(PVDF)2(PEO)2 miktoarm star copolymers: Synthesis and isothermal crystallization leading to exclusive β-phase formation

In this work, we study how chain topology can induce different polymorphic behaviors in poly(vinylidene fluoride) (PVDF)-based materials. A linear PVDF precursor with two azido groups at the junction point, (PVDFx-N3)2 and three 4-miktoarm star copolymers (PVDFx)2-b-(PEOy)2 with two poly(ethylene oxide) (PEO) and two PVDF arms were synthesized and employed in this study. The amphiphilic miktoarm copolymers were prepared by a combination of anionic ring-opening polymerization, iodine transfer radical polymerization (ITP), and copper-catalyzed azide-alkyne cycloaddition (CuAAC). They have practically similar overall molar mass but different compositions, ideal for performing bulk morphology and crystallization investigations. The isothermal overall crystallization kinetics of the PVDF and PEO arms of the 4-miktoarm star copolymers and representative PEO and PVDF precursors was determined by Differential Scanning Calorimetry (DSC). The results indicate that the star arms crystallized faster than the equivalent precursors as the kinetics are dominated by nucleation effects. The phases formed by the PVDF components in the materials examined were analyzed by studying their melting behavior by DSC, their superstructural morphology by Polarized Light Optical Microscopy (PLOM), and the phase structure by Fourier Transform Infrared Spectroscopy (FTIR). The linear PVDF and (PVDF29-N3)2, exhibited α, β and γ-phases (with a majority of β-phase formation) during melting after isothermal crystallization. The ratio of the different phases depends on the crystallization temperature. An analysis of the multiple melting behavior indicated that the sample forms both α and β-phases initially, and the α-phase partially transforms into the γ-phase during isothermal crystallization when the temperature of crystallization increases. We found a remarkable behavior for the 4-miktoarm star copolymers, as the PVDF arms only form the ferroelectric β-phase when all three materials were isothermally crystallized regardless of the crystallization temperature employed. The presence of the polymorphism in the PVDF was detected by DSC, PLOM, and FTIR. Hence, we have shown that tailoring chain topology in PVDF copolymers can lead to exclusive β-phase formation, a path that can be exploited for future piezoelectric applications.We acknowledge funding from MICINN through grant PID2020-113045GB-C21. We would also like to acknowledge the support of the Basque Government through grant IT1503-22. N. M. thankfully acknowledges his Ph.D. fellowship from the POLYMAT Basque Center for Macromolecular Design and Engineering. J. M. acknowledges partial financial support from the IBERDROLA Foundation. Y.P., G.P., A.P., V.R., and N.H. thankfully acknowledge the support of King Abdullah University of Science and Technology (KAUST)

Site-specific perturbations of alpha-synuclein fibril structure by the Parkinson's disease associated mutations A53T and E46K.

PMCID: PMC3591419This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Parkinson's disease (PD) is pathologically characterized by the presence of Lewy bodies (LBs) in dopaminergic neurons of the substantia nigra. These intracellular inclusions are largely composed of misfolded α-synuclein (AS), a neuronal protein that is abundant in the vertebrate brain. Point mutations in AS are associated with rare, early-onset forms of PD, although aggregation of the wild-type (WT) protein is observed in the more common sporadic forms of the disease. Here, we employed multidimensional solid-state NMR experiments to assess A53T and E46K mutant fibrils, in comparison to our recent description of WT AS fibrils. We made de novo chemical shift assignments for the mutants, and used these chemical shifts to empirically determine secondary structures. We observe significant perturbations in secondary structure throughout the fibril core for the E46K fibril, while the A53T fibril exhibits more localized perturbations near the mutation site. Overall, these results demonstrate that the secondary structure of A53T has some small differences from the WT and the secondary structure of E46K has significant differences, which may alter the overall structural arrangement of the fibrils

The LRRK2-macroautophagy axis and its relevance to Parkinson's Disease

A wide variety of different functions and an impressive array of interactors have been associated with leucine-rich repeat kinase 2 (LRRK2) over the years. Here, I discuss the hypothesis that LRRK2 may be capable of interacting with different proteins at different times and places, therefore, controlling a plethora of diverse functions based on the different complexes formed. Among these, I will then focus on macroautophagy in the general context of the endolysosomal system. First, the relevance of autophagy in Parkinson's disease will be evaluated giving a brief overview of all the relevant Parkinson's disease genes; then, the association of LRRK2 with macroautophagy and the endolysosomal pathway will be analyzed based on the supporting literature

Pre-Fibrillar α-Synuclein Mutants Cause Parkinson's Disease-Like Non-Motor Symptoms in Drosophila

Parkinson's disease (PD) is linked to the formation of insoluble fibrillar aggregates of the presynaptic protein α-Synuclein (αS) in neurons. The appearance of such aggregates coincides with severe motor deficits in human patients. These deficits are often preceded by non-motor symptoms such as sleep-related problems in the patients. PD-like motor deficits can be recapitulated in model organisms such as Drosophila melanogaster when αS is pan-neurally expressed. Interestingly, both these deficits are more severe when αS mutants with reduced aggregation properties are expressed in flies. This indicates that that αS aggregation is not the primary cause of the PD-like motor symptoms. Here we describe a model for PD in Drosophila which utilizes the targeted expression of αS mutants in a subset of dopadecarboxylase expressing serotonergic and dopaminergic (DA) neurons. Our results show that targeted expression of pre-fibrillar αS mutants not only recapitulates PD-like motor symptoms but also the preceding non-motor symptoms such as an abnormal sleep-like behavior, altered locomotor activity and abnormal circadian periodicity. Further, the results suggest that the observed non-motor symptoms in flies are caused by an early impairment of neuronal functions rather than by the loss of neurons due to cell death

Progressive Neurodegeneration or Endogenous Compensation in an Animal Model of Parkinson's Disease Produced by Decreasing Doses of Alpha-Synuclein

The pathological hallmarks of Parkinson's disease (PD) are degeneration of dopamine (DA) neurons of the substantia nigra (SN) and the presence of alpha-synuclein (α-syn)-rich Lewy bodies in DA cells that remain. To model these aspects of the disease, we previously showed that high titer (5.1×10exp12 gp/ml) AAV1/2 driven expression of A53T α-syn in the SN of rats caused nigrostriatal pathology including a loss of DA neurons, but also with toxicity in the GFP control group. In the current study, we evaluate the effects of two lower titers by dilution of the vector (1∶3 [1.7×10exp12] and 1∶10 [5.1×10exp11]) to define a concentration that produced pathology specific for α-syn. In GFP and empty vector groups there were no behavioural or post-mortem changes at 3 or 6 weeks post-administration at either vector dose. Dilution of the AAV1/2 A53T α-syn (1∶3) produced significant paw use asymmetry, reductions in striatal tyrosine hydroxylase (TH), and increases in DA turnover at 3 weeks in the absence of overt pathology. By 6 weeks greater evidence of pathology was observed and included, reductions in SN DA neurons, striatal DA, TH and DA-transporter, along with a sustained behavioural deficit. In contrast, the 1∶10 AAV1/2 A53T α-syn treated animals showed normalization between 3 and 6 weeks in paw use asymmetry, reductions in striatal TH, and increased DA turnover. Progression of dopaminergic deficits using the 1∶3 titer of AAV1/2 A53Tα-syn provides a platform for evaluating treatments directed at preventing and/or reversing synucleinopathy. Use of the 1∶10 titer of AAV1/2 A53T α-syn provides an opportunity to study mechanisms of endogenous compensation. Furthermore, these data highlight the need to characterize the titer of vector being utilized, when using AAV to express pathogenic proteins and model disease process, to avoid producing non-specific effects

Acute increase of alpha-synuclein inhibits synaptic vesicle recycling evoked during intense stimulation

This work was supported by grants from the NIH/National Institute of Neurological Disorder and Stroke RO1 NS078165 (to J.R.M.), the Morton Cure Paralysis Fund (to J.R.M.), and the Branfman Family Foundation (to J.M.G.) and by a Dorothea Bennett graduate fellowship (to D.J.B.)

Physiological and Pathological Role of Alpha-synuclein in Parkinson’s Disease Through Iron Mediated Oxidative Stress; The Role of a Putative Iron-responsive Element

Parkinson’s disease (PD) is the second most common progressive neurodegenerative disorder after Alzheimer’s disease (AD) and represents a large health burden to society. Genetic and oxidative risk factors have been proposed as possible causes, but their relative contribution remains unclear. Dysfunction of alpha-synuclein (α-syn) has been associated with PD due to its increased presence, together with iron, in Lewy bodies. Brain oxidative damage caused by iron may be partly mediated by α-syn oligomerization during PD pathology. Also, α-syn gene dosage can cause familial PD and inhibition of its gene expression by blocking translation via a newly identified Iron Responsive Element-like RNA sequence in its 5’-untranslated region may provide a new PD drug target

Parkinson’s disease mouse models in translational research

Animal models with high predictive power are a prerequisite for translational research. The closer the similarity of a model to Parkinson’s disease (PD), the higher is the predictive value for clinical trials. An ideal PD model should present behavioral signs and pathology that resemble the human disease. The increasing understanding of PD stratification and etiology, however, complicates the choice of adequate animal models for preclinical studies. An ultimate mouse model, relevant to address all PD-related questions, is yet to be developed. However, many of the existing models are useful in answering specific questions. An appropriate model should be chosen after considering both the context of the research and the model properties. This review addresses the validity, strengths, and limitations of current PD mouse models for translational research

Whole-genome sequencing reveals host factors underlying critical COVID-19

Critical COVID-19 is caused by immune-mediated inflammatory lung injury. Host genetic variation influences the development of illness requiring critical care1 or hospitalization2–4 after infection with SARS-CoV-2. The GenOMICC (Genetics of Mortality in Critical Care) study enables the comparison of genomes from individuals who are critically ill with those of population controls to find underlying disease mechanisms. Here we use whole-genome sequencing in 7,491 critically ill individuals compared with 48,400 controls to discover and replicate 23 independent variants that significantly predispose to critical COVID-19. We identify 16 new independent associations, including variants within genes that are involved in interferon signalling (IL10RB and PLSCR1), leucocyte differentiation (BCL11A) and blood-type antigen secretor status (FUT2). Using transcriptome-wide association and colocalization to infer the effect of gene expression on disease severity, we find evidence that implicates multiple genes—including reduced expression of a membrane flippase (ATP11A), and increased expression of a mucin (MUC1)—in critical disease. Mendelian randomization provides evidence in support of causal roles for myeloid cell adhesion molecules (SELE, ICAM5 and CD209) and the coagulation factor F8, all of which are potentially druggable targets. Our results are broadly consistent with a multi-component model of COVID-19 pathophysiology, in which at least two distinct mechanisms can predispose to life-threatening disease: failure to control viral replication; or an enhanced tendency towards pulmonary inflammation and intravascular coagulation. We show that comparison between cases of critical illness and population controls is highly efficient for the detection of therapeutically relevant mechanisms of disease