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.

Safety and efficacy of voxelotor in pediatric patients with sickle cell disease aged 4 to 11 years.

BACKGROUND: Sickle cell disease (SCD) is a devastating, multisystemic disorder that affects millions of people worldwide. The earliest clinical manifestations of SCD can affect infants as young as 6 months of age, and pediatric patients are at risk for acute and life-threatening complications. Early intervention with treatments that target the underlying pathophysiological mechanism of SCD, sickle hemoglobin (HbS) polymerization, are expected to slow disease progression and circumvent disease-associated morbidity and mortality. PROCEDURE: The HOPE-KIDS 1 trial (NCT02850406) is an ongoing four-part, phase 2a, open-label, single- and multiple-dose study to evaluate the pharmacokinetics, efficacy, and safety of voxelotor-a first-in-class HbS polymerization inhibitor-in patients aged 6 months to 17 years with SCD. Initial findings from a cohort of 45 patients aged 4 to 11 years who received voxelotor treatment for up to 48 weeks are reported. RESULTS: Hemoglobin (Hb) response, defined as a >1.0 g/dl increase from baseline, was achieved at week 24 by 47% (n = 16/34) of patients with Hb measurements at baseline and week 24. At week 24, 35% (n = 12/34) and 21% (n = 7/34) of patients had a >1.5 g/dl increase and a >2.0 g/dl increase from baseline in Hb concentration, respectively. Concurrent improvements in hemolytic markers were observed. Voxelotor was well tolerated in this young cohort, with no newly emerging safety signals. CONCLUSIONS: Based on its mechanism as an HbS polymerization inhibitor, voxelotor improves Hb levels and markers of hemolysis and has the potential to mitigate SCD-related complications; these results support its use in patients aged ≥4 years.

Assessing child care providers' knowledge and attitudes regarding support of breastfeeding in a region with low breastfeeding prevalence.

BACKGROUND: Working mothers who place their infants into out-of-home child care face many challenges to sustaining breastfeeding. Child care providers, who are in frequent close contact with young families, may be potential resources for promoting breastfeeding. OBJECTIVES: This study focused on identifying child care providers' attitudes toward and knowledge about breastfeeding as well as providers' perceptions about strategies to increase breastfeeding rates among mothers of infants in child care centers. METHODS: Seventy-five providers from 11 child care centers in the Baton Rouge, Louisiana, area were surveyed using paper and pencil questionnaires. Self-reported demographics, attitudes, knowledge, and perceptions about breastfeeding were collected. RESULTS: Responses demonstrated a generally positive attitude toward breastfeeding among child care providers but a knowledge deficit in terms of the health impacts and proper handling of breast milk. A minority of providers reported that their center's staff currently receives breastfeeding education, but most providers believed that measures to promote the use of breast milk in their center should target parents rather than the center staff. CONCLUSION: Child care providers need resources about the benefits of human milk, proper handling of expressed milk, and ways to make centers more breastfeeding friendly. Many providers feel ineffective in supporting breastfeeding and are unaware of the role they may play in mothers' infant feeding decisions. Though child care providers do not appear to believe they can influence parents' decisions about breastfeeding, educating and empowering them could play an important role in increasing breastfeeding rates.