A Sendai Virus-Based Cytoplasmic RNA Vector as a Novel Platform for Long-Term Expression of MicroRNAs

Viral vectors: design and delivery for small RNA

RNA interference regulates gene expression by selectively silencing target genes through the introduction of small RNA molecules, such as microRNA, small interfering RNA and short hairpin RNA. These molecules offer significant therapeutic potential for diverse human ailments like cancer, viral infections and neurodegenerative disorders. Whilst non-viral vectors like nanoparticles have been extensively explored for delivering these RNAs, viral vectors, with superior specificity and delivery efficiency, remain less studied. This review examines current viral vectors for small RNA delivery, focusing on design strategies and characteristics. It compares the advantages and drawbacks of each vector, aiding readers in selecting the optimal one for small RNA delivery.

Ubiquitin-Derived Fragment as a Peptide Linker for the Efficient Cleavage of a Target Protein from a Degron

The chemogenetic control of cellular protein stability using degron tags is a powerful experimental strategy in biomedical research. However, this technique requires permanent fusion of the degron to a target protein, which may interfere with the proper function of the protein. Here, we report a peptide fragment from the carboxyl terminus of ubiquitin as a cleavable linker that exhibits the slow but efficient cleavage of a degron tag via cellular deubiquitinating enzymes (DUBs). We designed a fusion protein consisting of a cleavable linker and a destabilizing domain (DD), which conditionally controls the expression and release of a target protein in a ligand-induced state, allowing the free unmodified protein to perform its function. Insertion of an AGIA epitope at the carboxyl terminus of the linker made space for the DUBs to access the site to assist the cleavage reaction when the amino terminus of the target protein caused steric hindrance. The developed system, termed a cleavable degron using ubiquitin-derived linkers (c-DUB), provides robust and tunable regulation of target proteins in their native forms. The c-DUB system is a useful tool for the regulation of proteins that have terminal sites that are essential for the proper localization and function. In addition, a mechanistic investigation using proximity labeling showed that DUBs associate with the refolded DD to reverse ubiquitination, suggesting a cellular surveillance system for distinguishing the refolded DD from misfolded proteins. The c-DUB method may benefit from this machinery so that DUBs subsequently cleave the neighboring linker.

LRRC15 expression indicates high level of stemness regulated by TWIST1 in mesenchymal stem cells

Mesenchymal stem cells (MSCs) are used as a major source for cell therapy, and its application is expanding in various diseases. On the other hand, reliable method to evaluate quality and therapeutic properties of MSC is limited. In this study, we focused on TWIST1 that is a transcription factor regulating stemness of MSCs and found that the transmembrane protein LRRC15 tightly correlated with the expression of TWIST1 and useful to expect TWIST1-regulated stemness of MSCs. The LRRC15-positive MSC populations in human and mouse bone marrow tissues highly expressed stemness-associated transcription factors and therapeutic cytokines, and showed better therapeutic effect in bleomycin-induced pulmonary fibrosis model mice. This study provides evidence for the important role of TWIST1 in the MSC stemness, and for the utility of the LRRC15 protein as a marker to estimate stem cell quality in MSCs before cell transplantation.

Non-Integrating Lentiviral Vectors in Clinical Applications: A Glance Through

Lentiviral vectors (LVs) play an important role in gene therapy and have proven successful in clinical trials. LVs are capable of integrating specific genetic materials into the target cells and allow for long-term expression of the cDNA of interest. The use of non-integrating LVs (NILVs) reduces insertional mutagenesis and the risk of malignant cell transformation over integrating lentiviral vectors. NILVs enable transient expression or sustained episomal expression, especially in non-dividing cells. Important modifications have been made to the basic human immunodeficiency virus (HIV) structures to improve the safety and efficacy of LVs. NILV-aided transient expression has led to more pre-clinical studies on primary immunodeficiencies, cytotoxic cancer therapies, and hemoglobinopathies. Recently, the third generation of self-inactivating LVs was applied in clinical trials for recombinant protein production, vaccines, gene therapy, cell imaging, and induced pluripotent stem cell (iPSC) generation. This review discusses the basic lentiviral biology and the four systems used for generating NILV designs. Mutations or modifications in LVs and their safety are addressed with reference to pre-clinical studies. The detailed application of NILVs in promising pre-clinical studies is also discussed.

Production of therapeutic iduronate-2-sulfatase enzyme with a novel single-stranded RNA virus vector

The Sendai virus vector has received a lot of attention due to its broad tropism for mammalian cells. As a result of efforts for genetic studies based on a mutant virus, we can now express more than 10 genes of up to 13.5 kilo nucleotides in a single vector with high protein expression efficiency. To prove this benefit, we examined the efficacy of the novel ribonucleic acid (RNA) virus vector harboring the human iduronate-2-sulfatase (IDS) gene with 1,653 base pairs, a causative gene for mucopolysaccharidosis type II, also known as a disorder of lysosomal storage disorders. As expected, this novel RNA vector with the human IDS gene exhibited its marked expression as determined by the expression of enhanced green fluorescent protein and IDS enzyme activity. While these cells exhibited a normal growth rate, the BHK-21 transformant cells stably expressing the human IDS gene persistently generated an active human IDS enzyme extracellularly. The human IDS protein produced failed to be incorporated into the lysosome when cells were pretreated with mannose-6-phosphate, demonstrating that this human IDS enzyme has potential for therapeutic use by cross-correction. These results suggest that our novel RNA vector may be applicable for further clinical settings.

Generation of Self-Inhibitory Recombinant Viral Hemorrhagic Septicemia Virus (VHSV) by Insertion of Viral P Gene-Targeting Artificial MicroRNA into Viral Genome and Effect of Dicer Gene Knockout on the Recombinant VHSV Replication

To produce artificial microRNA (amiR)-mediated self-inhibitory viral hemorrhagic septicemia virus (VHSV), we inserted VHSV P gene-targeting amiR sequence (amiR-P) or control amiR sequence (amiR-C) between N and P genes of VHSV genome, and rescued recombinant VHSVs (rVHSV-A-amiR-P and rVHSV-A-amiR-C) using reverse genetic technology. The growth of rVHSV-A-amiR-P was significantly retarded compared to the control virus, rVHSV-A-amiR-C, due to the production of self P gene transcript-attacking microRNAs in infected cells. To enhance the replication of rVHSV-A-amiR-P, we generated the Dicer gene-knockout epithelioma papulosum cyprini (EPC-ΔDicer) cells using a CRISPR/Cas9 system, and evaluated the effect of Dicer knockout on the titer of rVHSV-A-amiR-P. The replication of rVHSV-A-amiR-C in EPC-ΔDicer cells was not different from that in control EPC cells, while the copy number of rVHSV-A-amiR-P was increasingly risen up in EPC-ΔDicer cells compared to that in control EPC cells, and the final viral titer of rVHSV-A-amiR-P was enhanced by culture in EPC-ΔDicer cells. These results indicate that VHSV can be attenuated by the equipment of self-mRNA-targeting microRNA sequence in the genome, and the titer of artificial miRNA-expressing attenuated recombinant VHSVs can be enhanced by the knockout of Dicer gene in EPC cells.

Engineering cell fate: Applying synthetic biology to cellular reprogramming

Cellular reprogramming drives cells from one stable identity to a new cell fate. By generating a diversity of previously inaccessible cell types from diverse genetic backgrounds, cellular reprogramming is rapidly transforming how we study disease. However, low efficiency and limited maturity have limited the adoption of in vitro-derived cellular models. To overcome these limitations and improve mechanistic understanding of cellular reprogramming, a host of synthetic biology tools have been deployed. Recent synthetic biology approaches have advanced reprogramming by tackling three significant challenges to reprogramming: delivery of reprogramming factors, epigenetic roadblocks, and latent donor identity. In addition, emerging insight from the molecular systems biology of reprogramming reveal how systems-level drivers of reprogramming can be harnessed to further advance reprogramming technologies. Furthermore, recently developed synthetic biology tools offer new modes for engineering cell fate.