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Site-directed RNA base editing enables the transient and dosable change of genetic information and represents a recent strategy to manipulate cellular processes, paving ways to novel therapeutic modalities. While tools to introduce adenosine-to-inosine changes have been explored quite intensively, the engineering of precise and programmable tools for cytidine-to-uridine editing is somewhat lacking behind. Here we demonstrate that the cytidine deaminase domain evolved from the ADAR2 adenosine deaminase, taken from the RESCUE-S tool, provides very efficient and highly programmable editing when changing the RNA targeting mechanism from Cas13-based to SNAP-tag-based. Optimization of the guide RNA chemistry further allowed to dramatically improve editing yields in the difficult-to-edit 5'-CCN sequence context thus improving the substrate scope of the tool. Regarding editing efficiency, SNAP-CDAR-S outcompeted the RESCUE-S tool clearly on all tested targets, and was highly superior in perturbing the β-catenin pathway. NGS analysis showed similar, moderate global off-target A-to-I and C-to-U editing for both tools., (© The Author(s) 2023. Published by Oxford University Press on behalf of Nucleic Acids Research.)

The SNAP-ADAR tool enables precise and efficient A-to-I RNA editing in a guideRNA-dependent manner by applying the self-labeling SNAP-tag enzyme to generate RNA-guided editases in cell culture. Here, we extend this platform by combining the SNAP-tagged tool with further effectors steered by the orthogonal HALO-tag. Due to their small size (ca. 2 kb), both effectors are readily integrated into one genomic locus. We demonstrate selective and concurrent recruitment of ADAR1 and ADAR2 deaminase activity for optimal editing with extended substrate scope and moderate global off-target effects. Furthermore, we combine the recruitment of ADAR1 and APOBEC1 deaminase activity to achieve selective and concurrent A-to-I and C-to-U RNA base editing of endogenous transcripts inside living cells, again with moderate global off-target effects. The platform should be readily transferable to further epitranscriptomic writers and erasers to manipulate epitranscriptomic marks in a programmable way with high molecular precision., (© The Author(s) 2021. Published by Oxford University Press on behalf of Nucleic Acids Research.)

Background: Human chorionic gonadotropin (hCG) assays are used to detect pregnancy, and urine point-of-care tests are frequently used to triage patients. Under certain conditions, urine tests can fail to detect pregnancy, which can have serious consequences for patient management., Objectives: To understand the prevalence of different factors contributing to false-negative urinary hCG testing results at our institution., Methods: Clinical data for patients with negative urine hCG results and subsequent positive or equivocal serum hCG results within a 1-year period were reviewed., Results: Out of 9447 negative urine hCG results, 11 potential missed diagnoses were identified, with early gestational age as the most common factor, followed by β-core hook effects., Conclusions: Although false-negative urine hCG test results are rare, understanding the commonly encountered reasons for inaccurate testing results can help clinical centers develop strategies to minimize risk for patients., (© American Society for Clinical Pathology 2019. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)