Utilizing AAV-mediated LEAPER 2.0 for programmable RNA editing in non-human primates and nonsense mutation correction in humanized Hurler syndrome mice.

BACKGROUND: The endogenous adenosine deaminases acting on RNA (ADAR) have been harnessed to facilitate precise adenosine-to-inosine editing on RNAs. However, the practicability of this approach for therapeutic purposes is still ambiguous due to the variable expression of intrinsic ADAR across various tissues and species, as well as the absence of all-encompassing confirmation for delivery methods. RESULTS: In this study, we demonstrate that AAV-mediated delivery of circular ADAR-recruiting RNAs (arRNAs) achieves effective RNA editing in non-human primates at dosages suitable for therapy. Within a time frame of 4 to 13 weeks following infection, the editing efficiency in AAV-infected cells can reach approximately 80%, with no discernible toxicity, even at elevated dosages. In addition, when AAV-delivered circular arRNAs are systematically administered to a humanized mouse model of Hurler syndrome, it rectifies the premature stop codon precisely and restores the functionality of IDUA enzyme encoded by the Hurler causative gene in multiple organs. CONCLUSIONS: These discoveries considerably bolster the prospects of employing AAV-borne circular arRNAs for therapeutic applications and exploratory translational research.

Engineered circular ADAR-recruiting RNAs increase the efficiency and fidelity of RNA editing in vitro and in vivo.

Current methods for programmed RNA editing using endogenous ADAR enzymes and engineered ADAR-recruiting RNAs (arRNAs) suffer from low efficiency and bystander off-target editing. Here, we describe LEAPER 2.0, an updated version of LEAPER that uses covalently closed circular arRNAs, termed circ-arRNAs. We demonstrate on average ~3.1-fold higher editing efficiency than their linear counterparts when expressed in cells or delivered as in vitro-transcribed circular RNA oligonucleotides. To lower off-target editing we deleted pairings of uridines with off-target adenosines, which almost completely eliminated bystander off-target adenosine editing. Engineered circ-arRNAs enhanced the efficiency and fidelity of editing endogenous CTNNB1 and mutant TP53 transcripts in cell culture. Delivery of circ-arRNAs using adeno-associated virus in a mouse model of Hurler syndrome corrected the pathogenic point mutation and restored α-L-iduronidase catalytic activity, lowering glycosaminoglycan accumulation in the liver. LEAPER 2.0 provides a new design of arRNA that enables more precise, efficient RNA editing with broad applicability for therapy and basic research.

Single-Cell RNA-Seq Reveals Dynamic Early Embryonic-like Programs during Chemical Reprogramming.

Chemical reprogramming provides a powerful platform for exploring the molecular dynamics that lead to pluripotency. Although previous studies have uncovered an intermediate extraembryonic endoderm (XEN)-like state during this process, the molecular underpinnings of pluripotency acquisition remain largely undefined. Here, we profile 36,199 single-cell transcriptomes at multiple time points throughout a highly efficient chemical reprogramming system using RNA-sequencing and reconstruct their progression trajectories. Through identifying sequential molecular events, we reveal that the dynamic early embryonic-like programs are key aspects of successful reprogramming from XEN-like state to pluripotency, including the concomitant transcriptomic signatures of two-cell (2C) embryonic-like and early pluripotency programs and the epigenetic signature of notable genome-wide DNA demethylation. Moreover, via enhancing the 2C-like program by fine-tuning chemical treatment, the reprogramming process is remarkably accelerated. Collectively, our findings offer a high-resolution dissection of cell fate dynamics during chemical reprogramming and shed light on mechanistic insights into the nature of induced pluripotency.

Direct Reprogramming of Fibroblasts via a Chemically Induced XEN-like State.

Direct lineage reprogramming, including with small molecules, has emerged as a promising approach for generating desired cell types. We recently found that during chemical induction of induced pluripotent stem cells (iPSCs) from mouse fibroblasts, cells pass through an extra-embryonic endoderm (XEN)-like state. Here, we show that these chemically induced XEN-like cells can also be induced to directly reprogram into functional neurons, bypassing the pluripotent state. The induced neurons possess neuron-specific expression profiles, form functional synapses in culture, and further mature after transplantation into the adult mouse brain. Using similar principles, we were also able to induce hepatocyte-like cells from the XEN-like cells. Cells in the induced XEN-like state were readily expandable over at least 20 passages and retained genome stability and lineage specification potential. Our study therefore establishes a multifunctional route for chemical lineage reprogramming and may provide a platform for generating a diverse range of cell types via application of this expandable XEN-like state.