RIP-Seq analysis of non-PPR chloroplast editing factors reveals broad RNA interactions and enrichment of less efficiently translated RNAs by OZ1 and ORRM1 complexes.

C-to-U RNA editing in angiosperm chloroplasts requires a large suite of proteins bound together in the editosome. The editosome is comprised of PPR proteins, RIP/MORFs, OZ proteins, and ORRM proteins that physically interact in high molecular weight complexes. The specific functions of non-PPR editing factors in the editosome are unclear, however, specific subsets of editing sites are affected by absence of non-PPR editing factors. Unlike the PPR components of editosomes that have predictable nucleotide specificities, domains present in non-PPR editing factors make RNA associations difficult to predict. In this study, chloroplast extracts were isolated from juvenile maize seedlings. RNAs were immunoprecipitated using polyclonal antibodies targeting non-PPR editing factors RIP9, OZ1, and ORRM1. RNA libraries from duplicate experiments were compared. RIP9 was associated with most of the non-ribosomal RNA content of chloroplasts, consistent with a general binding function to PPR L-motifs and tethering of large ribonucleoprotein complexes. The breadth of RNA associations was greater than predicted and include mRNAs without predicted editing sites, tRNA sequences, and introns. OZ1 and ORRM1 were associated with a highly similar pool of RNAs that have a bias toward lower translational efficiency values in mature chloroplasts. Lower translational efficiency was also associated with the pool of edited RNAs compared to RNAs without editing sites. The unexpected breadth of interactions by non-PPR editing factors suggests the editosome is large, diverse, and associated with RNAs with lower relative translational efficiency in mature chloroplasts.

Emergency Medicine Physician Attitudes toward Anticoagulant Initiation for Patients with Atrial Fibrillation.

BACKGROUND AND AIM: Guidelines for the primary prevention of stroke recognize the emergency department as a location for physicians to identify atrial fibrillation and to initiate oral anticoagulants. Numerous studies have shown low anticoagulant prescription rates-approximately 18%-in OAC-naïve patients with atrial fibrillation discharged from the emergency department. We sought to obtain the opinions of Emergency Medicine physicians regarding anticoagulant decision-making for patients with atrial fibrillation seen in the emergency department. METHODS: 14-item paper surveys were distributed to emergency department physicians within a single hospital system. The survey consisted of single-, multi- answer and open-ended questions regarding knowledge and usage frequency of the CHA2DS2-VASc score, knowledge of anticoagulant options and reasons for why an anticoagulant was not initiated. RESULTS: 55 emergency department physicians completed the survey (overall response rate 59%). 89% (49/55) agreed the emergency department is an important location to initiate anticoagulation depending on comorbidities. A lower proportion reported ever starting a patient in the emergency department on a new anticoagulant prescription upon discharge (55% (30/55) p <.0001). The belief that a new anticoagulant prescription is the responsibility of the PCP/ Cardiologist/ Neurologist (52%; 15/29), not wanting to be held responsible in the event of a life-threatening bleeding event (41%; 12/29), and concerns about inadequate follow-up and/or lack of insurance (24%; 7/29) were the most commonly cited reasons for not starting an appropriate patient with atrial fibrillation on an anticoagulant. CONCLUSION: Emergency Medicine physicians support initiating oral anticoagulants in the ED for patients with atrial fibrillation; however, discrepancies exist between their intentions and actual practice.

The Use of Oral Anticoagulants in Patients with Atrial Fibrillation in the Emergency Department.

BACKGROUND AND AIM: Atrial Fibrillation is the leading cause of embolic stroke, yet less than half of high-risk patients with atrial fibrillation are on adequate stroke prevention with oral anticoagulants. Guidelines for the primary prevention of stroke recognize the emergency department as a location for physicians to identify atrial fibrillation and initiate anticoagulants. We sought to compare anticoagulant prescription rates in patients with atrial fibrillation in various provider settings to identify opportunities for improvement in cardioembolic stroke prevention. METHODS: A retrospective cohort study of 436 patients with atrial fibrillation presenting to the emergency department from 2014 to 2018 was performed. Baseline characteristics, stroke risk, and rates of anticoagulant prescription were compared across 3 groups: (1) patients discharged from the emergency department, (2) patients admitted under observation status, and (3) patients admitted to inpatient hospital service. RESULTS: Among 436 patients (47% women, 51% Hispanic), we identified 105 in the emergency department cohort, 131 in the observation cohort and 200 in the inpatient cohort. The average CHA2DS2-VASc score was 2.5 in the emergency department cohort, 2.6 in the observation cohort and 3.3 in the inpatient cohort. Anticoagulants were prescribed for high-risk patients (CHA2DS2-VASc score ≥ 2) in 17.5% (7/40) of the emergency department cohort compared to 73% (38/52, P< .0001) of the observation cohort and 80% (82/103 P< .0001) of the inpatient cohort. CONCLUSION: Patients with atrial fibrillation are more likely to be prescribed anticoagulants if admitted to inpatient or under observation status compared to the emergency department.

Regulation of dendrite growth and maintenance by exocytosis.

Dendrites lengthen by several orders of magnitude during neuronal development, but how membrane is allocated in dendrites to facilitate this growth remains unclear. Here, we report that Ras opposite (Rop), the Drosophila ortholog of the key exocytosis regulator Munc18-1 (also known as STXBP1), is an essential factor mediating dendrite growth. Neurons with depleted Rop function exhibit reduced terminal dendrite outgrowth followed by primary dendrite degeneration, suggestive of differential requirements for exocytosis in the growth and maintenance of different dendritic compartments. Rop promotes dendrite growth together with the exocyst, an octameric protein complex involved in tethering vesicles to the plasma membrane, with Rop-exocyst complexes and exocytosis predominating in primary dendrites over terminal dendrites. By contrast, membrane-associated proteins readily diffuse from primary dendrites into terminals, but not in the reverse direction, suggesting that diffusion, rather than targeted exocytosis, supplies membranous material for terminal dendritic growth, revealing key differences in the distribution of materials to these expanding dendritic compartments.