Angela Chen

Astrocytes play important roles in neurological disorders such as stroke, injury, and neurodegeneration. Most knowledge on astrocyte biology is based on studies of mouse models and the similarities and differences between human and mouse astrocytes are insufficiently characterized, presenting a barrier in translational research. Based on analyses of acutely purified astrocytes, serum-free cultures of primary astrocytes, and xenografted chimeric mice, we find extensive conservation in astrocytic gene expression between human and mouse samples. However, the genes involved in defense response and metabolism show species-specific differences. Human astrocytes exhibit greater susceptibility to oxidative stress than mouse astrocytes, due to differences in mitochondrial physiology and detoxification pathways. In addition, we find that mouse but not human astrocytes activate a molecular program for neural repair under hypoxia, whereas human but not mouse astrocytes activate the antigen presentation pathway under inflammatory conditions. Here, we show species-dependent properties of astrocytes, which can be informative for improving translation from mouse models to humans.

Generating primordial germ cells (PGCs) from human pluripotent stem cells (hPSCs) advances studies of human reproduction and development of infertility treatments, but currently entails complex 3D aggregates. Here we develop a simplified, monolayer method to differentiate hPSCs into PGCs within 3.5 days. We used our simplified differentiation platform and single-cell RNA-sequencing to uncover new insights into PGC specification. Transient WNT activation for 12 hours followed by WNT inhibition specified PGCs; by contrast, sustained WNT instead induced primitive streak. Thus, somatic (primitive streak) and PGCs are related—yet distinct—lineages segregated by temporally-dynamic signaling. Pluripotency factors including NANOG are continuously expressed during the transition from pluripotency to posterior epiblast to PGCs, thus bridging pluripotent and germline states. Finally, hPSC-derived PGCs can be easily purified by virtue of their CXCR4⁺PDGFRA⁻GARP⁻ surface-marker profile and single-cell RNA-sequencing reveals that they harbor strong transcriptional similarities with fetal PGCs.

Enteric viruses, such as human norovirus (NoV) and hepatitis A virus (HAV), are the major causes of foodborne illnesses worldwide. These viruses have low infectious dose, and may remain infectious for weeks in the environment and food. Limited information is available regarding viral survival and transmission in low-moisture foods (LMF). LMFs are generally considered as ready-to-eat products, which undergo no or minimal pathogen reduction steps. However, numerous foodborne viral outbreaks associated with LMFs have been reported in recent years. The objective of this study was to examine the survival of foodborne viruses in LMFs during 4-week storage at ambient temperature and to evaluate the efficacy of advanced oxidative process (AOP) treatment in the inactivation of these viruses. For this purpose, select LMFs such as pistachios, chocolate, and cereal were inoculated with HAV and the norovirus surrogates, murine norovirus (MNV) and feline calicivirus (FCV), then viral survival on these food matrices was measured over a four-week incubation at ambient temperature, by both plaque assay and droplet-digital RT-PCR (ddRT-PCR) using the modified ISO-15216 method as well as the magnetic bead assay for viral recovery. We observed an approximately 0.5 log reduction in viral genome copies, and 1 log reduction in viral infectivity for all three tested viruses following storage of select inoculated LMFs for 4 weeks. Therefore, the present study shows that the examined foodborne viruses can persist for a long time in LMFs. Next, we examined the inactivation efficacy of AOP treatment, which combines UV-C, ozone, and hydrogen peroxide vapor, and observed that while approximately 100% (4 log) inactivation can be achieved for FCV, and MNV in chocolate, the inactivation efficiency diminishes to approximately 90% (1 log) in pistachios and 70% (< 1 log) in cereal. AOP treatment could therefore be a good candidate for risk reduction of foodborne viruses from certain LMFs depending on the food matrix and surface of treatment.

Background: Prescription hormonal contraceptive methods are vital to prevention of unplanned pregnancies. New legislation among 23 states has expanded access to contraception. In California, a 2017 law requires pharmacists to dispense year-long supplies of contraception and insurance plans to cover it upon patients’ request. This study assesses pharmacist knowledge of this new law 6 months after enactment. Methods: From July to November 2017, a random selection of 600 community pharmacies were called requesting a pharmacist (n = 532, 88.7% response). Pharmacists were asked if they had heard of the new law, if they would dispense a year-long supply to cash-pay, privately or publicly insured patients, and what they perceived as obstacles to dispensing year-long supplies. Results: Awareness of this law was assessed through these surveys. Most pharmacists responded they would dispense year-long supplies to cash-pay patients, regardless of knowledge of the new law (81% of “knew”, 70% of “did not know”, p = 0.1046). The top two perceived obstacles were insurance reimbursement (55.8%) and store policy (13.4%). Conclusion: Despite a new law requiring insurance coverage of a year-long supply of prescription birth control, most pharmacists were unaware at six months after the policy went into effect. Of those who were aware, the majority did not clearly understand it. Compliance among insurance plans is unknown. There was no implementation plan or awareness campaign for the new law.

Association of chromatin with lamin proteins at the nuclear periphery has emerged as a potential mechanism to coordinate cell type-specific gene expression and maintain cellular identity via gene silencing. Unlike many histone modifications and chromatin-associated proteins, lamin-associated domains (LADs) have yet to be mapped genome-wide in a diverse panel of human cell types, which has limited our understanding of the role peripheral chromatin plays in development and disease. To address this gap, we mapped LAMIN B1 (LB1) across twelve human cell types encompassing pluripotent stem cells, intermediate progenitors, and differentiated cells from all three germ layers. Integrative analyses of this atlas of peripheral chromatin with publicly available genomic data, as well as gene expression and repressive histone maps generated for this study, revealed that in all twelve cellular contexts lamin-associated chromatin is organized into at least two subtypes defined by differences in LB1 occupancy, gene expression, chromatin accessibility, transposable elements, replication timing, and radial positioning. Most genes gain or lose LB1 occupancy consistent with their cell type along developmental trajectories; however, we also identified examples where the enhancer, but not the gene body and promoter, change LAD state. Imaging of fluorescently labeled DNA in single cells validated these transitions and showed intermediate radial positioning of LADs that are gene dense, relatively accessible, and dynamic across development. This atlas represents the largest resource to date for peripheral chromatin organization studies.

Summary: Human-mouse differences are a major barrier in translational research. Astrocytes play important roles in neurological disorders such as stroke, injury, and neurodegeneration. However, the similarities and differences between human and mouse astrocytes are largely unknown. Combining analyses of acutely purified astrocytes, experiments using serum-free cultures of primary astrocytes, and xenografted chimeric mice, we found extensive conservation in astrocytic gene expression between human and mouse. However, genes involved in defense response and metabolism showed species differences. Human astrocytes exhibited greater susceptibility to oxidative stress than mouse astrocytes, due to differences in mitochondria physiology and detoxification pathways. Mouse astrocytes, but not human astrocytes, activate a molecular program for neural repair under hypoxia. Human astrocytes, but not mouse astrocytes, activate the antigen presentation pathway under inflammatory conditions. These species-dependent properties of astrocytes may contribute to differences between mouse models and human neurological and psychiatric disorders.

Summary: Hematopoietic stem cell (HSC) transplantation can replace diseased blood systems with a healthy one, thereby treating or curing genetic blood and immune disorders including autoimmune diseases and immunodeficiencies. However, toxic chemotherapy or radiation is necessary to ablate an animal’s existing blood system prior to HSC transplantation, leading to significant morbidity. To accomplish safer blood-system replacement we developed a combination of six monoclonal antibodies to safely and specifically deplete the HSCs, T cells and NK cells of immune-competent mice. Remarkably, immunologically-foreign (allogeneic) HSCs mismatched at half or all the MHC genes could engraft these antibody-treated mice, generating donor blood systems that stably co-existed with host blood cells. These chimeric immune systems were immunologically tolerant to heart tissue from the HSC donor, providing a safe platform for HSC transplantation as a means to solid organ transplantation. The ability to transplant MHC -mismatched HSCs without chemotherapy or radiation has significant ramifications for regenerative medicine.

INTRODUCTION: Access to birth control is the cornerstone to preventing unplanned pregnancies. In California, women qualifying for state-funded reproductive insurance get yearlong supplies of contraception from participating dispensaries. A 2011 study found a 30% odds reduction in unplanned pregnancies when women received yearlong supplies of birth control as compared to one- or three-month supplies (Foster, 2011). Subsequently, in 2016, California Senate Bill-999 was passed, designating that women could receive yearlong supplies of birth control from pharmacists while requiring insurance companies to fund these prescriptions. Using secret shopper methods, we will conduct a cross-sectional survey of California pharmacies to inquire whether they are able to comply with SB-999. METHODS: 19,693 pharmacies met our inclusion criteria: commercial retail pharmacies in California. 13,660 were excluded for revoked/cancelled licenses or because they were affiliated with managed care or publicly funded networks. Based on our pilot study, for a power of 80%, 600 pharmacies were randomly selected from the remaining 6033. Using a secret shopper technique, these pharmacies are called and asked whether they can dispense yearlong supplies of prescription birth control to customers. RESULTS: We are currently collecting date. Based on preliminary review of 200 pharmacies called, with approximately 80% completed calls, 44% of pharmacists have not heard of SB-999. The top two obstacles to dispensing yearlong supplies of birth control quoted were insurance coverage (37%) and company policy (16%). CONCLUSION: Implementation of new laws take time and require institutional accountability. In revealing obstacles to accessing yearlong supplies of birth control, we aim to expedite implementation of SB-999.

Research has shown linkages between environmental exposures and population health metrics such as low birth weight and incidence of congenital anomalies. While the exact causal relationship between specific environmental teratogens and suspected corresponding congenital anomalies has largely not been established, spatial analysis of anomaly incidence can identify potential locations of increased risk. This study uses the Vital Statistics Birth Master File to map and analyze the rates of congenital anomalies of births from non-smoking mothers 15–35 years old within Los Angeles County. Hot spot analysis shows that the distribution of congenital anomalies is not randomly distributed throughout the county and identified the Antelope Valley and San Gabriel Foothills as two areas with elevated incidence rates. These results are not explained by potential confounders such as maternal age, race, smoking status, or socioeconomic status and seem to correlate well with the concentration of atmospheric ozone. This approach demonstrates the value of using spatial techniques to inform future research efforts and the need to establish and maintain a comprehensive reproductive health surveillance system.