Cells in multicellular eukaryotic systems are diverse biological units, with characteristics and functions determined by their molecular profiles. CRISPR–Cas9 genome editing has been widely used across biology to modulate gene expression and study gene function. However, there is currently no versatile and scalable method for editing a cell’s genome in response to endogenous cellular signals. Here, we report the engineering of a CRISPR guide RNA that efficiently confers genome editing in response to the catalytic activity of a target microRNA (miRNA) within a cell. miRNAs are short non-coding RNAs that are widely conserved across eukaryotes and can cleave their target RNA through almost perfect base pairing. In mammals, miRNAs are largely involved in development and homeostasis as well as disease progression and developmental disorders. To leverage these properties for genome editing, we developed a cuffed guide RNA (cgRNA) which is composed of a permutated order of sequence domains from the commonly used single guide RNA (sgRNA). These permutated domains were then concatenated with a miRNA target sequence, yielding a warped guide RNA that is inactive until cleaved by a complementary miRNA. We demonstrated that cgRNA enabled efficient miRNA activity-dependent genome editing in human and mouse cell lines. Biochemical and structural analyses revealed three stages of inhibition of the CRISPR genome-editing pathway for unprocessed cgRNA. Utilizing a lentiviral library of cgRNAs containing miRNA targets covering mouse genome-wide miRNAs, we identified miRNA cleavage activities and their sequence specificities in mouse embryonic stem cells and during smooth muscle cell differentiation. Furthermore, we showed that endogenous mRNA expression could be irreversibly recorded into a DNA sequence using a cgRNA targeted by a synthetic miRNA repeat. cgRNA is a simple, robust, miRNA activity-gated genome editing system that could facilitate the development of cell state-specific genome editing, the mapping of miRNA activity and gene expression landscapes, and the recording of molecularly determined cell states during the long-term progression of multicellular systems.
Noncoding RNA (NCRNA), once considered genomic
"dark matter," has emerged as an essential regulator of
gene expression and is rapidly implicated in the
pathogenesis of various human diseases. Functional
genomics has brought a revolution to our
understanding of these RNA molecules, including
microRNAs, long noncoding RNAs and circular RNAs
(circRNAs), by enabling their expression, interaction
and large-scale analysis of the regulatory network.
With the advancement of high-throughput sequencing,
CRISPR-based gene editing and transcription,
functional genomics offers a wealth of insights into how
ncRNAs contribute to the onset, progression and tissue
specificity of diseases. These approaches facilitate the
identification of NCRNA biomarkers, highlight their
epigenetic and transcriptional control mechanisms and
illustrate their interactions with DNA, RNA and
proteins. In cancer, heart, neurodegenerative and
autoimmune diseases, converted NCRNA profiles are
now recognized as a significant reorganization of
signaling pathways and cellular homeostasis.
Additionally, a functional genomics background
improves transcriptional noise, enhancing AIDS,
clinical accuracy and medical goal discovery in
separating disease-specific NCRNAs. The integration
of computational biology, machine learning and
systems biology further enhances our ability to
interpret NCRNA tasks and predict their roles in the
disease network. Despite significant progress,
challenges remain in functionally validating NCRNAs
and translating genomic data into clinical
applications. This study discusses the latest functional
genomics strategies used to examine NCRNAS and
highlights their transformative ability in accurate
therapy.
Deepak Kumar Sahu, Harish Jaiswal· Research journal of biotechn...· 0 citations
Rationale Efficient gene activation or repression through programmable CRISPR-Cas9 has revolutionized molecular biology and drug development. Nonetheless, the currently available CRISPRa/i approaches are modestly potent and require multi-component delivery, which hampers the wide use of the technology in both research and therapy. Methods We developed a modular CRISPR-condensate platform by appending a multivalent RNA nanostar to the 3’ end of a single-guide RNA, producing a sgRNA-nanostar chimera that mediates phase separation at Cas9-bound genomic loci. The nanostar scaffold also contains MS2 stem-loops, which recruit MCP-tagged transcriptional effectors (VP64 for activation, KRAB for repression) to the condensate microenvironment at high local concentration. We examined condensate formation, genome targeting, and transcriptional output by using live-cell imaging, RT-qPCR, ChIP-seq, RNA-seq and CUT&Tag in HEK293T, HeLa, U-2 OS, MDA-MB-231, as well as human iPSC cell lines. Results The CRISPR-condensate design resulted in up to 50–100-fold target-gene activation, compared with 5–10-fold activation by direct VP64 fusion, and 20–30-fold transcriptional repression, compared with 3–5-fold repression by direct KRAB fusion, with high target specificity (12 versus 28 non-target differentially expressed genes assessed by RNA-seq). Orthogonal kissing-loop (KL) pairings enabled independent condensate systems for simultaneous activation and repression of multiplexed targets. Janus condensates containing both activating and repressive domains enabled bidirectional regulation at a single locus. The system requires delivery of only three independently expressible components—dCas9-NLS, an sgRNA-nanostar chimera bearing MS2 stem-loops (MS2SLs), and an MCP-fused effector (VP64-MCP for activation or KRAB-MCP for repression)—and showed minimal innate immune response and high cell viability. Conclusions The CRISPR-condensate system merges the dramatically enhanced transcriptional efficacy with the reduced complexity of components, providing a modular system for fine-tuned gene expression regulation. This strategy makes biomolecular condensation a general principle for enhancing CRISPR gene regulation, opening up possibilities for functional genomics, cell engineering, and therapy development.
Aolin Li, Congcong Cao, Chunyan Yang et al.· Theranostics· 0 citations
To systematically map cellular factors constraining nonviral genome editing, influencing uptake and intracellular trafficking, we develop a genome-wide CRISPR screening platform linking perturbation of 19,114 genes to editing outcomes in human cells. We identify six negative regulators of delivery whose depletion increases editing efficiency by up to six-fold across diverse payloads, loci, and cell types. We test the top two factors, GJB2 and BET1L, in two distinct human models: correction of a pathogenic adenine base mutation in KCNJ13 and introduction of a cytosine base mutation in the GABAA receptor gene. Depletion of either improves base-editing outcomes by 6-fold, potentially through effects on delivery. In a patient-derived model of retinal channelopathy, knockdown of either gene improves lipid nanoparticle base editing efficiency by over 3.5-fold. This enables functional restoration of Kir7.1 ion channels in a subset of edited cells, highlighting cellular barriers as actionable targets to enhance the potency of genetic therapies. Low editing efficiency of nonviral delivery in post mitotic tissues presents a challenge to the field of gene therapy. Here, authors dissect the genetic regulators of nonviral delivery in post mitotic retinal epithelial cells describe strategies for improved base editor delivery and editing.
Shivani Saxena, Meha Kabra, Amr A. Abdeen et al.· Nature Communications· 0 citations
A novel genome-wide CRISPR screening strategy that will facilitate the systematic engineering of novel nonviral genome editing delivery methods, where the identified novel gene hits can be further used to increase editing efficiency for other therapeutically relevant cell types.
Shivani Saxena, Meha Kabra, Amr A. Abdeen et al.· bioRxiv· 2 citations