Parent-to-Parent Advice on Considering Spinal Fusion in Children with Neuromuscular Scoliosis.

OBJECTIVES: To convey advice from families whose children recently underwent spinal fusion to families whose children are under consideration for initial spinal fusion for neuromuscular scoliosis and to providers who counsel families on this decision. STUDY DESIGN: We interviewed 18 families of children who underwent spinal fusion between August 2017 and January 2019 at a freestanding children's hospital. We conducted phone interviews a median of 65 (IQR 51-77) days after surgery. We audio recorded, transcribed, and coded (line-by-line) interviews using grounded theory by 2 independent reviewers, and discussed among investigators to induce themes associated with surgical decision making and preparation. RESULTS: Six themes emerged about decision making and preparation for spinal fusion: (1) simplify risks and benefits; it is easy to get lost in the details; (2) families prolonging the decision whether or not to pursue spinal fusion surgery may not benefit the child; (3) anticipate anxiety and fear when making a decision about spinal fusion; (4) realize that your child might experience a large amount of pain; (5) anticipate a long recovery and healing process after spinal fusion; and (6) be engaged and advocate for your child throughout the perioperative spinal fusion process. CONCLUSIONS: Parents of children who had recently undergone spinal fusion had strong perceptions about what information to convey to families considering surgery, which may improve communication between future parents and physicians. Further investigation is needed to assess how best to incorporate the wisdom and experiences of parent peers into shared decision making and preparation for spinal fusion in children with neuromuscular scoliosis.

Drosha as an interferon-independent antiviral factor.

Utilization of antiviral small interfering RNAs is thought to be largely restricted to plants, nematodes, and arthropods. In an effort to determine whether a physiological interplay exists between the host small RNA machinery and the cellular response to virus infection in mammals, we evaluated antiviral activity in the presence and absence of Dicer or Drosha, the RNase III nucleases responsible for generating small RNAs. Although loss of Dicer did not compromise the cellular response to virus infection, Drosha deletion resulted in a significant increase in virus levels. Here, we demonstrate that diverse RNA viruses trigger exportin 1 (XPO1/CRM1)-dependent Drosha translocation into the cytoplasm in a manner independent of de novo protein synthesis or the canonical type I IFN system. Additionally, increased virus infection in the absence of Drosha was not due to a loss of viral small RNAs but, instead, correlated with cleavage of viral genomic RNA and modulation of the host transcriptome. Taken together, we propose that Drosha represents a unique and conserved arm of the cellular defenses used to combat virus infection.

MicroRNA-based strategy to mitigate the risk of gain-of-function influenza studies.

Recent gain-of-function studies in influenza A virus H5N1 strains revealed that as few as three-amino-acid changes in the hemagglutinin protein confer the capacity for viral transmission between ferrets. As transmission between ferrets is considered a surrogate indicator of transmissibility between humans, these studies raised concerns about the risks of gain-of-function influenza A virus research. Here we present an approach to strengthen the biosafety of gain-of-function influenza experiments. We exploit species-specific endogenous small RNAs to restrict influenza A virus tropism. In particular, we found that the microRNA miR-192 was expressed in primary human respiratory tract epithelial cells as well as in mouse lungs but absent from the ferret respiratory tract. Incorporation of miR-192 target sites into influenza A virus did not prevent influenza replication and transmissibility in ferrets, but did attenuate influenza pathogenicity in mice. This molecular biocontainment approach should be applicable beyond influenza A virus to minimize the risk of experiments involving other pathogenic viruses.

Processing of virus-derived cytoplasmic primary-microRNAs.

MicoRNAs (miRNAs) are small noncoding RNAs that associate with Argonaute (AGO) family member proteins to mediate silencing of host mRNA transcripts. A number of DNA viruses and a single retrovirus exploit this pathway to generate their own miRNAs in an effort to self regulate or combat the host immune response to infection. While natural examples of viral miRNAs have been limited to nuclear viruses, manipulation of cytoplasmic-restricted RNA virus genomes revealed the ability of these vectors to produce abundant levels of mature, functional miRNAs, exclusively within the cytoplasm. This novel processing mechanism is found to be dependent upon the ribonuclease (RNAse) III proteins Drosha and Dicer, while processing is able to proceed in the absence of the canonical dsRNA binding proteins DiGeorge syndrome critical region gene 8 (DGCR8), Tar RNA binding protein 2 (TRBP2), and protein kinase R activating protein (PACT). Processing of cytoplasmic restricted primary-miRNA transcripts (c-pri-miRNAs) corresponds with virus-induced redistribution of Drosha, implicating the formation of a noncanonical microprocessor. This review will discuss c-pri-miRNA processing, the mechanism of miRNA production, and the implications of a virus-induced cytoplasmic microprocessor.

Degradation of host microRNAs by poxvirus poly(A) polymerase reveals terminal RNA methylation as a protective antiviral mechanism.

The life cycle of several viruses involves host or virally encoded small noncoding RNAs, which play important roles in posttranscriptional regulation. Small noncoding RNAs include microRNAs (miRNAs), which modulate the transcriptome, and small interfering RNAs (siRNAs), which are involved in pathogen defense in plants, worms, and insects. We show that insect and mammalian poxviruses induce the degradation of host miRNAs. The virally encoded poly(A) polymerase, which polyadenylates viral transcripts, also mediates 3' polyadenylation of host miRNAs, resulting in their degradation by the host machinery. In contrast, siRNAs, which are protected by 2'O-methylation (2'OMe), were not targeted by poxviruses. These findings suggest that poxviruses may degrade host miRNAs to promote replication and that virus-mediated small RNA degradation likely contributed to 2'OMe evolution.

Evidence for a cytoplasmic microprocessor of pri-miRNAs.

microRNAs (miRNAs) represent a class of noncoding RNAs that fine-tune gene expression through post-transcriptional silencing. While miRNA biogenesis occurs in a stepwise fashion, initiated by the nuclear microprocessor, rare noncanonical miRNAs have also been identified. Here we characterize the molecular components and unique attributes associated with the processing of virus-derived cytoplasmic primary miRNAs (c-pri-miRNAs). RNA in situ hybridization and inhibition of cellular division demonstrated a complete lack of nuclear involvement in c-pri-miRNA cleavage while genetic studies revealed that maturation still relied on the canonical nuclear RNase III enzyme, Drosha. The involvement of Drosha was mediated by a dramatic relocalization to the cytoplasm following virus infection. Deep sequencing analyses revealed that the cytoplasmic localization of Drosha does not impact the endogenous miRNA landscape during infection, despite allowing for robust synthesis of virus-derived miRNAs in the cytoplasm. Taken together, this research describes a unique function for Drosha in the processing of highly structured cytoplasmic RNAs in the context of virus infection.

In vivo delivery of cytoplasmic RNA virus-derived miRNAs.

The discovery of microRNAs (miRNAs) revealed an unappreciated level of post-transcriptional control used by the cell to maintain optimal protein levels. This process has represented an attractive strategy for therapeutics that is currently limited by in vivo delivery constraints. Here, we describe the generation of a single-stranded, cytoplasmic virus of negative polarity capable of producing functional miRNAs. Cytoplasmic RNA virus-derived miRNAs accumulated to high levels in vitro, generated significant amounts of miRNA star strand, associated with the RNA-induced silencing complex (RISC), and conferred post transcriptional gene silencing in a sequence-specific manner. Furthermore, we demonstrate that these vectors could deliver miRNAs to a wide range of tissues, and sustain prolonged expression capable of achieving measurable knockdown of physiological targets in vivo. Taken together, these results validate noncanonical processing of cytoplasmic-derived miRNAs and provide a novel platform for small RNA delivery.

Noncanonical cytoplasmic processing of viral microRNAs.

Cellular utilization of RNA interference (RNAi) as a mechanism to combat virus infection is thought to be restricted to plants and invertebrates. In vertebrates, antiviral defenses are largely dependent on interferons (IFNs), with the use of small RNAs restricted to microRNA (miRNA)-mediated targeting of host transcripts. Here we demonstrate that incorporation of a primary miRNA into a cytoplasmic virus results in the formation of a Dicer-dependent, DGCR8-independent, mature miRNA capable of conferring RNAi-like activity. Processing of the viral mirtron-like product (virtron) is indistinguishable from endogenous miRNA maturation and elicits post-transcriptional gene silencing, albeit at a reduced level. Furthermore, virtrons impose Dicer-dependent, microprocessor-independent, and IFN-independent interference on virus replication in a sequence-specific manner. Taken together, these results suggest the existence of a noncanonical, small-RNA-based activity capable of processing cytoplasmic hairpins and perhaps contributing to the cell's antiviral arsenal.