Actin chromobody imaging reveals sub-organellar actin dynamics

The actin cytoskeleton plays multiple critical roles in cells, from cell migration to organelle dynamics. The small and transient actin structures regulating organelle dynamics are challenging to detect with fluorescence microscopy, making it difficult to determine whether actin filaments are directly associated with specific membranes. To address these limitations, we developed fluorescent-protein-tagged actin nanobodies, termed 'actin chromobodies' (ACs), targeted to organelle membranes to enable high-resolution imaging of sub-organellar actin dynamics.

Age-Onset Phosphorylation of a Minor Actin Variant Promotes Intestinal Barrier Dysfunction

Age-associated decay of intercellular interactions impairs the cells' capacity to tightly associate within tissues and form a functional barrier. This barrier dysfunction compromises organ physiology and contributes to systemic failure. The actin cytoskeleton represents a key determinant in maintaining tissue architecture. Yet, it is unclear how age disrupts the actin cytoskeleton and how this, in turn, promotes mortality. Here, we show that an uncharacterized phosphorylation of a low-abundant actin variant, ACT-5, compromises integrity of the C. elegans intestinal barrier and accelerates pathogenesis. Age-related loss of the heat-shock transcription factor, HSF-1, disrupts the JUN kinase and protein phosphatase I equilibrium which increases ACT-5 phosphorylation within its troponin binding site. Phosphorylated ACT-5 accelerates decay of the intestinal subapical terminal web and impairs its interactions with cell junctions. This compromises barrier integrity, promotes pathogenesis, and drives mortality. Thus, we provide the molecular mechanism by which age-associated loss of specialized actin networks impacts tissue integrity.

A201 PREVALENCE OF NONALCOHOLIC FATTY LIVER DISEASE IN A COHORT OF HEALTHY CHILDREN IN ONTARIO

Aims

To determine the prevalence of hepatic steatosis in a cohort of previously healthy children and adolescents, with the use of abdominal computer tomography (CT).

Methods

Retrospective review of the Sickkids trauma database from (year 2004 to 2015). Inclusion criteria: previously healthy children ages 1-17yr having undergone an abdominal CT scan as a part of routine trauma assessment. Exclusion criteria: Involvement of spleen and/or liver in the injury, known metabolic condition, concurrent use of medications that could predispose to hepatic steatosis. Steatosis was defined as a liver spleen attenuation index (L/S AI) of <0.8. Anthropometrics and baseline demographics were collected. Statistical analyses were performed using Graphpad Prism 7.

Results

A total of 143 children were included in the analyses with a mean (SD) age of 7.12(4.26) years. 88 children were male (7.10(4.24) years old). The mean (SD) weight z score was 0.48 (0.97). Fifteen percent of the 137 children with a weight z-score between -2 to 2 had evidence of hepatic steatosis on imaging (using liver/spleen index <0.8). Twenty seven percent (6/22) of children with weight z-scores less than the 33rd percentile had L/S AI <0.8. An inverse correlation between weight z-scores and L/S AI was found in children >10 years (P<0.016) (Fig 1); however there was no correlation in pre-pubertal children (P<0.374).

Conclusions

Hepatic steatosis is highly prevalent in this cohort of healthy children in Ontario. Larger population based studies are needed to investigate the prevalence of hepatic steatosis in children across Canada.

Funding Agencies

None

Correction: Gene Expression Differences in Peripheral Blood of Parkinson's Disease Patients with Distinct Progression Profiles

[This corrects the article DOI: 10.1371/journal.pone.0157852.].

Calcium-mediated actin reset (CaAR) mediates acute cell adaptations

Actin has well established functions in cellular morphogenesis. However, it is not well understood how the various actin assemblies in a cell are kept in a dynamic equilibrium, in particular when cells have to respond to acute signals. Here, we characterize a rapid and transient actin reset in response to increased intracellular calcium levels. Within seconds of calcium influx, the formin INF2 stimulates filament polymerization at the endoplasmic reticulum (ER), while cortical actin is disassembled. The reaction is then reversed within a few minutes. This Calcium-mediated actin reset (CaAR) occurs in a wide range of mammalian cell types and in response to many physiological cues. CaAR leads to transient immobilization of organelles, drives reorganization of actin during cell cortex repair, cell spreading and wound healing, and induces long-lasting changes in gene expression. Our findings suggest that CaAR acts as fundamental facilitator of cellular adaptations in response to acute signals and stress.

DOI:http://dx.doi.org/10.7554/eLife.19850.001

Our skeleton plays a vital role in giving shape and structure to our body, it also allows us to make coordinated movements. Similarly, each cell contains a microscopic network of structures and supports called the cytoskeleton that helps cells to adopt specific shapes and is crucial for them to move around. Unlike our skeleton, which is relatively unchanging, the cytoskeleton of each cell constantly changes and adapts to the specific needs of the cell.

One part of the cytoskeleton is a dense, flexible meshwork of fibers called the cortex that lies just beneath the surface of the cell. The cortex is constructed using a protein called actin, and many of these proteins join together to form each fiber. When cells need to adapt rapidly to an injury or other sudden changes in their environment they activate a so-called stress response. This response often begins with a rapid increase in the amount of calcium ions inside a cell, which can then trigger changes in actin organization. However, it is not clear how cells under stress are able to globally remodel their actin cytoskeleton without compromising stability and integrity of the cortex.

Wales, Schuberth, Aufschnaiter et al. used a range of mammalian cells to investigate how actin responds to stress signals. All cells responded to the resulting influx of calcium ions by deconstructing large parts of the actin cortex and simultaneously forming actin filaments near the center of the cell. Wales, Schuberth, Aufschnaiter et al. termed this response calcium-mediated actin reset (CaAR), as it lasted for only a few minutes before the actin cortex reformed. The experiments show that a protein called INF2 controls CaAR by rapidly removing actin from the cortex and forming new filaments near a cell compartment called the endoplasmic reticulum.

CaAR allows cells to rapidly and drastically alter the cortex in response to stress. The experiments also show that this sudden shift in actin can change the activity of certain genes, leading to longer-term effects on the cell. The findings of Wales, Schuberth, Aufschnaiter et al. suggest that calcium ions globally regulate the actin cytoskeleton and hence cell shape and movement under stress. This could be relevant for many important processes and conditions such as wound healing, inflammation and cancer. A future challenge will be to understand the role of CaAR in these processes.

DOI:http://dx.doi.org/10.7554/eLife.19850.002

Gene Expression Differences in Peripheral Blood of Parkinson's Disease Patients with Distinct Progression Profiles

The prognosis of neurodegenerative disorders is clinically challenging due to the inexistence of established biomarkers for predicting disease progression. Here, we performed an exploratory cross-sectional, case-control study aimed at determining whether gene expression differences in peripheral blood may be used as a signature of Parkinson’s disease (PD) progression, thereby shedding light into potential molecular mechanisms underlying disease development. We compared transcriptional profiles in the blood from 34 PD patients who developed postural instability within ten years with those of 33 patients who did not develop postural instability within this time frame. Our study identified >200 differentially expressed genes between the two groups. The expression of several of the genes identified was previously found deregulated in animal models of PD and in PD patients. Relevant genes were selected for validation by real-time PCR in a subset of patients. The genes validated were linked to nucleic acid metabolism, mitochondria, immune response and intracellular-transport. Interestingly, we also found deregulation of these genes in a dopaminergic cell model of PD, a simple paradigm that can now be used to further dissect the role of these molecular players on dopaminergic cell loss. Altogether, our study provides preliminary evidence that expression changes in specific groups of genes and pathways, detected in peripheral blood samples, may be correlated with differential PD progression. Our exploratory study suggests that peripheral gene expression profiling may prove valuable for assisting in prediction of PD prognosis, and identifies novel culprits possibly involved in dopaminergic cell death. Given the exploratory nature of our study, further investigations using independent, well-characterized cohorts will be essential in order to validate our candidates as predictors of PD prognosis and to definitively confirm the value of gene expression analysis in aiding patient stratification and therapeutic intervention.

Elevated α-synuclein caused by SNCA gene triplication impairs neuronal differentiation and maturation in Parkinson's patient-derived induced pluripotent stem cells

We have assessed the impact of α-synuclein overexpression on the differentiation potential and phenotypic signatures of two neural-committed induced pluripotent stem cell lines derived from a Parkinson's disease patient with a triplication of the human SNCA genomic locus. In parallel, comparative studies were performed on two control lines derived from healthy individuals and lines generated from the patient iPS-derived neuroprogenitor lines infected with a lentivirus incorporating a small hairpin RNA to knock down the SNCA mRNA. The SNCA triplication lines exhibited a reduced capacity to differentiate into dopaminergic or GABAergic neurons and decreased neurite outgrowth and lower neuronal activity compared with control cultures. This delayed maturation phenotype was confirmed by gene expression profiling, which revealed a significant reduction in mRNA for genes implicated in neuronal differentiation such as delta-like homolog 1 (DLK1), gamma-aminobutyric acid type B receptor subunit 2 (GABABR2), nuclear receptor related 1 protein (NURR1), G-protein-regulated inward-rectifier potassium channel 2 (GIRK-2) and tyrosine hydroxylase (TH). The differentiated patient cells also demonstrated increased autophagic flux when stressed with chloroquine. We conclude that a two-fold overexpression of α-synuclein caused by a triplication of the SNCA gene is sufficient to impair the differentiation of neuronal progenitor cells, a finding with implications for adult neurogenesis and Parkinson's disease progression, particularly in the context of bioenergetic dysfunction.

The sirtuin-2 inhibitor AK7 is neuroprotective in models of Parkinson's disease but not amyotrophic lateral sclerosis and cerebral ischemia

Sirtuin deacetylases regulate diverse cellular pathways and influence disease processes. Our previous studies identified the brain-enriched sirtuin-2 (SIRT2) deacetylase as a potential drug target to counteract neurodegeneration. In the present study, we characterize SIRT2 inhibition activity of the brain-permeable compound AK7 and examine the efficacy of this small molecule in models of Parkinson’s disease, amyotrophic lateral sclerosis and cerebral ischemia. Our results demonstrate that AK7 is neuroprotective in models of Parkinson’s disease; it ameliorates alpha-synuclein toxicity in vitro and prevents 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced dopamine depletion and dopaminergic neuron loss in vivo. The compound does not show beneficial effects in mouse models of amyotrophic lateral sclerosis and cerebral ischemia. These findings underscore the specificity of protective effects observed here in models of Parkinson’s disease, and previously in Huntington’s disease, and support the development of SIRT2 inhibitors as potential therapeutics for the two neurodegenerative diseases.

Limelight on alpha-synuclein: pathological and mechanistic implications in neurodegeneration

The pathogenesis of many neurodegenerative disorders arises in association with the misfolding and accumulation of a wide variety of proteins. Much emphasis has been placed on understanding the nature of these protein accumulations, including their composition, the process by which they are formed and the physiological impact they impose at cellular and, ultimately, organismal levels. Alpha-synuclein (ASYN) is the major component of protein inclusions known as Lewy bodies and Lewy neurites, which are the typical pathological hallmarks in disorders referred to as synucleinopathies. In addition, mutations or multiplications in the gene encoding for ASYN have also been shown to cause familial cases of PD, the most common synucleinopathy. Although the precise function of ASYN remains unclear, it appears to be involved in a vast array of cellular processes. Here, we review, in depth, a spectrum of cellular and molecular mechanisms that have been implicated in synucleinopathies. Importantly, detailed understanding of the biology/pathobiology of ASYN may enable the development of novel avenues for diagnosis and/or therapeutic intervention in synucleinopathies.

Solution-focused brief therapy in primary care

Solution-focused brief therapy (SFBT) offers mental health nurses a robust framework on which to build appropriate and effective nursing care. This article describes efforts to apply ideas derived from this type of therapy in a new nurse practitioner post offering a mental health service to patients based in GP practices. The approach described develops Brimblecombe's (1995) idea of combining a brief therapy approach with nursing care plans in a way ideally suited to time-limited mental health nursing in primary care.

Perception of body image in children with burns, five years after burn injury

Burn injuries and subsequent disfigurement may place children at high risk for psychologic dysfunction. If medical professionals are to aid the child in achieving psychologic resolution and acceptance of the injury, they must be aware of the stage of body-image perception that the child is experiencing. This study was designed to determine differences in body image between children with burns and children without burns through the use of human figure drawings. The experimental group consisted of 32 children with burns, aged 5 to 15 years, studied at approximately 5 years after burn injury. The control group consisted of 32 children without burns, aged 6 to 15 years. Subjects in the burn group were matched to control subjects by age and sex. There were no significant differences in body image in relation to any of the demographic measures except age. Age was inversely related to body image both in patients with burns and in control subjects.

Comparison of Various Carbon Adsorbents and Quantitative Elution and Separation of Forty-two Pesticides from a Carbon-Solka Floe Cleanup Column

Ten different carbons were investigated as adsorbents in a column cleanup procedure for extracts of lettuce and carrots. Organochlorine pesticides were eluted with 175 nil of 1.5% acetonitrile in hexane. The quantitative elution of 13 pesticides as a mixture with and without the presence of carrot or lettuce extract was determined by gas-liquid chromatography (GLC) with electron capture detection (ECD). The mean recovery values for each pesticide from all carbons, excluding Norit A neutral, ranged from 87 to 106% with a coefficient of variation (C) of 3 to 11. In the presence of plant extracts the individual pesticide recoveries for 6 carbons ranged from 75 lo 99% with a C of 6 to 16. All pesticides from 9 individual carbons had mean recovery values ranging from 93 to 108% with a C of 5 to 10. In the presence of plant extracts these values were 81 to 100% with a C of 8 to 12. Four carbons (Darco G60, Darco S51, Nuchar C-190N, Norit FQP) were considered satisfactory in the cleanup procedure. The procedure was applied to quantitative elution of 42 pesticides representing insecticides, fungicides, and herbicides from a Darco G60-Solka Floe cleanup column. The mean per cent recoveries (3 determinations) ranged from 82 to 112 with C from 2 to 10 for 38 compounds. The mean per cent recovery of EPN was 108 with a C of 13. The per cent recoveries of three compounds were considered low: Thimet 72, Daconil 73, and Guthion 77. Twenty of the pesticides as three mixtures containing 2, 4, and 14 compounds were added to plant extracts of carrots, potatoes, wheat, and pineapples. The mean per cent recovery values ranged from 81 to 108 with a C range of 2 to 10 for 17 compounds