Faculty Bibliography

Oculocutaneous albinism (OCA) is an inherited condition characterised by significantly reduced pigment in skin, hair and eyes, visual defects and an increased risk of skin cancer. In the South African black population, 1 in 4 000 people is affected. Quality of life in children with albinism is influenced not only by health problems, but also by stigmatisation, rejection and cultural issues. This review aims to explore the latest literature available on the epidemiology, genetics, clinical characteristics, psychosocial issues and possible management strategies, focusing on affected children. The knowledge provided here is required of health professionals if a more fully informed service is to be offered to these children and their families.

Lipid metabolism plays an important role in the regulation of cellular homeostasis. However, since it is difficult to measure the actual rates of synthesis and degradation of individual lipid species, lipid compositions are used often as a surrogate to evaluate lipid metabolism even though they provide only static snapshots of the lipodome. Here, we designed a simple method to determine the turnover rate of phospholipid and acylglycerol species based on the incorporation of ¹³C₆-glucose combined with LC-MS/MS. We labeled adult Drosophila melanogaster with ¹³C₆-glucose that incorporates into the entire lipidome, derived kinetic parameters from mass spectra, and studied effects of deletion of CG6718, the fly homologue of the calcium-independent phospholipase A2β, on lipid metabolism. Although ¹³C₆-glucose gave rise to a complex pattern of ¹³C incorporation, we were able to identify discrete isotopomers in which ¹³C atoms were confined to the glycerol group. With these isotopomers, we calculated turnover rate constants, half-life times, and fluxes of the glycerol backbone of multiple lipid species. To perform these calculations, we estimated the fraction of labeled molecules in glycerol-3-phosphate, the lipid precursor, by mass isotopomer distribution analysis of the spectra of phosphatidylglycerol. When we applied this method to D. melanogaster, we found a range of lipid half-lives from 2 to 200 days, demonstrated tissue-specific fluxes of individual lipid species, and identified a novel function of CG6718 in triacylglycerol metabolism. This method provides fluxomics-type data with significant potential to improve the understanding of complex lipid regulation in a variety of research models.

BACKGROUND:Cholesterol Efflux Capacity (CEC) is considered to be a key atheroprotective property of high-density lipoproteins (HDL). However, the role of HDL-CEC in atherosclerosis and cardiovascular (CV) risk is still controversial, and data in individuals with diabetes are limited. OBJECTIVE:In this study, we have investigated the relationship of CEC and other HDL characteristics with clinical and subclinical atherosclerosis in subjects with elevated cardiovascular diseases (CVD) risk and Type 2 Diabetes Mellitus (T2DM). METHODS:Using multiple linear regression analyses, we determined the relationship of HDL-CEC with carotid intima-media thickness (cIMT, Z-Score), an endothelial dysfunction (EnD) Score (Z-Score), prevalent CVD (n = 150 cases) and history of CV events (CVE, n = 85 cases) in an observational cohort (CODAM, n = 574, 59.6 ± 0.3 yr, 61.3% men, 24.4% T2DM). Stratified analyses were performed to determine if the associations differed between individuals with normal glucose metabolism (NGM) and those with disturbed glucose metabolism. RESULTS: = .074 and .034, respectively), but not in those with NGM. CONCLUSION/CONCLUSIONS:HDL-CEC is not associated with clinical or subclinical atherosclerosis, neither in the whole population nor in individuals with (pre)diabetes, while other HDL characteristics show atheroprotective associations. The atheroprotective associations of HDL-size and HDL-P are lost in (pre)diabetes, while higher concentrations of HDL-C and apoA-I are associated with a lower prevalence of CVD in (pre)diabetes.

Type 1 diabetes mellitus (T1DM) is an autoimmune disease characterized by insulin deficiency, and patients with diabetes have an increased risk of bone fracture and significantly impaired fracture healing. Proinflammatory cytokine tumor necrosis factor-alpha is significantly upregulated in diabetic fractures and is believed to underlie delayed fracture healing commonly observed in diabetes. Our previous genetic screen for the binding partners of progranulin (PGRN), a growth factor-like molecule that induces chondrogenesis, led to the identification of tumor necrosis factor receptors (TNFRs) as the PGRN-binding receptors. In this study, we employed several in vivo models to ascertain whether PGRN has therapeutic effects in diabetic fracture healing. Here, we report that deletion of PGRN significantly delayed bone fracture healing and aggravated inflammation in the fracture models of mice with T1DM. In contrast, recombinant PGRN effectively promoted diabetic fracture healing by inhibiting inflammation and enhancing chondrogenesis. In addition, both TNFR1 proinflammatory and TNFR2 anti-inflammatory signaling pathways are involved in PGRN-stimulated diabetic fracture healing. Collectively, these findings illuminate a novel understanding concerning the role of PGRN in diabetic fracture healing and may have an application in the development of novel therapeutic intervention strategies for diabetic and other types of impaired fracture healing.

Axonal sorting, the controlled passage of specific cargoes from the cell soma into the axon compartment, is critical for establishing and maintaining the polarity of mature neurons. To delineate axonal sorting events, we took advantage of two neuroinvasive alpha-herpesviruses. Human herpes simplex virus 1 (HSV-1) and pseudorabies virus of swine (PRV; suid herpesvirus 1) have evolved as robust cargo of axonal sorting and transport mechanisms. For efficient axonal sorting and subsequent egress from axons and presynaptic termini, progeny capsids depend on three viral membrane proteins (Us7 (gI), Us8 (gE), and Us9), which engage axon-directed kinesin motors. We present evidence that Us7-9 of the veterinary pathogen pseudorabies virus (PRV) form a tripartite complex to recruit Kif1a, a kinesin-3 motor. Based on multi-channel super-resolution and live TIRF microscopy, complex formation and motor recruitment occurs at the trans-Golgi network. Subsequently, progeny virus particles enter axons as enveloped capsids in a transport vesicle. Artificial recruitment of Kif1a using a drug-inducible heterodimerization system was sufficient to rescue axonal sorting and anterograde spread of PRV mutants devoid of Us7-9. Importantly, biophysical evidence suggests that Us9 is able to increase the velocity of Kif1a, a previously undescribed phenomenon. In addition to elucidating mechanisms governing axonal sorting, our results provide further insight into the composition of neuronal transport systems used by alpha-herpesviruses, which will be critical for both inhibiting the spread of infection and the safety of herpesvirus-based oncolytic therapies.

This retrospective, matched-cohort study analyzed 1,556 patients with diabetic ulcers treated at 470 wound centers throughout the United States to determine the effectiveness of a cryopreserved bioactive split-thickness skin allograft plus standard of care when compared to standard of care alone. There were 778 patients treated with the graft in the treatment cohort, who were paired with 778 patients drawn from a pool of 126,864 candidates treated with standard of care alone (controls), by using propensity matching to create nearly identical cohorts. Both cohorts received standard wound care, including surgical debridement, moist wound care, and offloading. Logistic regression analysis of healing rates according to wound size, wound location, wound duration, volume reduction, exposed deep structures, and Wagner grade was performed. Amputation rates and recidivism at 3 months, 6 months, and 1 year after wound closure were analyzed. Diabetic ulcers were 59% more likely to close in the treatment cohort compared to the control cohort (p = .0045). The healing rate with the graft was better than standard of care across multiple subsets, but the most significant improvement was noted in the worst wounds that had a duration of 90-179 days prior to treatment (p =.0073), exposed deep structures (p = .036), and/or Wagner Grade 4 ulcers (p = 0.04). Furthermore, the decrease in recidivism was statistically significant at 3 months, 6 months, and 1 year, with and without initially exposed deep structures (p < .05). The amputation rate in the treatment cohort was 41.7% less than that of the control cohort at 20 weeks (0.9% vs 1.5%, respectively). This study demonstrated that diabetic ulcers treated with a cryopreserved bioactive split-thickness skin allograft were more likely to heal and remain closed compared to ulcers treated with standard of care alone. This article is protected by copyright. All rights reserved.

Hepatitis B virus (HBV) remains a major global health problem with 257 million chronically infected individuals worldwide, of whom approximately 20 million are co-infected with hepatitis delta virus (HDV). Progress toward a better understanding of the complex interplay between these two viruses and the development of novel therapies have been hampered by the scarcity of suitable cell culture models that mimic the natural environment of the liver. Here, we established HBV and HBV/HDV co-infections and super-infections in self-assembling co-cultured primary human hepatocytes (SACC-PHHs) for up to 28 days in a 384-well format and highlight the suitability of this platform for high-throughput drug testing. We performed RNA sequencing at days 8 and 28 on SACC-PHHs, either HBV mono-infected or HBV/HDV co-infected. Our transcriptomic analysis demonstrates that hepatocytes in SACC-PHHs maintain a mature hepatic phenotype over time, regardless of infection condition. We confirm that HBV is a stealth virus, as it does not induce a strong innate immune response; rather, oxidative phosphorylation and extracellular matrix-receptor interactions are dysregulated to create an environment that promotes persistence. Notably, HDV co-infection also did not lead to statistically significant transcriptional changes across multiple donors and replicates. The lack of innate immune activation is not due to SACC-PHHs being impaired in their ability to induce interferon stimulated genes (ISGs). Rather, polyinosinic:polycytidylic acid exposure activates ISGs, and this stimulation significantly inhibits HBV infection, yet only minimally affects the ability of HDV to infect and persist. Conclusion: These data demonstrate that the SACC-PHH system is a versatile platform for studying HBV/HDV co-infections and holds promise for performing chemical library screens and improving our understanding of the host response to such infections.

PURPOSE/OBJECTIVE:To investigate the effect of a change in USMLE Step 1 timing on Step 2 Clinical Knowledge (CK) scores, the effect of lag-time on Step 2 CK performance, and the relationship of incoming MCAT score to Step 2 CK performance pre- and post-change. METHOD/METHODS:Four LCME-accredited schools that moved Step 1 after core clerkships between academic years 2008-2009 and 2017-2018 were analyzed in a pre-post format. Standard t-tests were used to examine the change in Step 2 CK scores pre- and post-change. Tests of differences in proportions were used to evaluate whether Step 2 CK failure rates differed between curricular change groups. Linear regressions were used to examine the relationships between Step 2 CK performance, lag-time and incoming MCAT score, and curricular change group. RESULTS:Step 2 CK performance did not change significantly (P = .20). Failure rates remained highly consistent (pre-change: 1.83%, post-change: 1.79%). The regression indicated that lag-time had a significant effect on Step 2 CK performance, with scores declining with increasing lag-time. The regression yielded small but significant interaction effects between MCAT and Step 2 CK scores. Students with lower incoming MCATs tended to perform better on Step 2 CK when Step 1 was after clerkships. CONCLUSIONS:Moving Step 1 after core clerkships appears to have had no significant impact on Step 2 CK scores or failure rates, supporting the argument that such a change is noninferior to the traditional model. Students with lower MCAT scores benefit most from the change.

PURPOSE/OBJECTIVE:Genetically engineered mouse models of sporadic cancers are critical for studying tumor biology and for preclinical testing of therapeutics. We present an MRI-based pipeline designed to produce high resolution, quantitative information about tumor progression and response to novel therapies in mouse models of medulloblastoma (MB). METHODS:Sporadic MB was modeled in mice by inducing expression of an activated form of the Smoothened gene (aSmo) in a small number of cerebellar granule cell precursors. aSmo mice were imaged and analyzed at defined time-points using a 3D manganese-enhanced MRI-based pipeline optimized for high-throughput. RESULTS:A semi-automated segmentation protocol was established that estimates tumor volume in a time-frame compatible with a high-throughput pipeline. Both an empirical, volume-based classifier and a linear discriminant analysis-based classifier were tested to distinguish progressing from nonprogressing lesions at early stages of tumorigenesis. Tumor centroids measured at early stages revealed that there is a very specific location of the probable origin of the aSmo MB tumors. The efficacy of the manganese-enhanced MRI pipeline was demonstrated with a small-scale experimental drug trial designed to reduce the number of tumor associated macrophages and microglia. CONCLUSION/CONCLUSIONS:Our results revealed a high level of heterogeneity between tumors within and between aSmo MB models, indicating that meaningful studies of sporadic tumor progression and response to therapy could not be conducted without an imaging-based pipeline approach.