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Search indexed bioRxiv preprints in genomics, neuroscience, cell biology and bioinformatics. Read source abstracts and check manuscript versions; preprints are not peer reviewed.

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bioRxiv2016

Nanoscale mechanical stimulation method for quantifying C. elegans mechanosensory behavior and memory

Here, we establish a novel economic system to quantify C. elegans mechanosensory behavior and memory by a controllable nanoscale mechanical stimulation. Using piezoelectric sheet speaker, we can flexibly change the vibration properties at a nanoscale displacement level and quantify behavioral responses and memory under the control of each vibration property. This system will facilitate understanding of physiological aspects of C. elegans mechanosensory behavior and memory.

Genetics↗

bioRxiv2016

Fate of glair glands and oocytes in unmated crayfish: a comparison between gonochoristic slough crayfish and parthenogenetic marbled crayfish

In the period before spawning, freshwater crayfish females develop glair glands on the underside of the pleon. These glands produce the mucus for a transient tent-like structure in which the eggs are fertilized and attached to the pleopods. Long-term observation of females of the bisexually reproducing slough crayfish, Procambarus fallax, kept in captivity revealed that glair glands developed in late winter and late summer of each year independent of the presence of males. However, in contrast to mated females unmated females did neither form a fertilization tent nor spawn. Their glair glands persisted for an unusually long period of time and disappeared only during the next moult. Apparently, females use information on sperm availability to either reproduce or save the resources. Marbled crayfish, Procambarus virginalis, a parthenogenetic descendant of slough crayfish, developed glair glands in approximately the same periods of the year but spawned despite of the absence of mating. These findings indicate that on their way from gonochorism to parthenogenesis regulation of glair gland activity and spawning has been decoupled from mating. Therefore, the species pair Procambarus fallax/Procambarus virginalis seems to be particularly suitable to investigate the physiological, molecular and genetic mechanisms underlying spawning in freshwater crayfish.

Zoology↗

bioRxiv2016

Nonsinusoidal oscillations underlie pathological phase-amplitude coupling in the motor cortex in Parkinson’s disease

Parkinsons disease (PD) is associated with abnormal beta oscillations (13-30 Hz) in the basal ganglia and motor cortex (M1). Recent reports show that M1 beta-high gamma (50-200 Hz) phase-amplitude coupling (PAC) is exaggerated in PD and is reduced following acute deep brain stimulation (DBS). Here we analyze invasive M1 electrocorticography recordings in PD patients on and off DBS, and in isolated cervical dystonia patients, and show that M1 beta oscillations are nonsinusoidal, having sharp and asymmetric features. These sharp oscillatory beta features underlie the previously reported PAC, providing an alternative to the standard interpretation of PAC as an interaction between two distinct frequency components. Specifically, the ratio between peak and trough sharpness is nearly perfectly correlated with beta-high gamma PAC (r = 0.96) and predicts PD-related motor deficit. Using a simulation of the local field potential, we demonstrate that sharp oscillatory waves can arise from synchronous synaptic activity. We propose that exaggerated beta-high gamma PAC may actually reflect such synchronous synaptic activity, manifesting as sharp beta oscillations that are \"smoothed out\" with DBS. These results support the \"desynchronization\" hypothesis of DBS wherein DBS counteracts pathological synchronization throughout the basal ganglia-thalamocortical loop. We argue that PAC can be influenced by more than one mechanism. In this case synaptic synchrony, rather than the often assumed spike-field coherence, may underlie exaggerated PAC. These often overlooked temporal features of the oscillatory waveform carry critical physiological information about neural processes and dynamics that may lead to better understanding of underlying neuropathology.

Neuroscience↗

bioRxiv2016

Epigenetic control of phenotypic plasticity in a filamentous fungus Neurospora crassa

Phenotypic plasticity is the ability of a genotype to produce different phenotypes under different environmental or developmental conditions. Phenotypic plasticity is an ubiquitous feature of living organisms, and is typically based on variable patterns of gene expression. However, the mechanisms by which gene expression is influenced and regulated during plastic responses are poorly understood in most organisms. While modifications to DNA and histone proteins have been implicated as likely candidates for generating and regulating phenotypic plasticity, specific details of each modification and its mode of operation have remained largely unknown. In this study, we investigated how epigenetic mechanisms affect phenotypic plasticity in the filamentous fungus Neurospora crassa. By measuring reaction norms of strains that are deficient in one of several key physiological processes we show that epigenetic mechanisms play a role in homeostasis and phenotypic plasticity of the fungus across a range of controlled environments. Effects on plasticity are specific to an environment and mechanism, indicating that epigenetic regulation is context dependent and is not governed by general plasticity genes. In our experiments with Neurospora, histone methylation and the RNA interference pathway had the greatest influence on phenotypic plasticity, while lack of DNA methylation had the least.

Genetics↗

bioRxiv2016

The Higher Plant Plastid Complex I (NDH) is a Reversible Proton Pump that increases ATP production by Cyclic Electron Flow Around Photosystem I

Cyclic electron flow around photosystem I (CEF) is critical for balancing the photosynthetic energy budget of the chloroplast, by generating ATP without net production of NADPH. We demonstrate that the chloroplast NADPH dehydrogenase complex (NDH), a homolog to respiratory Complex I, pumps approximately two protons from the chloroplast stroma to the lumen per electron transferred from ferredoxin to plastoquinone, effectively increasing the efficiency of ATP production via CEF by two-fold compared to CEF pathways involving non-proton-pumping plastoquinone reductases. Under certain physiological conditions, the coupling of proton and electron transfer reactions within NDH should enable a non-canonical mode of photosynthetic electron transfer, allowing electron transfer from plastoquinol to NADPH to be driven by the thylakoid proton motive force possibly helping to sense or remediate mismatches in the photosynthetic budget.

Biochemistry↗

bioRxiv2016

Scalable Production of Human Erythrocytes from Induced Pluripotent Stem Cells

In vitro production of erythrocytes in physiologic numbers from human induced pluripotent stem cells (hiPSCs) holds great promise for improved transfusion medicine and novel cell therapies. We report here, for the first time, a strategy for scalable and xeno-free differentiation of hematopoietic stem/progenitor cells from hiPSCs and subsequent erythrocytes specification, by using stepwise cell culture conditions and by integrating spinner flasks and rocker. This system supported robust and reproducible definitive hematopoietic differentiation of multiple hiPSC lines. We demonstrated an ultra-high yield of up to 4x109 CD235a+ erythrocytes at >98% purity when using a 1-litre spinner flask for suspension culture. Erythrocytes generated from our system can reach a mature stage with red blood cell (RBC) characteristics of enucleation, {beta}-globin protein expression and oxygen-binding ability. The entire process is xeno-free and clinically compliant, allowing future mass production of hiPSC-derived RBCs for transfusion medicine purposes.

Bioengineering↗

bioRxiv2016

Integrated Biomedical System

Capabilities for generating and storing large amounts of data relevant to individual health and performance are rapidly evolving and have the potential to accelerate progress toward quantitative and individualized understanding of many important issues in health and medicine. Recent advances in clinical and laboratory technologies provide increasingly complete and dynamic characterization of individual genomes, gene expression levels for genes, relative abundance of thousands of proteins, population levels for thousands of microbial species, quantitative imaging data, and more - all on the same individual. Personal and wearable electronic devices are increasingly enabling these same individuals to routinely and continuously capture vast amounts of quantitative data including activity, sleep, nutrition, environmental exposures, physiological signals, speech, and neurocognitive performance metrics at unprecedented temporal resolution and scales. While some of the companies offering these measurement technologies have begun to offer systems for integrating and displaying correlated individual data, these are either closed/proprietary platforms that provide limited access to sensor data or have limited scope that focus primarily on one data domain (e.g. steps/calories/activity, genetic data, etc.). The Integrated Biomedical System is being developed to demonstrate an adaptable open-source tool for reducing the burden associated with integrating heterogeneous genome, interactome, and exposome data from a constantly evolving landscape of biomedical data generating technologies. The Integrated Biomedical System provides a scalable and modular framework that can be extended to include support for numerous types of analyses and applications at scales ranging from personal users, communities and groups, to large populations.\n\nDisclaimerThis work is sponsored by the Assistant Secretary of Defense for Research & Engineering under Air Force Contract #FA8721-05-C-0002. Opinions, interpretations, recommendations and conclusions are those of the author and are not necessarily endorsed by the United States Government.

Bioinformatics↗

bioRxiv2016

Membrane tension is a key determinant of bud morphology in clathrin-mediated endocytosis

A critical step in cellular trafficking pathways is the budding of membranes by protein coats, which recent experiments have demonstrated can be inhibited by elevated membrane tension. The robustness of processes like clathrin-mediated endocytosis (CME) across a diverse range of organisms and mechanical environments suggests that the protein machinery in this process has evolved to take advantage of some set of physical design principles to ensure robust vesiculation against opposing forces like membrane tension. Using a theoretical model for membrane mechanics and membrane protein interaction, we have systematically investigated the influence of membrane rigidity, curvature induced by the protein coat, area covered by the protein coat, membrane tension and force from actin polymerization on bud formation. Under low tension, the membrane smoothly evolves from a flat to budded morphology as the coat area or spontaneous curvature increases, whereas the membrane remains essentially flat at high tensions. At intermediate, physiologically relevant, tensions, the membrane undergoes a snapthrough instability in which small changes in the coat area, spontaneous curvature or membrane tension cause the membrane to \"snap\" from an open, U-shape to a closed bud. This instability can be smoothed out by increasing the bending rigidity of the coat, allowing for successful budding at higher membrane tensions. Additionally, applied force from actin polymerization can bypass the instability by inducing a smooth transition from an open to a closed bud. Finally, a combination of increased coat rigidity and force from actin polymerization enables robust vesiculation even at high membrane tensions.\n\nSignificance statementPlasma membrane tension plays an important role in various biological processes. In particular, recent experimental studies have shown that membrane tension inhibits membrane budding processes like clathrin-mediated endocytosis (CME). We have identified a mathematical relationship between the curvature-generating capability of the protein coat and membrane tension that can predict whether the coat alone is sufficient to produce closed buds. Additionally, we show that a combination of increased coat rigidity and applied force from actin polymerization can produce closed buds at high membrane tensions. These findings are general to any membrane budding process, suggesting that biology has evolved to take advantage of a set of physical design principles to ensure robust vesicle formation across a range of organisms and mechanical environments.\n\nAuthor ContributionsJ.E.H., G.O., and P.R. designed research. J.E.H. performed research. J.E.H., D.G.D., and P.R. analyzed data. J.E.H., G.O., D.G.D., and P.R. wrote the paper.

Biophysics↗

bioRxiv2016

MALT: Fast alignment and analysis of metagenomic DNA sequence data applied to the Tyrolean Iceman

Modern next generation sequencing technologies produce vast amounts of data in the context of large-scale metagenomic studies, in which complex microbial communities can be reconstructed to an unprecedented level of detail. Most prominent examples are human microbiome studies that correlate the bacterial taxonomic profile with specific physiological conditions or diseases.\n\nIn order to perform these analyses high-throughput computational tools are needed that are able to process these data within a short time while preserving a high level of sensitivity and specificity.\n\nHere we present MALT (MEGAN ALignment Tool) a program for the ultrafast alignment and analysis of metagenomic DNA sequencing data. MALT processes hundreds of millions of sequencing reads within only a few hours. In addition to the alignment procedure MALT implements a taxonomic binning algorithm that is able to specifically assign reads to bacterial species. Its tight integration with the interactive metagenomic analysis software MEGAN allows for visualization and further analyses of results.\n\nWe demonstrate MALT by its application to the metagenomic analysis of two ancient microbiomes from oral cavity and lung samples of the 5,300-year-old Tyrolean Iceman. Despite the strong environmental background, MALT is able to pick up the weak signal of the original microbiomes and identifies multiple species that are typical representatives of the respective host environment.

Bioinformatics↗

bioRxiv2016

Complex molecular mixtures under cycling gradients as basis for lifes origins

We consider life as a cyclic physicochemical process that makes heredity and Darwinian evolution observable through living cells. We elaborate four principles that constrain current speculations about lifes emergence to natural processes driven by diurnal physicochemical gradients, primarily of temperature, water activity and electromagnetic radiation. First, Earths prebiotic chemical evolution is historically continuous with Darwinian evolution; second, cycling energies of solar radiation are primary drivers of chemical evolution; third, environmental molecular complexity must be high at the origin of life; and fourth, non-covalent molecular forces determine molecular recognition and cellular organization. Under normal physiological conditions of high ionic strength and high macromolecular crowding, hydration interactions (hydrogen bonding), screened electrostatic forces and excluded volume repulsions act over a commensurate distance of about one nanometer. This intermolecular distance governs chemical coevolution of proto-biomacromolecular surfaces (nucleic acids, proteins and membranes) toward Darwinian thresholds and living states. The above physicochemical principles of lifes emergence are consistent with the second law of thermodynamics, and with the current facts of molecular microbiology and planetary sciences. New kinds of experimentation with crowded molecular mixtures under oscillating temperature gradients - a PCR-like mechanism of lifes origins - can further illuminate how living states come about.\n\nGraphical abstractLifes emergence follows from chemical and Darwinian evolution, a high degree of molecular complexity and a high crowdedness, and non-covalent molecular forces that determine molecular recognition and cellular organization. The macromolecules divide the cytoplasm into dynamically crowded macromolecular regions and topologically complementary electrolyte pools. Small ions and ionic metabolites are transported vectorially between the electrolyte pools and through the (semi-conducting) electrolyte pathways of the crowded macromolecular regions.\n\n\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=103 SRC=\"FIGDIR/small/050740_fig1.gif\" ALT=\"Figure 1\">\nView larger version (36K):\norg.highwire.dtl.DTLVardef@1963682org.highwire.dtl.DTLVardef@d49be0org.highwire.dtl.DTLVardef@45ac46org.highwire.dtl.DTLVardef@312efc_HPS_FORMAT_FIGEXP M_FIG C_FIG

Microbiology↗

bioRxiv2016

Serotonin-dependent kinetics of bursts of feeding underlie a graded response to food availability

Animals integrate physiological and environmental signals to modulate their food uptake. Failure to regulate feeding may have devastating results, including obesity and diabetes, underscoring the importance of understanding its underlying mechanisms. The nematode C. elegans, whose food uptake consists of pumping bacteria from the environment into the gut, provides excellent opportunities for discovering principles of conserved regulatory mechanisms. Here we show that worms implement a graded feeding response to the concentration of environmental bacteria by modulating a commitment to bursts of fast pumping. Using long-term, high-resolution, longitudinal recordings of feeding dynamics under defined conditions, we find that the frequency and duration of pumping bursts increase and the duration of long pauses diminishes in environments richer in bacteria. The bioamine serotonin, a known feeding regulator in metazoa, is required for food-dependent induction of bursts as well as for maintaining their high rate of pumping through two distinct mechanisms. Following this phenotype quantitatively we identify the essential serotonergic neurons and the differential roles of distinct families of serotonin receptors. We propose that regulation of bursts is a conserved mechanism of behavior and motor control.

Animal Behavior and Cognition↗

bioRxiv2016

Acidic pH is a Metabolic Switch for 2‐Hydroxyglutarate Generation and Signaling

2-hydroxyglutarate (2-HG) is an important epigenetic regulator, with potential roles in cancer and stem cell biology. The D (R) enantiomer (D-2-HG) is an oncometabolite generated from ketoglutarate (-KG) by mutant isocitrate dehydrogenase (ICDH), while L (S) 2-HG is generated by lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) in response to hypoxia. Since acidic pH is a common feature of hypoxia, as well as tumor and stem cell microenvironments, we hypothesized that pH may regulate cellular 2-HG levels. Herein we report that cytosolic acidification under normoxia moderately elevated 2-HG in cells, and boosting endogenous substrate -KG levels further stimulated this elevation. Studies with isolated LDH-1 and MDH-2 revealed that generation of 2-HG by both enzymes was stimulated several-fold at acidic pH, relative to normal physiologic pH. In addition, acidic pH was found to inhibit the activity of the mitochondrial L-2-HG removal enzyme L-2-HG dehydrogenase, and to stimulate the reverse reaction of ICDH (carboxylation of KG to isocitrate). Furthermore, since acidic pH is known to stabilize hypoxia-inducible factor (HIF), and 2-HG is a known inhibitor of HIF prolyl hydroxylases, we hypothesized that 2-HG may be required for acid-induced HIF stabilization. Accordingly, cells stably over-expressing L-2HGDH exhibited a blunted HIF response to acid. Together these results suggest that acidosis is an important and previously overlooked regulator of 2-HG accumulation and other oncometabolic events, with implications for HIF signaling.

Biochemistry↗

bioRxiv2016

Shear-induced nitric oxide production by endothelial cells

We present a biochemical model of the wall shear stress (WSS)-induced activation of endothelial nitric oxide synthase (eNOS) in an endothelial cell (EC). The model includes three key mechanotransducers: mechanosensing ion channels, integrins and G-protein-coupled receptors. The reaction cascade consists of two interconnected parts. The first is rapid activation of calcium, which results in formation of calcium-calmodulin complexes, followed by recruitment of eNOS from caveolae. The second is phosphoryaltion of eNOS by protein kinases PKC and AKT. The model also includes a negative feedback loop due to inhibition of calcium influx into the cell by cyclic guanosine monophosphate (cGMP). In this feedback, increased nitric oxide (NO) levels cause an increase in cGMP levels, so that cGMP inhibition of calcium influx can limit NO production. The model was used to predict the dynamics of NO production by an EC subjected to a step increase of WSS from zero to a finite physiologically relevant value. Among several experimentally observed features, the model predicts a highly nonlinear, bipha-sic transient behavior of eNOS activation and NO production: a rapid initial activation due to the very rapid influx of calcium into the cytosol (occurring within 1 to 5 minutes) is followed by a sustained period of activation due to protein kinases.\n\nAcronymsAKT, protein kinase B; [Ca2+]c, [Ca2+]s, [Ca2+]e and [Ca2+]b, cytosolic, stored, external and buffer concentrations of calcium ions, respectively; Ca3-CaM and Ca4-CaM, calcium-calmodulin complexes with 3 and 4 calcium ions bound to CaM, respectively; CaM, calmodulin; CCE, capacitative calcium entry; cGMP, cyclic guanosine monophosphate; EC, endothelial cell; ECM, extracellular matrix; eNOS, endothelial nitric oxide synthase; eNOScav, eNOS bound to caveolin; eNOS*, eNOS-CaM complex phosphorylated at Ser-1197; eNOS0, caveolin-bound eNOS phosphorylated at Thr-495; ER, endoplasmic reticulum; FAK, focal adhesion kinase; G, active G proteins; Gt, total G proteins; GPCR, G-protein-coupled receptors; Hsp90, heat shock protein 90; GTP, guanosine triphosphate; IP3, inositol triphosphate; L-Arg, L-form of arginine; MSIC, mechanosensing ion channel; NO, nitric oxide; O2, oxygen; PIP2, phosphatidylinositol 4,5-bisphosphate; PIP3, phos-phatidylinositol (3,4,5)-triphosphate; PI3K, phosphatidylinositide 3-kinases; PKC, protein kinase C; RBC, red blood cell; sGC, soluble guanylate cyclase; WSS, wall shear stress

Systems Biology↗

bioRxiv2016

Nicotine affects protein complex rearrangement in Caenorhabditis elegans cells

Nicotine may affect cell function by rearranging protein complexes. We aimed to determine nicotine-induced alterations of protein complexes in Caenorhabditis elegans cells, thereby revealing links between nicotine exposure and protein complex modulation. We compared the proteomic alterations induced by low and high nicotine concentrations (0.01 mM and 1 mM) with the control (no nicotine) in vivo by using mass spectrometry (MS)-based techniques, specifically the CTAB discontinuous gel electrophoresis coupled with liquid chromatography (LC-MS/MS and spectral counting. As a result, we identified dozens of C. elegans proteins that are present exclusively or in higher abundance in either nicotine-treated or untreated worms. Based on these results, we report a network that captures the key protein components of nicotine-induced protein complexes and speculate how the different protein modules relate to their distinct physiological roles. Using functional annotation of detected proteins, we hypothesize that the identified complexes can modulate the energy metabolism and level of oxidative stress. These proteins can also be involved in modulation of gene expression and may be crucial in Alzheimers disease. The findings reported in our study reveal intracellular interactions of many proteins with cytoskeleton and may contribute to the understanding of the mechanisms of nicotinic acetylcholine receptor (nAChR) signaling and trafficking in cells.\n\nSignificance of the studyMost of us are affected by nicotine, not only because of the common use of tobacco products. Nicotine is also included in many popular vegetables of the family Solanaceae, such as tomatoes and peppers. However, these two sources provide the body with radically different doses of nicotine.\n\nStrong biological effects of nicotine rely on binding to the nicotinic receptor, which partially mimics the action of the natural hormone acetylcholine. In our study we used the nematode Caenorhabditis elegans as a model organism. General principles of functioning of human cells and C. elegans cells are similar. The worm is, however, a compromise between simplicity and complexity, which may facilitate understanding of the more complex systems, like the human body. Our study revealed in the presence of a low nicotine concentration a different composition of polypeptides in the organism than in the presence of a high nicotine concentration. The rearrangements of protein complexes concern proteins involved e.g. in the course of Alzheimers disease, which seems interesting in the context of our aging societies. From the perspective of the development of biological research, the ability to identify the components of large protein complexes can contribute to a better understanding of the functioning of cells.

Cell Biology↗

bioRxiv2016

Cerebellar learning using perturbations

The cerebellum aids the learning and execution of fast coordinated movements, with acquired information being stored by plasticity of parallel fibre--Purkinje cell synapses. According to the current consensus, erroneously active parallel fibre synapses are depressed by complex spikes arising when climbing fibres signal movement errors. However, this theory cannot solve the credit assignment problem of using the limited information from a global movement evaluation to optimise behaviour by guiding the plasticity in numerous neurones. We identify the possible implementation of an algorithm solving this problem, whereby spontaneous complex spikes perturb ongoing movements, create an eligibility trace for plasticity and signal resulting error changes to guide plasticity. These error changes are extracted by adaptively cancelling the average error. This framework, stochastic gradient descent with estimated global errors, generates specific predictions for synaptic plasticity rules that contradict the current consensus. However, in vitro plasticity experiments under physiological conditions verified our predictions, highlighting the sensitivity of plasticity studies to unphysiological conditions. Using numerical and analytical approaches we demonstrate the convergence and estimate the capacity of learning in our implementation. Finally, a similar mechanism may operate during optimisation of action sequences by the basal ganglia, where dopamine could both initiate movements and signal rewards, analogously to the dual perturbation and correction role of the climbing fibre outlined here.

Neuroscience↗

bioRxiv2016

Circadian rhythms have significant effects on leaf-to-canopy gas exchange under field conditions

Molecular clocks drive oscillations in leaf photosynthesis, stomatal conductance and other cell and leaf level processes over ~24 h under controlled laboratory conditions. The influence of such circadian regulation over whole canopy fluxes remains uncertain and diurnal CO2 and H2O vapor flux dynamics in the field are currently interpreted as resulting almost exclusively from direct physiological responses to variations in light, temperature and other environmental factors. We tested whether circadian regulation would affect plant and canopy gas exchange at the CNRS Ecotron. Canopy and leaf level fluxes were constantly monitored under field-like environmental conditions, and also under constant environmental conditions (no variation in temperature, radiation or other environmental cues). Here we show first direct experimental evidence at canopy scales of circadian gas exchange regulation: 20-79% of the daily variation range in CO2 and H2O fluxes occurred under circadian entrainment in canopies of an annual herb (bean) and of a perennial shrub (cotton). We also observed that considering circadian regulation improved performance in commonly used stomatal conductance models. Overall, our results show that overlooked circadian controls affect diurnal patterns of CO2 and H2O fluxes in entire canopies and in field-like conditions, although this process is currently unaccounted for in models.

Plant Biology↗

bioRxiv2016

Substoichiometric molecular control and amplification of the initiation and nature of amyloid fibril formation: lessons from and for blood clotting. BioRXiv preprint.

The chief and largely terminal element of normal blood clotting is considered to involve the polymerisation of the mainly -helical fibrinogen to fibrin, with a binding mechanism involving knobs and holes but with otherwise littl change in protein secondary structure. We recognise, however, that extremely unusual mutations, or mechanical stressing, can cause fibrinogen to adopt a conformation containing extensive {beta}-sheets. Similarly, prions can change morphology from a largely alpha-helical to a largely {beta}-sheet conformation, and the latter catalyses both the transition and the self-organising polymerisation of the {beta}-sheet structures. Many other proteins can do this, where it is known as amyloidogenesis. When fibrin is formed in samples from patients harbouring different diseases it can have widely varying diameters and morphologies. We here develop the idea, and summarise the evidence, that in many cases the anomalous fibrin fibre formation seen in such diseases actually amounts to amyloidogenesis. In particular, fibrin can interact withthe amyloid-{beta} (A{beta}) protein that is misfolded in Alzheimer's disease. Seeing these unusual fibrin morphologies as true amyloids explains a great deal about fibrin(ogen) biology that was previously opaque, and provides novel strategies for treating such coagulopathies. The literature on blood clotting can usefully both inform and be informed by that on prions and on the many other widely recognised ({beta})-amyloid proteins.\n\n\"Novel but physiologically important factors that affect fibrinolysis have seldom been discovered and characterized in recent years\" [1]

Pathology↗

bioRxiv2016

Genetic Influences on Hormonal Markers of Chronic HPA Function in Human Hair

Cortisol is the primary output of the hypothalamic-pituitary-adrenal (HPA) axis and is central to the human biological stress response, with wide-ranging effects on physiological function and psychiatric health. In both humans and animals, cortisol is frequently studied as a biomarker for exposure to environmental stress. Relatively little attention has been paid to the possible role of genetic variation in heterogeneity in chronic cortisol, in spite of well-studied biological pathways of glucocorticoid function. Using recently developed technology, hair samples can now be used to measure accumulation of cortisol over several months. In contrast to more conventional salivary measures, hair cortisol is not influenced by diurnal variation or transient hormonal reactivity. In an ethnically and socioeconomically diverse sample of 1 070 child and adolescent twins and multiples from 556 unique families, we estimated genetic and environmental influences on hair concentrations of cortisol and its inactive metabolite, cortisone. We identified sizable genetic influences on cortisol that decrease with age, concomitant with genetic influences on cortisone that increase with age. Shared environmental influences on cortisol and cortisone were modest and, for cortisol, decreased with age. Twin-specific, non-shared environmental contributions to cortisol and cortisone became increasingly correlated with age. We find some evidence for sex differences in the biometric contributions to cortisol, but no strong evidence for main or moderating effects of family socioeconomic status on cortisol or cortisone. This study constitutes the first genetic study of hormone concentrations in human hair, and provides the most definitive characterization to-date of age and socioeconomic influences on hair cortisol.

Genetics↗