5). Taken together, our results highlight specific and non-redundant roles for Ern1, Arf4 and Hdac1 in the early steps of plasma cell differentiation.
Project description:Self-renewal and pluripotency of the embryonic stem cell (ESC) state is established and maintained by multiple regulatory networks that comprise transcription factors and epigenetic regulators. Although many studies have been performed, the function of epigenetic regulators in these networks is incompletely defined. We conducted a CRISPR-Cas9 mediated loss-of-function genetic screen to target 323 epigenetic and ESC-specific transcription factor genes. This screen identified two new epigenetic regulators—TAF5L and TAF6L—with high confidence for the mouse ESC state. TAF5L and TAF6L are also essential for the efficient somatic reprogramming. In-depth analyses demonstrate that TAF5L and TAF6L belong to and establish a regulatory circuitry with MYC and CORE networks. Moreover, detailed molecular studies reveal TAF5L and TAF6L predominantly regulate their target genes through the c-MYC and MYC regulatory network to control self-renewal of mouse ESCs. Our findings illuminate the multi-layered regulatory networks of TAF5L and TAF6L for gene regulation to maintain the ESC state.