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Generation of a CRISPR activation mouse that enables modelling of aggressive lymphoma and interrogation of venetoclax resistance.

ABSTRACT: CRISPR technologies have advanced cancer modelling in mice, but CRISPR activation (CRISPRa) methods have not been exploited in this context. We establish a CRISPRa mouse (dCas9a-SAM^KI) for inducing gene expression in vivo and in vitro. Using dCas9a-SAM^KI primary lymphocytes, we induce B cell restricted genes in T cells and vice versa, demonstrating the power of this system. There are limited models of aggressive double hit lymphoma. Therefore, we transactivate pro-survival BCL-2 in Eµ-Myc^T/+;dCas9a-SAM^KI/+ haematopoietic stem and progenitor cells. Mice transplanted with these cells rapidly develop lymphomas expressing high BCL-2 and MYC. Unlike standard Eµ-Myc lymphomas, BCL-2 expressing lymphomas are highly sensitive to the BCL-2 inhibitor venetoclax. We perform genome-wide activation screens in these lymphoma cells and find a dominant role for the BCL-2 protein A1 in venetoclax resistance. Here we show the potential of our CRISPRa model for mimicking disease and providing insights into resistance mechanisms towards targeted therapies.

SUBMITTER: Deng Y

PROVIDER: S-EPMC9374748 | biostudies-literature | 2022 Aug

REPOSITORIES: biostudies-literature

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Generation of a CRISPR activation mouse that enables modelling of aggressive lymphoma and interrogation of venetoclax resistance.

Deng Yexuan Y Diepstraten Sarah T ST Potts Margaret A MA Giner Göknur G Trezise Stephanie S Ng Ashley P AP Healey Gerry G Kane Serena R SR Cooray Amali A Behrens Kira K Heidersbach Amy A Kueh Andrew J AJ Pal Martin M Wilcox Stephen S Tai Lin L Alexander Warren S WS Visvader Jane E JE Nutt Stephen L SL Strasser Andreas A Haley Benjamin B Zhao Quan Q Kelly Gemma L GL Herold Marco J MJ

Nature communications 20220812 1

CRISPR technologies have advanced cancer modelling in mice, but CRISPR activation (CRISPRa) methods have not been exploited in this context. We establish a CRISPRa mouse (dCas9a-SAM<sup>KI</sup>) for inducing gene expression in vivo and in vitro. Using dCas9a-SAM<sup>KI</sup> primary lymphocytes, we induce B cell restricted genes in T cells and vice versa, demonstrating the power of this system. There are limited models of aggressive double hit lymphoma. Therefore, we transactivate pro-survival ...[more]

PMID: 35961968

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Project description:The B cell receptor (BCR) signaling, required for the survival and maturation of B cells, is a major deregulated pathway in B cell lymphomas. Several mutations are known to enhance the tonic BCR signal in Burkitt lymphomas (BL) or to mimic an activated receptor in some diffuse large B cell lymphomas (DLBCL). While the proximal events and kinases of the BCR signaling are well studied, less is known about the interactions of downstream effector pathways. In order to reach a less abstract description of this pathway we decided to employ the Modular Response Analysis-based modelling approach STASNet on more directly connected phosphorylation data. Using a Luminex proteomics platform we measured the phosphorylation of fourteen signaling and effector proteins after activating the B cell receptor (BCR) signaling and/or using inhibitors directed against seven intracellular signaling molecules in two independent Burkitt lymphoma cells (BL-2, BL-41). Application of a novel two step STASNet modelling pipeline unveiled novel feedback and crosstalk structures in the BCR-driven signaling network, including a crosstalk from p38 which negatively regulates MEK/ERK-activity in the presence of active BCR. Using Western Blot measurements, we verified and further characterized the p38-MEK/ERK crosstalk and demonstrated that it is a general mechanism in BL cells. Global Tandem Mass Tag (TMT) phosphoproteomic analysis on BL-2 cells found PI3K to be a major mediator of B-cell receptor signaling and manifested the p38-ERK crosstalk directly on ERK phosphosites and indirectly on seven bona fide ERK targets. We also noticed that the BL-2-learned pathway network structure was transferable to perturbation data from closely related BL-41 cells. Moreover, - compared to a literature-derived network - the BL-2-developed predictive pathway proved also to be a better starting point for network development in cells with aberrant BCR signaling in two representative cell lines derived from Diffuse large B cells (HBL-1, OCI-LY3). This indicates that models trained on activated B-cells are highly informative to be transferred to closely related cancer signaling network.

Project description:BackgroundMicroglia are an integral part of central nervous system, but our understanding of microglial biology is limited due to the challenges in obtaining and culturing primary human microglia. HMC3 is an important cell line for studying human microglia because it is readily accessible and straightforward to maintain in standard laboratories. Although HMC3 is widely used for microglial research, a robust genetic method has not been described. Here, we report a CRISPR genome editing platform, by the electroporation of Cas9 ribonucleoproteins (Cas9 RNP) and synthetic DNA repair templates, to enable rapid and precise genetic modifications of HMC3. For proof-of-concept demonstrations, we targeted the genes implicated in the regulation of amyloid beta (Aβ) and glioblastoma phagocytosis in microglia. We showed that CRISPR genome editing could enhance the phagocytic activities of HMC3.MethodsWe performed CRISPR gene knockout (KO) in HMC3 by the electroporation of pre-assembled Cas9 RNP. Co-introduction of DNA repair templates allowed site-specific knock-in (KI) of an epitope tag, a synthetic promoter and a fluorescent reporter gene. The editing efficiencies were determined genotypically by DNA sequencing and phenotypically by immunofluorescent staining and flow cytometry. The gene-edited HMC3 cells were examined in vitro by fluorescent Aβ and glioblastoma phagocytosis assays.ResultsOur platform enabled robust single (>90%) and double (>70%) KO without detectable off-target editing by high throughput DNA sequencing. We also inserted a synthetic SFFV promoter to efficiently upregulate the expression of endogenous CD14 and TREM2 genes associated with microglial phagocytosis. The CRISPR-edited HMC3 showed stable phenotypes and enhanced phagocytosis of fluorescence-labeled Aβ1-42 peptides. Confocal microscopy further confirmed the localization of Aβ1-42 aggregates in the acidified lysosomes. HMC3 mutants also changed the phagocytic characteristic toward apoptotic glioblastoma cells.ConclusionCRISPR genome editing by Cas9 RNP electroporation is a robust approach to genetically modify HMC3 for functional studies such as the interrogation of Aβ and tumor phagocytosis, and is readily adoptable to investigate other aspects of microglial biology.

Dataset Information

Generation of a CRISPR activation mouse that enables modelling of aggressive lymphoma and interrogation of venetoclax resistance.

Publications

Generation of a CRISPR activation mouse that enables modelling of aggressive lymphoma and interrogation of venetoclax resistance.

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