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Multi-electrode arrays (MEAs) non-invasively record extracellular action potentials (eAPs, also known as spikes) from hundreds of neurons simultaneously. However, because extracellular electrodes sample from the local electrical field, each electrode can detect eAPs from multiple nearby neurons. Interpreting spike trains at individual electrodes of high-density arrays requires spike sorting, a computational process which groups eAPs from single ’units’ based on assumptions of how spike waveforms correlate with different neuronal sources. Additionally, when experimental conditions result in changes to eAP waveforms, spike sorting routines may have difficulty correlating eAPs from multiple neurons at single electrodes before and after such waveform changes. We present here a novel, empirical method for unambiguously isolating eAPs from individual, uniquely identifiable neurons, based on automated multi- point detection of action potential propagation. This method is insensitive to changes in eAP waveform morphology because it makes no assumptions about the relationship between spike waveform and neuronal source. Our algorithm for automated detection of action potential propagation produces a ’fingerprint’ that uniquely identifies those spikes from each neuron. By unambiguously isolating eAPs from multiple neurons in each recording, on a range of platforms and experimental preparations, our method now enables high-content screening with contemporary MEAs. We outline the limitations and strengths of propagation-based isolation of eAPs from single neurons and propose how our automated method complements spike sorting and could be adapted to in vivo use.

The liquid-liquid phase separation (LLPS) of Tau has been postulated to play a role in modulating the aggregation property of Tau, a process known to be critically associated with the pathology of a broad range of neurodegenerative diseases including Alzheimer's Disease. Tau can undergo LLPS by homotypic interaction through self-coacervation (SC) or by heterotypic association through complex-coacervation (CC) between Tau and binding partners such as RNA. What is unclear is in what way the formation mechanisms for self and complex coacervation of Tau are similar or different, and the addition of a binding partner to Tau alters the properties of LLPS and Tau. A combination of in vitro experimental and computational study reveals that the primary driving force for both Tau CC and SC is electrostatic interactions between Tau-RNA or Tau-Tau macromolecules. The liquid condensates formed by the complex coacervation of Tau and RNA have distinctly higher micro-viscosity and greater thermal stability than that formed by the SC of Tau. Our study shows that subtle changes in solution conditions, including molecular crowding and the presence of binding partners, can lead to the formation of different types of Tau condensates with distinct micro-viscosity that can coexist as persistent and immiscible entities in solution. We speculate that the formation, rheological properties and stability of Tau droplets can be readily tuned by cellular factors, and that liquid condensation of Tau can alter the conformational equilibrium of Tau.

The farnesyltransferase inhibitor, Lonafarnib, reduces tau inclusions and associated atrophy in familial tauopathy models through activation of autophagy, mediated by the inhibition of farnesylation of the Ras GTPase, Rhes. While hinting at a role of Rhes in tau aggregation, it is unclear how translatable these results are for sporadic forms of tauopathy. We examined histological slides of allocortex and neocortex from multiple postmortem cases in five different tauopathies, FTLD-TDP, and healthy controls using immunofluorescence for Rhes, several tau post-translational modifications, and phospho-TDP-43. Single nucleus RNA data suggest that Rhes is found in all cortical neuron subpopulations but not in glia. Histologic investigation showed that nearly all neurons in control brains display a pattern of diffuse cytoplasmic Rhes positivity. However, in the presence of abnormal tau, but not abnormal TDP-43, the patterns of neuronal cytoplasmic Rhes tend to present as either punctiform or entirely absent. This observation reinforces the relevance of findings that link Rhes changes and tau pathology from the in vivo and in vitro models of tauopathy. The results here support a potential clinical application of Lonafarnib to tauopathies.

Oligodendrocytes exist in a heterogenous state and are implicated in multiple neuropsychiatric diseases including dementia. Cortical oligodendrocytes are a glial population uniquely positioned to play a key role in neurodegeneration by synchronizing circuit connectivity but molecular pathways specific to this role are lacking. We utilized oligodendrocyte-specific translating ribosome affinity purification and RNA-seq (TRAP-seq) to transcriptionally profile adult mature oligodendrocytes from different regions of the central nervous system. Weighted gene co-expression network analysis reveals distinct region-specific gene networks. Two of these mature myelinating oligodendrocyte gene networks uniquely define cortical oligodendrocytes and differentially regulate cortical myelination (M8) and synaptic signaling (M4). These two cortical oligodendrocyte gene networks are enriched for genes associated with dementia including MAPT and include multiple gene targets of the regulatory microRNA, miR-142-3p. Using a combination of TRAP-qPCR, miR-142-3p overexpression in vitro, and miR-142-null mice, we show that miR-142-3p negatively regulates cortical myelination. In rTg4510 tau-overexpressing mice, cortical myelination is compromised, and tau-mediated neurodegeneration is associated with gene co-expression networks that recapitulate both the M8 and M4 cortical oligodendrocyte gene networks identified from normal cortex. We further demonstrate overlapping gene networks in mature oligodendrocytes present in normal cortex, rTg4510 and miR-142-null mice, and existing datasets from human tauopathies to provide evidence for a critical role of miR-142-3p-regulated cortical myelination and oligodendrocyte-mediated synaptic signaling in neurodegeneration.

This article explore the avenues opened by single cell genomics in medical research and clinical practice, with focus on brain and neurodevelopmental disorders such as autism.

Across Latin American and Caribbean countries (LACs), the fight against dementia faces pressing challenges, such as heterogeneity, diversity, political instability, and socioeconomic disparities. These can be addressed more effectively in a collaborative setting that fosters open exchange of knowledge. In this work, the Latin American and Caribbean Consortium on Dementia (LAC-CD) proposes an agenda for integration to deliver a Knowledge to Action Framework (KtAF). First, we summarize evidence-based strategies (epidemiology, genetics, biomarkers, clinical trials, nonpharmacological interventions, networking, and translational research) and align them to current global strategies to translate regional knowledge into transformative actions. Then we characterize key sources of complexity (genetic isolates, admixture in populations, environmental factors, and barriers to effective interventions), map them to the above challenges, and provide the basic mosaics of knowledge toward a KtAF. Finally, we describe strategies supporting the knowledge creation stage that underpins the translational impact of KtAF. Fil: Parra, Mario Alfredo. Universidad Autónoma del Caribe; Colombia Fil: Baez, Sandra. Universidad de los Andes; Colombia Fil: Sedeño, Lucas. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Gonzalez Campo, Cecilia. Universidad de San Andrés; Argentina Fil: Santamaría García, Hernando. Pontificia Universidad Javeriana; Colombia Fil: Aprahamian, Ivan. No especifíca; Fil: Bertolucci, Paulo. Universidade Federal de Sao Paulo; Brasil Fil: Bustin, Julian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencia Cognitiva. Fundación Favaloro. Instituto de Neurociencia Cognitiva; Argentina Fil: Camargos Bicalho, Maria Aparecida. Universidade Federal de Minas Gerais; Brasil Fil: Cano Gutierrez, Carlos. Hospital Universitario San Ignacio; Colombia Fil: Caramelli, Paulo. Universidade Federal de Minas Gerais; Brasil Fil: Chaves, Marcia L. F.. Universidade Federal do Rio Grande do Sul; Brasil Fil: Perez Cogram, Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencia Cognitiva. Fundación Favaloro. Instituto de Neurociencia Cognitiva; Argentina Fil: Beber, Bárbara Costa. Universidade Federal do Rio Grande do Sul; Brasil Fil: Court, Felipe A.. Universidad Mayor; Chile Fil: de Souza, Leonardo Cruz. Universidade Federal de Minas Gerais; Brasil Fil: Custodio, Nilton. Peruvian Institute of Neurosciences; Perú Fil: Damian, Andres. Universidad de la República; Uruguay Fil: de la Cruz, Myriam. University of California; Estados Unidos Fil: Diehl Rodriguez, Roberta. Universidade de Sao Paulo; Brasil Fil: Dozzi Brucki, Sonia Maria. Universidade de Sao Paulo; Brasil Fil: Fajersztajn, Lais. Universidade de Sao Paulo; Brasil Fil: Farías, Gonzalo A.. Universidad de Chile; Chile Fil: De Felice, Fernanda G.. Universidade Federal do Rio de Janeiro; Brasil Fil: Ferrari, Raffaele. Colegio Universitario de Londres; Reino Unido Fil: Ferreira de Oliveira, Fabricio. Universidade de Sao Paulo; Brasil Fil: Ferreira, Sergio Teixeira. Universidade Federal do Rio de Janeiro; Brasil Fil: Ferretti, Ceres. Universidade de Sao Paulo; Brasil Fil: Figueredo Balthazar, Marcio Luiz. Universidade Estadual de Campinas; Brasil Fil: Ferreira Frota, Norberto Anizio. Universidade de Fortaleza; Brasil Fil: Fuentes, Patricio. No especifíca; Fil: García, Adolfo Martín. Universidad Nacional de Cuyo; Argentina. Universidad de San Andrés; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Garcia, Patricia J.. Cayetano Heredia University; Perú Fil: de Gobbi Porto, Fábio Henrique. Universidade de Sao Paulo; Brasil Fil: Duque Peñailillo, Lissette. Ecuadorian Dementia Association; Ecuador Fil: Engler, Henry Willy. Universidad de la República; Uruguay Fil: Maier, Irene. Universidad de Chile; Chile Fil: Mata, Ignacio F.. University of Pittsburgh; Estados Unidos Fil: González Billault, Christian. Universidad de Chile; Chile Fil: Lopez, Oscar L.. University of Pittsburgh; Estados Unidos Fil: Morelli, Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; Argentina Fil: Nitrini, Ricardo. Universidade de Sao Paulo; Brasil Fil: Quiroz, Yakeel T.. Harvard Medical School; Estados Unidos Fil: Guerrero Barragan, Alejandra. Universidad de la Sabana; Colombia Fil: Huepe, David. Universidad Adolfo Ibañez; Chile Fil: Pio, Fabricio Joao. Hospital Governador Celso Ramos; Brasil Fil: Suemoto, Claudia Kimie. Universidade de Sao Paulo; Brasil Fil: Kochhann, Renata. Pontificia Universidade Católica do Rio Grande do Sul; Brasil Fil: Kochen, Sara Silvia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; Argentina Fil: Kumfor, Fiona. University of Western Sydney; Australia Fil: Lanata, Serggio. University of California; Estados Unidos Fil: Miller, Bruce. University of California; Estados Unidos Fil: Lessa Mansur, Leticia. Universidade de Sao Paulo; Brasil Fil: Lie Hosogi, Mirna. Universidade de Sao Paulo; Brasil Fil: Lillo, Patricia. Universidad de Chile; Chile Fil: Llibre Guerra, Jorge. University of California; Estados Unidos Fil: Lira, David. Peruvian Institute of Neurosciences; Perú Fil: Lopera, Francisco. Universidad de Antioquia; Colombia Fil: Comas, Adelina. No especifíca; Fil: Avila Funes, José Alberto. Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán; México Fil: Sosa, Ana Luisa. Instituto Nacional de Neurología y Neurocirugía; México Fil: Ramos, Claudia. University of California; Estados Unidos Fil: de Paula França Resende, Elisa. University of California; Estados Unidos Fil: Snyder, Heather M.. No especifíca; Fil: Tarnanas, Ioannis. University of California; Estados Unidos Fil: Yokoyama, Jenifer. University of California; Estados Unidos Fil: Llibre, Juan. Centro de Estudios de Alzheimer; Cuba Fil: Cardona Londoño, Juan Felipe. Universidad del Valle; Colombia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Possin, Kate. University of California; Estados Unidos Fil: Kosik, Kenneth. University of California; Estados Unidos Fil: Montesinos, Rosa. Peruvian Institute of Neurosciences; Perú Fil: Moguilner, Sebastian Gabriel. University of California; Estados Unidos Fil: Solis, Patricia Cristina Lourdes. Provincia de Buenos Aires. Ministerio de Salud. Hospital Alta Complejidad en Red El Cruce Dr. Néstor Carlos Kirchner Samic; Argentina. Universidad Nacional Arturo Jauretche; Argentina. Universidad de Buenos Aires; Argentina Fil: de Lucena Ferretti Rebustini, Renata Eloah. Universidade de Sao Paulo; Brasil Fil: Ramirez, Jeronimo Martin. No especifíca; Fil: Matallana, Diana. Pontificia Universidad Javeriana; Colombia Fil: Mbakile Mahlanza, Lingani. University of California; Estados Unidos Fil: Mendonça Marques Ton, Alyne. Universidade Federal do Rio de Janeiro; Brasil Fil: Melo Tavares, Ronnielly. Centro Universitario de Belo Horizonte.; Brasil Fil: Miotto, Eliane C.. Universidade de Sao Paulo; Brasil Fil: Muniz-Terrera, Graciela. University of Edinburgh; Reino Unido Fil: MuñozN evárez, Luis Arnoldo. University of California; Estados Unidos Fil: Orozco, David. Universidad Nacional del Sur; Argentina Fil: Okada de Oliveira, Maira. University of California; Estados Unidos Fil: Piguet, Olivier. University of Western Sydney; Australia Fil: Pintado Caipa, Maritza. University of California; Estados Unidos Fil: Piña Escudero, Stefanie Danielle. University of California; Estados Unidos Fil: Porcello Schilling, Lucas. Pontificia Universidade Católica do Rio Grande do Sul; Brasil Fil: Rodrigues Palmeira, André Luiz. Hospital Ernesto Dornelles; Brasil Fil: Sanches Yassuda, Mônica. Universidade de Sao Paulo; Brasil Fil: Santacruz Escudero, Jose Manuel. Pontificia Universidad Javeriana; Colombia Fil: Serafim, Rodrigo Bernardo. Universidade Federal do Rio de Janeiro; Brasil Fil: Smid, Jerusa. Universidade de Sao Paulo; Brasil Fil: Slachevsky, Andrea. Universidad de Chile; Chile Fil: Serrano, Cecilia Mariela. No especifíca; Fil: Soto Añari, Marcio. Universidad Católica San Pablo; Perú Fil: Takada, Leonel Tadao. Universidade de Sao Paulo; Brasil Fil: Tenenholz Grinberg, Lea. Universidade de Sao Paulo; Brasil Fil: Teixeira, Antonio Lucio. Universidade Federal de Minas Gerais; Brasil Fil: Tonidandel Barbosa, Maira. Universidade Federal de Minas Gerais; Brasil Fil: Trépel, Dominic. Trinity College; Estados Unidos Fil: Ibañez, Agustin Mariano. Universidad Autónoma del Caribe; Colombia. Universidad Adolfo Ibañez; Chile. Universidad de San Andrés; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

The COVID-19 pandemic has taken a devastating human toll worldwide. The development of impactful guidelines and measures for controlling the COVID-19 pandemic requires continuous and widespread testing of suspected cases and their contacts through accurate, accessible, and reliable methods for SARS-CoV-2 detection. Here we describe a CRISPR-Cas13-based method for the detection of SARS-CoV-2. The assay is called CREST (Cas13-based, rugged, equitable, scalable testing), and is specific, sensitive, and highly accessible. As such, CREST may provide a low-cost and dependable alternative for SARS-CoV-2 surveillance. © 2022 Wiley Periodicals LLC. Basic Protocol: Cas13-ased detection of SARS-CoV-2 genetic material using a real-time PCR detection system Alternate Protocol: Cas13-based detection of SARS-CoV-2 genetic material using a fluorescence viewer Support Protocol 1: LwaCas13a purification Support Protocol 2: In vitro transcription of synthetic targets.

BackgroundThe triggering receptor expressed on myeloid cell 2 (TREM2) is a major regulator of neuroinflammatory processes in neurodegeneration. To date, the p.H157Y variant ofTREM2has been reported only in patients with Alzheimer’s disease. Here, we report three patients with frontotemporal dementia (FTD) from three unrelated families with heterozygous p.H157Y variant ofTREM2: two patients from Colombian families (study 1) and a third Mexican origin case from the USA (study 2).MethodsTo determine if the p.H157Y variant might be associated with a specific FTD presentation, we compared in each study the cases with age-matched, sex-matched and education-matched groups—a healthy control group (HC) and a group with FTD with neitherTREM2mutations nor family antecedents (Ng-FTD and Ng-FTD-MND).ResultsThe two Colombian cases presented with early behavioural changes, greater impairments in general cognition and executive function compared with both HC and Ng-FTD groups. These patients also exhibited brain atrophy in areas characteristic of FTD. Furthermore, TREM2 cases showed increased atrophy compared with Ng-FTD in frontal, temporal, parietal, precuneus, basal ganglia, parahippocampal/hippocampal and cerebellar regions. The Mexican case presented with FTD and motor neuron disease (MND), showing grey matter reduction in basal ganglia and thalamus, and extensive TDP-43 type B pathology.ConclusionIn all TREM2 cases, multiple atrophy peaks overlapped with the maximum peaks ofTREM2gene expression in crucial brain regions including frontal, temporal, thalamic and basal ganglia areas. These results provide the first report of an FTD presentation potentially associated with the p.H157Y variant with exacerbated neurocognitive impairments.

Human brain organoids replicate much of the cellular diversity and developmental anatomy of the human brain. However, the physiology of neuronal circuits within organoids remains under-explored. With high-density CMOS microelectrode arrays and shank electrodes, we captured spontaneous extracellular activity from brain organoids derived from human induced pluripotent stem cells. We inferred functional connectivity from spike timing, revealing a large number of weak connections within a skeleton of significantly fewer strong connections. A benzodiazepine increased the uniformity of firing patterns and decreased the relative fraction of weakly connected edges. Our analysis of the local field potential demonstrate that brain organoids contain neuronal assemblies of sufficient size and functional connectivity to co-activate and generate field potentials from their collective transmembrane currents that phase-lock to spiking activity. These results point to the potential of brain organoids for the study of neuropsychiatric diseases, drug action, and the effects of external stimuli upon neuronal networks.

Around the globe, family members provide unpaid care for their loved ones. However, caregivers are at increased-risk for stress, lower quality of life, and diminished empathy. Mind-body practices provide one non-invasive, affordable and practical solution for ailments, stress, and aging-related health issues. This study examined the effects of a 6-week yoga program (with daily at-home practice) associated with caregivers’ well-being, empathy, and brain connectivity. Twenty-three caregivers with spouses experiencing Mild Cognitive Impairment completed questionnaires, pre- and post-intervention, and some also underwent functional MRI scanning post-intervention. Following the 6-week intervention, participants reported significant improvements in empathy (specifically, lower Personal Distress [PD]) which were associated with greater life satisfaction and better social functioning. Furthermore, improvements in PD were associated with widespread patterns of stronger RS-connectivity across nearly the whole-brain, with the strongest PD effects shown in visual, attention and perceptual regions. Other improvements in empathy, notably Empathic Concern and Perspective-Taking, showed enhanced RS-brain connectivity in brain regions important for social cognition, executive function, and behavior. In sum, this pilot study showed that engagement in a 6-week yoga program resulted in improved empathy and well-being among caregivers, which were associated with enhanced RS-connectivity across nearly the whole-brain.

Mutations in MAPT (microtubule-associated protein tau) cause frontotemporal dementia (FTD). MAPT mutations are associated with abnormal tau phosphorylation levels and accumulation of misfolded tau protein that can propagate between neurons ultimately leading to cell death (tauopathy). Recently, a p.A152T tau variant was identified as a risk factor for FTD, Alzheimer's disease, and synucleinopathies. Here we used induced pluripotent stem cells (iPSC) from a patient carrying this p.A152T variant to create a robust, functional cellular assay system for probing pathophysiological tau accumulation and phosphorylation. Using stably transduced iPSC-derived neural progenitor cells engineered to enable inducible expression of the pro-neural transcription factor Neurogenin 2 (Ngn2), we generated disease-relevant, cortical-like glutamatergic neurons in a scalable, high-throughput screening compatible format. Utilizing automated confocal microscopy, and an advanced image-processing pipeline optimized for analysis of morphologically complex human neuronal cultures, we report quantitative, subcellular localization-specific effects of multiple kinase inhibitors on tau, including ones under clinical investigation not previously reported to affect tau phosphorylation. These results demonstrate the potential for using patient iPSC-derived ex vivo models of tauopathy as genetically accurate, disease-relevant systems to probe tau biochemistry and support the discovery of novel therapeutics for tauopathies.

Background The Colombian population, as well as those in other Latin American regions, arose from a recent tri-continental admixture among Native Americans, Spanish invaders, and enslaved Africans, all of whom passed through a population bottleneck due to widespread infectious diseases that left small isolated local settlements. As a result, the current population reflects multiple founder effects derived from diverse ancestries. Methods We characterized the role of admixture and founder effects on the origination of the mutational landscape that led to neurodegenerative disorders under these historical circumstances. Genomes from 900 Colombian individuals with Alzheimer’s disease (AD) [n = 376], frontotemporal lobar degeneration-motor neuron disease continuum (FTLD-MND) [n = 197], early-onset dementia not otherwise specified (EOD) [n = 73], and healthy participants [n = 254] were analyzed. We examined their global and local ancestry proportions and screened this cohort for deleterious variants in disease-causing and risk-conferring genes. Results We identified 21 pathogenic variants in AD-FTLD related genes, and PSEN1 harbored the majority (11 pathogenic variants). Variants were identified from all three continental ancestries. TREM2 heterozygous and homozygous variants were the most common among AD risk genes (102 carriers), a point of interest because the disease risk conferred by these variants differed according to ancestry. Several gene variants that have a known association with MND in European populations had FTLD phenotypes on a Native American haplotype. Consistent with founder effects, identity by descent among carriers of the same variant was frequent. Conclusions Colombian demography with multiple mini-bottlenecks probably enhanced the detection of founder events and left a proportionally higher frequency of rare variants derived from the ancestral populations. These findings demonstrate the role of genomically defined ancestry in phenotypic disease expression, a phenotypic range of different rare mutations in the same gene, and further emphasize the importance of inclusiveness in genetic studies.

The formation of membraneless organelles can be a proteotoxic stress control mechanism that locally condenses a set of components capable of mediating protein degradation decisions. The breadth of mechanisms by which cells respond to stressors and form specific functional types of membraneless organelles, is incompletely understood. We found that Bcl2-associated athanogene 2 (BAG2) marks a distinct phase-separated membraneless organelle, triggered by several forms of stress, particularly hyper-osmotic stress. Distinct from well-known condensates such as stress granules and processing bodies, BAG2-containing granules lack RNA, lack ubiquitin and promote client degradation in a ubiquitin-independent manner via the 20S proteasome. These organelles protect the viability of cells from stress and can traffic to the client protein, in the case of Tau protein, on the microtubule. Components of these ubiquitin-independent degradation organelles include the chaperone HSP-70 and the 20S proteasome activated by members of the PA28 (PMSE) family. BAG2 condensates did not co-localize with LAMP-1 or p62/SQSTM1. When the proteasome is inhibited, BAG2 condensates and the autophagy markers traffic to an aggresome-like structure.

Alzheimer’s disease (AD) is a progressive, degenerative disorder that mainly results in memory loss and a cognitive disorder. Although the cause of AD is still unknown, a minor percentage of AD cases are produced by genetic mutations in the presenilin-1 (PSEN1) gene. Differentiated neuronal cells derived from induced pluripotent stem cells (iPSCs) of patients can recapitulate key pathological features of AD in vitro; however, iPSCs studies focused on the p.E280 A mutation, which afflicts the largest family in the world with familial AD, have not been carried out yet. Although a link between the loss of the Y (LOY) chromosome in peripheral blood cells and risk for AD has been reported, LOY-associated phenotype has not been previously studied in PSEN1 E280 A carriers. Here, we report the reprogramming of fibroblast cells into iPSCs from a familial AD patient with the PSEN1 E280 A mutation, followed by neuronal differentiation into neural precursor cells (NPCs), and the differentiation of NPCs into differentiated neurons that lacked a Y chromosome. Although the PSEN1 E280 A iPSCs and NPCs were successfully obtained, after 8 days of differentiation, PSEN1 E280 A differentiated neurons massively died reflected by release and/ or activation of death markers, and failed to reach complete neural differentiation compared to PSEN 1 wild type cells.

Background Understanding how neuronal signals propagate in local network is an important step in understanding information processing. As a result, spike trains recorded with multi-electrode arrays (MEAs) have been widely used to study the function of neural networks. Studying the dynamics of neuronal networks requires the identification of both excitatory and inhibitory connections. The detection of excitatory relationships can robustly be inferred by characterizing the statistical relationships of neural spike trains. However, the identification of inhibitory relationships is more difficult: distinguishing endogenous low firing rates from active inhibition is not obvious. New method In this paper, we propose an in silico interventional procedure that makes predictions about the effect of stimulating or inhibiting single neurons on other neurons, and thereby gives the ability to accurately identify inhibitory effects. Comparison To experimentally test these predictions, we have developed a Neural Circuit Probe (NCP) that delivers drugs transiently and reversibly on individually identified neurons to assess their contributions to the neural circuit behavior. Results Using the NCP, putative inhibitory connections identified by the in silico procedure were validated through in vitro interventional experiments. Conclusions Together, these results demonstrate how detailed microcircuitry can be inferred from statistical models derived from neurophysiology data.

Introduction A small percentage of Alzheimer's disease (AD) cases are caused by genetic mutations with autosomal dominant inheritance. We report a family with a novel variant in PSEN1. Methods We performed clinical and genetic evaluation of 93 related individuals from a Colombian admixed population. 31 individuals had whole-genome sequencing. Results Genetic analysis revealed a missense variant in PSEN1 (NM_000021.3: c.1247T>C p.Ile416Thr), which originated on an African haplotype and segregated with AD logarithm of the odds score of 6. Their clinical phenotype is similar to sporadic AD except for earlier age at onset: the mean age at onset for mild cognitive impairment was 47.6 years (standard deviation 5.83) and for dementia 51.6 years (standard deviation 5.03). Discussion Ile416Thr is a novel pathogenic variant that causes AD in the sixth decade of life. The history of the region that included slave importation and admixtures within a confined geographic locale represents a "mini-population bottleneck" and subsequent emergence of a rare dominant mutation.

Developing tools to enable non-invasive, high-throughput electrophysiology measurements of large functional-networks of electrogenic cells used as in vitro disease models for the heart and brain remains an outstanding challenge for preclinical drug discovery, where failures are costly and can prove to be fatal during clinical trials. Here we demonstrate, for the first time, that it is possible to perform non-contact monitoring of extra-cellular field potentials with a multi-electrode array (MEA). To do this preliminary demonstration we built a prototype with a custom mechanical stage to micro-position cells grown on conventional glass coverslips over the recording surface of a MEA sensor. The prototype can monitor extra-cellular fields generated by multi-cellular networks in a non-contact configuration, enabling a single MEA sensor to probe different cultures in succession, without fouling or degrading its sensitive electronic surface. This first demonstration with easy to culture cardiomyocyte cells and a prototype device points to the exciting possibility for instrument development leading to more efficient and cost-effective drug screening paradigms for cardiovascular and neurological diseases.

Human brain organoids replicate much of the cellular diversity and developmental anatomy of the human brain. However, the physiological behavior of neuronal circuits within organoids remains relatively under-explored. With high-density CMOS microelectrode arrays (26,400 electrodes) and shank electrodes (960 electrodes), we probed broadband and three-dimensional extracellular field recordings generated by spontaneous activity of human brain organoids. These recordings simultaneously captured local field potentials (LFPs) and single-unit activity extracted through spike sorting. From spiking activity, we estimated a directed functional connectivity graph of synchronous neural network activity, which showed a large number of weak functional connections enmeshed within a network skeleton of significantly fewer strong connections. Treatment of the organoid with a benzodiazepine induced a reproducible signature response that shortened the inter-burst intervals, increased the uniformity of the firing pattern within each burst and decreased the population of weakly connected edges. Simultaneously examining the spontaneous LFPs and their phase alignment to spiking showed that spike bursts were coherent with theta oscillations in the LFPs. Our results demonstrate that human brain organoids have self-organized neuronal assemblies of sufficient size, cellular orientation, and functional connectivity to co-activate and generate field potentials from their collective transmembrane currents that phase-lock to spiking activity. These results point to the potential of brain organoids for the study of neuropsychiatric diseases, drug mechanisms, and the effects of external stimuli upon neuronal networks.

Amyloid aggregation of tau protein is implicated in neurodegenerative diseases, yet its facilitating factors are poorly understood. Recently, tau has been shown to undergo liquid liquid phase separation (LLPS) bothin vivoandin vitro. LLPS was shown to facilitate tau amyloid aggregation in certain cases, while independent of aggregation in other cases. It is therefore important to understand the differentiating properties that resolve this apparent conflict. We report on a model system of hydrophobically driven LLPS induced by high salt concentration (LLPS-HS), and compare it to electrostatically driven LLPS represented by tau-RNA/heparin complex coacervation (LLPS-ED). We show that LLPS-HS promotes tau protein dehydration, undergoes maturation and directly leads to canonical tau fibrils, while LLPS-ED is reversible, remains hydrated and does not promote amyloid aggregation. We show that the nature of the interaction driving tau condensation is the differentiating factor between aggregation-prone and aggregation-independent LLPS.

Human brain organoids replicate much of the cellular diversity and developmental anatomy of the human brain. However, neurophysiology within organoids remains relatively under-explored. With high-density CMOS microelectrode arrays and shank electrodes, we probed broadband and three-dimensional activity of human brain organoids. From spiking activity, we estimated a directed functional connectivity graph of neural network activity which showed a large number of weak functional connections enmeshed within a network skeleton of significantly fewer strong connections. Increasing the intrinsic inhibitory tone with a benzodiazepine suppressed the network skeleton of the functional network. We further demonstrate that human brain organoids have self-organized neuronal assemblies of sufficient size, cellular orientation, and functional connectivity to generate local field potentials from their collective transmembrane currents that phase-lock to spiking activity. These results point to the potential of brain organoids for the study of neuropsychiatric diseases, drug mechanisms, and the effects of external stimuli upon neuronal networks.

To elucidate the role of Tau isoforms and post-translational modification (PTM) stoichiometry in Alzheimer's disease (AD), we generated a high-resolution quantitative proteomics map of 95 PTMs on multiple isoforms of Tau isolated from postmortem human tissue from 49 AD and 42 control subjects. Although Tau PTM maps reveal heterogeneity across subjects, a subset of PTMs display high occupancy and frequency for AD, suggesting importance in disease. Unsupervised analyses indicate that PTMs occur in an ordered manner, leading to Tau aggregation. The processive addition and minimal set of PTMs associated with seeding activity was further defined by analysis of size-fractionated Tau. To summarize, features in the Tau protein critical for disease intervention at different stages of disease are identified, including enrichment of 0N and 4R isoforms, underrepresentation of the C terminus, an increase in negative charge in the proline-rich region (PRR), and a decrease in positive charge in the microtubule binding domain (MBD).

The current COVID-19 pandemic provides a unique opportunity to investigate the hypothesis that viral infections can precipitate neurodegeneration. Severe acute respiratory syndrome coronavirus 1 (SARSCoV-1), a pathogenic homolog of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), invades the brain through ACE2,1 and SARSCoV-2 might be neurotropic too. SARSCoV-2 also enters cells via the ACE2 receptor,1 which is widely expressed in the CNS, including in the striatum,2 where the virus might precipitate or accelerate neurodegeneration. Fil: Ibañez, Agustin Mariano. Universidad Autónoma del Caribe; Colombia. Universidad de San Andrés; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Adolfo Ibañez; Chile Fil: Kosik, Kenneth. University of California; Estados Unidos

Importance The re-opening of colleges and universities through the US during the COVID-19 pandemic is a significant public health challenge. The development of accessible and practical approaches for SARS-CoV-2 detection in the college population is paramount for deploying recurrent surveillance testing as an essential strategy for virus detection, containment, and mitigation. Objectives In this study, we set out to determine the prevalence of SARS-CoV-2 in asymptomatic subjects in a university community, using, for the first time, CREST, a CRISPR-Cas13-based test that we developed for accessible and large scale viral surveillance1. Study Design, Setting, and Participants We enrolled 1,808 asymptomatic persons to undergo SARS-CoV-2 testing. We compared viral prevalence in self-collected oropharyngeal swab samples obtained in two time periods: May 28th-June 11th and June 23rd-July 2nd, 2020. We detected viral genomes in these samples using CREST, and we corroborated our results with a point-of-reference RT-qPCR test. Positive samples were confirmed by a clinical laboratory and reported to the local Public Health Department. Results All the 732 tests performed between late May to early June were negative. In contrast, tests performed on 1,076 samples collected between late June to early July revealed eight positive cases by CREST, confirmed by RT-qPCR and CLIA-diagnostic testing. The average age of the positive cases was 21.7 years; all individuals self-identified as students. These metrics showed that CREST was effective at capturing positive SARS-CoV-2 cases in our student population. Notably, the viral loads detected in these asymptomatic cases resemble those seen in clinical samples, highlighting the potential of covert viral transmission. Conclusions and Relevance Our study revealed a substantial shift in SARS-CoV-2 prevalence in a young and asymptomatic population, and uncovered the leading wave of a local outbreak that coincided with rising case counts in the surrounding county and the state of California. Moreover, and most notably, the almost perfect concordance between CRISPR- and PCR-based testing indicated that CREST using self-collected OP swabs is reliable and it allows expanding options for large-scale surveillance testing and detection of SARS-CoV-2 outbreaks, as is required to resume operations in higher education institutions in the US and abroad. Key Points Question Are CRISPR-based methods a reliable and accessible option to capture SARS-CoV-2 outbreaks in a college population? Findings We tested 1,808 asymptomatic individuals from a university population for SARS-CoV-2, using, for the first time, a CRISPR-based assay for virus surveillance. We detected eight positive cases, corroborated by RT-qPCR and confirmed by a clinical laboratory. Our CRISPR-based method captured a change in viral prevalence coinciding with the relaxation of lockdown measures and the rise of COVID-19 cases in the community. Significance We demonstrate that CRISPR-based methods offer scalable and reliable SARS-CoV-2 testing for virus surveillance and allow capturing the leading edge of an outbreak.

Tau protein in vitro can undergo liquid liquid phase separation (LLPS); however, observations of this phase transition in living cells are limited. To investigate protein state transitions in living cells we found that Cry2 can optogentically increase the association of full lengh tau with microtubules. To probe this mechanism, we identified tau domains that drive tau clustering on microtubules in living cells. The polyproline rich domain (PRD) drives LLPS and does so under the control of phosphorylation. These readily observable cytoplasmic condensates underwent fusion and fluorescence recovery after photobleaching consistent with the ability of the PRD to undergo LLPS in vitro. In absence of the MTBD, the tau PRD co-condensed with EB1, a regulator of plus-end microtubule dynamic instability. The specific domain properties of the MTBD and PRD serve distinct but mutually complementary roles that utilize LLPS in a cellular context to implement emergent functionalities that scale their relationship from binding alpha-beta tubulin heterodimers to the larger proportions of microtubules.

The COVID-19 pandemic has created massive demand for widespread, distributed tools for detecting SARS-CoV-2 genetic material. The hurdles to scalable testing include reagent and instrument accessibility, availability of highly-trained personnel, and large upfront investment. Here we showcase an orthogonal pipeline we call CREST (Cas13-based, Rugged, Equitable, Scalable Testing) that addresses some of these hurdles. Specifically, CREST pairs commonplace and reliable biochemical methods (PCR) with low-cost instrumentation, without sacrificing detection sensitivity. By taking advantage of simple fluorescence visualizers, CREST allows for a binary interpretation of results. CREST may provide a point- of-care solution to increase the distribution of COVID-19 surveillance.

Many proteins, particularly those that are intrinsically disordered and carry charges have a tendency to undergo liquid liquid phase separation (LLPS). Phase separation is a widespread mechanism by which cells concentrate a set of proteins to perform molecular reactions, and appear to compartmentalize molecular functions. Among the intrinsically disordered proteins are a subset that tend to form solid inclusions in cells and contribute to the pathology of several neurodegenerative diseases. Among this subset is the tau protein, a critically important inclusion in a class of conditions known as the tauopathies, which include Alzheimer's disease. Tau in neurons strongly and selectively associates with RNA species, most notably tRNA with a nanomolar dissociation constant. Furthermore, tau and RNA, under charge matching conditions, undergo LLPS in a process known as complex coacervation. Tau-RNA LLPS is reversible, and can persist for more than 15 h without subsequent fibrilization, although after longer time periods β-sheet content can be detected by thioflavin T. These findings suggest that LLPS tau droplets or condensates can be placed on a pathway to fibrillization and be arrested by solidification or dissolve into a soluble state, depending on the condition at hand, suggesting a regulatory and physiological role for the phase separated state of tau.

Management of the coronavirus disease 2019 (COVID-19) pandemic requires widespread testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A main limitation for widespread SARS-CoV-2 testing is the global shortage of essential supplies, among them RNA extraction kits., Management of the coronavirus disease 2019 (COVID-19) pandemic requires widespread testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A main limitation for widespread SARS-CoV-2 testing is the global shortage of essential supplies, among them RNA extraction kits. The need for commercial RNA extraction kits places a bottleneck on tests that detect SARS-CoV-2 genetic material, including PCR-based reference tests. Here, we propose an alternative method we call PEARL (precipitation-enhanced analyte retrieval) that addresses this limitation. PEARL uses a lysis solution that disrupts cell membranes and viral envelopes while simultaneously providing conditions suitable for alcohol-based precipitation of RNA, DNA, and proteins. PEARL is a fast, low-cost, and simple method that uses common laboratory reagents and offers performance comparable to that of commercial RNA extraction kits. PEARL offers an alternative method to isolate host and pathogen nucleic acids and proteins to streamline the detection of DNA and RNA viruses, including SARS-CoV-2.

The SARS-CoV-2 global pandemic will disproportionately impact countries with weak economies and vulnerable populations including people with dementia. Latin American and Caribbean countries (LACs) are burdened with unstable economic development, fragile health systems, massive economic disparities, and a high prevalence of dementia. Here, we underscore the selective impact of SARS-CoV-2 on dementia among LACs, the specific strain on health systems devoted to dementia, and the subsequent effect of increasing inequalities among those with dementia in the region. Implementation of best practices for mitigation and containment faces particularly steep challenges in LACs. Based upon our consideration of these issues, we urgently call for a coordinated action plan, including the development of inexpensive mass testing and multilevel regional coordination for dementia care and related actions. Brain health diplomacy should lead to a shared and escalated response across the region, coordinating leadership, and triangulation between governments and international multilateral networks. Fil: Ibañez, Agustin Mariano. Universidad Adolfo Ibáñez; Chile. Universidad de San Andrés; Argentina. Universidad Autónoma del Caribe; Colombia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Santamaria Garcia, Hernando. Pontificia Universidad Javeriana; Colombia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Guerrero Barragan, Alejandra. University of California; Estados Unidos Fil: Kornhuber, Alexander. University of California; Estados Unidos Fil: Mendonca Marques Ton, Alyne. Universidade Vila Velha; Brasil Fil: Slachevsky, Andrea. Universidad de Chile; Chile Fil: Teixeira, Antonio Lucio. No especifíca; Fil: Mar Meza, Beatriz Marcela. University of California; Estados Unidos Fil: Serrano, Cecilia Mariela. Unidad Asistencial "Dr. César Milstein"; Argentina Fil: Cano, Carlos. Pontificia Universidad Javeriana; Colombia Fil: Arias Gonzalez, Carolina. University of California; Estados Unidos Fil: González Billault, Christian. Universidad de Chile; Chile Fil: Butler, Christopher. University of Oxford; Reino Unido. Pontificia Universidad Católica de Chile; Chile Fil: Bustin, Julian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt | Instituto de Neurología Cognitiva. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt | Fundación Favaloro. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt; Argentina Fil: Duran Aniotz, Claudia. Universidad Adolfo Ibañez; Chile Fil: Acosta, Daisy. Universidad Nacional Pedro Henríquez Ureña; República Dominicana Fil: Matallana, Diana L.. Pontificia Universidad Javeriana; Colombia Fil: Acosta Alvear, Diego. University of California; Estados Unidos Fil: Trépel, Dominic. No especifíca; Fil: De Paula França Resende, Elisa. University of California; Estados Unidos. Universidade Federal do Rio de Janeiro; Brasil Fil: Ferreira de Oliveira, Fabricio. Universidade Federal de Sao Paulo; Brasil Fil: Ibanez, Francisco. Universidad Nacional de San Juan; Argentina Fil: De Felice, Fernanda G.. Universidade Federal do Rio de Janeiro; Brasil Fil: Navarrete, Gorka. Universidad Adolfo Ibañez; Chile Fil: Tarnanas, Ioannis. No especifíca; Fil: Meier, Irene B.. No especifíca; Fil: Smid, Jerusa. No especifíca; Fil: Llibre-Guerra, Jorge. University of California; Estados Unidos Fil: Llibre Rodriguez, Juan J.. Universidad de Ciencias Médicas; Cuba Fil: Fajersztajn, Laís. University of California; Estados Unidos. Universidade de Sao Paulo; Brasil Fil: Tadao Takada, Leonel. Universidade de Sao Paulo; Brasil Fil: Duque, Lissette. National Commission In Bioethics; Ecuador Fil: Okada de Oliveira, Maira. Universidade de Sao Paulo; Brasil Fil: Aparecida Camargos Bicalho, Maria. Universidade Federal de Minas Gerais; Brasil Fil: Behrens, María Isabel. Universidad Nacional de San Juan; Argentina. Universidad de Chile; Chile Fil: Pintado Caipa, Maritza. University of California; Estados Unidos Fil: Parra, Mario. University of Strathclyde; Reino Unido Fil: Wilson, Maxwell Z.. University of California; Estados Unidos Fil: De La Cruz Puebla, Myriam. Universidad de Barcelona; España. University of California; Estados Unidos Fil: Custodio, Nilton. Peruvian National Institute Of Health; Perú Fil: Santibanez, Rodrigo. Pontificia Universidad Católica de Chile; Chile. Universidad Católica de Chile; Chile Fil: Serafim, Rodrigo Bernardo. No especifíca; Fil: Melo Tavares, Ronnielly. Universidade Federal do Rio de Janeiro; Brasil Fil: Piña Escudero, Stefanie Danielle. University of California; Estados Unidos Fil: Rodriguez, Tomas Leon. Universidad de Chile; Chile Fil: Dawson, Walter. University of California; Estados Unidos Fil: Miller, Bruce L.. University of California; Estados Unidos Fil: Kosik, Kenneth. University of California; Estados Unidos

© 2018, The Author(s), under exclusive licence to Springer Nature America, Inc. MicroRNAs (miRNAs) regulate many cellular events during brain development by interacting with hundreds of mRNA transcripts. However, miRNAs operate nonuniformly upon the transcriptional profile with an as yet unknown logic. Shortcomings in defining miRNA–mRNA networks include limited knowledge of in vivo miRNA targets and their abundance in single cells. By combining multiple complementary approaches, high-throughput sequencing of RNA isolated by cross-linking immunoprecipitation with an antibody to AGO2 (AGO2-HITS-CLIP), single-cell profiling and computational analyses using bipartite and coexpression networks, we show that miRNA-mRNA interactions operate as functional modules that often correspond to cell-type identities and undergo dynamic transitions during brain development. These networks are highly dynamic during development and over the course of evolution. One such interaction is between radial-glia-enriched ORC4 and miR-2115, a great-ape-specific miRNA, which appears to control radial glia proliferation rates during human brain development.

Neurodegenerative disorders are complex multifactorial diseases that have poorly understood selective vulnerabilities among discrete cell populations. We performed single cell RNA sequencing of whole hippocampi from the rTg4510 mouse tauopathy model, which expresses a P301L MAPT mutation at two time points—before and after the onset of pathology. One population of neurons showed a robust size reduction in both the young and the old transgenic animals. Differential expression of genes expressed in this group of neurons suggested an enrichment in granule cell neurons. We identified genes that characterize this population of neurons using Pareto optimization of the specificity and precision of gene pairs for the population of interest. The resulting optimal marker genes were overwhelmingly associated with neuronal projections and their expression was enriched in the dentate gyrus suggesting that the rTg4510 mouse is a good model for Pick’s disease. This observation suggested that the tau mutation affects the population of neurons associated with neuronal projections even before overt tau inclusions can be observed. Out of the optimal pairs of genes identified as markers of the population of neurons of interest, we selected Purkinje cell protein 4 (Pcp4+) and Syntaxin binding protein 6 (Stxbp6+) for experimental validation. Single-molecule RNA fluorescence in situ hybridization confirmed preferential expression of these markers and localized them to the dentate gyrus.

The mechanism that leads to liquid-liquid phase separation (LLPS) of the tau protein, whose pathological aggregation is implicated in neurodegenerative disorders, is not well understood. Establishing a phase diagram that delineates the boundaries of phase co-existence is key to understanding whether LLPS is an equilibrium or intermediate state. We demonstrate that tau and RNA reversibly form complex coacervates. While the equilibrium phase diagram can be fit to an analytical theory, a more advanced model is investigated through field theoretic simulations (FTS) that provided direct insight into the thermodynamic driving forces of tau LLPS. Together, experiment and simulation reveal that tau-RNA LLPS is stable within a narrow equilibrium window near physiological conditions over experimentally tunable parameters including temperature, salt and tau concentrations, and is entropy-driven. Guided by our phase diagram, we show that tau can be driven toward LLPS under live cell coculturing conditions with rationally chosen experimental parameters., eLife digest Proteins make up much of the machinery of cells and perform many roles that are essential for life. Some important proteins – known as intrinsically disordered proteins – lack any stable three-dimensional structure. One such protein, called tau, is best known for its ability to form tangles in the brain, and a buildup of these tangles is a hallmark of Alzheimer’s disease and many other dementias. Tau is also one of a number of proteins that can undergo a process called liquid-liquid phase separation: essentially, a solution of tau separates into a very dilute solution interspersed with droplets of a concentrated tau solution, similar to an oil-water mixture separating into a very watery solution with drops of oil. Understanding the conditions that lead to spontaneous liquid-liquid phase separation might give insight into how the tau tangles form. However, it was not known whether it is possible in principle for liquid-liquid phase separation of tau to occur in a living brain. Lin, McCarty et al. have now used an advanced computer simulation method together with experiments to map the conditions under which a solution containing tau undergoes liquid-liquid phase separation. Temperature as well as the concentrations of salt and the tau protein all influenced how easily tau droplets formed or dissolved, and the narrow range of conditions that encouraged droplet formation fell within the normal conditions found in the body, also known as “physiological conditions”. This suggested that tau droplets might form and dissolve easily in living systems, and possibly in the brain, depending on the precise physiological conditions. To explore this possibility further, tau protein was added to a dish containing living cells. As the map suggested, slightly adjusting temperature or protein concentrations caused tau droplets to form and dissolve, all while the cells remained alive. The map provided by this study may offer guides to researchers looking for liquid-liquid phase separation in the brain. If liquid-liquid phase separation of tau occurs in living brains, it may be important for determining whether and when damaging tau tangles emerge. For example, the high concentration of tau in droplets might speed up tangle formation. Ultimately, a better understanding of the conditions and mechanism for liquid-liquid phase separation of tau can help researchers understand the role of protein droplet formation in living systems. This may be a process that promotes, or possibly a regulatory mechanism that prevents, the formation of tau tangles associated with dementia.

We identified a PSEN1 (presenilin 1) mutation carrier from the world's largest autosomal dominant Alzheimer's disease kindred, who did not develop mild cognitive impairment until her seventies, three decades after the expected age of clinical onset. The individual had two copies of the APOE3 Christchurch (R136S) mutation, unusually high brain amyloid levels and limited tau and neurodegenerative measurements. Our findings have implications for the role of APOE in the pathogenesis, treatment and prevention of Alzheimer's disease.

The study of individuals with autosomal dominant Alzheimer’s disease affords one of the best opportunities to characterize the biological and cognitive changes of Alzheimer’s disease that occur over the course of the preclinical and symptomatic stages. Unifying the knowledge gained from the past three decades of research in the world’s largest single-mutation autosomal dominant Alzheimer’s disease kindred — a family in Antioquia, Colombia with the E280A mutation in the Presenilin1 gene — will provide new directions for Alzheimer’s research and a framework for generalizing the findings from this cohort to the more common sporadic form of Alzheimer’s disease. As this specific mutation is virtually 100% penetrant for the development of the disease by midlife, we use a previously defined median age of onset for mild cognitive impairment for this cohort to examine the trajectory of the biological and cognitive markers of the disease as a function of the carriers’ estimated years to clinical onset. Studies from this cohort suggest that structural and functional brain abnormalities — such as cortical thinning and hyperactivation in memory networks — as well as differences in biofluid and in vivo measurements of Alzheimer’s-related pathological proteins distinguish Presenilin1 E280A mutation carriers from non-carriers as early as childhood, or approximately three decades before the median age of onset of clinical symptoms. We conclude our review with discussion on future directions for Alzheimer’s disease research, with specific emphasis on ways to design studies that compare the generalizability of research in autosomal dominant Alzheimer’s disease to the larger sporadic Alzheimer’s disease population.

Tau inclusions are a shared feature of many neurodegenerative conditions and tau mutations lead to frontotemporal dementia. Approaches to treatment of these conditions have focused directly on the tau protein by targeting its post-translational modifications, its levels and its tendency to aggregate. We discovered a novel regulatory pathway for tau degradation that operates through the Rhes protein, a GTPase. Rhes is farnesylated and treatment with the farnesyl transferase inhibitor, lonafarnib, reduced Rhes, attenuated behavioral abnormalities, significantly reduced atrophy, tau inclusions, sumoylation and ubiquitination, as well as microgliosis in the rTg4510 tauopathy mouse. Direct reduction of Rhes levels reproduced the results observed with lonafarnib. The mechanism of lonafarnib action, as mediated by Rhes to reduce tau pathology, operates through the lysosome without involvement of the proteasome. Finally we show that the developmental increase in Rhes levels can be homeostatically regulated in the presence of tau mutations as a protective mechanism through which cells sense abnormal tau before any pathology is present. The extensive human trials of lonafarnib for other conditions, makes this drug ideal for repurposing to treat tauopathies.