Spatiotemporal Live-Cell Analysis of Photoreceptor Outer Segment Membrane Ingestion by the Retinal Pigment Epithelium Reveals Actin-Regulated Scission.

The photoreceptor outer segment (OS) is the phototransductive organelle in the vertebrate retina. OS tips are regularly ingested and degraded by the adjacent retinal pigment epithelium (RPE), offsetting the addition of new disk membrane at the base of the OS. This catabolic role of the RPE is essential for photoreceptor health, with defects in ingestion or degradation underlying different forms of retinal degeneration and blindness. Although proteins required for OS tip ingestion have been identified, spatiotemporal analysis of the ingestion process in live RPE cells is lacking; hence, the literature reflects no common understanding of the cellular mechanisms that affect ingestion. We imaged live RPE cells from mice (both sexes) to elucidate the ingestion events in real time. Our imaging revealed roles for f-actin dynamics and specific dynamic localizations of two BAR (Bin-Amphiphysin-Rvs) proteins, FBP17 and AMPH1-BAR, in shaping the RPE apical membrane as it surrounds the OS tip. Completion of ingestion was observed to occur by scission of the OS tip from the remainder of the OS, with a transient concentration of f-actin forming around the site of imminent scission. Actin dynamics were also required for regulating the size of the ingested OS tip, and the time course of the overall ingestion process. The size of the ingested tip is consistent with the term "phagocytosis." However, phagocytosis usually refers to engulfment of an entire particle or cell, whereas our observations of OS tip scission indicate a process that is more specifically described as "trogocytosis," in which one cell "nibbles" another cell.SIGNIFICANCE STATEMENT The ingestion of the photoreceptor outer segment (OS) tips by the retinal pigment epithelium (RPE) is a dynamic cellular process that has fascinated scientists for 60 years. Yet its molecular mechanisms had not been addressed in living cells. We developed a live-cell imaging approach to investigate OS tip ingestion, and focused on the dynamic participation of actin filaments and membrane-shaping BAR proteins. We observed scission of OS tips for the first time, and were able to monitor local changes in protein concentration preceding, during, and following scission. Our approach revealed that actin filaments were concentrated at the site of OS scission and were required for regulating the size of the ingested OS tip and the time course of the ingestion process.

Association of Neighborhood Opportunity With Severity of Retinoblastoma at Presentation.

PURPOSE: To examine the relationship between the Child Opportunity Index (COI) and severity of retinoblastoma at presentation. DESIGN: Cross-sectional study. METHODS: Children (age <18 years) treated for retinoblastoma at a tertiary care center between January 2000 and May 2023 were included. Residential census tract was used to determine the overall and domain-specific COI score for each child. Collected variables included age, sex, race/ethnicity, insurance type, and the International Classification of Retinoblastoma (ICRB) Group at initial examination. The primary outcome was Group D or E retinoblastoma at presentation. Mixed effects regression models were used to estimate the association of COI scores with disease severity at presentation. RESULTS: This study included 125 children (51.2% male). Median age at diagnosis was 13 months (IQR, 5-24 months). One hundred nine (87.2%) children presented with Group D or E retinoblastoma and 33 (26.4%) resided in low or very low opportunity neighborhoods. Children residing in neighborhoods with low overall COI scores (OR, 1.62; 95% CI, 1.01-2.58; P = .044) and low education COI scores (OR, 1.77; 95% CI, 1.13-2.79; P = .013) were at increased odds of presenting with ICRB Group D or E retinoblastoma after adjusting for individual-level socioeconomic factors. CONCLUSION: Children residing in low opportunity neighborhoods-particularly low education opportunity-more often presented with advanced stage retinoblastoma than children residing in neighborhoods with higher opportunity scores. Efforts to improve preventative vision care and access to eye specialty care for children residing in low-resource areas are needed to reduce existing disparities in retinoblastoma.

Perceptions and acceptance of COVID-19 vaccine among pregnant and lactating women in Singapore: A pre-vaccine rollout cross-sectional study.

Introduction: Vaccination is critical in controlling the coronavirus disease 2019 (COVID-19) pandemic. However, vaccine perception and acceptance among pregnant and lactating women is unknown in Singapore. We aimed to determine the acceptance of COVID-19 vaccination among these two groups of women in Singapore and the factors associated with vaccine acceptance. Methods: We conducted an anonymous, online survey on the perceptions of the COVID-19 vaccine and its acceptance by pregnant and lactating women at a tertiary maternal and child hospital in Singapore from 1 March to 31 May 2021. Information on their demographics and knowledge was collected. These factors were assessed for their relationship with vaccine acceptance. Results: A total of 201 pregnant and 207 lactating women participated. Vaccine acceptance rates in pregnant and lactating women were 30.3% and 16.9%, respectively. Pregnant women who were unsure or unwilling to take the vaccine cited concerns about safety of the vaccine during pregnancy (92.9%), while lactating women were concerned about its potential long-term negative effects on the breastfeeding child (75.6%). Factors that were positively associated with vaccine acceptance included a lower monthly household income or education level, appropriate knowledge regarding vaccine mechanism and higher perceived maternal risk of COVID-19. Most pregnant (70.0%) and lactating women (83.7%) were willing to take the vaccine only when more safety data during pregnancy and breastfeeding were available. Conclusion: COVID-19 vaccine acceptance was low among pregnant and lactating women in Singapore. Addressing the safety concerns when more data are available and education on the mechanism of vaccine action will likely improve acceptance among these women.

Knowledge and Expectations of Perinatal Care Among Pregnant Women During the COVID-19 Pandemic.

Introduction: This study aimed to investigate the knowledge and expectations of pregnant women on perinatal care during the coronavirus disease 2019 (COVID-19) pandemic. Methods: A cross-sectional survey was conducted among pregnant women ≥21 years, without a history of confirmed COVID-19, attending antenatal clinics between August and September 2020 via a secure online platform. The survey consisted of 10 questions which evaluated the knowledge and expectations on perinatal and neonatal care during the current pandemic. Results: A total of 313 pregnant women completed the survey. The mean age of the participants was 30 years (SD 4; range 22-43 years). The median gestational age was 25 weeks (range 4-40 weeks). The participants were predominantly multiparous (54%) and almost all (98%) had completed secondary level education. Majority of participants were aware of the spread of COVID-19 by respiratory secretions and contact (90%), and the importance of prevention strategies (94%). Up to 72% agreed or strongly agreed that in-utero transmission of SARS-CoV-2 was possible. Most were unsure of the optimal mode of delivery (77%) and only 22% believed that breastfeeding was safe in a pregnant woman with active COVID-19. Although 46% were concerned about increased transmission risk with antenatal clinic visits, only 37% were agreeable to teleconferencing of clinic appointments. Maternal age >35 years was significantly associated with agreement with separation of mother-infant after birth [AOR 1.89 (95% CI 1.05, 3.39)], restrictions of visitors during the postnatal period [1.92 (1.05, 3.49)] and having their confinement practices were affected [2.3 (1.26, 4.17)]. Pregnant women who were multiparous disagreed that breastfeeding was safe in women with active COVID-19 [0.42 (0.23, 0.75)]. Conclusions: There was significant uncertainty about the optimal delivery method and safety of breastfeeding with COVID-19 among expectant mothers, along with variable agreement with alterations to routine perinatal care.