Ribosomal quality control factors inhibit repeat-associated non-AUG translation from GC-rich repeats.

A GGGGCC (G4C2) hexanucleotide repeat expansion in C9ORF72 causes amyotrophic lateral sclerosis and frontotemporal dementia (C9ALS/FTD), while a CGG trinucleotide repeat expansion in FMR1 leads to the neurodegenerative disorder Fragile X-associated tremor/ataxia syndrome (FXTAS). These GC-rich repeats form RNA secondary structures that support repeat-associated non-AUG (RAN) translation of toxic proteins that contribute to disease pathogenesis. Here we assessed whether these same repeats might trigger stalling and interfere with translational elongation. We find that depletion of ribosome-associated quality control (RQC) factors NEMF, LTN1 and ANKZF1 markedly boost RAN translation product accumulation from both G4C2 and CGG repeats while overexpression of these factors reduces RAN production in both reporter assays and C9ALS/FTD patient iPSC-derived neurons. We also detected partially made products from both G4C2 and CGG repeats whose abundance increased with RQC factor depletion. Repeat RNA sequence, rather than amino acid content, is central to the impact of RQC factor depletion on RAN translation-suggesting a role for RNA secondary structure in these processes. Together, these findings suggest that ribosomal stalling and RQC pathway activation during RAN translation inhibits the generation of toxic RAN products. We propose augmenting RQC activity as a therapeutic strategy in GC-rich repeat expansion disorders.

Constructing an Individualized Middle Cerebral Artery Model Using 3D Printing and Hydrogel for Bypass Training.

The importance and complexity of cerebral bypass surgery (CBS) highlight the necessity for intense and dedicated training. Several available training models are yet to satisfy this need. In this technical note, we share the steps to construct a digital imaging and communications in medicine (DICOM)-based middle cerebral artery (MCA) model that is anatomically accurate, resembles handling properties of living tissue, and enables trainers to observe the cerebrovascular anatomy, improve and maintain microsurgical dexterity, and train in the essential steps of CBS. The internal and external molds were created from the geometry of DICOM-based MCA using Fusion 360 software (Autodesk, San Rafael, USA). They were then three-dimension (3D) printed using a polylactic acid filament. The 15% w/v solution of polyvinyl alcohol (PVA) was prepared and injected between the molds. Using five freeze-thaw cycles the solution was converted to tissue-mimicking cryo-gel. The model was then placed in a chloroform bath until the internal mold dissolved. To evaluate the accuracy of the MCA model, selected characteristics were measured and compared with the MCA mesh. The DICOM-based MCA model was produced using 3D printing that was available in the lab and the overall cost was less than $5 per model. The external mold required six and a half hours to be 3D printed, while the internal mold only required 23 minutes. Overall, the time required to 3D print the DICOM-based MCA model was just short of seven hours. The greatest statistically significant difference between the virtual MCA model and the DICOM-based MCA model was found in the length of the pre-bifurcation part of the M1 segment and the total length of the superior bifurcation trunk of M1 and superior branch of M2. The smallest statistically significant difference was found at the diameter of the inferior post-bifurcation trunk of the M1 segment and the diameter at the origin of the artery. This technical report aims to show the construction of a CBS training system involving the DICOM-based MCA model that demonstrates the shape of the vascular tree, resembles the handling/suturing properties of living tissue, and helps set up a homemade training station. We believe that our DICOM-based MCA model can serve as a valuable resource for CBS training throughout the world due to its cost-effectiveness and straightforward construction steps. Moreover, once the DICOM-based MCA model is used with our training station, it may offer an option for trainers to gain and maintain CBS skills despite limitations on time, cost, and space. This work was presented in February 2019 at the American Association of Neurological Surgeons/Congress of Neurological Surgeons (AANS/CNS) Cerebrovascular Section Annual Meeting held in Honolulu, Hawaii.

Using Immersive Technologies to Develop Medical Education Materials.

Principles of modern surgical education for clerkship and residency were established by the novel approaches of Sir William Osler, MD, Flexner report, and Halsted's principles. The evaluation of surgical education has continued to benefit from the wisdom of the past by harnessing technologies. Rapidly changing and improving the nature of the surgery fostered that evaluation and enforced the institutions to find new solutions for surgical education. In the present descriptive technical report, our aim was threefold: (1) to share acquired educational materials based on immersive technologies involving 3D-printing, Augmented Reality (AR), and 360-degree video recording to improve ongoing pediatric surgery student training at our faculty, (2) to describe workflow underlying the construction of the materials, and (3) to provide approaches that may help other students and lecturers to develop their educational materials. The educational materials, including 3D-printed models, AR hybrid student book, a hydrogel-based simulation model of the kidney, and Mirror World Simulation, were constructed. The authors, who are medical students, led the construction of the educational materials, so the educational materials were shaped by a collaboration between students and pediatric surgeons. The materials constructed enabled the students to practice surgical procedures and experience different surgical environments. We believe these educational materials can serve as a valuable resource for training in many medical specialties in the future. This work was presented at the American College of Surgeons (ACS) Quality and Safety Conference Virtual, August 21-24, 2020.

Replicating Skull Base Anatomy With 3D Technologies: A Comparative Study Using 3D-scanned and 3D-printed Models of the Temporal Bone.

HYPOTHESIS: 3D technologies, including structured light scanning (SLS), microcomputed tomography (micro-CT), and 3D printing, are valuable tools for reconstructing temporal bone (TB) models with high anatomical fidelity and cost-efficiency. BACKGROUND: Operations involving TB require intimate knowledge of neuroanatomical structures-a demand that is currently met through dissection of limited cadaveric resources. We aimed to document the volumetric reconstruction of TB models using 3D technologies and quantitatively assess their anatomical fidelity. METHODS: In the primary analysis, 14 anatomical characteristics of right-side TB from 10 dry skulls were measured. Each skull was 3D-scanned using SLS to generate virtual models, which were measured using mesh processing software. Metrics were analyzed using mean absolute differences and one-sample t tests with Bonferroni correction. In the secondary analysis, an individualized right-side TB specimen (TBi) was 3D-scanned using SLS and micro-CT, and 3D-printed on a stereolithography printer. Measurements of each virtual and 3D-printed model were compared to measurements of TBi. RESULTS: Significant differences between the physical skulls and virtual models were observed for 11 of 14 parameters (p < 0.0036), with the greatest mean difference in the length of petrous ridge (2.85 mm) and smallest difference in the diameter of stylomastoid foramen (0.67 mm). In the secondary analysis, greater mean differences were observed between TBi and virtual models than between TBi and 3D-printed models. CONCLUSION: For the first time, our study provides quantitative measurements of TB anatomy to demonstrate that 3D technologies can facilitate individualized and highly accurate reconstructions of TB, which may benefit anatomy education, clinical training, and preoperative planning.