The silencing of transgene expression at the level of transcription in the soma of Caenorhabditis elegans through an RNAi-dependent pathway has not been previously characterized. Most gene silencing due to RNAi in C. elegans occurs at the post-transcriptional level. We observed transcriptional silencing when worms containing the elt-2ϻgfp/LacZ transgene were fed RNA produced from the commonly used L4440 vector. The transgene and the vector share plasmid backbone sequences. This transgene silencing depends on multiple RNAi pathway genes, including dcr-1, rde-1, rde-4, and rrf-1. Unlike post-transcriptional gene silencing in worms, elt-2ϻgfp/LacZ silencing is dependent on the PAZ-PIWI protein Alg-1 and on the HP1 homolog Hpl-2. The latter is a chromatin silencing factor, and expression of the transgene is inhibited at the level of intron-containing precursor mRNA. This inhibition is accompanied by a decrease in the acetylation of histones associated with the transgene. This transcriptional silencing in the soma can be distinguished from transgene silencing in the germline by its inability to be transmitted across generations and its dependence on the rde-1 gene. We therefore define this type of silencing as RNAi-induced Transcriptional Gene Silencing (RNAi-TGS). Additional chromatin-modifying components affecting RNAi-TGS were identified in a candidate RNAi screen.[Keywords: RNAi; RNAi-TGS; RNAi-PTGS; dsRNA; siRNA; L4440] Supplemental material is available at http://www.genesdev.org.

BACKGROUND: Perioperative pediatric anxiety is common and can have a negative psychological impact on children undergoing surgery and anesthesia. Studies have shown an incidence of anxiety at induction of up to 50%. Audiovisual distraction, including virtual reality (VR), is a noninvasive, nonpharmacological modality that may reduce perioperative anxiety. The goal of this study was to determine whether immersive audiovisual distraction with a VR headset during induction of general anesthesia (GA) in pediatric patients reduced preoperative anxiety. METHODS: In this randomized-controlled, parallel-group study, 71 children 5–12 years of age scheduled for elective surgery with GA were randomly allocated to a VR group or a non-VR (No VR) control group. VR group patients underwent audiovisual distraction with a VR headset during induction in the operating room, whereas the control group received no audiovisual distraction. The primary outcome was the Modified Yale Preoperative Anxiety Scale (mYPAS), which was measured at 3 time points to assess patient anxiety: in the preoperative holding area before randomization, on entering the operating room, and during induction of GA. The primary outcome was analyzed using univariate analysis and a linear mixed-effects model. Secondary outcomes included postinduction parental anxiety measured by the State-Trait Anxiety Inventory, pediatric induction compliance, and parental satisfaction. RESULTS: Average patient age was 8.0 ± 2.3 years (mean ± standard deviation [SD]), and 51.4% of patients were female. Baseline variables were not substantially different between the VR group (33 patients) and the No VR group (37 patients). No patients received preoperative anxiolytic medication. Baseline mYPAS scores were not different between the groups, with scores of 28.3 (23.3–28.3) (median [interquartile range {IQR}]) in both. The change in mYPAS scores from baseline to time of induction was significantly lower in the VR group versus control group (0.0 [0.0–5.0] vs 13.3 [5.0–26.7]; P < .0001). In the mixed-effects model, the VR group had an estimated 6.0-point lower mYPAS score (95% confidence interval [CI], 0.7–11.3; P = .03) at room entry than the No VR group, and 14.5-point lower score (95% CI, 9.3–19.8; P < .0001) at induction versus control. Randomization to VR did not alter parental anxiety (0 [−2 to 2]), pediatric induction compliance (0 [0–0]), or parental satisfaction (−3 [−8 to 2]) (difference in medians [95% CI]). CONCLUSIONS: This study demonstrates a reduction in pediatric preoperative anxiety with the use of VR. Preoperative VR may be an effective noninvasive modality for anxiolysis during induction of anesthesia in children.

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