Biology subjects

Harris, M.

Publications and source records attributed to Harris, M..

7 recordsLinked to original sources

bioRxiv2018

Genetic Determinants of Cortical Structure (Thickness, Surface Area and Volumes) among Disease Free Adults in the CHARGE Consortium

Cortical thickness, surface area and volumes (MRI cortical measures) vary with age and cognitive function, and in neurological and psychiatric diseases. We examined heritability, genetic correlations and genome-wide associations of cortical measures across the whole cortex, and in 34 anatomically predefined regions. Our discovery sample comprised 22,822 individuals from 20 cohorts within the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) consortium and the United Kingdom Biobank. Significant associations were replicated in the Enhancing Neuroimaging Genetics through Meta-analysis (ENIGMA) consortium, and their biological implications explored using bioinformatic annotation and pathway analyses. We identified genetic heterogeneity between cortical measures and brain regions, and 161 genome-wide significant associations pointing to wnt/{beta}-catenin, TGF-{beta} and sonic hedgehog pathways. There was enrichment for genes involved in anthropometric traits, hindbrain development, vascular and neurodegenerative disease and psychiatric conditions. These data are a rich resource for studies of the biological mechanisms behind cortical development and aging.

genetics↗

bioRxiv2018

A pivotal role of serine 225 phosphorylation in the function of hepatitis C virus NS5A revealed with the application of a phosphopeptide antiserum and super-resolution microscopy

NS5A is a multi-functional phosphoprotein that plays a key role in both viral replication and assembly. The identity of the kinases that phosphorylate NS5A, and the consequences for HCV biology, remain largely undefined. We previously identified serine 225 (S225) within low complexity sequence (LCS) I as a major phosphorylation site and used a phosphoablatant mutant (S225A) to define a role for S225 phosphorylation in the regulation of genome replication, interactions of NS5A with several host proteins and the sub-cellular localisation of NS5A. To investigate this further, we raised an antiserum to S225 phosphorylated NS5A (pS225). Western blot analysis revealed that pS225 was exclusively found in the hyper-phosphorylated NS5A species. Furthermore, using kinase inhibitors we demonstrated that S225 was phosphorylated by casein kinase 1 (CK1) and polo-like kinase 1 (PLK1). Using a panel of phosphoablatant mutants of other phosphorylation sites in LCSI we obtained the first direct evidence of bidirectional hierarchical phosphorylation initiated by phosphorylation at S225.\n\nUsing super-resolution microscopy (Airyscan and Expansion), we revealed a unique architecture of NS5A-positive clusters in HCV-infected cells - pS225 was concentrated on the surface of these clusters, close to lipid droplets. Pharmacological inhibition of S225 phosphorylation resulted in the condensation of NS5A-positive clusters into larger structures, recapitulating the S225A phenotype. Although S225 phosphorylation was not specifically affected by daclatasvir treatment, the latter also resulted in a similar condensation. These data are consistent with a key role for S225 phosphorylation in the regulation of NS5A function.\n\nImportanceNS5A has obligatory roles in the hepatitis C virus lifecycle, and is proposed to be regulated by phosphorylation. As NS5A is a target for highly effective direct-acting antivirals (DAAs) such as daclatasvir (DCV) it is vital to understand how phosphorylation occurs and regulates NS5A function. We previously identified serine 225 (S225) as a major phosphorylation site. Here we used an antiserum specific for NS5A phosphorylated at S225 (pS225-NS5A) to identify which kinases phosphorylate this residue. Using super-resolution microscopy we showed that pS225 was present in foci on the surface of larger NS5A-positive clusters likely representing genome replication complexes. This location would enable pS225-NS5A to interact with cellular proteins and regulate the function and distribution of these complexes. Both loss of pS225 and DCV treatment resulted in similar changes to the structure of these complexes, suggesting that DAA treatment might target a function of NS5A that is also regulated by phosphorylation.

microbiology↗

bioRxiv2018

Multiple roles of the non-structural protein 3 (nsP3) alphavirus unique domain (AUD) during Chikungunya virus genome replication and transcription

Chikungunya virus (CHIKV) is a re-emerging Alphavirus causing fever, joint pain, skin rash, arthralgia, and occasionally death. Antiviral therapies and/or effective vaccines are urgently required. CHIKV biology is poorly understood, in particular the functions of the non-structural protein 3 (nsP3). Here we present the results of a mutagenic analysis of the alphavirus unique domain (AUD) of nsP3. Informed by the structure of the Sindbis virus AUD and an alignment of amino acid sequences of multiple alphaviruses, a series of mutations in the AUD were generated in a CHIKV sub-genomic replicon. This analysis revealed an essential role for the AUD in CHIKV RNA replication, with mutants exhibiting species- and cell-type specific phenotypes. To test if the AUD played a role in other stages of the virus lifecycle, the mutant panel was also analysed in the context of infectious CHIKV. Results indicated that, in addition to a role in RNA replication, the AUD was also required for virus assembly. Further analysis revealed that one mutant (P247A/V248A) specifically blocked transcription of the subgenomic RNA leading to a dramatic reduction in synthesis of the structural proteins and concomitant reduction in virus production. This phenotype could be explained by both a reduction in the binding of the P247A/V248A mutant nsP3 to viral genomic RNA in vivo, and the reduced affinity of the mutant AUD for the subgenomic promoter RNA in vitro. We propose that the AUD is a pleiotropic protein domain, with multiple functions during CHIKV RNA synthesis.\n\nAuthor summaryChikungunya virus (CHIKV) is an emerging threat to world health. It is transmitted by Aedes species mosquitos, and has caused massive epidemics across the globe. The virus causes fever, rash, arthritis and can sometimes be fatal. The biology of CHIKV is poorly understood, to address this deficiency we aimed to identify functions of one of the viral proteins, nsP3. We focussed on the central part of this protein, termed the alphavirus unique domain (AUD) because it is unique to the genus of viruses to which CHIKV belongs - the Alphaviruses - and not present in other related viruses. By making changes (mutations) in the AUD and analysing the effects of these changes we show that it is involved in multiple stages of the virus lifecycle. These observations identify nsP3 and the AUD in particular as a potential target for antiviral therapy or rational vaccine design.

microbiology↗

bioRxiv2018

Targeting hepatitis C virus p7 channel activity reveals prospect for bimodal antiviral prophylaxis

Since the 1960s, a single class of agent has been licensed targeting virus-encoded ion channels, or \"viroporins\", contrasting the success of channel blocking drugs in other areas of medicine. Although resistance arose to these prototypic adamantane inhibitors of the influenza A virus (IAV) M2 proton channel, a growing number of clinically and economically important viruses are now recognised to encode essential viroporins providing potential targets for modern drug discovery.\n\nWe describe the first rationally designed viroporin inhibitor with a comprehensive structure-activity relationship (SAR). This step-change in understanding not only revealed a second biological function for the p7 viroporin from hepatitis C virus (HCV) during virus entry, but also enabled the synthesis of a labelled tool compound that retained biological activity. Hence, p7 inhibitors (p7i) represent a unique class of HCV antiviral targeting both the spread and establishment of infection, as well as a precedent for future viroporin-targeted drug discovery.

microbiology↗

bioRxiv2018

Persistent Chikungunya Virus Replication in Human Cells is Associated with Presence of Stable Cytoplasmic Granules Containing Non-structural Protein 3

Chikungunya virus (CHIKV), a mosquito-borne human pathogen, causes a disabling disease characterized by severe joint pain that can persist for weeks, months or even years in patients. The non-structural protein 3 (nsP3) plays essential roles during acute infection, but little is known about the function of nsP3 during chronic disease. Here, we used sub-diffraction multi-color microscopy for a spatial and temporal analysis of CHIKV nsP3 within human cells that persistently replicate viral RNA. Round cytoplasmic granules of various sizes (i) contained nsP3 and G3BP Stress Granule Assembly factor; (ii) were next to double-stranded RNA foci, and nsP1-positive structures; and (iii) made contact with markers of the cytoskeleton and cellular structures, such as early endosomes and nucleopores. Analysis of protein turnover and mobility by live-cell microscopy revealed that granules could persist for hours to days, can accumulate newly synthesized protein, and move at differently through the cytoplasm. Granules also had a static internal architecture and were stable in cell lysates. Whereas cells with active replication and stable nsP3-granules did not respond to oxidative stress, refractory cells that had cleared the non-cytotoxic replicon could. In summary, nsP3 can form uniquely stable granular structures that persist long-term within the host cell. This continued presence of viral and cellular protein-complexes has implications for the study of the pathogenic consequences of lingering CHIKV infection and the development of strategies to mitigate the burden of chronic musculoskeletal disease brought about by a medically important arthropod-borne virus (arbovirus).\n\nImportanceChikungunya virus (CHIKV) is a re-emerging alphavirus transmitted by mosquitos and causes widespread transient sickness but also chronic disease affecting muscles and joints. Although no approved vaccines or antivirals are available, a better understanding of the viral life cycle and the role of individual viral proteins can aid in identifying new therapeutic targets. Advances in microscopy and persistent CHIKV model systems now allow researchers to study viral proteins within controlled laboratory environments. Here we established human cells that stably replicate viral RNA and express a tagged version of non-structural protein 3. The ability to track this viral protein within the host cell and during persistent replication can benefit fundamental research efforts to better understand long-term consequences of the persistence of viral protein complexes and thereby provide the foundation for new therapeutic targets to control CHIKV infection and treat chronic disease symptoms.

microbiology↗

bioRxiv2018

Bioelectric-calcineurin signaling module regulates allometric growth and size of the zebrafish fin

The establishment of relative size of organs and structures is paramount for attaining final form and function of an organism. Importantly, variation in the proportions of structures frequently underlies adaptive change in morphology in evolution and maybe a common mechanism underlying selection. However, the mechanism by which growth is integrated within tissues during development to achieve proper proportionality is poorly understood. We have shown that signaling by potassium channels mediates coordinated size regulation in zebrafish fins. Recently, calcineurin inhibitors were shown to elicit changes in zebrafish fin allometry as well. Here, we identify the potassium channel kcnk5b as a key player in integrating calcineurins growth effects, in part through regulation of the cytoplasmic C-terminus of the channel. We propose that the interaction between Kcnk5b and calcineurin acts as a signaling node to regulate allometric growth. Importantly, we find that this regulation is epistatic to inherent mechanisms instructing overall size as inhibition of calcineurin is able to bypass genetic instruction of size as seen in sof and wild-type fins, however, it is not sufficient to re-specify positional memory of size of the fin. These findings integrate classic signaling mediators such as calcineurin with ion channel function in the regulation of size and proportion during growth.

developmental biology↗

bioRxiv2016

Ghrelin-Reactive Autoantibodies are elevated in Children with Prader-Willi Syndrome

Prader-Willi Syndrome (PWS) is a complex genetic disorder characterized by developmental and growth abnormalities, insatiable appetite, and excessive eating (hyperphagia). The underlying cause of hyperphagia in PWS is currently unknown, however, elevated levels of the peptide hormone ghrelin is believed to contribute. Recently, ghrelin-reactive autoantibodies (isotype IgG) were identified in non-genetic obesity. These autoantibodies act as ghrelin carrier proteins and potentiate its orexigenic effects. Here, we describe the identification of ghrelin-reactive autoantibodies in a cohort of 16 children with PWS. In comparison to unaffected siblings, autoantibody levels are significantly increased in PWS children. We further show that autoantibody levels are unaffected by food intake, unlike plasma ghrelin which declines postprandially in both groups. Critically, we also demonstrate that the autoantibodies bind the major circulating ghrelin isoforms, unacylated ghrelin, which does not stimulate appetite, and the orexigen acylated ghrelin. In excess, unacylated ghrelin may compete with acylated ghrelin for autoantibody binding. Taken together, this is the first report on ghrelin-reactive antibodies in a pediatric population, and the first to demonstrate that the antibodies do not discriminate between orexigenic and non-orexigenic ghrelin isoforms. Our work suggests that ghrelin autoantibodies can be targeted using non-orexigenic forms of ghrelin, thereby providing a novel therapeutic target for PWS and for obesity in general.

physiology↗