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A randomized clinical trial that began in 1984 was conducted to determine the efficacy of vitamin A and E supplementation to reduce the rate of disease progression in patients with retinitis pigmentosa (RP). Vitamin A was shown to provide benefit while vitamin E had an adverse effect. Although genetic testing was unavailable at that time, banked DNA samples now provide the opportunity to combine modern genetic classifications with this extensively phenotyped longitudinal cohort. We hypothesized that the beneficial effects of vitamin A would vary by genetic subtype, and that the electroretinogram (ERG) 30Hz cone flicker implicit time could serve as a biomarker to predict disease progression. Existing genetic solutions or usable DNA samples were available for 96% of subjects. The overall genetic solution rate was 587/765 (77%) of sequenced samples. Combining genetic solutions with ERG outcomes produced a coherent dataset describing the natural history of RP among patients with multiple genetic causes of disease. There were systematic differences in severity and progression seen among different genetic subtypes of RP, confirming and extending findings made for disease caused by mutations in the most common causative genes, includingUSH2A, RHO, RPGR, PRPF31, andEYS. Baseline 30Hz flicker implicit time was a strong predictor of progression rate. Analyses using additional data from the original trial in combination with using the implicit time as a predictive biomarker showed the deleterious effect of vitamin E on progression was still present, but surprisingly found that the effect of vitamin A progression in the cohort as a whole was not detectable. Adding additional subjects from later trials to increase power gave similar results. Subgroup analyses among the largest gene groups revealed a potential adverse effect of vitamin A supplementation in patients with disease due to mutations in theUSH2Agene and a trend toward benefit in patients with the p.Pro23His mutation in theRHOgene, based only on small groups. This study also demonstrated how genetic subtype and implicit time have significant predictive power for a patient’s rate of progression, which is useful prognostically. Validation of implicit time as a biomarker of disease progression, as demonstrated in this large cohort, may help with subject selection and endpoint selection in clinical trials for future experimental therapies. While vitamin E supplementation should still be avoided, these data do not support a generalized neuroprotective effect of vitamin A for all types of RP.

Machine learning (ML) models, and Long Short-Term Memory (LSTM) networks in particular, have demonstrated remarkable performance in streamflow prediction and are increasingly being used by the hydrological research community. However, most of these applications do not include uncertainty quantification (UQ). ML models are data driven and may suffer from large extrapolation errors when applied to changing climate/environmental conditions. UQ is required to ensure model trustworthiness, improve understanding of data limits and model deficiencies, and avoid overconfident predictions in extrapolation. Here, we propose a novel UQ method, called PI3NN, to quantify prediction uncertainty of ML models and integrate the method with LSTM networks for streamflow prediction. PI3NN calculates Prediction Intervals by training 3 Neural Networks and uses root-finding methods to determine the interval precisely. Additionally, PI3NN can identify out-of-distribution (OOD) data in a nonstationary condition to avoid overconfident prediction. We apply the proposed PI3NN-LSTM method in both the snow-dominant East River Watershed in the western US and the rain-driven Walker Branch Watershed in the southeastern US. Results indicate that for the prediction data (which have similar features as the training data), PI3NN precisely quantifies the prediction uncertainty with the desired confidence level; and for the OOD data where the LSTM network fails to make accurate predictions, PI3NN produces a reasonably large uncertainty bound indicating the untrustworthy result to avoid overconfidence. PI3NN is computationally efficient, reliable in training, and generalizable to various network structures and data with no distributional assumptions. It can be broadly applied in ML-based hydrological simulations for credible prediction.

Total mercury content (THg) in hair is an accepted biomarker for chronic dietary methylmercury (MeHg) exposure. In artisanal and small-scale gold mining (ASGM) communities, the validity of this biomarker is questioned because of the potential for contamination from inorganic mercury. As mining communities may have both inorganic and organic mercury exposures, the efficacy of the hair-THg biomarker needs to be evaluated, particularly as nations begin population exposure assessments under their commitments to the Minamata Convention. We sought to validate the efficacy of hair THg for public health monitoring of MeHg exposures for populations living in ASGM communities. We quantified both THg and MeHg contents in hair from a representative subset of participants (N = 287) in a large, population-level mercury exposure assessment in the ASGM region in Madre de Dios (MDD), Peru. We compared population MeHg-THg correlations and %MeHg values with demographic variables including community location, sex, occupation, and nativity. We observed that hair MeHg-THg correlations were high (r > 0.7) for all communities, regardless of location or nativity. Specifically, for individuals within ASGM communities, 81% (121 of 150 total) had hair THg predominantly in the form of MeHg (i.e., >66% of THg) and reflective of dietary exposure to mercury. Furthermore, for individuals with hair THg exceeding the U.S. EPA threshold (1.0 μg/g), 88 out of 106 (83%) had MeHg as the predominant form. As a result, had urine THg solely been used for mercury exposure monitoring, approximately 59% of the ASGM population would have been misclassified as having low mercury exposure. Our results support the use of hair THg for monitoring of MeHg exposure of populations in ASGM settings where alternative biomarkers of MeHg exposure are not feasible.

Reliable projections of wildfire and associated socioeconomic risks are crucial for the development of efficient and effective adaptation and mitigation strategies. The lack of or limited observational constraints for modeling outputs impairs the credibility of wildfire projections. Here, we present a machine learning framework to constrain the future fire carbon emissions simulated by 13 Earth system models from the Coupled Model Intercomparison Project phase 6 (CMIP6), using historical, observed joint states of fire-relevant variables. During the twenty-first century, the observation-constrained ensemble indicates a weaker increase in global fire carbon emissions but higher increase in global wildfire exposure in population, gross domestic production, and agricultural area, compared with the default ensemble. Such elevated socioeconomic risks are primarily caused by the compound regional enhancement of future wildfire activity and socioeconomic development in the western and central African countries, necessitating an emergent strategic preparedness to wildfires in these countries.

e19016 Background: The standard remission induction regimen for medically fit patients with AML consists of a backbone of cytarabine & an anthracycline (“7+3” therapy). However, the choice & dose of the anthracycline varies between institutions & practitioner preference, particularly in patients with favorable risk cytogenetics. Gemtuzumab ozogamicin (GO) may improve outcomes in this patient population but is associated with increased toxicities. Methods: We performed a retrospective analysis on medically fit patients ≥ 18 yo with favorable risk AML from 2015-2020 treated with 7+3 at the University of Virginia. Patients were stratified based on standard dose (45 or 60 mg/m2 daunorubicin) (SD) vs higher dose (90 mg/m2 daunorubicin or 12 mg/m2 idarubicin) (HD) of anthracycline vs the addition of GO. Measures included rates of remission, EFS, RFS, and OS as well as rates of treatment-related complications. Results: In total, 58 patients were identified, of which 33 received induction with SD, 19 received HD, & 6 received GO. The majority (75%) of patients were < 60 years old & 93% had de novo AML. The rates of complete remission in the SD, HD & GO groups were 90.9%, 89.5% & 100%, respectively (p = 0.57). EFS at 2-years was 43.9%, 36.7%, & 66.7%, respectively (p = 0.85). RFS at 2-years was 53.0%, 39.0%, & 100%, respectively (p = 0.18). OS at 2-years was similar between all groups (58.9%, 56.9%, & 66.7%, p = 0.92). The rate & duration of cytopenias after induction were similar among all groups (median duration 29 days), however cytopenias were more common in the GO group following consolidation. The rates of major bleeding, admission to the intensive care unit (ICU), and new onset cardiomyopathy (EF < 50%) were higher in the GO group (major bleeding: 0% in SD, 5.3% in HD, 33.3% in GO; ICU admission: 12.1% in SD, 21.1% in HD, 33.3% in GO; cardiomyopathy: 12.1% in SD, 26.3% in HD, 33.3% in GO). The rate of infection, liver dysfunction, & acute renal injury were similar among all groups. No patients developed veno-occlusive disease. Conclusions: Patients receiving GO had a trend toward improved EFS & RFS, however with a similar OS at the expense of higher rates of cytopenias, major bleeding, ICU admission, & cardiotoxicity. Patients receiving HD had a trend toward worse outcomes than those who received SD. A major limitation of our study is the small sample size & single institution experience, however multi-institutional analysis is ongoing for further investigation.[Table: see text]

e19015 Background: The prognosis of adult patients with acute lymphoblastic leukemia (ALL) has improved with the adoption of pediatric-inspired chemotherapy regimens. PEGylated asparaginase (PEG-Asp) is essential to these regimens. Although PEG-Asp is associated with an increased risk of coagulopathy, venous thromboembolism, and depletion of antithrombin III (AT3), there is limited data evaluating the risk of thrombosis and bleeding and optimal antithrombotic interventions in these patients are unknown. Methods: We performed a single-center retrospective study of patients ≥ 18 years-old who received PEG-Asp for B- or T-ALL at the University of Virginia between 2015 and 2020. The primary outcomes were the incidence of thrombosis and bleeding events. All patients received prophylactic AT3 repletion for activity level

6561 Background: Hospital readmissions are associated with increased health care utilization and unfavorable patient outcomes. Oncology patients have an increased risk of hospital readmission compared to the general patient population. The 30-day readmission rate for cancer patients at our institution is 27.7% which is higher than the reported national average of 20.2%. We sought to reduce 30-day hospital readmission rates by 25% for solid tumor oncology patients through a prospective integrated multidisciplinary discharge approach. Methods: Hospital readmissions for adult patients with a known solid tumor cancer diagnosis admitted to the oncology service at UVA from Jan 2019 – Apr 2019 were identified. Baseline information on tumor type, reason for readmission, interventions, length of stay (LOS), and inpatient morbidity and mortality (including ICU admission and transition to hospice) were collected via retrospective review. Qualitative and quantitative tools including process maps, cause-and-effect diagrams, Pareto charts, and priority matrix were used to identify potential areas for intervention. Two PDSA cycles were implemented: daily multidisciplinary discharge rounds with physicians, nursing, social work, case management, and PT/OT (PDSA1), and a templated discharge email to patients’ primary oncology team including attending oncologist, mid-level providers, nurse coordinator, pharmacist, and urgent care team (PDSA2). An SPC chart with 3-σ limits and t-test of unequal variance with 2-sided p-value was used to evaluate impact on readmission rates from baseline to PDSA2. Results: Following PDSA1 (May 2019 – Oct 2019), the 30-day readmission was 25.7%; PDSA2 was postponed due to COVID-19, however the 30-day readmission rate remained stable during the pandemic. Following PDSA2 (Sept 2021 – Dec 2021), the 30-day readmission rate was 18.2% corresponding to an absolute decrease of 34.3% which was statistically significant (p≤0.05). This was associated with a trend towards increased LOS, rate of ICU admission, and case-mix severity index although not statistically significant. There was no significant difference in inpatient mortality or transition to hospice (Table). Conclusions: Implementation of multidisciplinary discharge rounds and templated discharge communication resulted in a significant decrease in rate of 30-day readmissions for solid tumor oncology patients. There was a trend towards increased LOS and ICU admissions without increased inpatient mortality. Improvement in discharge email compliance and implementation of an urgent symptom clinic may further reduce the 30-day readmission rate. [Table: see text]

BackgroundData for frontline healthcare workers (HCWs) and risk of SARS-CoV-2 infection are limited and whether personal protective equipment (PPE) mitigates this risk is unknown. We evaluated risk for COVID-19 among frontline HCWs compared to the general community and the influence of PPE.MethodsWe performed a prospective cohort study of the general community, including frontline HCWs, who reported information through the COVID Symptom Study smartphone application beginning on March 24 (United Kingdom, U.K.) and March 29 (United States, U.S.) through April 23, 2020. We used Cox proportional hazards modeling to estimate multivariate-adjusted hazard ratios (aHRs) of a positive COVID-19 test.FindingsAmong 2,035,395 community individuals and 99,795 frontline HCWs, we documented 5,545 incident reports of a positive COVID-19 test over 34,435,272 person-days. Compared with the general community, frontline HCWs had an aHR of 11·6 (95% CI: 10·9 to 12·3) for reporting a positive test. The corresponding aHR was 3·40 (95% CI: 3·37 to 3·43) using an inverse probability weighted Cox model adjusting for the likelihood of receiving a test. A symptom-based classifier of predicted COVID-19 yielded similar risk estimates. Compared with HCWs reporting adequate PPE, the aHRs for reporting a positive test were 1·46 (95% CI: 1·21 to 1·76) for those reporting PPE reuse and 1·31 (95% CI: 1·10 to 1·56) for reporting inadequate PPE. Compared with HCWs reporting adequate PPE who did not care for COVID-19 patients, HCWs caring for patients with documented COVID-19 had aHRs for a positive test of 4·83 (95% CI: 3·99 to 5·85) if they had adequate PPE, 5·06 (95% CI: 3·90 to 6·57) for reused PPE, and 5·91 (95% CI: 4·53 to 7·71) for inadequate PPE.InterpretationFrontline HCWs had a significantly increased risk of COVID-19 infection, highest among HCWs who reused PPE or had inadequate access to PPE. However, adequate supplies of PPE did not completely mitigate high-risk exposures.FundingZoe Global Ltd., Wellcome Trust, EPSRC, NIHR, UK Research and Innovation, Alzheimer’s Society, NIH, NIOSH, Massachusetts Consortium on Pathogen ReadinessRESEARCH IN CONTEXTEvidence before this studyThe prolonged course of the coronavirus disease 2019 (COVID-19) pandemic, coupled with sustained challenges supplying adequate personal protective equipment (PPE) for frontline healthcare workers (HCW), have strained global healthcare systems in an unprecedented fashion. Despite growing awareness of this problem, there are few data to inform policy makers on the risk of COVID-19 among HCWs and the impact of PPE on their disease burden. Prior reports of HCW infections are based on cross sectional data with limited individual-level information on risk factors for infection. A PubMed search for articles published between January 1, 2020 and May 5, 2020 using the terms “covid-19”, “healthcare workers”, and “personal protective equipment,” yielded no population-scale investigations exploring this topic.Added value of this studyIn a prospective study of 2,135,190 individuals, frontline HCWs may have up to a 12-fold increased risk of reporting a positive COVID-19 test. Compared with those who reported adequate availability of PPE, frontline HCWs with inadequate PPE had a 31% increase in risk. However, adequate availability of PPE did not completely reduce risk among HCWs caring for COVID-19 patients.Implications of all the available evidenceBeyond ensuring adequate availability of PPE, additional efforts to protect HCWs from COVID-19 are needed, particularly as lockdown is lifted in many regions of the world.

Purpose The paper aims to describe the macro-level realities driving change for learning organizations and professionals including: volatility, uncertainty, complexity and ambiguity (VUCA) environment; information explosion; flattening organization; mobile and virtual workforce; and generational mix. It also describes implications for these realities and the critical shift from learning development to enablement via practices like learning curation, learning personalization, social learning and new and diverse learning modalities. Design/methodology/approach The paper opted for a review of marketplace, business and industry trends, as well as reviews of specific primary research and current publications, to support its viewpoint. Findings The VUCA of global; social; governmental; and economical systems is catalyzing the need for systemic change in the learning and development (L&D) industry. This will change the learning content that organizations will need to offer and the processes by which L&D leaders will need to identify and curate it. Originality/value This paper fulfills the need to explain the necessity of changes required in skill sets and best practices for the modern learning organization.

The US Navy initiated design concepts for a Medical Mission Module Support Container (M3SC), a mobile operating room capable of rapid installation aboard maneuverable ships within proximity of active combat units. The M3SC provides an alternative echelon of care in the current trauma system by decreasing the time between point of injury, arrival, and surgical intervention. The mobile ships used as M3SC platforms, however, are more susceptible to oceanic conditions that can induce detrimental physiologic motion sickness in medical personnel and patients aboard the vessels. This study investigated the effects of different sea-state motion conditions on the performance of surgical teams.Six four-person surgical teams performed 144 procedures in an M3SC aboard a Stewart motion table that simulated motion profiles of sea states 0, 3, and 4. A modified human-worn partial- task surgical simulator was used as a surgical surrogate to simulate the four most common, wartime, improvised explosive device injuries in the past 10 years. Electroencephalographs and heart rate variability (HRV) data were collected from surgeons and surgical technologists during each procedure to assess real-time physiologic responses to motion. Two postprocedure surveys, a Surgical Task Load Index and a Motion Sickness Assessment Questionnaire, were given to assess subjective responses of workload stress and motion-induced kinetosis. Surgical subject matter experts quantified surgical performance after each procedure by measuring blood loss and orthopedic pin placement to evaluate each intervention.Motion did not significantly influence overall performance (ρ = .002). Surgical procedure was the strongest predictor of performance. HRV was used to measure stress and was increased in surgical technologists; however, HRV was decreased for surgeons and technologists in motion. There was a significant interaction between role and motion (ρ = .002): Surgeons had higher workloads than did surgical technologists and neither demonstrated differences between motion and no motion. Surgeons demonstrated significantly decreased workloads under motion conditions (ρ = 0.002); however, surgeons perceived their workload to be higher. We attribute this to their increased critical thinking and physical execution of procedures. Surgeons and surgical technologists showed a trend toward HRV suppression within the motion conditions. This may indicate a coping response to the increased stress of the motion setting. Procedure and team dynamic were the strongest predictors of overall performance, suggesting a learning curve exists and that added focus on training should be enforced.Based on data collected in this study, similar surgical procedures should be implemented aboard these classes of ships. By doing so, injured military personnel would have more timely access to care. Surgical team members were aware of craft motion, used compensatory measures, and exhibited some physiological response.

SummaryMutations in pre-mRNA processing factors (PRPFs) cause 40% of autosomal dominant retinitis pigmentosa (RP), but it is unclear why mutations in ubiquitously expressed PRPFs cause retinal disease. To understand the molecular basis of this phenotype, we have generated RP type 11 (PRPF31-mutated) patient-specific retinal organoids and retinal pigment epithelium (RPE) from induced pluripotent stem cells (iPSC). Impaired alternative splicing of genes encoding pre-mRNA splicing proteins occurred in patient-specific retinal cells and Prpf31+/− mouse retinae, but not fibroblasts and iPSCs, providing mechanistic insights into retinal-specific phenotypes of PRPFs. RPE was the most affected, characterised by loss of apical-basal polarity, reduced trans-epithelial resistance, phagocytic capacity, microvilli, and cilia length and incidence. Disrupted cilia morphology was observed in patient-derived-photoreceptors that displayed progressive features associated with degeneration and cell stress. In situ gene-editing of a pathogenic mutation rescued key structural and functional phenotypes in RPE and photoreceptors, providing proof-of-concept for future therapeutic strategies.eTOCPRPF31 is a ubiquitously expressed pre-mRNA processing factor that when mutated causes autosomal dominant RP. Using a patient-specific iPSC approach, Buskin and Zhu et al. show that retinal-specific defects result from altered splicing of genes involved in the splicing process itself, leading to impaired splicing, loss of RPE polarity and diminished phagocytic ability as well as reduced cilia incidence and length in both photoreceptors and RPE.HighlightsSuccessful generation of iPSC-derived RPE and photoreceptors from four RP type 11 patientsRPE cells express the mutant PRPF31 protein and show the lowest expression of wildtype proteinPRPF31 mutations result in altered splicing of genes involved in pre-mRNA splicing in RPE and retinal organoidsPrpf31 haploinsufficiency results in altered splicing of genes involved in pre-mRNA splicing in mouse retinaRPE cells display loss of polarity, reduced barrier function and phagocytosisPhotoreceptors display shorter and fewer cilia and degenerative featuresRPE cells display most abnormalities suggesting they might be the primary site of pathogenesisIn situ gene editing corrects the mutation and rescues key phenotypes

A panel of experienced usability professionals discusses the challenges of working in a rapid-prototyping environment and lessons learned during the system development of a wide range of military equipment. The panelists will provide examples, “war stories” and recommendations for implementing a variety of methods and approaches that foster collaboration among design team members as well as the creation of usable designs that meet targeted end-users' needs. Discussion topics will include: prioritizing design options effectively, cultivating multidisciplinary working relationships, selecting usability methods that work best, building strategies to address human system integration requirements for different milestones, and taking advantage of spiral development in a rapid-prototyping environment. The panel discussions will reveal key success factors and insights that are generalizable across a wide array of product domains and businesses.

The lack of a suitable infection model remains an important obstacle for the pathophysiological understanding of Bartonella spp. The following pilot study was designed to determine whether cell culture-grown Bartonella henselae SA2 and Bartonella vinsonii subsp. berkhoffii genotype III would cause persistent bacteremia in dogs. Pre-inoculation screening established that two laboratory-raised Golden retrievers were naturally-infected with Bartonella koehlerae. Despite prior infection, one dog each was inoculated subcutaneously with 5 × 10(4)B. henselae (SA2 strain) or 3 × 10(4)B. vinsonii subsp. berkhoffii genotype III. Dogs were bled weekly for serological testing and culture using Bartonella alpha proteobacteria growth medium (BAPGM) diagnostic platform. Dog 1 seroconverted to B. henselae and Dog 2 seroconverted to B. vinsonii subsp. berkhoffii genotype III. Throughout the study period, Bartonella spp. DNA was neither amplified nor isolated in ante-mortem BAPGM enrichment blood cultures. B. henselae SA2 was isolated from a postmortem bone marrow from Dog 1 and B. koehlerae DNA was amplified from postmortem lung from Dog 2 following BAPGM enrichment culture. Limitations include lack of uninfected controls, a potentially suboptimal B. vinsonii subsp. berkhoffii inoculum and a relatively short duration of study. We conclude that following intradermal infection, sequestration of Bartonella spp. in tissues may limit diagnostic detection of these bacteria in dog blood samples.

To compare visual acuity at 6 years of age in eyes that received early treatment for high-risk prethreshold retinopathy of prematurity (ROP) with conventionally managed eyes.Infants with symmetrical, high-risk prethreshold ROP (n = 317) had one eye randomized to earlier treatment at high-risk prethreshold disease and the other eye managed conventionally, treated if ROP progressed to threshold severity. For asymmetric cases (n = 84), the high-risk prethreshold eye was randomized to either early treatment or conventional management. The main outcome measure was ETDRS visual acuity measured at 6 years of age by masked testers. Retinal structure was assessed as a secondary outcome.Analysis of all subjects with high-risk prethreshold ROP showed no statistically significant benefit for early treatment (24.3% vs 28.6% [corrected] unfavorable outcome; P = .15). Analysis of 6-year visual acuity results according to the Type 1 and 2 clinical algorithm showed a benefit for Type 1 eyes (25.1% vs 32.8%; P = .02) treated early but not Type 2 eyes (23.6% vs 19.4%; P = .37). Early-treated eyes showed a significantly better structural outcome compared with conventionally managed eyes (8.9% vs 15.2% unfavorable outcome; P.001), with no greater risk of ocular complications.Early treatment for Type 1 high-risk prethreshold eyes improved visual acuity outcomes at 6 years of age. Early treatment for Type 2 high-risk prethreshold eyes did not. Application to Clinical Practice Type 1 eyes, not Type 2 eyes, should be treated early. These results are particularly important considering that 52% of Type 2 high-risk prethreshold eyes underwent regression of ROP without requiring treatment. Trial Registration clinicaltrials.gov Identifier: NCT00027222.

To determine the disease expression in heterozygotes for mutations in the RP1 gene, a newly identified cause of autosomal dominant retinitis pigmentosa (adRP).Screening strategies were used to detect disease-causing mutations in the RP1 gene, and detailed studies of phenotype were performed in a subset of the detected RP1 heterozygotes using electroretinography (ERG), psychophysics, and optical coherence tomography (OCT).Seventeen adRP families had heterozygous RP1 changes. Thirteen families had the Arg677ter mutation, whereas four others had one of the following: Pro658 (1-bp del), Ser747 (1-bp del), Leu762-763 (5-bp del), and Tyr1053 (1-bp del). In Arg677ter RP1 heterozygotes, there was regional retinal variation in disease, with the far peripheral inferonasal retina being most vulnerable; central and superior temporal retinal regions were better preserved. The earliest manifestation of disease was rod dysfunction, detectable as reduced rod ERG photoresponse maximum amplitude, even in heterozygotes with otherwise normal clinical, functional, and OCT cross-sectional retinal imaging results. At disease stages when cone abnormalities were present, there was greater rod than cone dysfunction. Patients with the RP1 frameshift mutations showed similarities in phenotype to those with the Arg677ter mutation.Earliest disease expression of RP1 gene mutations causing adRP involves primarily rod photoreceptors, and there is a gradient of vulnerability of retinopathy with more pronounced effects in the inferonasal peripheral retina. At other disease stages, cone function is also affected, and severe retina-wide degeneration can occur. The nonpenetrance or minimal disease expression in some Arg677ter mutation-positive heterozygotes suggests important roles for modifier genes or environmental factors in RP1-related disease.

Red cells synthesize large amounts of heme during terminal differentiation. Central to this process is the transport and trafficking of heme synthesis intermediates within the cell. Despite the importance of transport during heme synthesis, the molecules involved in this process are largely unknown. In a screen for genes that are upregulated during erythroid terminal differentiation, we identified Tmem14c, a predicted multi-pass transmembrane protein as an essential component of the porphyrin metabolism pathway. Here, we report that Tmem14c facilitates the synthesis of mitochondrial protoporphyrin IX from coproporphyrinogen III and is thus required for heme synthesis. Tmem14c is a mitochondrial inner-membrane protein enriched in vertebrate hematopoietic tissues and is required for terminal erythropoiesis. Tmem14c gene-trap mouse embryos are severely anemic and mostly die by E13.5 (Fig. A). Fetal liver erythroid cells derived from gene-trap embryos experience maturation arrest. shRNA silencing of Tmem14c in Friend murine erythroleukemia (MEL) cells results in a significant decrease in de-novo heme synthesis. The biochemical defect is due to a decrease in mitochondrial protoporphyrin IX synthesis, while cytoplasmic porphyrin levels remain normal (Fig. B). The heme synthesis defect in Tmem14c-silenced MEL cells is complemented with a protoporphyrin IX analog. These data show the role of Tmem14c in regulating the terminal steps in mitochondrial porphyrin trafficking. Our findings collectively demonstrate that Tmem14c is required for the transport of mitochondrial porphyrins in developing erythroid cells. Due to its inner-mitochondrial localization and its relative proximity to heme synthetic enzymes coproporphyrinogen oxidase and protoporphyrinogen oxidase (Rhee et al., 2013 Science), Tmem14c can function as a molecular adaptor that facilitates the interaction of proteins involved in porphyrin transport, or as a protoporphyrinogen IX transporter (Fig. C). The identification of Tmem14c as an essential regulator of porphyrin transport and heme synthesis provides a novel genetic tool for exploring erythropoiesis and disorders of heme synthesis such as porphyria and anemia. Disclosures: No relevant conflicts of interest to declare.

The 1,25-dihydroxyvitamin D3 receptor from porcine intestine has been characterized by immunoprecipitation and immunoblotting experiments. Immunoprecipitation studies demonstrate that monoclonal antibodies to the receptor that recognize two different epitopes on the receptor protein quantitatively precipitate the 1,25-dihydroxyvitamin D3 binding activity from nuclear and whole cell extracts of intestinal mucosa. These antibodies were then used to study the porcine receptor by both one- and two-dimensional immunoblotting techniques. One-dimensional immunoblots of nuclear extract and whole cell extract show the receptor to be a single polypeptide of Mr approximately 55,000. The migration of the receptor on one-dimensional gels was unchanged by preassociation in vitro with 1,25-dihydroxyvitamin D3. In two-dimensional immunoblots two receptor proteins were detected, both of molecular weight 55,000. In addition, a form of the receptor did not enter the isoelectric focusing gel from either the acidic or basic direction. It did, however, migrate in the Mr 55,000 region in the molecular separation. The major receptor protein has a pI of 6.1; the minor protein has a pI of 5.9. These studies represent the first determinations of the size and charge of a mammalian 1,25-dihydroxyvitamin D3 receptor in crude tissue preparations, and they indicate that the pig receptor is a Mr 55,000 protein that exhibits charge heterogeneity in vivo. The nature of this apparent charge heterogeneity and its significance in receptor function are under investigation.