APP, PSEN1, and PSEN2 mutations in early-onset Alzheimer disease: A genetic screening study of familial and sporadic cases

Genetic analysis of Vietnamese patients with early-onset Alzheimer's disease

Purpose of the study: Alzheimer's disease (AD) is the most common type of dementia and its prevalence is rapidly increasing worldwide. Early-onset Alzheimer's disease (EOAD) constitutes of patients with age of onset earlier than 65 year-old and is known to be associated with genetic mutations. In this study, we reported the first genetic analysis of Vietnamese patients with EOAD.Materials and methods: We analyzed targeted sequencing data obtained from a cohort of 51 Vietnamese EOAD patients to identify pathogenic variants in twenty nine well-characterized neurodengerative genes.Results: We identified four missense mutations in APP/PSEN1 genes from six individuals, which accounts for 11.8% of all tested cases. Three of these mutations were previously reported as pathogenic and one mutation in the APP gene was newly identified and might be specific for Vietnamese patients. Our study also found eight individuals carrying homozygous APOE ε4 allele, the main risk factor gene for late-onset AD.Conclusions: Our findings showed that mutation rate in APP/PSEN genes in Vietnamese EOAD patients is consistent with that in other ethnic groups. Although further functional studies are required to validate the pathogenesis of the new mutations, our study demonstrated the necessity of genetic screening for EOAD patients as well as additional genetic data collection in Vietnamese population.

Patient-derived iPSCs, a reliable in vitro model for the investigation of Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disease and a common cause of dementia among elderly individuals. The disease is characterized by progressive cognitive decline, accumulation of senile amyloid plaques and neurofibrillary tangles, oxidative stress, and inflammation. Human-derived cell models of AD are scarce, and over the years, non-human-derived models have been developed to recapitulate clinical AD, investigate the disease's pathogenesis and develop therapies for the disease. Several pharmacological compounds have been developed for AD based on findings from non-human-derived cell models; however, these pharmacological compounds have failed at different phases of clinical trials. This necessitates the application of human-derived cell models, such as induced pluripotent stem cells (iPSCs) in their optimized form in AD mechanistic studies and preclinical drug testing. This review provides an overview of AD and iPSCs. The AD-relevant phenotypes of iPSC-derived AD brain cells and the usefulness of iPSCs in AD are highlighted. Finally, the various recommendations that have been made to enhance iPSC/AD modelling are discussed.

The expanding role of CDR1-AS in the regulation and development of cancer and human diseases

CircRNAs are a superabundant and highly conserved group of noncoding RNAs (ncRNAs) that are characterized by their high stability and integrity compared with linear forms of ncRNAs. Recently, their critical role in gene expression regulation has been shown; thus, it is not far-fetched to believe that their abnormal expression can be a cause of different kinds of diseases such as cancer, neurodegenerative, and autoimmune diseases. They can have a function in variety of biological processes such as microRNA (miRNA) sponging, interacting with RNA-binding proteins, or even an ability to translate to proteins. A huge challenge in finding diagnostic biomarkers is finding noninvasive biomarkers that can be detected in human fluids, especially blood samples. CircRNAs are becoming candidate biomarkers for diagnosis and prognosis of these diseases through their ability to transverse from the blood-brain barrier and their broad presence in circulating exosomes. The circRNA for miRNA-7 (ciRS-7) is newly recognized, and acknowledged to being related to human pathology and cancer progression. In this review, we first briefly summarize the latest studies about their characteristics, biogenesis, and their mechanisms of action in the regulation and development of human diseases. Finally, we provide a list of diseases that are linked to one member of this novel class of ncRNAs called ciRS-7.

Microvascular Alterations in Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder associated with continual decline in cognition and ability to perform routine functions such as remembering familiar places or understanding speech. For decades, amyloid beta (Aβ) was viewed as the driver of AD, triggering neurodegenerative processes such as inflammation and formation of neurofibrillary tangles (NFTs). This approach has not yielded therapeutics that cure the disease or significant improvements in long-term cognition through removal of plaques and Aβ oligomers. Some researchers propose alternate mechanisms that drive AD or act in conjunction with amyloid to promote neurodegeneration. This review summarizes the status of AD research and examines research directions including and beyond Aβ, such as tau, inflammation, and protein clearance mechanisms. The effect of aging on microvasculature is highlighted, including its contribution to reduced blood flow that impairs cognition. Microvascular alterations observed in AD are outlined, emphasizing imaging studies of capillary malfunction. The review concludes with a discussion of two therapies to protect tissue without directly targeting Aβ for removal: (1) administration of growth factors to promote vascular recovery in AD; (2) inhibiting activity of a calcium-permeable ion channels to reduce microglial activation and restore cerebral vascular function.

Gene therapy-mediated enhancement of protective protein expression for the treatment of Alzheimer's disease

Alzheimer's disease (AD) is the leading form of dementia but lacks curative treatments. Current understanding of AD aetiology attributes the development of the disease to the misfolding of two proteins; amyloid-β (Aβ) and hyperphosphorylated tau, with their pathological accumulation leading to concomitant oxidative stress, neuroinflammation, and neuronal death. These processes are regulated at multiple levels to maintain homeostasis and avert disease. However, many of the relevant regulatory proteins appear to be downregulated in the AD-afflicted brain. Enhancement/restoration of these 'protective' proteins, therefore, represents an attractive therapeutic avenue. Gene therapy is a desirable means of achieving this because it is not associated with the side-effects linked to systemic protein administration, and sustained protein expression virtually eliminates compliance issues. The current article represents a focused and succinct review of the better established 'protective' protein targets for gene therapy enhancement/restoration rather than being designed as an exhaustive review incorporating less validated protein subjects. In addition, we will discuss how the risks associated with uncontrolled or irreversible gene expression might be mitigated through combining neuronal-specific promoters, inducible expression systems and localised injections. Whilst many of the gene therapy targets reviewed herein are yet to enter clinical trials, preclinical testing has thus far demonstrated encouraging potential for the gene therapy-based treatment of AD.

Exercise as Potential Therapeutic Target to Modulate Alzheimer's Disease Pathology in APOE ε4 Carriers: A Systematic Review

Alzheimer's disease (AD) is a progressive neurodegenerative disease for which no effective treatment exists at present. Previous research has found that exercise reduces the risk of AD. Since the apolipoprotein E (APOE) ε4 allele increases the risk of AD and is associated with faster disease progression than the other isoforms, we aimed to highlight the impact of exercise on AD pathology in APOE ε4 carriers. This review focuses on the effect of exercise on cognitive function, dementia risk, amyloid-β (Aβ) metabolism, lipid metabolism, neuroinflammation, neurotrophic factors and vascularization in APOE ε4 carriers. We searched the literature in the PubMed electronic database using the following search terms: physical activity, exercise, aerobic fitness, training, sport, APOE4, Alzheimer's disease, AD and dementia. By cross-referencing, additional publications were identified. Selected studies required older adults to take part in an exercise intervention or to make use of self-reported physical activity questionnaires. All included studies were written and published in English between 2000 and 2020. From these studies, we conclude that exercise is a non-pharmacological treatment option for high-risk APOE ε4 carriers to ameliorate the AD pathological processes including reducing Aβ load, protecting against hippocampal atrophy, improving cognitive function, stabilizing cholesterol levels and lowering pro-inflammatory signals. Variation in study design related to age, cognitive outcomes and the type of intervention explained the differences in study outcomes. However, exercise seems to be effective in delaying the onset of AD and may improve the quality of life of AD patients.

The Links between Cardiovascular Diseases and Alzheimer's Disease

The root cause of non-inherited Alzheimer's disease (AD) remains unknown despite hundreds of research studies performed to attempt to solve this problem. Since proper prophylaxis remains the best strategy, many scientists have studied the risk factors that may affect AD development. There is robust evidence supporting the hypothesis that cardiovascular diseases (CVD) may contribute to AD progression, as the diseases often coexist. Therefore, a lack of well-defined diagnostic criteria makes studying the relationship between AD and CVD complicated. Additionally, inflammation accompanies the pathogenesis of AD and CVD, and is not only a consequence but also implicated as a significant contributor to the course of the diseases. Of note, АроЕε4 is found to be one of the major risk factors affecting both the cardiovascular and nervous systems. According to genome wide association and epidemiological studies, numerous common risk factors have been associated with the development of AD-related pathology. Furthermore, the risk of developing AD and CVDs appears to be increased by a wide range of conditions and lifestyle factors: hypertension, dyslipidemia, hypercholesterolemia, hyperhomocysteinemia, gut/oral microbiota, physical activity, and diet. This review summarizes the literature and provides possible mechanistic links between CVDs and AD.

The Roles of Matrix Metalloproteinases and Their Inhibitors in Human Diseases

Matrix metalloproteinases (MMPs) are a family of zinc-dependent extracellular matrix (ECM) remodeling endopeptidases that have the capacity to degrade almost every component of the ECM. The degradation of the ECM is of great importance, since it is related to embryonic development and angiogenesis. It is also involved in cell repair and the remodeling of tissues. When the expression of MMPs is altered, it can generate the abnormal degradation of the ECM. This is the initial cause of the development of chronic degenerative diseases and vascular complications generated by diabetes. In addition, this process has an association with neurodegeneration and cancer progression. Within the ECM, the tissue inhibitors of MMPs (TIMPs) inhibit the proteolytic activity of MMPs. TIMPs are important regulators of ECM turnover, tissue remodeling, and cellular behavior. Therefore, TIMPs (similar to MMPs) modulate angiogenesis, cell proliferation, and apoptosis. An interruption in the balance between MMPs and TIMPs has been implicated in the pathophysiology and progression of several diseases. This review focuses on the participation of both MMPs (e.g., MMP-2 and MMP-9) and TIMPs (e.g., TIMP-1 and TIMP-3) in physiological processes and on how their abnormal regulation is associated with human diseases. The inclusion of current strategies and mechanisms of MMP inhibition in the development of new therapies targeting MMPs was also considered.

Comprehensive Review on Alzheimer's Disease: Causes and Treatment

Alzheimer's disease (AD) is a disorder that causes degeneration of the cells in the brain and it is the main cause of dementia, which is characterized by a decline in thinking and independence in personal daily activities. AD is considered a multifactorial disease: two main hypotheses were proposed as a cause for AD, cholinergic and amyloid hypotheses. Additionally, several risk factors such as increasing age, genetic factors, head injuries, vascular diseases, infections, and environmental factors play a role in the disease. Currently, there are only two classes of approved drugs to treat AD, including inhibitors to cholinesterase enzyme and antagonists to N-methyl d-aspartate (NMDA), which are effective only in treating the symptoms of AD, but do not cure or prevent the disease. Nowadays, the research is focusing on understanding AD pathology by targeting several mechanisms, such as abnormal tau protein metabolism, β-amyloid, inflammatory response, and cholinergic and free radical damage, aiming to develop successful treatments that are capable of stopping or modifying the course of AD. This review discusses currently available drugs and future theories for the development of new therapies for AD, such as disease-modifying therapeutics (DMT), chaperones, and natural compounds.

Identification of Somatic Mutations in Dementia-related Genes in Cancer Patients

BACKGROUND

Dementia is an overall term of brain diseases, including Alzheimer's disease (AD), tauopathies and synucleinopathies. To date, somatic mutations in dementia-related genes, including the amyloid precursor protein (APP) gene, presenilin 1 (PSEN1) gene, PSEN2 gene, microtubule- associated protein tau (MAPT) gene, alpha-synuclein (SNCA) gene and leucine-rich repeat kinase 2 (LRRK2) gene, have been considered one cause of dementia. We have questioned the impact of somatic mutations in dementia-related genes on cancer.

METHODS

In the present study, we investigated somatic mutations in the APP, PSEN1, PSEN2, MAPT, SNCA and LRRK2 genes and the impact of these somatic mutations.

RESULTS

From The Cancer Genome Atlas (TCGA) database, we found 1,643 somatic mutations in the APP, PSEN1, PSEN2, MAPT, SNCA and LRRK2 genes in cancer patients. Strikingly, compared to the distributions of cancer types in total cancer patients, somatic mutations in the dementia-related genes showed an extremely low distribution in glioblastoma patients.

CONCLUSION

To the best of our knowledge, this is the first investigation of dementia-related genes in cancer patients.

Endothelial Mitochondrial Dysfunction in Cerebral Amyloid Angiopathy and Alzheimer's Disease

Alzheimer's disease (AD) is the most prevalent form of dementia. Cerebrovascular dysfunction is one of the earliest events in the pathogenesis of AD, as well as in vascular and mixed dementias. Cerebral amyloid angiopathy (CAA), the deposition of amyloid around cerebral vessels, is observed in up to 90% of AD patients and in approximately 50% of elderly individuals over 80 years of age. CAA is a strong contributor to vascular dysfunction in AD. CAA-laden brain vessels are characterized by dysfunctional hemodynamics and leaky blood-brain barrier (BBB), contributing to clearance failure and further accumulation of amyloid-β (Aβ) in the cerebrovasculature and brain parenchyma. Mitochondrial dysfunction is increasingly recognized as an important early initiator of the pathogenesis of AD and CAA. The objective of this review is to discuss the effects of Aβ on cerebral microvascular cell function, focusing on its impact on endothelial mitochondria. After introducing CAA and its etiology and genetic risk factors, we describe the pathological relationship between cerebrovascular amyloidosis and brain microvascular endothelial cell dysfunction, critically analyzing its roles in disease progression, hypoperfusion, and BBB integrity. Then, we focus on discussing the effect of Aβ challenge on endothelial mitochondrial dysfunction pathways, and their contribution to the progression of neurovascular dysfunction in AD and dementia. Finally, we report potential pharmacological and non-pharmacological mitochondria-targeted therapeutic strategies which may help prevent or delay cerebrovascular failure.

Beta-amyloid deposition around hepatic bile ducts is a novel pathobiological and diagnostic feature of biliary atresia

BACKGROUND AND AIMS

Biliary atresia (BA) is a poorly understood and devastating obstructive bile duct disease of newborns. It is often diagnosed late, is incurable and frequently requires liver transplantation. In this study, we aimed to investigate the underlying pathogenesis and molecular signatures associated with BA.

METHODS

We combined organoid and transcriptomic analysis to gain new insights into BA pathobiology using patient samples and a mouse model of BA.

RESULTS

Liver organoids derived from patients with BA and a rhesus rotavirus A-infected mouse model of BA, exhibited aberrant morphology and disturbed apical-basal organization. Transcriptomic analysis of BA organoids revealed a shift from cholangiocyte to hepatocyte transcriptional signatures and altered beta-amyloid-related gene expression. Beta-amyloid accumulation was observed around the bile ducts in BA livers and exposure to beta-amyloid induced the aberrant morphology in control organoids.

CONCLUSION

The novel observation that beta-amyloid accumulates around bile ducts in the livers of patients with BA has important pathobiological implications, as well as diagnostic potential.

LAY SUMMARY

Biliary atresia is a poorly understood and devastating obstructive bile duct disease of newborns. It is often diagnosed late, is incurable and frequently requires liver transplantation. Using human and mouse 'liver mini-organs in the dish', we unexpectedly identified beta-amyloid deposition - the main pathological feature of Alzheimer's disease and cerebral amyloid angiopathy - around bile ducts in livers from patients with biliary atresia. This finding reveals a novel pathogenic mechanism that could have important diagnostic and therapeutic implications.

Store-Operated Calcium Channels in Physiological and Pathological States of the Nervous System

Store-operated calcium channels (SOCs) are widely expressed in excitatory and non-excitatory cells where they mediate significant store-operated calcium entry (SOCE), an important pathway for calcium signaling throughout the body. While the activity of SOCs has been well studied in non-excitable cells, attention has turned to their role in neurons and glia in recent years. In particular, the role of SOCs in the nervous system has been extensively investigated, with links to their dysregulation found in a wide variety of neurological diseases from Alzheimer’s disease (AD) to pain. In this review, we provide an overview of their molecular components, expression, and physiological role in the nervous system and describe how the dysregulation of those roles could potentially lead to various neurological disorders. Although further studies are still needed to understand how SOCs are activated under physiological conditions and how they are linked to pathological states, growing evidence indicates that SOCs are important players in neurological disorders and could be potential new targets for therapies. While the role of SOCE in the nervous system continues to be multifaceted and controversial, the study of SOCs provides a potentially fruitful avenue into better understanding the nervous system and its pathologies.

[18F] FBB cortical uptake is not related to the age of onset of Alzheimer's disease

AIM

To investigate the relationships between amyloid burden in brain and the age of onset of Alzheimer's disease.

MATERIALS AND METHODS

We examined 60 patients with clinical diagnosis of Alzheimer's disease. Of them, 22 were early-onset of Alzheimer's disease and 38 were late-onset of Alzheimer's disease. All of them underwent a brain PET scan 90 minutes after the injection of 4-[(E)-2-[4-[2-[2-(2-fluoranylethoxy)ethoxy]ethoxy]phenyl]ethenyl]-N-methylaniline ([F] FBB); 300 ± 10 MBq). Relationships between amyloid burden in brain and age of onset of Alzheimer's disease were assessed by means of statistical parametric mapping version 12.

RESULTS

There were no significant differences [F] FBB uptake between early-onset of Alzheimer's disease and late-onset of Alzheimer's disease patients.

CONCLUSION

In our study group, the age of onset is not related to brain amyloid burden in Alzheimer's disease patients.

Module Analysis Using Single-Patient Differential Expression Signatures Improves the Power of Association Studies for Alzheimer's Disease

The causal mechanism of Alzheimer's disease is extremely complex. Achieving great statistical power in association studies usually requires a large number of samples. In this work, we illustrated a different strategy to identify AD risk genes by clustering AD patients into modules based on their single-patient differential expression signatures. The evaluation suggested that our method could enrich AD patients with similar clinical manifestations. Applying this to a cohort of only 310 AD patients, we identified 174 AD risk loci at a strict threshold of empirical p < 0.05, while only two loci were identified using all the AD patients. As an evaluation, we collected 23 AD risk genes reported in a recent large-scale meta-analysis and found that 18 of them were rediscovered by association studies using clustered AD patients, while only three of them were rediscovered using all AD patients. Functional annotation suggested that AD-associated genetic variants mainly disturbed neuronal/synaptic function. Our results suggested module analysis helped to enrich AD patients affected by the common risk variants.

Modeling neurodegenerative diseases with cerebral organoids and other three-dimensional culture systems: focus on Alzheimer's disease

Many neurodegenerative diseases (NDs) such as Alzheimer’s disease, Parkinson’s disease, frontotemporal dementia, amyotrophic lateral sclerosis and Huntington’s disease, are characterized by the progressive accumulation of abnormal proteinaceous assemblies in specific cell types and regions of the brain, leading to cellular dysfunction and brain damage. Although animal- and in vitro-based studies of NDs have provided the field with an extensive understanding of some of the mechanisms underlying these diseases, findings from these studies have not yielded substantial progress in identifying treatment options for patient populations. This necessitates the development of complementary model systems that are better suited to recapitulate human-specific features of ND pathogenesis. Three-dimensional (3D) culture systems, such as cerebral organoids generated from human induced pluripotent stem cells, hold significant potential to model NDs in a complex, tissue-like environment. In this review, we discuss the advantages of 3D culture systems and 3D modeling of NDs, especially AD and FTD. We also provide an overview of the challenges and limitations of the current 3D culture systems. Finally, we propose a few potential future directions in applying state-of-the-art technologies in 3D culture systems to understand the mechanisms of NDs and to accelerate drug discovery.

A Urinary Metabolomics Analysis Based on UPLC-MS and Effects of Moxibustion in APP/PS1 Mice

OBJECTIVE

Alzheimer's disease (AD) is a common neurodegenerative disorder with the symptoms of cognitive impairment and decreased learning and memory abilities. Metabolomics can reflect the related functional status and physiological and pathological changes in the process of AD. Moxibustion is a unique method in traditional Chinese medicine, which has been used in the treatment and prevention of diseases for thousands of years.

METHODS

A total of 32 APP/PS1 mice were randomly divided into the model group, moxibustion group, moxa smoke group and smoke-free moxibustion group (n=8/group), using the random number table method, while eight C57BL/6 mice were used as the control group. The five groups were measured for 20 min/day, 6 days/week, for 4 weeks. After 4 weeks' experiment, all the mice were placed in metabolic cages to collect urine continuously for 24 hours, for UPLC-MS analysis.

RESULTS

Principal component analysis (PCA) was used to identify the different metabolites among the five groups, and partial least squares discriminant analysis (PLS-DA) was performed to reveal the effects on the metabolic variance. Sixteen potential biomarkers were identified among the five groups, primarily related to amino acid metabolism, starch metabolism, sucrose metabolism, interconversion of pentose and glucuronate, and aminoacyl biosynthesis. There were 17 differences in the potential metabolites between the control and model groups, involving the metabolism of amino acid, purine, pyrimidine, nicotinic acid and nicotinamide, and biosynthesis of pantothenate and coenzyme A. Fifteen potential biomarkers were identified between the model and moxibustion groups, related to starch metabolism, sucrose metabolism, interconversion of pentose and glucuronate, glyoxylate, dicarboxylate anions and some amino acid metabolism.

CONCLUSION

Moxibustion can regulate the metabolism of substance and energy by improving the synthesis and decomposition of carbohydrates and amino acids in APP/PS1 transgenic AD model mice.

Non-Coding RNAs as Sensors of Oxidative Stress in Neurodegenerative Diseases

Oxidative stress (OS) results from an imbalance between the production of reactive oxygen species and the cellular antioxidant capacity. OS plays a central role in neurodegenerative diseases, where the progressive accumulation of reactive oxygen species induces mitochondrial dysfunction, protein aggregation and inflammation. Regulatory non-protein-coding RNAs (ncRNAs) are essential transcriptional and post-transcriptional gene expression controllers, showing a highly regulated expression in space (cell types), time (developmental and ageing processes) and response to specific stimuli. These dynamic changes shape signaling pathways that are critical for the developmental processes of the nervous system and brain cell homeostasis. Diverse classes of ncRNAs have been involved in the cell response to OS and have been targeted in therapeutic designs. The perturbed expression of ncRNAs has been shown in human neurodegenerative diseases, with these changes contributing to pathogenic mechanisms, including OS and associated toxicity. In the present review, we summarize existing literature linking OS, neurodegeneration and ncRNA function. We provide evidences for the central role of OS in age-related neurodegenerative conditions, recapitulating the main types of regulatory ncRNAs with roles in the normal function of the nervous system and summarizing up-to-date information on ncRNA deregulation with a direct impact on OS associated with major neurodegenerative conditions.

Common genetic signatures of Alzheimer's disease in Down Syndrome

Background: People with Down Syndrome (DS) are born with an extra copy of Chromosome (Chr) 21 and many of these individuals develop Alzheimer's Disease (AD) when they age. This is due at least in part to the extra copy of the APP gene located on Chr 21. By 40 years, most people with DS have amyloid plaques which disrupt brain cell function and increase their risk for AD. About half of the people with DS develop AD and the associated dementia around 50 to 60 years of age, which is about the age at which the hereditary form of AD, early onset AD, manifests. In the absence of Chr 21 trisomy, duplication of APP alone is a cause of early onset Alzheimer's disease, making it likely that having three copies of APP is important in the development of AD and in DS. In individuals with both DS and AD, early behavior and cognition-related symptoms may include a reduction in social behavior, decreased enthusiasm, diminished ability to pay attention, sadness, fearfulness or anxiety, irritability, uncooperativeness or aggression, seizures that begin in adulthood, and changes in coordination and walking. Methods: We investigate the relationship between AD and DS through integrative analysis of genesets derived from a MeSH query of AD and DS associated beta amyloid peptides, Chr 21, GWAS identified AD risk factor genes, and differentially expressed genes in DS individuals. Results: Unique and shared aspects of each geneset were evaluated based on functional enrichment analysis, transcription factor profile and network analyses. Genes that may be important to both disorders: ACSM1, APBA2, APLP1, BACE2, BCL2L, COL18A1, DYRK1A, IK, KLK6, METTL2B, MTOR, NFE2L2, NFKB1, PRSS1, QTRT1, RCAN1, RUNX1, SAP18 SOD1, SYNJ1, S100B. Conclusions: Our findings indicate that oxidative stress, apoptosis, and inflammation/immune system processes likely underlie the pathogenesis of AD and DS.

Contributions of Molecular and Optical Techniques to the Clinical Diagnosis of Alzheimer's Disease

Alzheimer's disease (AD) is the most common neurodegenerative disorder worldwide. The distinctive neuropathological feature of AD is the intracerebral accumulation of two abnormally folded proteins: β-amyloid (Aβ) in the form of extracellular plaques, and tau in the form of intracellular neurofibrillary tangles. These proteins are considered disease-specific biomarkers, and the definite diagnosis of AD relies on their post-mortem identification in the brain. The clinical diagnosis of AD is challenging, especially in the early stages. The disease is highly heterogeneous in terms of clinical presentation and neuropathological features. This phenotypic variability seems to be partially due to the presence of distinct Aβ conformers, referred to as strains. With the development of an innovative technique named Real-Time Quaking-Induced Conversion (RT-QuIC), traces of Aβ strains were found in the cerebrospinal fluid of AD patients. Emerging evidence suggests that different conformers may transmit their strain signature to the RT-QuIC reaction products. In this review, we describe the current challenges for the clinical diagnosis of AD and describe how the RT-QuIC products could be analyzed by a surface-enhanced Raman spectroscopy (SERS)-based systems to reveal the presence of strain signatures, eventually leading to early diagnosis of AD with the recognition of individual disease phenotype.

PSEN1, PSEN2, and APP mutations in 404 Chinese pedigrees with familial Alzheimer's disease

INTRODUCTION

The PSENs/APP mutation distribution in Chinese patients with familial Alzheimer's disease (FAD) remains unclear. We aimed to analyze the genetic features of Chinese FAD pedigrees with and without PSENs/APP mutations.

METHODS

In total, 1330 patients with Alzheimer's disease (AD) or mild cognitive impairment in 404 pedigrees were enrolled from the Chinese Familial Alzheimer's Disease Network. PSENs/APP mutations and APOE frequencies were determined.

RESULTS

In total, 13.12% of pedigrees carried PSENs/APP missense mutations, 3.71% carried PSENs/APP synonymous/untranslated region variants, and 83.17% did not carry PSENs/APP mutations. Eleven missense mutations were first identified. In patients without PSENs/APP mutations, 44.31% carried one APOEε4 allele, and 14.85% two APOEε4 alleles.

DISCUSSION

The new PSENs/APP mutations indicate heterogeneity in AD pathogenesis between Chinese and other ethnic groups. The low mutation rate suggests the involvement of other genes/factors in Chinese FAD. APOEε4 might be a major gene for some FAD without PSENs/APP mutations.

Protein Homeostasis Networks and the Use of Yeast to Guide Interventions in Alzheimer's Disease

Alzheimer's Disease (AD) is a progressive multifactorial age-related neurodegenerative disorder that causes the majority of deaths due to dementia in the elderly. Although various risk factors have been found to be associated with AD progression, the cause of the disease is still unresolved. The loss of proteostasis is one of the major causes of AD: it is evident by aggregation of misfolded proteins, lipid homeostasis disruption, accumulation of autophagic vesicles, and oxidative damage during the disease progression. Different models have been developed to study AD, one of which is a yeast model. Yeasts are simple unicellular eukaryotic cells that have provided great insights into human cell biology. Various yeast models, including unmodified and genetically modified yeasts, have been established for studying AD and have provided significant amount of information on AD pathology and potential interventions. The conservation of various human biological processes, including signal transduction, energy metabolism, protein homeostasis, stress responses, oxidative phosphorylation, vesicle trafficking, apoptosis, endocytosis, and ageing, renders yeast a fascinating, powerful model for AD. In addition, the easy manipulation of the yeast genome and availability of methods to evaluate yeast cells rapidly in high throughput technological platforms strengthen the rationale of using yeast as a model. This review focuses on the description of the proteostasis network in yeast and its comparison with the human proteostasis network. It further elaborates on the AD-associated proteostasis failure and applications of the yeast proteostasis network to understand AD pathology and its potential to guide interventions against AD.

Epigenetics: Recent Advances and Its Role in the Treatment of Alzheimer's Disease

Objective: This review summarizes recent findings on the epigenetics of Alzheimer's disease (AD) and provides therapeutic strategies for AD.

Methods: We searched the following keywords: “genetics,” “epigenetics,” “Alzheimer's disease,” “DNA methylation,” “DNA hydroxymethylation,” “histone modifications,” “non-coding RNAs,” and “therapeutic strategies” in PubMed.

Results: In this review, we summarizes recent studies of epigenetics in AD, including DNA methylation/hydroxymethylation, histone modifications, and non-coding RNAs. There are no consistent results of global DNA methylation/hydroxymethylation in AD. Epigenetic genome-wide association studies show that many differentially methylated sites exist in AD. Several studies investigate the role of histone modifications in AD; for example, histone acetylation decreases, whereas H3 phosphorylation increases significantly in AD. In addition, non-coding RNAs, such as microRNA-16 and BACE1-antisense transcript (BACE1-AS), are associated with the pathology of AD. These epigenetic changes provide us with novel insights into the pathogenesis of AD and may be potential therapeutic strategies for AD.

Conclusion: Epigenetics is associated with the pathogenesis of AD, including DNA methylation/hydroxymethylation, histone modifications, and non-coding RNAs, which provide potential therapeutic strategies for AD.

Detecting Oxidative Stress Biomarkers in Neurodegenerative Disease Models and Patients

Oxidative stress is prominent in many neurodegenerative diseases. Along with mitochondrial dysfunction and pathological protein aggregation, increased levels of reactive oxygen and nitrogen species, together with impaired antioxidant defense mechanisms, are frequently observed in Alzheimer's, Parkinson's, Huntington's disease and amyotrophic lateral sclerosis. The presence of oxidative stress markers in patients' plasma and cerebrospinal fluid may aid early disease diagnoses, as well as provide clues regarding the efficacy of experimental disease-modifying therapies in clinical trials. In preclinical animal models, the detection and localization of oxidatively damaged lipids, proteins and nucleic acids helps to identify most vulnerable neuronal populations and brain areas, and elucidate the molecular pathways and the timeline of pathology progression. Here, we describe the protocol for the detection of oxidative stress markers using immunohistochemistry on formaldehyde-fixed, paraffin-embedded tissue sections, applicable to the analysis of postmortem samples and tissues from animal models. In addition, we provide a simple method for the detection of malondialdehyde in tissue lysates and body fluids, which is useful for screening and the identification of tissues and structures in the nervous system which are most affected by oxidative stress.

Mutation Analysis of the Genes Linked to Early Onset Alzheimer's Disease and Frontotemporal Lobar Degeneration

A lot of effort has been done to unravel the genetics underlying early-onset Alzheimer's disease (AD) and frontotemporal lobar degeneration (FTLD). However, many familial early-onset dementia (EOD) cases still show an unclear genetic background. The aim of this study was to evaluate the role of the known causative mutations and possible pathogenic variants associated with AD and FTLD in a Finnish EOD cohort. The cohort consisted of 39 patients (mean age at onset 54.8 years, range 39-65) with a positive family history of dementia or an atypical or rapidly progressive course of the disease. None of the patients carried the C9orf72 hexanucleotide repeat expansion. Mutations and variants in APP, PSEN1, PSEN2, MAPT, GRN, VCP, CHMP2B, FUS, TARDBP, TREM2, TMEM106B, UBQLN2, SOD1, PRNP, UBQLN1, and BIN1 were screened by using a targeted next generation sequencing panel. Two previously reported pathogenic mutations (PSEN1 p.His163Arg and MAPT p.Arg406Trp) were identified in the cohort. Both patients had familial dementia with an atypical early onset phenotype. In addition, a heterozygous p.Arg71Trp mutation in PSEN2 with an uncertain pathogenic nature was identified in a patient with neuropathologically confirmed AD. In conclusion, targeted investigation of the known dementia-linked genes is worthwhile in patients with onset age under 55 and a positive family history, as well as in patients with atypical features.

Behavioral and neural network abnormalities in human APP transgenic mice resemble those of App knock-in mice and are modulated by familial Alzheimer's disease mutations but not by inhibition of BACE1

BACKGROUND

Alzheimer's disease (AD) is the most frequent and costly neurodegenerative disorder. Although diverse lines of evidence suggest that the amyloid precursor protein (APP) is involved in its causation, the precise mechanisms remain unknown and no treatments are available to prevent or halt the disease. A favorite hypothesis has been that APP contributes to AD pathogenesis through the cerebral accumulation of the amyloid-β peptide (Aβ), which is derived from APP through sequential proteolytic cleavage by BACE1 and γ-secretase. However, inhibitors of these enzymes have failed in clinical trials despite clear evidence for target engagement.

METHODS

To further elucidate the roles of APP and its metabolites in AD pathogenesis, we analyzed transgenic mice overexpressing wildtype human APP (hAPP) or hAPP carrying mutations that cause autosomal dominant familial AD (FAD), as well as App knock-in mice that do not overexpress hAPP but have two mouse App alleles with FAD mutations and a humanized Aβ sequence.

RESULTS

Although these lines of mice had marked differences in cortical and hippocampal levels of APP, APP C-terminal fragments, soluble Aβ, Aβ oligomers and age-dependent amyloid deposition, they all developed cognitive deficits as well as non-convulsive epileptiform activity, a type of network dysfunction that also occurs in a substantive proportion of humans with AD. Pharmacological inhibition of BACE1 effectively reduced levels of amyloidogenic APP C-terminal fragments (C99), soluble Aβ, Aβ oligomers, and amyloid deposits in transgenic mice expressing FAD-mutant hAPP, but did not improve their network dysfunction and behavioral abnormalities, even when initiated at early stages before amyloid deposits were detectable.

CONCLUSIONS

hAPP transgenic and App knock-in mice develop similar pathophysiological alterations. APP and its metabolites contribute to AD-related functional alterations through complex combinatorial mechanisms that may be difficult to block with BACE inhibitors and, possibly, also with other anti-Aβ treatments.

The Other Side of Alzheimer's Disease: Influence of Metabolic Disorder Features for Novel Diagnostic Biomarkers

Nowadays, the amyloid cascade hypothesis is the dominant model to explain Alzheimer's disease (AD) pathogenesis. By this hypothesis, the inherited genetic form of AD is discriminated from the sporadic form of AD (SAD) that accounts for 85-90% of total patients. The cause of SAD is still unclear, but several studies have shed light on the involvement of environmental factors and multiple susceptibility genes, such as Apolipoprotein E and other genetic risk factors, which are key mediators in different metabolic pathways (e.g., glucose metabolism, lipid metabolism, energetic metabolism, and inflammation). Furthermore, growing clinical evidence in AD patients highlighted the presence of affected systemic organs and blood similarly to the brain. Collectively, these findings revise the canonical understating of AD pathogenesis and suggest that AD has metabolic disorder features. This review will focus on AD as a metabolic disorder and highlight the contribution of this novel understanding on the identification of new biomarkers for improving an early AD diagnosis.

Genetic architecture of Alzheimer's disease

Advances in genetic and genomic technologies over the last thirty years have greatly enhanced our knowledge concerning the genetic architecture of Alzheimer's disease (AD). Several genes including APP, PSEN1, PSEN2, and APOE have been shown to exhibit large effects on disease susceptibility, with the remaining risk loci having much smaller effects on AD risk. Notably, common genetic variants impacting AD are not randomly distributed across the genome. Instead, these variants are enriched within regulatory elements active in human myeloid cells, and to a lesser extent liver cells, implicating these cell and tissue types as critical to disease etiology. Integrative approaches are emerging as highly effective for identifying the specific target genes through which AD risk variants act and will likely yield important insights related to potential therapeutic targets in the coming years. In the future, additional consideration of sex- and ethnicity-specific contributions to risk as well as the contribution of complex gene-gene and gene-environment interactions will likely be necessary to further improve our understanding of AD genetic architecture.

Endoplasmic Reticulum Stress and Unfolded Protein Response in Neurodegenerative Diseases

The endoplasmic reticulum (ER) is an important organelle involved in protein quality control and cellular homeostasis. The accumulation of unfolded proteins leads to an ER stress, followed by an adaptive response via the activation of the unfolded protein response (UPR), PKR-like ER kinase (PERK), inositol-requiring transmembrane kinase/endoribonuclease 1α (IRE1α) and activating transcription factor 6 (ATF6) pathways. However, prolonged cell stress activates apoptosis signaling leading to cell death. Neuronal cells are particularly sensitive to protein misfolding, consequently ER and UPR dysfunctions were found to be involved in many neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and prions diseases, among others characterized by the accumulation and aggregation of misfolded proteins. Pharmacological UPR modulation in affected tissues may contribute to the treatment and prevention of neurodegeneration. The association between ER stress, UPR and neuropathology is well established. In this review, we provide up-to-date evidence of UPR activation in neurodegenerative disorders followed by therapeutic strategies targeting the UPR and ameliorating the toxic effects of protein unfolding and aggregation.

Amyloid precursor protein intracellular domain-dependent regulation of FOXO3a inhibits adult hippocampal neurogenesis

The amyloid precursor protein (APP) intracellular domain (AICD) is a metabolic by-product of APP produced through sequential proteolytic cleavage by α-, β-, and γ-secretases. The interaction between AICD and Fe65 has been reported to impair adult neurogenesis in vivo. However, the exact role of AICD in mediating neural stem cell fate remains unclear. To identify the role of AICD in neuronal proliferation and differentiation, as well as to clarify the molecular mechanisms underlying the role of AICD in neurogenesis, we first generated a mouse model expressing the Rosa26-based AICD transgene. AICD overexpression did not alter the spatiotemporal expression pattern of full-length APP or accumulation of its metabolites. In addition, AICD decreased the newly generated neural progenitor cell (NPC) pool, inhibited the proliferation and differentiation efficiency of NPCs, and increased cell death both in vitro and in vivo. Given that abnormal neurogenesis is often associated with depression-like behavior in adult mice, we conducted a forced swim test and tail suspension test with AICD mice and found a depression-like behavioral phenotype in AICD transgenic mice. Moreover, AICD stimulated FOXO3a transcriptional activation, which in turn negatively regulated AICD. In addition, functional loss of FOXO3a in NPCs derived from the hippocampal dentate gyrus of adult AICD transgenic mice rescued neurogenesis defects. AICD also increased the mRNA expression of FOXO3a target genes related to neurogenesis and cell death. These results suggest that FOXO3a is the functional target of AICD in neurogenesis regulation. Our study reveals the role of AICD in mediating neural stem cell fate to maintain homeostasis during brain development via interaction with FOXO3a.

Genetics of Chronic Traumatic Encephalopathy

Although chronic traumatic encephalopathy (CTE) garners substantial attention in the media and there have been marked scientific advances in the last few years, much remains unclear about the role of genetic risk in CTE. Two athletes with comparable contact-sport exposure may have varying amounts of CTE neuropathology, suggesting that other factors, including genetics, may contribute to CTE risk and severity. In this review, we explore reasons why genetics may be important for CTE, concepts in genetic study design for CTE (including choosing controls, endophenotypes, gene by environment interaction, and epigenetics), implicated genes in CTE (including APOE, MAPT, and TMEM106B), and whether predictive genetic testing for CTE should be considered.

Molecular and cellular mechanisms underlying the pathogenesis of Alzheimer's disease

Alzheimer’s disease (AD) is the most common neurodegenerative disorder seen in age-dependent dementia. There is currently no effective treatment for AD, which may be attributed in part to lack of a clear underlying mechanism. Studies within the last few decades provide growing evidence for a central role of amyloid β (Aβ) and tau, as well as glial contributions to various molecular and cellular pathways in AD pathogenesis. Herein, we review recent progress with respect to Aβ- and tau-associated mechanisms, and discuss glial dysfunction in AD with emphasis on neuronal and glial receptors that mediate Aβ-induced toxicity. We also discuss other critical factors that may affect AD pathogenesis, including genetics, aging, variables related to environment, lifestyle habits, and describe the potential role of apolipoprotein E (APOE), viral and bacterial infection, sleep, and microbiota. Although we have gained much towards understanding various aspects underlying this devastating neurodegenerative disorder, greater commitment towards research in molecular mechanism, diagnostics and treatment will be needed in future AD research.

Diagnostic Approach of Early-Onset Dementia with Negative Family History: Implications from Two Cases of Early-Onset Alzheimer's Disease with De Novo PSEN1 Mutation

For early-onset Alzheimer's disease (EOAD) cases with unclear family history, most cases are sporadic. Some cases are positive in genetic findings, that is, either incomplete penetrance or de novo mutation. We aimed to focus on EOAD cases with de novo mutations. Case reports and literature review were performed. The implication for diagnostic approach of early-onset dementia with negative family history was developed. We reported two Chinese EOAD cases with de novo mutations. The genotype PSEN1 G206S appeared to correlate with the phenotype of EOAD with pure cognitive problems. The second case had a PSEN1 M233V mutation with an earlier age of onset of 25 with cognitive decline, parkinsonism, and epilepsy. Although EOAD due to de novo mutations is not common, it should be considered in patients with a phenotype of progressive cognitive decline and amyloid positivity on PET or CSF analysis.

Neuroinflammation drives APOE genotype-dependent differential expression of neprilysin

Alzheimer's disease (AD) is a devastating neurodegenerative disorder characterized by the deposition of amyloid-beta (Aβ) plaques and widespread neuroinflammation. While the cause of AD remains unknown, multiple factors likely contribute to the disease, including heart disease, diabetes, previous head injury, as well as a number of genetic determinants. Inheritance of the apolipoprotein (APOE) ε4 allele represents the strongest genetic risk factor for development of AD, driving pathogenesis and increasing overall disease severity. APOE has long been recognized as a key regulator of cholesterol homeostasis, although a greater appreciation now exists for its role in various innate immune system processes. Indeed, APOE modulates inflammatory environments in brain in large part by altering gene expression profiles in glia, important mediators of immunity in the CNS. While the association between APOE and AD was first observed nearly three decades ago, the mechanism by which APOE ε4 influences the etiology and pathophysiology of AD is not well characterized. Overwhelming data supports the hypothesis that APOE ε4 dysregulates central amyloid metabolism by an undetermined molecular mechanism, thus laying the foundation for disease. A host of amyloid-degrading enzymes (ADEs) regulate Aβ accumulation in brain, and therefore represent valuable therapeutic targets. Neprilysin (NEP), a metalloendopeptidase expressed by activated microglia and astrocytes, is a broad-spectrum ADE able to degrade a variety of Aβ species. Here we describe in vivo and in vitro experiments designed to investigate the potential for APOE genotype to differentially regulate glial NEP in brain under neuroinflammatory conditions. Our results provide a novel mechanism by which APOE genotype-dependent differential expression of NEP by glia during neuroinflammation may contribute to AD pathogenesis.

Immunotherapies for Aging-Related Neurodegenerative Diseases-Emerging Perspectives and New Targets

Neurological disorders such as Alzheimer's disease (AD), Lewy body dementia (LBD), frontotemporal dementia (FTD), and vascular dementia (VCID) have no disease-modifying treatments to date and now constitute a dementia crisis that affects 5 million in the USA and over 50 million worldwide. The most common pathological hallmark of these age-related neurodegenerative diseases is the accumulation of specific proteins, including amyloid beta (Aβ), tau, α-synuclein (α-syn), TAR DNA-binding protein 43 (TDP43), and repeat-associated non-ATG (RAN) peptides, in the intra- and extracellular spaces of selected brain regions. Whereas it remains controversial whether these accumulations are pathogenic or merely a byproduct of disease, the majority of therapeutic research has focused on clearing protein aggregates. Immunotherapies have garnered particular attention for their ability to target specific protein strains and conformations as well as promote clearance. Immunotherapies can also be neuroprotective: by neutralizing extracellular protein aggregates, they reduce spread, synaptic damage, and neuroinflammation. This review will briefly examine the current state of research in immunotherapies against the 3 most commonly targeted proteins for age-related neurodegenerative disease: Aβ, tau, and α-syn. The discussion will then turn to combinatorial strategies that enhance the effects of immunotherapy against aggregating protein, followed by new potential targets of immunotherapy such as aging-related processes.

BaiHui: cross-species brain-specific network built with hundreds of hand-curated datasets

MOTIVATION

Functional gene networks, representing how likely two genes work in the same biological process, are important models for studying gene interactions in complex tissues. However, a limitation of the current network-building scheme is the lack of leveraging evidence from multiple model organisms as well as the lack of expert curation and quality control of the input genomic data.

RESULTS

Here, we present BaiHui, a brain-specific functional gene network built by probabilistically integrating expertly-hand-curated (by reading original publications) heterogeneous and multi-species genomic data in human, mouse and rat brains. To facilitate the use of this network, we deployed a web server through which users can query their genes of interest, visualize the network, gain functional insight from enrichment analysis and download network data. We also illustrated how this network could be used to generate testable hypotheses on disease gene prioritization of brain disorders.

AVAILABILITY AND IMPLEMENTATION

BaiHui is freely available at: http://guanlab.ccmb.med.umich.edu/BaiHui/.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

A Three-Dimensional Alzheimer's Disease Cell Culture Model Using iPSC-Derived Neurons Carrying A246E Mutation in PSEN1

Alzheimer's disease (AD) is a chronic brain disorder characterized by progressive intellectual decline and memory and neuronal loss, caused mainly by extracellular deposition of amyloid-β (Aβ) and intracellular accumulation of hyperphosphorylated tau protein, primarily in areas implicated in memory and learning as prefrontal cortex and hippocampus. There are two forms of AD, a late-onset form that affects people over 65 years old, and the early-onset form, which is hereditable and affect people at early ages ~45 years. To date, there is no cure for the disease; consequently, it is essential to develop new tools for the study of processes implicated in the disease. Currently, in vitro AD three-dimensional (3D) models using induced pluripotent stem cells (iPSC)-derived neurons have broadened the horizon for in vitro disease modeling and gained interest for mechanistic studies and preclinical drug discovery due to their potential advantages in providing a better physiologically relevant information and more predictive data for in vivo tests. Therefore, this study aimed to establish a 3D cell culture model of AD in vitro using iPSCs carrying the A246E mutation. We generated human iPSCs from fibroblasts from a patient with AD harboring the A246E mutation in the PSEN1 gene. Cell reprogramming was performed using lentiviral vectors with Yamanaka's factors (OSKM: Oct4, Sox2, Klf4, and c-Myc). The resulting iPSCs expressed pluripotency genes (such as Nanog and Oct4), alkaline phosphatase activity, and pluripotency stem cell marker expression, such as OCT4, SOX2, TRA-1-60, and SSEA4. iPSCs exhibited the ability to differentiate into neuronal lineage in a 3D environment through dual SMAD inhibition as confirmed by Nestin, MAP2, and Tuj1 neural marker expression. These iPSC-derived neurons harbored Aβ oligomers confirmed by Western Blot (WB) and immunostaining. With human iPSC-derived neurons able to produce Aβ oligomers, we established a novel human hydrogel-based 3D cell culture model that recapitulates Aβ aggregation without the need for mutation induction or synthetic Aβ exposure. This model will allow the study of processes implicated in disease spread throughout the brain, the screening of molecules or compounds with therapeutic potential, and the development of personalized therapeutic strategies.

Crocin attenuates the granular cells damages on the dentate gyrus and pyramidal neurons in the CA3 regions of the hippocampus and frontal cortex in the rat model of Alzheimer's disease

Amyloid β-peptides (Aβ) are considered as a major hallmark of Alzheimer's disease (AD) that can induce synaptic loss and apoptosis in brain regions, particularly in the cortex and the hippocampus. Evidence suggests that crocin, as the major component of saffron, can exhibit neuromodulatory effects in AD. However, specific data related to their efficacy to attenuate the synaptic loss and neuronal death in animal models of AD are limited. Hence, we investigated the efficacy of crocin in the CA3 and dentate gyrus (DG) regions of the hippocampus and also in frontal cortex neurons employing a rat model of AD. Male Wistar rats were randomly divided into control, sham, AD model, crocin, and AD model + crocin groups, with 8 rats per group. AD model was established by injecting Aβ1-42 into the frontal cortex rats, and thereafter the rats were administrated by crocin (30 mg/kg) for a duration of 12-day. The number of live cells, neuronal arborization and apoptosis were measured using a Cresyl violet, Golgi-Cox and TUNEL staining, respectively. Results showed that, the number of live cells in the hippocampus pyramidal neurons in the CA3 and granular cells in the DG regions of the AD rats significantly decreased, which was significantly rescued by crocin. Compared with the control group, the axonal, spine and dendrites arborization in the frontal cortex and CA3 region of the AD model group significantly decreased. The crocin could significantly reverse this arborization loss in the AD rats (P < 0.05). The apoptotic cell number in the CA3 and DG regions in the AD model group was significantly higher than that of the control group (P < 0.05), while crocin significantly decreased the apoptotic cell number in the AD group (P < 0.05). Conclusion. Crocin can improve the synaptic loss and neuronal death of the AD rats possibly by reducing the neuronal apoptosis.

Molecular Insight into the Therapeutic Promise of Targeting APOE4 for Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease that causes chronic cognitive dysfunction. Most of the AD cases are late onset, and the apolipoprotein E (APOE) isoform is a key genetic risk factor. The APOE gene has 3 key alleles in humans including APOE2, APOE3, and APOE4. Among them, APOE4 is the most potent genetic risk factor for late-onset AD (LOAD), while APOE2 has a defensive effect. Research data suggest that APOE4 leads to the pathogenesis of AD through various processes such as accelerated beta-amyloid aggregations that raised neurofibrillary tangle formation, cerebrovascular diseases, aggravated neuroinflammation, and synaptic loss. However, the precise mode of actions regarding in what way APOE4 leads to AD pathology remains unclear. Since APOE contributes to several pathological pathways of AD, targeting APOE4 might serve as a promising strategy for the development of novel drugs to combat AD. In this review, we focus on the recent studies about APOE4-targeted therapeutic strategies that have been advanced in animal models and are being prepared for use in humans for the management of AD.

Shared (epi)genomic background connecting neurodegenerative diseases and type 2 diabetes

The progressive aging of populations has resulted in an increased prevalence of chronic pathologies, especially of metabolic, neurodegenerative and movement disorders. In particular, type 2 diabetes (T2D), Alzheimer’s disease (AD) and Parkinson’s disease (PD) are among the most prevalent age-related, multifactorial pathologies that deserve particular attention, given their dramatic impact on patient quality of life, their economic and social burden as well the etiopathogenetic mechanisms, which may overlap in some cases. Indeed, the existence of common triggering factors reflects the contribution of mutual genetic, epigenetic and environmental features in the etiopathogenetic mechanisms underlying T2D and AD/PD. On this subject, this review will summarize the shared (epi)genomic features that characterize these complex pathologies. In particular, genetic variants and gene expression profiles associated with T2D and AD/PD will be discussed as possible contributors to determine the susceptibility and progression to these disorders. Moreover, potential shared epigenetic modifications and factors among T2D, AD and PD will also be illustrated. Overall, this review shows that findings from genomic studies still deserves further research to evaluate and identify genetic factors that directly contribute to the shared etiopathogenesis. Moreover, a common epigenetic background still needs to be investigated and characterized. The evidences discussed in this review underline the importance of integrating large-scale (epi)genomic data with additional molecular information and clinical and social background in order to finely dissect the complex etiopathogenic networks that build up the “disease interactome” characterizing T2D, AD and PD.

Application of Next-Generation Sequencing in Neurodegenerative Diseases: Opportunities and Challenges

Genetic factors (gene mutations) lead to various rare and prevalent neurological diseases. Identification of underlying mutations in neurodegenerative diseases is of paramount importance due to the heterogeneous nature of the genome and different clinical manifestations. An early and accurate molecular diagnosis are cardinal for neurodegenerative patients to undergo proper therapeutic regimens. The next-generation sequencing (NGS) method examines up to millions of sequences at a time. As a result, the rare molecular diagnoses, previously presented with "unknown causes", are now possible in a short time. This method generates a large amount of data that can be utilized in patient management. Since each person has a unique genome, the NGS has transformed diagnostic and therapeutic strategies into sequencing and individual genomic mapping. However, this method has disadvantages like other diagnostic methods. Therefore, in this review, we aimed to briefly summarize the NGS method and correlated studies to unravel the genetic causes of neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, epilepsy, and MS. Finally, we discuss the NGS challenges and opportunities in neurodegenerative diseases.

Sorting Out the Role of the Sortilin-Related Receptor 1 in Alzheimer's Disease

Sortilin-related receptor 1 (SORL1) encodes a large, multi-domain containing, membrane-bound receptor involved in endosomal sorting of proteins between the trans-Golgi network, endosomes and the plasma membrane. It is genetically associated with Alzheimer's disease (AD), the most common form of dementia. SORL1 is a unique gene in AD, as it appears to show strong associations with the common, late-onset, sporadic form of AD and the rare, early-onset familial form of AD. Here, we review the genetics of SORL1 in AD and discuss potential roles it could play in AD pathogenesis.

The Important Interface Between Apolipoprotein E and Neuroinflammation in Alzheimer's Disease

Alzheimer’s disease (AD) is the most prevalent form of neurodegenerative disease, currently affecting over 5 million Americans with projections expected to rise as the population ages. The hallmark pathologies of AD are Aβ plaques composed of aggregated beta-amyloid (Aβ), and tau tangles composed of hyperphosphorylated, aggregated tau. These pathologies are typically accompanied by an increase in neuroinflammation as an attempt to ameliorate the pathology. This idea has pushed the field toward focusing on mechanisms and the influence neuroinflammation has on disease progression. The vast majority of AD cases are sporadic and therefore, researchers investigate genetic risk factors that could lead to AD. Apolipoprotein E (ApoE) is the largest genetic risk factor for developing AD. ApoE has 3 isoforms-ApoE2, ApoE3, and ApoE4. ApoE4 constitutes an increased risk of AD, with one copy increasing the risk about 4-fold and two copies increasing the risk about 15-fold compared to those with the ApoE3 allele. ApoE4 has been shown to play a role in Aβ deposition, tau tangle formation, neuroinflammation and many subsequent pathways. However, while we know that ApoE4 plays a role in these pathways and virtually all aspects of AD, the exact mechanism of how ApoE4 impacts AD progression is murky at best and therefore the role ApoE4 plays in these pathways needs to be elucidated. This review aims to discuss the current literature regarding the pathways and mechanisms of ApoE4 in AD progression with a focus on its role in neuroinflammation.

New Insights into the Molecular Bases of Familial Alzheimer's Disease

Like several neurodegenerative disorders, such as Prion and Parkinson diseases, Alzheimer's disease (AD) is characterized by spreading mechanism of aggregated proteins in the brain in a typical "prion-like" manner. Recent genetic studies have identified in four genes associated with inherited AD (amyloid precursor protein-APP, Presenilin-1, Presenilin-2 and Apolipoprotein E), rare mutations which cause dysregulation of APP processing and alterations of folding of the derived amyloid beta peptide (A). Accumulation and aggregation of A in the brain can trigger a series of intracellular events, including hyperphosphorylation of tau protein, leading to the pathological features of AD. However, mutations in these four genes account for a small of the total genetic risk for familial AD (FAD). Genome-wide association studies have recently led to the identification of additional AD candidate genes. Here, we review an update of well-established, highly penetrant FAD-causing genes with correlation to the protein misfolding pathway, and novel emerging candidate FAD genes, as well as inherited risk factors. Knowledge of these genes and of their correlated biochemical cascade will provide several potential targets for treatment of AD and aging-related disorders.

Use of ocular biomarkers as a potential tool for early diagnosis of Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disease worldwide which unfortunately has no known effective cure to date. Despite many clinical trials indicating the effectiveness of preclinical treatment, a sensitive tool for screening of AD is yet to be developed. Due to multiple similarities between ocular and the brain tissue, the eye is being explored by researchers for this purpose, with utmost attention focused on the retinal tissue. Besides visual functional impairment, neuronal degeneration and apoptosis, retinal nerve fiber degeneration, increase in the cup-to-disc ratio, and retinal vascular thinning and tortuosity are the changes observed in the retinal tissue which are related to AD. Studies have shown that targeting these changes in the retina is an effective way of reducing the degeneration of retinal neuronal tissue. Similar mechanisms of neurodegeneration have been demonstrated in the brain and the eyes of AD patients. Multiple studies are underway to investigate the potential of diagnosing AD and detection of amyloid-β (Aβ) levels in the retinal tissue. Since the tissues in the anterior segment of the eye are more accessible for in vivo imaging and examination, they have more potential as screening biomarkers. This article provides a concise review of available literature on the ocular biomarkers in anterior and posterior segments of the eye including the cornea, aqueous humour (AH), crystalline lens, and retina in AD. This review will also highlight the newer technological tools available for the detection of potential biomarkers in the eye for early diagnosis of AD.