A Fluorescent Reporter Mouse for In Vivo Assessment of Genome Editing with Diverse Cas Nucleases and Prime Editors.

CRISPR-based genome-editing technologies, including nuclease editing, base editing, and prime editing, have recently revolutionized the development of therapeutics targeting disease-causing mutations. To advance the assessment and development of genome editing tools, a robust mouse model is valuable, particularly for evaluating in vivo activity and delivery strategies. In this study, we successfully generated a knock-in mouse line carrying the Traffic Light Reporter design known as TLR-multi-Cas variant 1 (TLR-MCV1). We comprehensively validated the functionality of this mouse model for both in vitro and in vivo nuclease and prime editing. The TLR-MCV1 reporter mouse represents a versatile and powerful tool for expediting the development of editing technologies and their therapeutic applications.

Divalent siRNAs are bioavailable in the lung and efficiently block SARS-CoV-2 infection.

The continuous evolution of SARS-CoV-2 variants complicates efforts to combat the ongoing pandemic, underscoring the need for a dynamic platform for the rapid development of pan-viral variant therapeutics. Oligonucleotide therapeutics are enhancing the treatment of numerous diseases with unprecedented potency, duration of effect, and safety. Through the systematic screening of hundreds of oligonucleotide sequences, we identified fully chemically stabilized siRNAs and ASOs that target regions of the SARS-CoV-2 genome conserved in all variants of concern, including delta and omicron. We successively evaluated candidates in cellular reporter assays, followed by viral inhibition in cell culture, with eventual testing of leads for in vivo antiviral activity in the lung. Previous attempts to deliver therapeutic oligonucleotides to the lung have met with only modest success. Here, we report the development of a platform for identifying and generating potent, chemically modified multimeric siRNAs bioavailable in the lung after local intranasal and intratracheal delivery. The optimized divalent siRNAs showed robust antiviral activity in human cells and mouse models of SARS-CoV-2 infection and represent a new paradigm for antiviral therapeutic development for current and future pandemics.

Intratracheally administered LNA gapmer antisense oligonucleotides induce robust gene silencing in mouse lung fibroblasts.

The lung is a complex organ with various cell types having distinct roles. Antisense oligonucleotides (ASOs) have been studied in the lung, but it has been challenging to determine their effectiveness in each cell type due to the lack of appropriate analytical methods. We employed three distinct approaches to study silencing efficacy within different cell types. First, we used lineage markers to identify cell types in flow cytometry, and simultaneously measured ASO-induced silencing of cell-surface proteins CD47 or CD98. Second, we applied single-cell RNA sequencing (scRNA-seq) to measure silencing efficacy in distinct cell types; to the best of our knowledge, this is the first time scRNA-seq has been applied to measure the efficacy of oligonucleotide therapeutics. In both approaches, fibroblasts were the most susceptible to locally delivered ASOs, with significant silencing also in endothelial cells. Third, we confirmed that the robust silencing in fibroblasts is broadly applicable by silencing two targets expressed mainly in fibroblasts, Mfap4 and Adam33. Across independent approaches, we demonstrate that intratracheally administered LNA gapmer ASOs robustly induce gene silencing in lung fibroblasts. ASO-induced gene silencing in fibroblasts was durable, lasting 4-8 weeks after a single dose. Thus, lung fibroblasts are well aligned with ASOs as therapeutics.

Effects of Larval Density on Gene Regulation in Caenorhabditis elegans During Routine L1 Synchronization.

Bleaching gravid C. elegans followed by a short period of starvation of the L1 larvae is a routine method performed by worm researchers for generating synchronous populations for experiments. During the process of investigating dietary effects on gene regulation in L1 stage worms by single-worm RNA-Seq, we found that the density of resuspended L1 larvae affects expression of many mRNAs. Specifically, a number of genes related to metabolism and signaling are highly expressed in worms arrested at low density, but are repressed at higher arrest densities. We generated a GFP reporter strain based on one of the most density-dependent genes in our dataset - lips-15 - and confirmed that this reporter was expressed specifically in worms arrested at relatively low density. Finally, we show that conditioned media from high density L1 cultures was able to downregulate lips-15 even in L1 animals arrested at low density, and experiments using daf-22 mutant animals demonstrated that this effect is not mediated by the ascaroside family of signaling pheromones. Together, our data implicate a soluble signaling molecule in density sensing by L1 stage C. elegans, and provide guidance for design of experiments focused on early developmental gene regulation.

Induced multipotency in adult keratinocytes through down-regulation of ΔNp63 or DGCR8.

The roles of microRNAs (miRNAs) and the miRNA processing machinery in the regulation of stem cell biology are not well understood. Here, we show that the p53 family member and p63 isoform, ΔNp63, is a transcriptional activator of a cofactor critical for miRNA processing (DGCR8). This regulation gives rise to a unique miRNA signature resulting in reprogramming cells to multipotency. Strikingly, ΔNp63(-/-) epidermal cells display profound defects in terminal differentiation and express a subset of markers and miRNAs present in embryonic stem cells and fibroblasts induced to pluripotency using Yamanaka factors. Moreover, ΔNp63(-/-) epidermal cells transduced with an inducible DGCR8 plasmid can differentiate into multiple cell fates in vitro and in vivo. We found that human primary keratinocytes depleted of ΔNp63 or DGCR8 can be reprogrammed in 6 d and express a unique miRNA and gene expression signature that is similar but not identical to human induced pluripotent stem cells. Our data reveal a role for ΔNp63 in the transcriptional regulation of DGCR8 to reprogram adult somatic cells into multipotent stem cells.

TAp63 is a master transcriptional regulator of lipid and glucose metabolism.

TAp63 prevents premature aging, suggesting a link to genes that regulate longevity. Further characterization of TAp63-/- mice revealed that these mice develop obesity, insulin resistance, and glucose intolerance similar to those seen in mice lacking two key metabolic regulators, Silent information regulator T1 (Sirt1) and AMPK. While the roles of Sirt1 and AMPK in metabolism have been well studied, their upstream regulators are not well understood. We found that TAp63 is important in regulating energy metabolism by accumulating in response to metabolic stress and transcriptionally activating Sirt1, AMPKα2, and LKB1, resulting in increased fatty acid synthesis and decreased fatty acid oxidation. Moreover, we found that TAp63 lowers blood glucose levels in response to metformin. Restoration of Sirt1, AMPKα2, and LKB1 in TAp63-/- mice rescued some of the metabolic defects of the TAp63-/- mice. Our study defines a role for TAp63 in metabolism and weight control.

ΔNp63 transcriptionally regulates brachyury, a gene with diverse roles in limb development, tumorigenesis and metastasis.

The phenotypes of the p63 mutant mice are complex and diverse. The p63-/- mice develop severe defects in morphogenesis of ectodermal appendages, and p63+/- mice are tumor prone. Transcriptional targets of p63 with functions in both of these biological processes likely exist. Here, we identified one such direct transcriptional target of p63, brachyury, a gene with diverse roles in limb development and tumorigenesis. We found that brachyury is not expressed in developing p63-/- mouse embryos, and that in osteosarcomas, ΔNp63 and brachyury are expressed at high levels. Knock down of ΔNp63 in tumor cells resulted in a concomitant diminution of brachyury, cell proliferation, migration and invasion. These data provide evidence that suppression of ΔNp63 in tumors may lead to tumor regression through loss of cell proliferative and metastatic potential.