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TheMAPTgene encodes Tau protein, a member of the large family of microtubule-associated proteins. Tau forms large insoluble aggregates that are toxic to neurons in several neurological disorders and neurofibrillary Tau tangles represent a key pathological hallmark of Alzheimer’s disease (AD) and other ‘tauopathies’1,2. Several Tau-lowering strategies are being investigated as a potential treatment for AD but the mechanisms that regulate Tau expression at the transcriptional or translational level are not well understood3,4. Recently, Simone etal.5reported the discovery of a new type of natural antisense transcripts called ‘MIR-NATs’ (referring to Mammalian-wide Interspersed Repeats – Natural Antisense Transcripts). Simone and colleagues usedMAPT-AS1, a MIR-NAT associated to theMAPTgene as an archetype of this new class of long non-coding RNAs. According to Simone etal.,MAPT-AS1represses Tau translation by competing for ribosomal RNA. We investigated the potential functions ofMAPT-AS1in neurons using the same gain- and loss-of-function experiments as described in the original report and expanded our analysis with complementary approaches. Our data do not support a role forMAPT-AS1in regulating Tau expression in human neurons and urge to cautiously interpret the data provided by Simone etal.5.

/SummaryNeuronal cell loss is a defining feature of Alzheimer’s disease (AD), but it remains unclear how neurons die and how this relates to other defining characteristics of the disease1. Existing in vivo AD models only partially recapitulate the neuropathology of AD with very mild or no neuronal cell loss. Here we demonstrate that human neurons xenografted in mouse brain exposed to amyloid pathology develop sarkosyl-insoluble tau filaments, positive Gallyas silver staining, release phosphorylated tau (P-tau181) into the blood, and display considerable neuronal cell loss, providing a model for the induction of full Tau pathology by simple exposure to amyloid pathology in AD. The alterations are specific to human neurons and contrast with the mild effects exhibited in mouse neurons. A core transcriptional program in the human neurons is characterized by strong upregulation of MEG3, a neuron-specific long noncoding RNA. MEG3 is also strongly upregulated in neurons from AD patients in situ. MEG3 expression alone is sufficient to induce necroptosis in human neurons in vitro. Orally administered small molecule receptor-interacting protein (RIP) kinase -1 and -3 inhibitors rescued the neuronal cell loss in this novel AD model. Thus, xenografted human neurons are uniquely sensitive to amyloid pathology, recapitulate all the defining neuropathological features of AD, and ultimately die by necroptosis.

Polygenic Risk Scores (PRS) for AD offer unique possibilities for reliable identification of individuals at high and low risk of AD. However, there is little agreement in the field as to what approach should be used for genetic risk score calculations, how to model the effect of APOE, what the optimal p-value threshold (pT) for SNP selection is and how to compare scores between studies and methods. We show that the best prediction accuracy is achieved with a model with two predictors (APOE and PRS excluding APOE region) with pT, While polygenic risk scores have been shown to be correlated with disease risk, there is little agreement on how the score should be calculated. Here the authors investigate risk scores for Alzheimer’s disease, finding that the most effective approach includes an APOE score and a polygenic score excluding APOE.

There is little agreement regarding the approach and optimal p-value threshold of SNPs to calculate genetic risk scores for Alzheimer’s disease (AD). This reflects a fundamental underlying debate on the polygenic versus oligogenic disease architecture. We re-investigated the assumptions underlying the choice of specific p-value thresholds defining genetic loci used to determine polygenic risk scores (PRS). We find the optimal p-value threshold for SNP selection is 0.1, which supports the polygenic architecture of AD. We found that previous studies supporting an oligogenic model of AD did not take account of the reduction of APOE-ε4 allele frequency in older individuals, which skewed the results towards lower p-value thresholds and eclipsed the contribution of genes associated to AD with higher p-values. The polygenic approach to AD is also effective to identify individuals at high or low AD risk, when only APOE-ε3 homozygous individuals are considered. We also introduce the standardisation of PRS against a population data which ensures comparability of the PRS between studies. In conclusion, our work demonstrates that AD is fundamentally a polygenic disease and that stratifying populations for AD risk best takes the full PRS score into account.

The relative lack of sensitive and clinically valid tests of rodent behavior might be one of the reasons for the limited success of the clinical translation of preclinical Alzheimer's disease (AD) research findings. There is a general interest in innovative behavioral methodology, and protocols have been proposed for touchscreen operant chambers that might be superior to existing cognitive assessment methods. We assessed and analyzed touchscreen performance in several novel ways to examine the possible occurrence of early signs of prefrontal (PFC) functional decline in the APP/PS1 mouse model of AD. Touchscreen learning performance was compared between APP/PS1-21 mice and wildtype littermates on a C57BL/6J background at 3, 6 and 12 months of age in parallel to the assessment of spatial learning, memory and cognitive flexibility in the Morris water maze (MWM). We found that older mice generally needed more training sessions to complete the touchscreen protocol than younger ones. Older mice also displayed defects in MWM working memory performance, but touchscreen protocols detected functional changes beginning at 3 months of age. Histological changes in PFC of APP/PS1 mice indeed occurred as early as 3 months. Our results suggest that touchscreen operant protocols are more sensitive to PFC dysfunction, which is of relevance to the use of these tasks and devices in preclinical AD research and experimental pharmacology. ispartof: GENES BRAIN AND BEHAVIOR vol:20 issue:1 ispartof: location:England status: published

INTRODUCTION: Tauopathies are neurodegenerative diseases characterized by TAU protein-related pathology, including frontotemporal dementia and Alzheimer's disease among others. Mutant TAU animal models are available, but none of them faithfully recapitulates human pathology and are not suitable for drug screening. METHODS: To create a new in vitro tauopathy model, we generated a footprint-free triple MAPT-mutant human induced pluripotent stem cell line (N279K, P301L, and E10+16 mutations) using clustered regularly interspaced short palindromic repeats-FokI and piggyBac transposase technology. RESULTS: Mutant neurons expressed pathogenic 4R and phosphorylated TAU, endogenously triggered TAU aggregation, and had increased electrophysiological activity. TAU-mutant cells presented deficiencies in neurite outgrowth, aberrant sequence of differentiation to cortical neurons, and a significant activation of stress response pathways. RNA sequencing confirmed stress activation, demonstrated a shift toward GABAergic identity, and an upregulation of neurodegenerative pathways. DISCUSSION: In summary, we generated a novel in vitro human induced pluripotent stem cell TAU-mutant model displaying neurodegenerative disease phenotypes that could be used for disease modeling and drug screening. ispartof: ALZHEIMERS & DEMENTIA vol:14 issue:10 pages:1261-1280 ispartof: location:United States status: published

Summary paragraphGenetics highlight the central role of microglia in Alzheimer’s disease but at least 36% of AD-risk genes lack good mouse orthologues. Here, we show that embryonic stem cell (ESC)-derived human microglia successfully engraft the mouse brain and recapitulate transcriptionally primary human microglia derived from human surgical samples. Upon exposure to oligomeric Aβ a wide range of AD-risk genes are expressed that are not readily studied in current mouse models for AD. This work provides a unique humanized animal model that will allow elucidating the role of genetic risk in the pathogenesis of AD.

Although genetics highlights the role of microglia in Alzheimer’s disease, one-third of putative Alzheimer’s disease risk genes lack adequate mouse orthologs. Here we successfully engraft human microglia derived from embryonic stem cells in the mouse brain. The cells recapitulate transcriptionally human primary microglia ex vivo and show expression of human-specific Alzheimer’s disease risk genes. Oligomeric amyloid-β induces a divergent response in human versus mouse microglia. This model can be used to study the role of microglia in neurological diseases. Human stem cell-derived microglia integrate into mouse brain, displaying transcriptome signatures of microglia directly isolated from human brain and providing a chimeric model to study human-specific aspects of Alzheimer’s disease and other brain diseases.

BackgroundThousands of SNPs associated with risk of Alzheimer’s disease (AD) in genome-wide association studies (GWAS) do not reach genome-wide significance. When combined, they contribute however to a highly predictive polygenic risk score. The relevance of these subthreshold risk genes to disease, and how their combined predictive power translates into functionally relevant disease pathways, is unknown. We investigate here at the genome-wide level and in an unbiased way to what extent AD risk genes show altered gene expression in the context of increasing Aβ or Tau pathology in mouse models of AD.MethodsWe used an existing GWAS data set to generate lists of candidate AD genes at different levels of significance. We performed transcriptomic analysis on wild-type and transgenic APP/PS1 (APPtg) and Thy-TAU22 (TAUtg) mouse models at early and late stage of disease. We used unbiased weighted gene co-expression network analysis (WGCNA) to identify clusters of co-regulated genes responsive to Aβ or TAU pathology. Gene set enrichment was used to identify clusters that were enriched for AD risk genes.FindingsConsistent and significant enrichment of AD risk genes was found in only one out of 63 coexpression modules. This module is highly responsive to Aβ but not to TAU pathology. We identify in this module 18 AD risk genes (p-value=6·5e-11) including 11 new ones, GPC2, TREML2, SYK, GRN, SLC2A5, SAMSN1, PYDC1, HEXB, RRBP1, LYN and BLNK. All are expressed in microglia, have a binding site for the transcription factor SPI1 (PU.1), and become significantly upregulated when exposed to Aβ. A subset regulates FC-gamma receptor mediated phagocytosis.InterpretationGenetic risk of AD is functionally translated into a microglia pathway responsive to Aβ pathology. This insight integrates aspects of the amyloid hypothesis with genetic risk associated to sporadic AD.

microRNA-132 (miR-132) is involved in prosurvival, anti-inflammatory and memory-promoting functions in the nervous system and has been found consistently downregulated in Alzheimer's disease (AD). Whether and how miR-132 deficiency impacts AD pathology remains, however, unaddressed. We show here that miR-132 loss exacerbates both amyloid and TAU pathology via inositol 1,4,5-trisphosphate 3-kinase B (ITPKB) upregulation in an AD mouse model. This leads to increased ERK1/2 and BACE1 activity and elevated TAU phosphorylation. We confirm downregulation of miR-132 and upregulation of ITPKB in three distinct human AD patient cohorts, indicating the pathological relevance of this pathway in AD. ispartof: EMBO Molecular Medicine vol:8 issue:9 pages:1005-1018 ispartof: location:England status: published

To provide better prevention and treatment, we need to understand the environmental and genetic risks of Alzheimer’s disease (AD). However, the definition of AD has been confounded with dementia in many studies. Thus, overinterpretation of genetic findings with regard to mechanisms and drug targets may explain, in part, controversies in the field. Here, we analyze the different forms of genetic risk of AD and how these can be used to model disease. We stress the importance of studying gene variants in the right cell types and in the right pathological context. The lack of mechanistic understanding of genetic variation has become the major bottleneck in the search for new drug targets for AD.