👤 Natasha K Fletcher

The accumulation and deposition of amyloid-beta (Aß) peptides is detrimental to neuronal networks and is driven by the cleavage of amyloid precursor protein (APP) by beta-secretase 1 (BACE1). The proteolytic processing of APP is tightly regulated by the opposing activities of BACE1 and ADAM10, with the latter producing a truncated, non-amyloidogenic fragment. Maintaining this balance is critical for normal physiological function, as complete inhibition of BACE1 has proven detrimental owing to the important physiological roles of its many substrates. Brain-derived neurotrophic factor (BDNF), an important mediator of neuronal function and survival, has recently been shown to reduce BACE1 activity in neural tissue, but the mechanism for this remains unknown. Previous research suggests that BACE1 cleavage of APP is favoured at acidic intracellular compartments, whereas non-amyloidogenic processing preferentially occurs at the plasma membrane. Hence, we hypothesized that BDNF alters the subcellular distribution of BACE1, reducing ß-cleavage of APP. Here, we show that acute BDNF treatment of differentiated neural cells (SH-SY5Y) reduced levels of sAPPß, a product of BACE1 cleavage of APP. Using confocal microscopy and quantitative image analysis, we found that this reduction in sAPPß levels is coincident with increased BACE1 localization to the plasma membrane, and a concomitant reduction of BACE1 localization to early endosomes. This effect appears to be independent of clathrin-mediated endocytosis (CME), as inhibition of CME by PitStop2 treatment increased a-cleavage of APP but did not reduce ß-cleavage independent of BDNF treatment. Hence, BDNF may reduce production of Aß by altering BACE1 distribution and decreasing upstream ß-cleavage. Show less

Self-collection of biospecimens at-home, without specialized equipment or training, are increasingly being adopted in clinical practice due to convenience and patient preferences. However, sample instability during shipment means that remote access to common blood tests remains challenging. We hypothesized that the inaccuracy and imprecision in test results that develop because of sample instability could be modeled and controlled using knowledge of transit conditions captured by environmental sensors. We subjected 2685 blood samples from 65 participants to temperature cycles derived from real-world transit conditions. Training a model called Remote Control to predict change enabled accurate calibration of test results to approximate the time zero value at the point of collection, despite sample degradation. With calibration, unprocessed whole blood could be transported, for up to 9 days under ambient conditions and exposed to temperatures between 3.4 and 47.4 °C. Under these conditions, agreement with CLIA TEa ranged between 98.1 and 100%, with a |%bias| of 0.1-1.6%, a %CV of 2.2-4.9%, and a minimum sigma metric between 3 and 8.8σ for lipids (Cholesterol, HDL, LDL, Triglycerides, APO-A1, and APO-B). Performance was linear across measurement intervals (R Show less

This study determines the phenotypic and functional characteristics that define distinct fibroblast-like synoviocyte (FLS) populations in rheumatoid arthritis (RA) vs psoriatic arthritis (PsA). Single-cell RNA sequencing and multiparametric flow cytometry analysis (21 markers) were performed on RA and PsA synovial cell suspensions to determine FLS phenotype/function. Podoplanin (PDPN) Flow analysis of PDPN RA and PsA possess distinct FLS populations with unique functional and metabolic properties, which may facilitate improved understanding of disease pathogenesis and therapeutic response. Show less

Typically expressed on T-cells and NK cells, FASLG induces apoptosis in target cells upon binding Fas. However, assessing potential FASLG expression in tumor cells with convenient genomics approaches has been challenging. This study applied a novel assessment of FASLG copy numbers (CNs) and gene expression levels, applicable to bulk exome and RNAseq files. Analyses indicated high FASLG CN associated with worse survival outcomes. Interestingly, higher FASLG gene expression was found to be associated with better survival outcomes, which led to a determination of whether this result was due to FASLG expression from tumor-infiltrating lymphocytes (TILs) instead of cancer cells demonstrating the higher CNs. In fact, T-cell markers CD4 and CD8A highly correlated with FASLG expression, consistent with the hypothesis that the high FASLG expression was associated with the TILs. Subsequent analyses confirmed that CN increases led to increased gene expression in the genomic region of the FASLG gene, particularly with an assessment of the expression of the neighboring PRRC2C gene. In sum, FASLG CN assessments, even independently of a corresponding gene expression correlation, may provide important characterizations of tumor cells. This study indicates that FASLG CN increases could represent a mechanism of tumor escape from TILs and a prognostic indicator; and tumor FASLG may be a suitable drug target for reducing tumor evasion of T-cells. Show less

In epithelial tissues, polarisation of microtubules and actin microvilli occurs along the apical-basal axis of each cell, yet how these cytoskeletal polarisation events are coordinated remains unclear. Here, we examine the hierarchy of events during cytoskeletal polarisation in Drosophila melanogaster epithelia. Core apical-basal polarity determinants polarise the spectrin cytoskeleton to recruit the microtubule-binding proteins Patronin (CAMSAP1, CAMSAP2 and CAMSAP3 in humans) and Shortstop [Shot; MACF1 and BPAG1 (also known as DST) in humans] to the apical membrane domain. Patronin and Shot then act to polarise microtubules along the apical-basal axis to enable apical transport of Rab11 endosomes by the Nuf-Dynein microtubule motor complex. Finally, Rab11 endosomes are transferred to the MyoV (also known as Didum in Drosophila) actin motor to deliver the key microvillar determinant Cadherin 99C to the apical membrane to organise the biogenesis of actin microvilli. Show less

Leiomyosarcoma is a malignant neoplasm with smooth muscle differentiation. Little is known about its molecular heterogeneity and no targeted therapy currently exists for leiomyosarcoma. Recognition of different molecular subtypes is necessary to evaluate novel therapeutic options. In a previous study on 51 leiomyosarcomas, we identified three molecular subtypes in leiomyosarcoma. The current study was performed to determine whether the existence of these subtypes could be confirmed in independent cohorts. Ninety-nine cases of leiomyosarcoma were expression profiled with 3'end RNA-Sequencing (3SEQ). Consensus clustering was conducted to determine the optimal number of subtypes. We identified 3 leiomyosarcoma molecular subtypes and confirmed this finding by analyzing publically available data on 82 leiomyosarcoma from The Cancer Genome Atlas (TCGA). We identified two new formalin-fixed, paraffin-embedded tissue-compatible diagnostic immunohistochemical markers; LMOD1 for subtype I leiomyosarcoma and ARL4C for subtype II leiomyosarcoma. A leiomyosarcoma tissue microarray with known clinical outcome was used to show that subtype I leiomyosarcoma is associated with good outcome in extrauterine leiomyosarcoma while subtype II leiomyosarcoma is associated with poor prognosis in both uterine and extrauterine leiomyosarcoma. The leiomyosarcoma subtypes showed significant differences in expression levels for genes for which novel targeted therapies are being developed, suggesting that leiomyosarcoma subtypes may respond differentially to these targeted therapies. We confirm the existence of 3 molecular subtypes in leiomyosarcoma using two independent datasets and show that the different molecular subtypes are associated with distinct clinical outcomes. The findings offer an opportunity for treating leiomyosarcoma in a subtype-specific targeted approach. Show less

Histone modifications play an important role in chromatin organization and gene regulation, and their interpretation is referred to as epigenetic control. The methylation levels of several lysine residues in histone tails are tightly controlled, and JmjC domain-containing proteins are one class of broadly expressed enzymes catalyzing methyl group removal. However, several JmjC proteins remain uncharacterized, gaps persist in understanding substrate recognition, and the integration of JmjC proteins into signaling pathways is just emerging. The KDM3 subfamily is an evolutionarily conserved group of histone demethylase proteins, thought to share lysine substrate specificity. Here we use a systematic approach to compare KDM3 subfamily members. We show that full-length KDM3A and KDM3B are H3K9me1/2 histone demethylases whereas we fail to observe histone demethylase activity for JMJD1C using immunocytochemical and biochemical approaches. Structure-function analyses revealed the importance of a single amino acid in KDM3A implicated in the catalytic activity towards H3K9me1/2 that is not conserved in JMJD1C. Moreover, we use quantitative proteomic analyses to identify subsets of the interactomes of the 3 proteins. Specific interactor candidates were identified for each of the three KDM3 subfamily members. Importantly, we find that SCAI, a known transcriptional repressor, interacts specifically with KDM3B. Taken together, we identify substantial differences in the biology of KDM3 histone demethylases, namely enzymatic activity and protein-protein interactions. Such comparative approaches pave the way to a better understanding of histone demethylase specificity and protein function at a systems level and are instrumental in identifying the more subtle differences between closely related proteins. Show less

Perfluorooctanoic acid (PFOA, 'C8') and perfluoroctane sulphonate (PFOS) are environmentally stable compounds with industrial and consumer uses and long half-lives in humans. Concern has been raised over chronic exposure effects to human health, especially in relation to cholesterol metabolism. Here, we explore the association between exposure to PFOA and PFOS and the in vivo expression of genes involved in cholesterol metabolism. We studied 290 individuals exposed to background levels of PFOS and elevated concentrations of PFOA through drinking water. Using adjusted linear regression models, we found inverse associations between serum PFOA levels and the whole blood expression level of genes involved in cholesterol transport (NR1H2, NPC1 and ABCG1; p=0.002, 0.026 and 0.014 respectively). A positive association was seen between PFOS and a transcript involved in cholesterol mobilisation (NCEH1; p=0.018), and a negative relationship with a transcript involved in cholesterol transport (NR1H3; p=0.044). When sexes were analysed separately, reductions in the levels of mRNAs involved in cholesterol transport were seen with PFOA in men (NPC1, ABCG1, and PPARA; p=0.025, 0.024 and 0.012 respectively) and in women (NR1H2 expression; p=0.019), whereas an increase in the levels of a cholesterol mobilisation transcript (NCEH1; p=0.036) was noted in women alone. PFOS was positively associated with expression of genes involved in both cholesterol mobilisation and transport in women (NCEH1 and PPARA; p=0.003 and 0.039 respectively), but no effects were evident in men. This is the first report of associations between the in vivo expression of genes involved in cholesterol metabolism and exposure to PFOA or PFOS, suggested that exposure to these compounds may promote a hypercholesterolaemic environment, with wider implications for human disease. Show less