Albert Cheng, PhD 郑瑚博士
Professor
Institute of Zoology, CAS
研究员
中国科学院动物研究所
RNA Splicing + RBPs
Publication Types:
Simultaneous multifunctional transcriptome engineering by CRISPR RNA scaffold
RNA processing and metabolism are subjected to precise regulation in the cell to ensure integrity and functions of RNA. Though targeted RNA engineering has become feasible with the discovery and engineering of the CRISPR-Cas13 system, simultaneous modulation of different RNA processing steps remains unavailable. In addition, off-target events resulting from effectors fused with dCas13 limit its application. Here we developed a novel platform, Combinatorial RNA Engineering via Scaffold Tagged gRNA (CREST), which can simultaneously execute multiple RNA modulation functions on different RNA targets. In CREST, RNA scaffolds are appended to the 3’ end of Cas13 gRNA and their cognate RNA binding proteins are fused with enzymatic domains for manipulation. Taking RNA alternative splicing, A-to-G and C-to-U base editing as examples, we developed bifunctional and tri-functional CREST systems for simultaneously RNA manipulation. Furthermore, by fusing two split fragments of the deaminase domain of ADAR2 to dCas13 and/or PUFc respectively, we reconstituted its enzyme activity at target sites. This split design can reduce nearly 99% of off-target events otherwise induced by a full-length effector. The flexibility of the CREST framework will enrich the transcriptome engineering toolbox for the study of RNA biology.
Multiplex RNA targeting
Provided herein, in some aspects, is a multiplex RNA targeting system that enables live cell imaging and/or modification of multiple RNA targets. Specifically, the disclosure provides a method of live cell imaging of ribonucleic acid (RNA), or targeting RNA in a live cell, comprising: (a) delivering to a cell an RNA-editing complex that comprises a catalytically inactive Cas13 (dCas13) nuclease, a Cas 13 guide RNA (gRNA) comprising an RNA aptamer sequence, and a detectable molecule linked to an RNA-binding domain (RBD), or an RNA effector molecule linked to an RBD sequence that specifically binds to the RNA aptamer sequence; and (b) imaging the detectable molecule or RNA aptamer and RBD binding.
Simultaneous multifunctional transcriptome engineering by CRISPR RNA scaffold
RNA processing and metabolism are subjected to precise regulation in the cell to ensure integrity and functions of RNA. Though targeted RNA engineering has become feasible with the discovery and engineering of the CRISPR-Cas13 system, simultaneous modulation of different RNA processing steps remains unavailable. In addition, off-target events resulting from effectors fused with dCas13 limit its application. Here we developed a novel platform, Combinatorial RNA Engineering via Scaffold Tagged gRNA (CREST), which can simultaneously execute multiple RNA modulation functions on different RNA targets. In CREST, RNA scaffolds are appended to the 3′ end of Cas13 gRNA and their cognate RNA binding proteins are fused with enzymatic domains for manipulation. We show that CREST is capable of simultaneously manipulating RNA alternative splicing and A-to-G or C-to-U base editing. Furthermore, by fusing two split fragments of the deaminase domain of ADAR2 to dCas13 and PUFc respectively, we reconstituted its enzyme activity at target sites. This split design can reduce more than 90% of off-target events otherwise induced by a full-length effector. The flexibility of the CREST framework will enrich the transcriptome engineering toolbox for the study of RNA biology and the development of RNA-focused therapeutics.
Poison exon splicing regulates a coordinated network of SR protein expression during differentiation and tumorigenesis
Artificial RNA-guided splicing factors
Provided herein, in some aspects, are compositions and methods for artificially modulating alternative splicing, for example, inducing exon inclusion and/or exon exclusion events. In some embodiments, a catalytically inactive programmable nuclease, such as dCasRx, is fused to an RNA-binding protein (or fragment or isoform thereof) and, when guided to a target of interest by a specific guide RNA (gRNA), can regulate alternative splicing in eukaryotic cells.
Casilio: a versatile CRISPR-Cas9-Pumilio hybrid for gene regulation and genomic labeling
Abstract
The RNA-guided DNA endonuclease system CRISPR-Cas9 has been exploited for
genome editing in various species. The nuclease-deficient mutant dCas9 protein can,
when coupled with sgRNAs, bind specific genomic loci without inducing DNA cleavage,
thus serving as a programmable DNA binding protein. To extend the utility of the dCas9
system, we have taken advantage of the ability of Pumilio PUF domains to bind specific
8-mer RNA sequences. By combining these two systems, we established the Casilio
system, which allows for specific and independent delivery of effector proteins to
specific genomic loci. We demonstrated that the Casilio system enables independent upand
down-regulation of multiple genes, as well as live-cell imaging of multiple genomic
loci simultaneously. Importantly, multiple copy of PUF binding sites can be incorporated
on sgRNA backbone, therefore allowing for local multimerization of effectors. In
addition, the PUF domain can be engineered to recognize any 8-mer RNA sequence,
therefore enabling the generation and simultaneous operation of many Casilio modules.
A website specifically for Casilio is at http://casil.io
Muscleblind-like 1 (Mbnl1) regulates pre-mRNA alternative splicing during terminal erythropoiesis
Abstract
The scope and roles of regulated isoform gene expression during erythroid terminal development are poorly understood. We identified hundreds of differentiation-associated isoform changes during terminal erythropoiesis. Sequences surrounding cassette exons of skipped exon events are enriched for motifs bound by the Muscleblind-like (MBNL) family of splicing factors. Knockdown of Mbnl1 in cultured murine fetal liver erythroid progenitors resulted in a strong block in erythroid differentiation and disrupted the developmentally regulated exon skipping of Ndel1 mRNA, which is bound by MBNL1 and critical for erythroid terminal proliferation. These findings reveal an unanticipated scope of the alternative splicing program and the importance of Mbnl1 during erythroid terminal differentiation.
Musashi proteins are post-transcriptional regulators of the epithelial-luminal cell state
The conserved Musashi (Msi) family of RNA binding proteins are expressed in stem/progenitor and cancer cells, but generally absent from differentiated cells, consistent with a role in cell state regulation. We found that Msi genes are rarely mutated but frequently overexpressed in human cancers and are associated with an epithelial-luminal cell state. Using ribosome profiling and RNA-seq analysis, we found that Msi proteins regulate translation of genes implicated in epithelial cell biology and epithelial-to-mesenchymal transition (EMT), and promote an epithelial splicing pattern. Overexpression of Msi proteins inhibited the translation of Jagged1, a factor required for EMT, and repressed EMT in cell culture and in mammary gland in vivo. Knockdown of Msis in epithelial cancer cells promoted loss of epithelial identity. Our results show that mammalian Msi proteins contribute to an epithelial gene expression program in neural and mammary cell types.
Alternatively spliced mRNA isoforms as prognostic indicators for metastatic cancer
The present invention provides a method for identifying a tumor as likely to metastasize, or likely to have metastasized, comprising obtaining a sample of the tumor and quantitating alternatively spliced mRNA isoforms of a cell motility gene, a cell adhesion gene and /or an actin cytoskeletal remodeling gene in the sample, or any specified genes or the level of RNA binding proteins compared to a predetermined non-metastasizing control.
An EMT–Driven Alternative Splicing Program Occurs in Human Breast Cancer and Modulates Cellular Phenotype
Abstract
Epithelial-mesenchymal transition (EMT), a mechanism important for embryonic development, plays a critical role during malignant transformation. While much is known about transcriptional regulation of EMT, alternative splicing of several genes has also been correlated with EMT progression, but the extent of splicing changes and their contributions to the morphological conversion accompanying EMT have not been investigated comprehensively. Using an established cell culture model and RNA–Seq analyses, we determined an alternative splicing signature for EMT. Genes encoding key drivers of EMT–dependent changes in cell phenotype, such as actin cytoskeleton remodeling, regulation of cell–cell junction formation, and regulation of cell migration, were enriched among EMT–associated alternatively splicing events. Our analysis suggested that most EMT–associated alternative splicing events are regulated by one or more members of the RBFOX, MBNL, CELF, hnRNP, or ESRP classes of splicing factors. The EMT alternative splicing signature was confirmed in human breast cancer cell lines, which could be classified into basal and luminal subtypes based exclusively on their EMT–associated splicing pattern. Expression of EMT–associated alternative mRNA transcripts was also observed in primary breast cancer samples, indicating that EMT–dependent splicing changes occur commonly in human tumors. The functional significance of EMT–associated alternative splicing was tested by expression of the epithelial-specific splicing factor ESRP1 or by depletion of RBFOX2 in mesenchymal cells, both of which elicited significant changes in cell morphology and motility towards an epithelial phenotype, suggesting that splicing regulation alone can drive critical aspects of EMT–associated phenotypic changes. The molecular description obtained here may aid in the development of new diagnostic and prognostic markers for analysis of breast cancer progression.