Massively parallel base editing to map variant effects in human hematopoiesis.

Systematic evaluation of the impact of genetic variants is critical for the study and treatment of human physiology and disease. While specific mutations can be introduced by genome engineering, we still lack scalable approaches that are applicable to the important setting of primary cells, such as blood and immune cells. Here, we describe the development of massively parallel base-editing screens in human hematopoietic stem and progenitor cells. Such approaches enable functional screens for variant effects across any hematopoietic differentiation state. Moreover, they allow for rich phenotyping through single-cell RNA sequencing readouts and separately for characterization of editing outcomes through pooled single-cell genotyping. We efficiently design improved leukemia immunotherapy approaches, comprehensively identify non-coding variants modulating fetal hemoglobin expression, define mechanisms regulating hematopoietic differentiation, and probe the pathogenicity of uncharacterized disease-associated variants. These strategies will advance effective and high-throughput variant-to-function mapping in human hematopoiesis to identify the causes of diverse diseases.

Time to Antibiotic for Pediatric Oncology Patients With Febrile Neutropenia at Regional Emergency Departments.

OBJECTIVES: We compared the time to antibiotic (TTA) for pediatric oncology patients with febrile neutropenia (FN) presenting at regional emergency departments (EDs) with those presenting at a pediatric referral ED, and examined its association with need for aggressive medical care. METHODS: We abstracted data for pediatric oncology patients (age, <21 years) admitted for FN between August 2012 and August 2017 at a single children's hospital and compared the TTA between those referred from a regional ED across the state and those admitted via the referral ED at the children's hospital. Factors associated with delay in antibiotic administration (TTA, >60 minutes) were estimated using generalized linear modeling with generalized estimating equations (GEEs). Delay in antibiotic administration was examined for its association with the need for aggressive medical care (>1 fluid bolus, intensive care unit admission, inotropic or invasive ventilator support) within 24 hours of admission as an exploratory aim. RESULTS: Three-hundred eighty-nine FN admissions (regional ED, 26.7%; referral ED, 73.3%) occurred in 205 eligible patients. Median TTA was significantly (P < 0.0001) greater among patients presenting at a regional ED (117.5 minutes [range, 9-722 minutes]) vs referral ED (46 minutes [range, 6-378 minutes]). Presentation at regional ED was the only factor associated with delay in antibiotic administration (odds ratio, 9.73; 95% confidence interval, 5.37-17.63; P < 0.0001). Delay in antibiotic administration was not associated with greater need for aggressive medical care (odds ratio, 1.34; 95% confidence interval, 0.55-3.29; P = 0.5). CONCLUSIONS: Pediatric oncology patients with FN presenting to regional EDs have longer TTA as compared with those presenting to a referral ED at a children's hospital.