Project description:Background: Beta-thalassemia is among the commonest monogenic disorders, posing a major global health challenge. Editing of genetic modifiers of β-thalassemia, such as BCL11A erythroid enhancer and HBG promoters, enhances fetal hemoglobin (HbF) expression and confers major therapeutic potential. Double-strand-break (DSB)-independent genome editing tools, such as base editors, are potentially safer and better suited for multiplexed application than traditional DSB-dependent CRISPR/Cas technology. However, harmful inadvertent on- and off-target events remain a concern and must be excluded before clinical application, including chromosomal rearrangements, which are invisible to standard detection technologies. Results: Using primary patient-derived CD34+ cells from three donors, we investigated simplex and duplex BE-based disruption of the BCL11A erythroid enhancer and the BCL11A binding site (-115bp) on the HBG promoter for DNA-level events and functional studies at the RNA, protein, and morphological level. Analyses included direct comparison to DSB-based editing, as the current clinically applied standard, and analysis of DNA recombination events by CAST-seq to allow wider inferences for relative safety of DSB-, BE- and duplex BE-based editing. Our study reveals the effectiveness of duplex base editing, with robust γ-globin and HbF induction and significantly improved functional correction over simplex editing. Moreover, duplex editing resulted in low incidence of simple and complex genomic alterations in both therapeutically relevant target loci. Conclusions: Here we display simultaneous duplex base editing by targeting both BCL11A erythroid enhancer and HBG promoter for functional correction and genome integrity. Our study highlights the efficacy, safety, and therapeutic potential of the present duplex BE approach
Project description:A subset of long-noncoding RNAs (lncRNAs) are spatially correlated with transcription factors (TFs) across the genome, but how these lncRNA-TF gene duplexes regulate tissue development and homeostasis is unclear. We have identified a feedback loop within the NANCI-Nkx2.1 gene duplex that is essential for buffering Nkx2.1 expression, lung epithelial cell identity, and tissue homeostasis. Within this locus, Nkx2.1 directly inhibits NANCI, while NANCI acts in cis to promote Nkx2.1 transcription. Although loss of NANCI alone does not adversely affect lung development, concurrent heterozygous mutations in both NANCI and Nkx2.1 leads to persistent Nkx2.1 deficiency and reprogramming of lung epithelial cells to a posterior endoderm fate. This disruption in the NANCI-Nkx2.1 gene duplex results in a defective perinatal innate immune response, tissue damage, and progressive degeneration of the adult lung. These data point to a mechanism where lncRNAs act as rheostats within lncRNA-TF gene duplex loci that buffer TF expression, thereby maintaining tissue specific cellular identity during development and postnatal homeostasis.
Project description:Here we describe a new class of immunostimulatory short duplex RNAs that potently induce production of type I interferon (IFN-I), and particularly IFN-β, in a wide range ofhuman cell types via end-to-end dimerization, direct binding to RIG-I, and activation of the RIG-I/IRF3 pathway. These RNAs require a minimum of 20 base pairs, lack any sequence or structural characteristics of known immunostimulatory RNAs, and instead require a unique conserved sequence motif (sense strand: 5’-C, antisense strand: 3’-GGG) that mediates the self-assembly of end-to-end RNA dimers by Hoogsteen G-G base-pairing. The presence of terminal hydroxyl or monophosphate groups, blunt or overhanging ends, or terminal RNA or DNA bases also did not affect their ability to induce IFN-I production. Immune stimulation mediated by these duplex RNAs results in broad spectrum inhibition of infections by many respiratory viruses with pandemic potential, including SARS-CoV-2, SARS-CoV, MERS-CoV, and influenza A, as well as the common cold virus HCoV-NL63 in cell lines and in human Lung Chips that mimic organlevel lung pathophysiology. These novel immunostimulatory motifs potentially could be harnessed to create broad-spectrum antiviral therapeutics, but they should be avoided when designing siRNAs to minimize immunological side effects.
Project description:Aberrant activation of innate immune receptors can cause a spectrum of immune disorders, such as Aicardi-Goutières syndrome (AGS). One such receptor is MDA5, a viral double-stranded RNA (dsRNA) sensor that induces antiviral immune response. We here demonstrate that constitutive activation of MDA5 in AGS results from the loss of tolerance to cellular dsRNAs formed by Alu retroelements. While wild-type MDA5 cannot efficiently recognize Alu-dsRNA because its filament formation on dsRNA is impaired by the imperfect duplex structure, AGS-variants of MDA5 display reduced sensitivity to duplex structural irregularities, assembling signaling-competent filaments on Alu-dsRNA. Moreover, we identified an unexpected role of RNA-rich cellular environment in suppressing aberrant MDA5 oligomerization, highlighting context-dependence of self vs. non-self discrimination. Overall, our work demonstrates that the increased efficiency of MDA5 to recognize dsRNA comes at a cost of self-recognition, and implicates a unique role of Alu RNAs as virus-like elements that shape the primate immune system.
Project description:Aberrant activation of innate immune receptors can cause a spectrum of immune disorders, such as Aicardi-Goutières syndrome (AGS). One such receptor is MDA5, a viral double-stranded RNA (dsRNA) sensor that induces antiviral immune response. We here demonstrate that constitutive activation of MDA5 in AGS results from the loss of tolerance to cellular dsRNAs formed by Alu retroelements. While wild-type MDA5 cannot efficiently recognize Alu-dsRNA because its filament formation on dsRNA is impaired by the imperfect duplex structure, AGS-variants of MDA5 display reduced sensitivity to duplex structural irregularities, assembling signaling-competent filaments on Alu-dsRNA. Moreover, we identified an unexpected role of RNA-rich cellular environment in suppressing aberrant MDA5 oligomerization, highlighting context-dependence of self vs. non-self discrimination. Overall, our work demonstrates that the increased efficiency of MDA5 to recognize dsRNA comes at a cost of self-recognition, and implicates a unique role of Alu RNAs as virus-like elements that shape the primate immune system.
Project description:Here we describe a new class of immunostimulatory short duplex RNAs that potently induce production of type I interferon (IFN-I), and particularly IFN-β, in a wide range of human cell types via end-to-end dimerization, direct binding to RIG-I, and activation of the RIG-I/IRF3 pathway. These RNAs require a minimum of 20 base pairs, lack any sequence or structural characteristics of known immunostimulatory RNAs, and instead require a unique conserved sequence motif (sense strand: 5’-C, antisense strand: 3’-GGG) that mediates the self-assembly of end-to-end RNA dimers by Hoogsteen G-G base-pairing. The presence of terminal hydroxyl or monophosphate groups, blunt or overhanging ends, or terminal RNA or DNA bases also did not affect their ability to induce IFN-I production. Immune stimulation mediated by these duplex RNAs results in broad spectrum inhibition of infections by many respiratory viruses with pandemic potential, including SARS-CoV-2, SARS-CoV, MERS-CoV, and influenza A, as well as the common cold virus HCoV-NL63 in cell lines and in human Lung Chips that mimic organlevel lung pathophysiology. These novel immunostimulatory motifs potentially could be harnessed to create broad-spectrum antiviral therapeutics, but they should be avoided when designing siRNAs to minimize immunological side effects.