Physiotherapists' Adoption and Perceptions of Tele-Rehabilitation for Cardiorespiratory Care in Response to COVID-19.

Purpose: The use of tele-rehabilitation as a mode for physiotherapy services was widely implemented following the onset of the coronavirus disease 2019 (COVID-19) pandemic. This study explored the perceived value and experiences of physiotherapists relating to tele-rehabilitation for cardiorespiratory care. Method: Semi-structured interviews were conducted with physiotherapists who provided tele-rehabilitation to adults with cardiorespiratory conditions between March 11 and December 31, 2020. Interviews were analyzed using conventional content analysis. Results: Seven participants were interviewed; six practising solely in pulmonary rehabilitation and one practising in both pulmonary and cardiac rehabilitation. Three major themes emerged: (1) the pandemic presented unique challenges to implementing tele-rehabilitation while exacerbating previous challenges inherent with virtual care, (2) tele-rehabilitation use during the pandemic was deemed as equally effective in quality of care and patient adherence when compared to in-person services, and (3) tele-rehabilitation had significant value during the pandemic and has potential as an alternative delivery model post pandemic. Conclusion: Despite the inherent challenges, tele-rehabilitation was endorsed by participants as a suitable and effective alternative to care delivery and holds promise as a post-pandemic delivery model. Further evaluation is needed to support and optimize tele-rehabilitation use in physiotherapy practice.

Objectif: les services de téléréadaptation en physiothérapie ont été largement mis en place après le début de la pandémie de maladie à coronavirus 2019 (COVID-19). La présente étude a exploré la perception d'utilité et les expériences des physiothérapeutes à l'égard des soins cardiorespiratoires en téléréadaptation. Méthodologie: les chercheurs ont fait des entrevues semi-structurées auprès de physiothérapeutes qui ont donné des services de réadaptation à des adultes atteints d'affections cardiorespiratoires entre le 11 mars et le 31 décembre 2020. Ils ont analysé les entrevues au moyen d'une analyse de contenu classique. Résultats: Sept participants ont participé à l'entrevue, dont six effectuaient seulement de la réadaptation pulmonaire et le dernier, à la fois de la réadaptation pulmonaire et cardiaque. Trois grands thèmes en sont ressortis : 1) la pandémie a soulevé des défis uniques liés à la mise en œuvre de la téléréadaptation tout en exacerbant des problèmes déjà inhérents aux soins virtuels, 2) le recours à la téléréadaptation pendant la pandémie était considéré comme aussi efficace pour la qualité des soins et l'adhésion des patients que les services en personne et 3) la téléréadaptation était très utile pendant la pandémie et a du potentiel comme autre modèle de prestation après la pandémie. Conclusion: malgré des difficultés inhérentes, les participants ont trouvé que la téléréadaptation était une solution appropriée à la prestation des soins et qu'elle se révélait un modèle de prestation prometteur après la pandémie. Une évaluation plus approfondie s'impose pour soutenir et optimiser le recours à la téléréadaptation en physiothérapie.

Time course of neuroinflammation after human stroke - a pilot study using co-registered PET and MRI.

BACKGROUND: Microglial activation contributes to both inflammatory damage and repair in experimental ischemic stroke. However, because of the logistical challenges, there have been few clinical imaging studies directly describing inflammatory activation and its resolution after stroke. The purpose of our pilot study was to describe the spatio-temporal profile of brain inflammation after stroke using 18kD translocator protein (TSPO) positron emission tomography (PET) with magnetic resonance (MR) co-registration in the subacute and chronic stage after stroke. METHODS: Three patients underwent magnetic resonance imaging (MRI) and PET scans with TSPO ligand [11C]PBR28 15 ± 3 and 90 ± 7 days after an ischaemic stroke. Regions of interest (ROI) were defined on MRI images and applied to the dynamic PET data to derive regional time-activity curves. Regional uptake was quantified as standardised uptake values (SUV) over 60 to 90 min post-injection. ROI analysis was applied to identify binding in the infarct, and in frontal, temporal, parietal, and occipital lobes and cerebellum excluding the infarcted area. RESULTS: The mean age of participants was 56 ± 20.4 years and mean infarct volume was 17.9 ± 18.1 ml. [11C]PBR28 showed increased tracer signal in the infarcted area compared to non-infarcted areas of the brain in the subacute phase of stroke (Patient 1 SUV 1.81; Patient 2 SUV 1.15; Patient 3 SUV 1.64). [11C]PBR28 uptake returned to the level of non-infarcted areas at 90 days Patient 1 SUV 0.99; Patient 3 SUV 0.80). No additional upregulation was detected elsewhere at either time point. CONCLUSIONS: The neuroinflammatory reaction after ischaemic stroke is limited in time and circumscribed in space suggesting that post-ischaemic inflammation is tightly controlled but regulatory mechanisms.

Increasing community engagement: Skills used by adults with schizophrenia participating in a psychosocial intervention.

OBJECTIVE: We present findings from a qualitative study aimed at understanding the experiences of Veterans with schizophrenia and negative symptoms who participated in trial of an intervention to increase social and community participation called Engaging in Community Roles and Experiences (EnCoRE). Our goal was to understand what participants (N = 36) perceived they learned in EnCoRE, how participants used what they learned in their daily lives, and if and how participants built on these experiences in ways that might lead to sustained change. METHOD: Our analysis approach was inductive (bottom up), drawing on interpretive phenomenological analysis (IPA; Conroy, 2003), plus some top-down examination of the role of EnCoRE elements in participants' accounts. RESULTS: We identified three themes: (a) Learning skills led to increased comfort talking to people and planning activities; (b) Increased comfort led to increased confidence to try new things; and (c) The group atmosphere offered support and accountability that helped participants practice and refine new skills. CONCLUSIONS AND IMPLICATIONS FOR PRACTICE: The process of learning skills, planning to use them, implementing them, and returning to the group for input helped many surmount feelings of low interest and low motivation. Our findings support having proactive discussions with patients about how building confidence can support improved social and community participation. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Tissue specific LRRK2 interactomes reveal a distinct striatal functional unit.

Mutations in LRRK2 are the most common genetic cause of Parkinson's disease. Despite substantial research efforts, the physiological and pathological role of this multidomain protein remains poorly defined. In this study, we used a systematic approach to construct the general protein-protein interactome around LRRK2, which was then evaluated taking into consideration the differential expression patterns and the co-expression behaviours of the LRRK2 interactors in 15 different healthy tissue types. The LRRK2 interactors exhibited distinct expression features in the brain as compared to the peripheral tissues analysed. Moreover, a high degree of similarity was found for the LRRK2 interactors in putamen, caudate and nucleus accumbens, thus defining a potential LRRK2 functional cluster within the striatum. The general LRRK2 interactome paired with the expression profiles of its members constitutes a powerful tool to generate tissue-specific LRRK2 interactomes. We exemplified the generation of the tissue-specific LRRK2 interactomes and explored the functions highlighted by the "core LRRK2 interactors" in the striatum in comparison with the cerebellum. Finally, we illustrated how the LRRK2 general interactome reported in this manuscript paired with the expression profiles can be used to trace the relationship between LRRK2 and specific interactors of interest, here focusing on the LRRK2 interactors belonging to the Rab protein family.

Correction: Mutations in LRRK2 linked to Parkinson disease sequester Rab8a to damaged lysosomes and regulate transferrin-mediated iron uptake in microglia.

[This corrects the article DOI: 10.1371/journal.pbio.3001480.].

Clinical, genetic, and functional characterization of the glycine receptor ß-subunit A455P variant in a family affected by hyperekplexia syndrome.

Hyperekplexia is a rare neurological disorder characterized by exaggerated startle responses affecting newborns with the hallmark characteristics of hypertonia, apnea, and noise or touch-induced nonepileptic seizures. The genetic causes of the disease can vary, and several associated genes and mutations have been reported to affect glycine receptors (GlyRs); however, the mechanistic links between GlyRs and hyperekplexia are not yet understood. Here, we describe a patient with hyperekplexia from a consanguineous family. Extensive genetic screening using exome sequencing coupled with autozygome analysis and iterative filtering supplemented by in silico prediction identified that the patient carries the homozygous missense mutation A455P in GLRB, which encodes the GlyR ß-subunit. To unravel the physiological and molecular effects of A455P on GlyRs, we used electrophysiology in a heterologous system as well as immunocytochemistry, confocal microscopy, and cellular biochemistry. We found a reduction in glycine-evoked currents in N2A cells expressing the mutation compared to WT cells. Western blot analysis also revealed a reduced amount of GlyR ß protein both in cell lysates and isolated membrane fractions. In line with the above observations, coimmunoprecipitation assays suggested that the GlyR α1-subunit retained coassembly with ßA455P to form membrane-bound heteromeric receptors. Finally, structural modeling showed that the A455P mutation affected the interaction between the GlyR ß-subunit transmembrane domain 4 and the other helices of the subunit. Taken together, our study identifies and validates a novel loss-of-function mutation in GlyRs whose pathogenicity is likely to cause hyperekplexia in the affected individual.

Convergence of signalling pathways in innate immune responses and genetic forms of Parkinson's disease.

In recent years progress in molecular biology and genetics have advanced our understanding of neurological disorders and highlighted synergistic relationships with inflammatory and age-related processes. Parkinson's disease (PD) is a common neurodegenerative disorder that is characterized by loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc). Increasing extensive evidence supports the contribution of genetic risk variants and inflammation in the pathobiology of this disease. Functional and genetic studies demonstrate an overlap between genes linked to increased risk for PD and autoimmune diseases. Variants identified in loci adjacent to LRRK2, GBA, and HLA establish a crosstalk between the pathobiologies of the two disease spectra. Furthermore, common signalling pathways associated with the pathogenesis of genetic PD are also relevant to inflammatory signaling include MAPK, NF-κB, Wnt and inflammasome signaling. Importantly, post-mortem analyses of brain and cerebrospinal fluid from PD patients show the accumulation of proinflammatory cytokines. In this review we will focus on the principal mechanisms of genetic, inflammatory and age-related risk that intersect in the pathogenesis of PD.

Ischemic stroke in oral anticoagulated patients with atrial fibrillation.

BACKGROUND: Ischemic strokes in orally anticoagulated patients pose challenges for acute management and secondary prevention but the characteristics of these strokes are poorly understood. We examined the clinical and imaging features, the presumed underlying etiology and the subsequent antithrombotic management. METHODS: We analyzed a consecutive series of patients enrolled into the EIDASAF study, a single center, observational study of ischemic stroke patients with a diagnosis atrial fibrillation (AF) prior to the index event who had been admitted to the Hyperacute Stroke Unit of Imperial College London between 2010 and 2017. We compared patients with oral anticoagulation therapy prior admission (OACprior ) with those without anticoagulation (OACnaive ). Brain imaging was analyzed centrally. RESULTS: 763 patients were included in the analysis. 481 (63%) were OACnaive while 282 (37%) were OACprior . Patients with OACprior were younger, more often had a previous history of stroke or transient ischemic attack (TIA), and more often suffered from hypertension and diabetes. In OACnaive, patients, large and deep middle cerebral artery infarcts occurred more often than in OACprior patients. The groups differed significantly in the distribution of competing etiologies underlying their stroke. At discharge, OACprior more frequently were (re)-anticoagulated compared to OACnaive patients. Within the OACprior group, patients with recurrent strokes did not differ from those with a first stroke regarding clinical characteristics and pattern of cerebral infarction but they were less frequently anticoagulated. CONCLUSIONS: Ischemic strokes on OAC represent a significant proportion of AF-related strokes. There is an unmet need to better understand the causes underlying these strokes and to optimize the medical management.

Validation of a rapid remote digital test for impaired cognition using clinical dementia rating and mini-mental state examination: An observational research study.

Background: The Clinical Dementia Rating (CDR) and Mini-Mental State Examination (MMSE) are useful screening tools for mild cognitive impairment (MCI). However, these tests require qualified in-person supervision and the CDR can take up to 60 min to complete. We developed a digital cognitive screening test (M-CogScore) that can be completed remotely in under 5 min without supervision. We set out to validate M-CogScore in head-to-head comparisons with CDR and MMSE. Methods: To ascertain the validity of the M-CogScore, we enrolled participants as healthy controls or impaired cognition, matched for age, sex, and education. Participants completed the 30-item paper MMSE Second Edition Standard Version (MMSE-2), paper CDR, and smartphone-based M-CogScore. The digital M-CogScore test is based on time-normalised scores from smartphone-adapted Stroop (M-Stroop), digit-symbols (M-Symbols), and delayed recall tests (M-Memory). We used Spearman's correlation coefficient to determine the convergent validity between M-CogScore and the 30-item MMSE-2, and non-parametric tests to determine its discriminative validity with a CDR label of normal (CDR 0) or impaired cognition (CDR 0.5 or 1). M-CogScore was further compared to MMSE-2 using area under the receiver operating characteristic curves (AUC) with corresponding optimal cut-offs. Results: 72 participants completed all three tests. The M-CogScore correlated with both MMSE-2 (rho = 0.54, p < 0.0001) and impaired cognition on CDR (Mann Whitney U = 187, p < 0.001). M-CogScore achieved an AUC of 0.85 (95% bootstrapped CI [0.80, 0.91]), when differentiating between normal and impaired cognition, compared to an AUC of 0.78 [0.72, 0.84] for MMSE-2 (p = 0.21). Conclusion: Digital screening tests such as M-CogScore are desirable to aid in rapid and remote clinical cognitive evaluations. M-CogScore was significantly correlated with established cognitive tests, including CDR and MMSE-2. M-CogScore can be taken remotely without supervision, is automatically scored, has less of a ceiling effect than the MMSE-2, and takes significantly less time to complete.

Extent of white matter lesion is associated with early hemorrhagic transformation in acute ischemic stroke related to atrial fibrillation.

BACKGROUND: Hemorrhagic transformation (HT) after stroke, related to atrial fibrillation (AF), is a frequent complication, and it can be associated with a delay in the (re-)initiation of oral anticoagulation therapy. We investigated the effect of the presence and severity of white matter disease (WMD) on early HT after stroke related to AF. METHODS: A consecutive series of patients with recent (<4 weeks) ischemic stroke and AF, treated at the Hyper Acute Stroke Unit of the Imperial College London between 2010 and 2017, were enrolled. Patients with brain MRI performed 24-72 h from stroke onset and not yet started on anticoagulant treatment were included. WMD was graded using the Fazekas score. RESULTS: Among the 441 patients eligible for the analysis, 91 (20.6%) had any HT. Patients with and without HT showed similar clinical characteristics. Patients with HT had a larger diffusion-weighted imaging (DWI) infarct volume compared to patients without HT (p < .001) and significant difference in the distribution of the Fazekas score (p = .001). On multivariable analysis, HT was independently associated with increasing DWI infarct volume (odd ratio (OR), 1.03; 95% confidence interval (CI), 1.01-1.05; p < .001), higher Fazekas scores (OR, 1.94; 95% CI, 1.47-2.57; p < .001) and history of previous intracranial hemorrhage (OR, 4.80; 95% CI, 1.11-20.80; p = .036). CONCLUSIONS: Presence and severity of WMD is associated with increased risk of development of early HT in patients with stroke and AF. Further evidence is needed to provide reliable radiological predictors of the risk of HT in cardioembolic stroke.

In vitro and in vivo biological assessment of dual drug-loaded coaxial nanofibers for the treatment of corneal abrasion.

The treatment of corneal abrasion currently involves the topical administration of antibiotics, with moxifloxacin HCl (0.5% w/v) eye drops being one of the most widely used treatments. Our previous work (Tawfik et al., 2020) involved the development of coaxial poly-lactic-co-glycolic acid (PLGA) and polyvinylpyrrolidone (PVP) nanofibers loaded with the antibiotic moxifloxacin HCl and the anti-scarring agent pirfenidone in the core (PVP) and shell (PLGA) respectively, with a view to the system comprising an ocular insert for the combination therapy of corneal abrasion. In this study, we examine the antimicrobial, anti-scarring and pharmacokinetic properties of the fibers alongside consideration of their toxicity and propensity for irritation. Minimum inhibitory concentration and zone of inhibition studies against S. aureus and P. aeruginosa were performed, while fibroblast cell viability and α-smooth muscle actin (α-SMA, a biomarker for scar formation) were measured using MTT and Western Blot assays, respectively. Pharmacokinetic studies and efficacy against infection were performed using a rabbit model, while ocular irritancy was assessed using the Draize test. The studies demonstrated that the antimicrobial activity of the moxifloxacin HCl was preserved following encapsulation into the nanofibers, while the downregulation of α-SMA was demonstrated using concentrations below the IC20 values (concentration required to decrease corneal fibroblast viability by no more than 20%). The pharmacokinetic study showed retention and sustained release of the moxifloxacin HCl over a 24-hour period, in contrast to equivalent eye drops which required four times daily dosing. Evidence of low level (according to the MMTS scale) irritation was detected for the nanofiber systems. Overall, the study has demonstrated that the dual drug-loaded nanofiber system shows potential for once daily dosing as an ocular insert for the treatment of corneal abrasion.

Sequential screening nominates the Parkinson's disease associated kinase LRRK2 as a regulator of Clathrin-mediated endocytosis.

Mutations in leucine-rich repeat kinase 2 (LRRK2) are an established cause of inherited Parkinson's disease (PD). LRRK2 is expressed in both neurons and glia in the central nervous system, but its physiological function(s) in each of these cell types is uncertain. Through sequential screens, we report a functional interaction between LRRK2 and Clathrin adaptor protein complex 2 (AP2). Analysis of LRRK2 KO tissue revealed a significant dysregulation of AP2 complex components, suggesting LRRK2 may act upstream of AP2. In line with this hypothesis, expression of LRRK2 was found to modify recruitment and phosphorylation of AP2. Furthermore, expression of LRRK2 containing the R1441C pathogenic mutation resulted in impaired clathrin-mediated endocytosis (CME). A decrease in activity-dependent synaptic vesicle endocytosis was also observed in neurons harboring an endogenous R1441C LRRK2 mutation. Alongside LRRK2, several PD-associated genes intersect with membrane-trafficking pathways. To investigate the genetic association between Clathrin-trafficking and PD, we used polygenetic risk profiling from IPDGC genome wide association studies (GWAS) datasets. Clathrin-dependent endocytosis genes were found to be associated with PD across multiple cohorts, suggesting common variants at these loci represent a cumulative risk factor for disease. Taken together, these findings suggest CME is a LRRK2-mediated, PD relevant pathway.

The Parkinson's Disease Protein LRRK2 Interacts with the GARP Complex to Promote Retrograde Transport to the trans-Golgi Network.

Mutations in Leucine-rich repeat kinase 2 (LRRK2) cause Parkinson's disease (PD). However, the precise function of LRRK2 remains unclear. We report an interaction between LRRK2 and VPS52, a subunit of the Golgi-associated retrograde protein (GARP) complex that identifies a function of LRRK2 in regulating membrane fusion at the trans-Golgi network (TGN). At the TGN, LRRK2 further interacts with the Golgi SNAREs VAMP4 and Syntaxin-6 and acts as a scaffolding platform that stabilizes the GARP-SNAREs complex formation. Therefore, LRRK2 influences both retrograde and post-Golgi trafficking pathways in a manner dependent on its GTP binding and kinase activity. This action is exaggerated by mutations associated with Parkinson's disease and can be blocked by kinase inhibitors. Disruption of GARP sensitizes dopamine neurons to mutant LRRK2 toxicity in C. elegans, showing that these pathways are interlinked in vivo and suggesting a link in PD.

Automated Continuous Electrocardiogram Monitoring Accelerates the Detection of Atrial Fibrillation after Ischemic Stroke or Transient Ischemic Attack on a Hyper Acute Stroke Unit.

BACKGROUND AND AIM: Rapid and sensitive detection of atrial fibrillation (AF) is of paramount importance for initiation of adequate preventive therapy after stroke. Stroke Unit care includes continuous electrocardiogram monitoring (CEM) but the optimal exploitation of the recorded ECG traces is controversial. In this retrospective single-center study, we investigated whether an automated analysis of continuous electrocardiogram monitoring (ACEM), based on a software algorithm, accelerates the detection of AF in patients admitted to our Stroke Unit compared to the routine CEM. METHODS: Patients with acute ischemic stroke or transient ischemic attack were consecutively enrolled. After a 12-channel ECG on admission, all patients received CEM. Additionally, in the second phase of the study the CEM traces of the patients underwent ACEM analysis using a software algorithm for AF detection. Patients with history of AF or with AF on the admission ECG were excluded. RESULTS: The CEM (n = 208) and ACEM cohorts (n= 114) did not differ significantly regarding risk factors, duration of monitoring and length of admission. We found a higher rate of newly-detected AF in the ACEM cohort compared to the CEM cohort (15.8% versus 10.1%, P < .001). Median time to first detection of AF was shorter in the ACEM compared to the CEM cohort [10 hours (IQR 0-23) versus 46.50 hours (IQR 0-108.25), P < .001]. CONCLUSIONS: ACEM accelerates the detection of AF in patients with stroke compared with the routine CEM. Further evidences are required to confirm the increased rate of AF detected using ACEM.

Glycine Receptor Complex Analysis Using Immunoprecipitation-Blue Native Gel Electrophoresis-Mass Spectrometry.

The pentameric glycine receptor (GlyR), comprising the α1 and ß subunits, is a major inhibitory ionotropic receptor in brainstem and spinal cord. GlyRs interact with gephyrin (GPHN), a scaffold protein that anchors the GlyR in the plasma membrane and enables it to form clusters in glycinergic postsynapses. Using an interaction proteomics approach, evidence of the ArfGEFs IQ motif and Sec7 domain 3 (IQSEC3) and IQ motif and Sec7 domain 2 (IQSEC2) as two novel synaptic proteins interacting with GlyR complexes is provided. When the affinity-isolated GlyR complexes are fractionated by blue native gel electrophoresis and characterized by mass spectrometry, GlyR α1ß-GPHN appears as the most abundant complex with a molecular weight of ≈1 MDa, and GlyR α1ß-GPHN-IQSEC3 as a minor protein complex of ≈1.2 MDa. A third GlyR α1ß-GPHN-IQSEC2 complex exists at the lowest amount with a mass similar to the IQSEC3 containing complex. Using yeast two-hybrid it is demonstrated that IQSEC3 interacts with the GlyR complex by binding to the GPHN G domain at the N-terminal of the IQSEC3 IQ-like domain. The data provide direct evidence of the interaction of IQSEC3 with GlyR-GPHN complexes, underscoring a potential role of these ArfGEFs in the function of glycinergic synapses.

LRRK2 Biology from structure to dysfunction: research progresses, but the themes remain the same.

Since the discovery of leucine-rich repeat kinase 2 (LRRK2) as a protein that is likely central to the aetiology of Parkinson's disease, a considerable amount of work has gone into uncovering its basic cellular function. This effort has led to the implication of LRRK2 in a bewildering range of cell biological processes and pathways, and probable roles in a number of seemingly unrelated medical conditions. In this review we summarise current knowledge of the basic biochemistry and cellular function of LRRK2. Topics covered include the identification of phosphorylation substrates of LRRK2 kinase activity, in particular Rab proteins, and advances in understanding the activation of LRRK2 kinase activity via dimerisation and association with membranes, especially via interaction with Rab29. We also discuss biochemical studies that shed light on the complex LRRK2 GTPase activity, evidence of roles for LRRK2 in a range of cell signalling pathways that are likely cell type specific, and studies linking LRRK2 to the cell biology of organelles. The latter includes the involvement of LRRK2 in autophagy, endocytosis, and processes at the trans-Golgi network, the endoplasmic reticulum and also key microtubule-based cellular structures. We further propose a mechanism linking LRRK2 dimerisation, GTPase function and membrane recruitment with LRRK2 kinase activation by Rab29. Together these data paint a picture of a research field that in many ways is moving forward with great momentum, but in other ways has not changed fundamentally. Many key advances have been made, but very often they seem to lead back to the same places.

LRRK2, alpha-synuclein, and tau: partners in crime or unfortunate bystanders?

The identification of genetic forms of Parkinson's disease (PD) has tremendously expanded our understanding of the players and mechanisms involved. Mutations in the genes encoding for alpha-synuclein (aSyn), LRRK2, and tau have been associated with familial and sporadic forms of the disease. aSyn is the major component of Lewy bodies and Lewy neurites, which are pathognomonic protein inclusions in PD. Hyperphosphorylated tau protein accumulates in neurofibrillary tangles in the brains of Alzheimer's disease patients but is also seen in the brains of PD patients. LRRK2 is a complex multi-domain protein with kinase and GTPase enzymatic activity. Since aSyn and tau are phosphoproteins, we review the possible interplay between the three proteins. Understanding the interplay between LRRK2, aSyn and tau is extremely important, as this may enable the identification of novel targets and pathways for therapeutic intervention.

Downregulated Wnt/ß-catenin signalling in the Down syndrome hippocampus.

Pathological mechanisms underlying Down syndrome (DS)/Trisomy 21, including dysregulation of essential signalling processes remain poorly understood. Combining bioinformatics with RNA and protein analysis, we identified downregulation of the Wnt/ß-catenin pathway in the hippocampus of adult DS individuals with Alzheimer's disease and the 'Tc1' DS mouse model. Providing a potential underlying molecular pathway, we demonstrate that the chromosome 21 kinase DYRK1A regulates Wnt signalling via a novel bimodal mechanism. Under basal conditions, DYRK1A is a negative regulator of Wnt/ß-catenin. Following pathway activation, however, DYRK1A exerts the opposite effect, increasing signalling activity. In summary, we identified downregulation of hippocampal Wnt/ß-catenin signalling in DS, possibly mediated by a dose dependent effect of the chromosome 21-encoded kinase DYRK1A. Overall, we propose that dosage imbalance of the Hsa21 gene DYRK1A affects downstream Wnt target genes. Therefore, modulation of Wnt signalling may open unexplored avenues for DS and Alzheimer's disease treatment.

Mutation p.R356Q in the Collybistin Phosphoinositide Binding Site Is Associated With Mild Intellectual Disability.

The recruitment of inhibitory GABAA receptors to neuronal synapses requires a complex interplay between receptors, neuroligins, the scaffolding protein gephyrin and the GDP-GTP exchange factor collybistin (CB). Collybistin is regulated by protein-protein interactions at the N-terminal SH3 domain, which can bind neuroligins 2/4 and the GABAAR α2 subunit. Collybistin also harbors a RhoGEF domain which mediates interactions with gephyrin and catalyzes GDP-GTP exchange on Cdc42. Lastly, collybistin has a pleckstrin homology (PH) domain, which binds phosphoinositides, such as phosphatidylinositol 3-phosphate (PI3P/PtdIns3P) and phosphatidylinositol 4-monophosphate (PI4P/PtdIns4P). PI3P located in early/sorting endosomes has recently been shown to regulate the postsynaptic clustering of gephyrin and GABAA receptors and consequently the strength of inhibitory synapses in cultured hippocampal neurons. This process is disrupted by mutations in the collybistin gene (ARHGEF9), which cause X-linked intellectual disability (XLID) by a variety of mechanisms converging on disrupted gephyrin and GABAA receptor clustering at central synapses. Here we report a novel missense mutation (chrX:62875607C>T, p.R356Q) in ARHGEF9 that affects one of the two paired arginine residues in the PH domain that were predicted to be vital for binding phosphoinositides. Functional assays revealed that recombinant collybistin CB3SH3- R356Q was deficient in PI3P binding and was not able to translocate EGFP-gephyrin to submembrane microaggregates in an in vitro clustering assay. Expression of the PI3P-binding mutants CB3SH3- R356Q and CB3SH3- R356N/R357N in cultured hippocampal neurones revealed that the mutant proteins did not accumulate at inhibitory synapses, but instead resulted in a clear decrease in the overall number of synaptic gephyrin clusters compared to controls. Molecular dynamics simulations suggest that the p.R356Q substitution influences PI3P binding by altering the range of structural conformations adopted by collybistin. Taken together, these results suggest that the p.R356Q mutation in ARHGEF9 is the underlying cause of XLID in the probands, disrupting gephyrin clustering at inhibitory GABAergic synapses via loss of collybistin PH domain phosphoinositide binding.

Aberrant Excitatory-Inhibitory Synaptic Mechanisms in Entorhinal Cortex Microcircuits During the Pathogenesis of Alzheimer's Disease.

Synaptic dysfunction is widely proposed as an initial insult leading to the neurodegeneration observed in Alzheimer's disease (AD). We hypothesize that the initial insult originates in the lateral entorhinal cortex (LEC) due to deficits in key interneuronal functions and synaptic signaling mechanisms, in particular, Wnt (Wingless/integrated). To investigate this hypothesis, we utilized the first knock-in mouse model of AD (AppNL-F/NL-F), expressing a mutant form of human amyloid-ß (Aß) precursor protein. This model shows an age-dependent accumulation of Aß, neuroinflammation, and neurodegeneration. Prior to the typical AD pathology, we showed a decrease in canonical Wnt signaling activity first affecting the LEC in combination with synaptic hyperexcitation and severely disrupted excitatory-inhibitory inputs onto principal cells. This synaptic imbalance was consistent with a reduction in the number of parvalbumin-containing (PV) interneurons, and a reduction in the somatic inhibitory axon terminals in the LEC compared with other cortical regions. However, targeting GABAA receptors on PV cells using allosteric modulators, diazepam, zolpidem, or a nonbenzodiazepine, L-838,417 (modulator of α2/3 subunit-containing GABAA receptors), restored the excitatory-inhibitory imbalance observed at principal cells in the LEC. These data support our hypothesis, providing a rationale for targeting the synaptic imbalance in the LEC for early stage therapeutic intervention to prevent neurodegeneration in AD.