Uncoupling of Genomic and Epigenetic Signals in the Maintenance and Inheritance of Heterochromatin Domains in Fission Yeast

Many essential aspects of genome function, including gene expression and chromosome segregation, are mediated throughout development and differentiation by changes in the chromatin state. Along with genomic signals encoded in the DNA, epigenetic processes regulate heritable gene expression patterns. Genomic signals such as enhancers, silencers, and repetitive DNA, while required for the establishment of alternative chromatin states, have an unclear role in epigenetic processes that underlie the persistence of chromatin states throughout development. Here, we demonstrate in fission yeast that the maintenance and inheritance of ectopic heterochromatin domains are independent of the genomic sequences necessary for their de novo establishment. We find that both structural heterochromatin and gene silencing can be stably maintained over an ∼10-kb domain for up to hundreds of cell divisions in the absence of genomic sequences required for heterochromatin establishment, demonstrating the long-term persistence and stability of this chromatin state. The de novo heterochromatin, despite the absence of nucleation sequences, is also stably inherited through meiosis. Together, these studies provide evidence for chromatin-dependent, epigenetic control of gene silencing that is heritable, stable, and self-sustaining, even in the absence of the originating genomic signals

speck, First Identified in Drosophila melanogaster in 1910, Is Encoded by the Arylalkalamine N-Acetyltransferase (AANAT1) Gene

The pigmentation mutation speck is a commonly used recombination marker characterized by a darkly pigmented region at the wing hinge. Identified in 1910 by Thomas Hunt Morgan, speck was characterized by Sturtevant as the most “workable” mutant in the rightmost region of the second chromosome and eventually localized to 2-107.0 and 60C1-2. Though the first speck mutation was isolated over 110 years ago, speck is still not associated with any gene. Here, as part of an undergraduate-led research effort, we show that speck is encoded by the Arylalkylamine N-acetyltransferase 1 (AANAT1) gene. Both alleles from the Morgan lab contain a retrotransposon in exon 1 of the RB transcript of the AANAT1 gene. We have also identified a new insertion allele and generated multiple deletion alleles in AANAT1 that all give a strong speck phenotype. In addition, expression of AANAT1 RNAi constructs either ubiquitously or in the dorsal portion of the developing wing generates a similar speck phenotype. We find that speck alleles have additional phenotypes, including ectopic pigmentation in the posterior pupal case, leg joints, cuticular sutures and overall body color. We propose that the acetylated dopamine generated by AANAT1 decreases the dopamine pool available for melanin production. When AANAT1 function is decreased, the excess dopamine enters the melanin pathway to generate the speck phenotype

Direct vs Video Laryngoscopy for Difficult Airway Patients in the Emergency Department: A National Emergency Airway Registry Study

Introduction: Previous studies suggest improved intubation success using video laryngoscopy (VL) vs direct laryngoscopy (DL), yet recent randomized trials have not shown clear benefit of one method over the other. These studies, however, have generally excluded difficult airways and rapid sequence intubation. In this study we looked to compare first-pass success (FPS) rates between VL and DL in adult emergency department (ED) patients with difficult airways.  Methods: We conducted a secondary analysis of prospectively collected observational data in the National Emergency Airway Registry (NEAR) (January 2016–December 2018). Variables included demographics, indications, methods, medications, devices, difficult airway characteristics, success, and adverse events. We included adult ED patients intubated with VL or DL who had difficult airways identified by gestalt or anatomic predictors. We stratified VL by hyperangulated (HAVL) vs standard geometry VL (SGVL). The primary outcome was FPS, and the secondary outcome was comparison of adverse event rates between groups. Data analyses included descriptive statistics with cluster-adjusted 95% confidence intervals (CI). Results: Of 18,123 total intubations, 12,853 had a predicted or identified anatomically difficult airway. The FPS for difficult airways was 89.1% (95% CI 85.9-92.3) with VL and 77.7% (95% CI 75.7-79.7) with DL (P <0.00001). The FPS rates were similar between VL subtypes for all difficult airway characteristics except airways with blood or vomit, where SGVL FPS (87.3%; 95% CI 85.8-88.8) was slightly better than HAVL FPS (82.4%; 95% CI, 80.3-84.4). Adverse event rates were similar except for esophageal intubations and vomiting, which were both less common in VL than DL. Esophageal intubations occurred in 0.4% (95% CI 0.1-0.7) of VL attempts and 1.5% (95% CI 1.1-1.9) of DL attempts. Vomiting occurred in 0.6% (95% CI 0.5-0.7) of VL attempts and 1.4% (95% CI 0.9-1.9) of DL attempts. Conclusion: Analysis of the NEAR database demonstrates higher first-pass success with VL compared to DL in patients with predicted or anatomically difficult airways, and reduced rate of esophageal intubations and vomiting