Molecular interaction of stress granules with Tau and autophagy in Alzheimer's disease.

Stress Granules (SGs) are RNA granules composed of untranslated mRNA and associated proteins, which are related to the cytoplasmic metabolism of mRNA in response to cellular stress and certain drug stimuli. Physiological SGs are dynamic structures that protect cells from the effects of stress, and continuous stress ripens the SGs into more stable complexes. Numerous studies have found that dysregulation of RNA metabolism in stress response led to misfolded protein aggregation in the pathophysiology of neurodegenerative diseases. For example, in neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), Alzheimer's disease (AD), and Parkinson's disease (PD), SGs aggregation is mainly due to up-regulation of SGs formation and down-regulation of SGs clearance. Recent studies have revealed the role of SGs in the pathogenesis and pathology of AD, especially the interaction of SGs and RNA-binding proteins with Tau and autophagy. Aggregation of SGs and increased RNA-binding proteins, especially TIA1, can facilitate Tau misfolding and propagation, and vice versa. Autophagy dysfunction disrupts the normal pathway of SGs clearance. In this review, we summarized the regulation of SGs and their relationship with Tau protein and autophagy, as well as the pathological mechanisms of AD such as RNA splicing, microglial cell proliferation and phagocytosis.

Application of Cerebrospinal Fluid AT(N) Framework on the Diagnosis of AD and Related Cognitive Disorders in Chinese Han Population.

BACKGROUND: Studies concerning the impact of the AT(N) framework on diagnostic capability in the dementia population are lacking. We aimed to explore the diagnostic application of CSF AT(N) framework in clinical routines of Alzheimer's disease (AD) as well as differential diagnosis of other cognitive diseases in the Chinese Han population. PATIENTS AND METHODS: A total of 137 patients with cognitive disorders received CSF tests of Aß42, t-tau and p-tau181. Their CSF biomarker results were categorized and interpreted by the AT(N) framework. Neurologists provided a diagnosis both pre- and post-CSF biomarker disclosure with corresponding diagnostic confidence. RESULTS: The total initial diagnosis included 79 patients with AD and 58 patients with non-AD (NAD). The results of CSF biomarkers led to a diagnostic change of 28% in the cohort. Approximately 81.5% (n=53) of 65 patients whose CSF biomarker showed an underlying AD pathology were finally diagnosed as AD, with an increase of 17.5% in diagnostic confidence. Thirty-seven CSF results indicating NAD pathologic changes contributed to an exclusion of AD in 56.8% (n=21) of the patients along with a modest increase of 9.8% in average confidence. Thirty-five patients with normal CSF biomarkers maintained the diagnosis of NAD in 68.6% (n=24) of the group, leading to a slight elevation of 7.6% in confidence. CONCLUSION: We found that the presence of amyloid pathology (A+) is contributable to diagnosing AD and improving confidence. On occasion of negative amyloid pathology (A-), with or without tau pathology, gaining uncertainty of the primary AD diagnosis would diminish the corresponding confidence. To the best of our knowledge, this is the first study performed in the Chinese Han population with cognitive disorders that explores the clinical capability of CSF AT(N) framework in a quantitative way.

The discriminative capacity of CSF ß-amyloid 42 and Tau in neurodegenerative diseases in the Chinese population.

INTRODUCTION: In the past few years, the ß-amyloid 42 peptide and tau protein in cerebrospinal fluid (CSF) have become primary diagnostic biomarkers in differentiating Alzheimer's disease (AD) and cognitive normal controls. As we know, several neurodegenerative diseases have been reported to overlap with AD in neuropathology and clinical symptoms. To examine the discriminative utility of these biomarkers in AD and other neurodegenerative diseases, we measured them in a cohort of Chinese population. METHODS: We measured CSF Aß42, t-tau and p-tau181 by ELISA tests and calculated the ratios of t-tau/Aß42 and p-tau181/Aß42 in 240 Chinese Han patients with AD (n = 82), frontotemporal dementia (FTD, n = 20), Huntington's disease (HD, n = 27), multiple system atrophy (MSA, n = 24), spinocerebellar ataxia type-3 (SCA3, n = 27), amyotrophic lateral sclerosis (ALS, n = 36) and controls (n = 24). RESULTS: As expected, all biomarkers showed high discriminative capacity between AD and non-AD groups (p < .05) except for the elevated CSF t-tau in FTD (p > .05). Comparing with the controls, tau related biomarkers significantly elevated in the FTD (p < .001) and MSA (p < .05) groups. Surprisingly, comparing with controls, we found that CSF Aß42 increased remarkably in the SCA3 (p < .05), HD and ALS groups (p < .001), achieving a high specificity, respectively. CONCLUSION: To our best knowledge, this is the first comprehensive study in the Han Chinese population that confirmed the discriminative utility of CSF Aß42 and tau biomarkers between AD and other neurodegenerative diseases.

Mutation screening in Chinese patients with familial Alzheimer's disease by whole-exome sequencing.

Familial Alzheimer's disease (FAD) is characterized by a positive family history of dementia and typically occurs at an early age with an autosomal dominant pattern of inheritance. Amyloid precursor protein (APP), presenilin1 (PSEN1), and presenilin2 (PSEN2) are the major causative genes of FAD. The spectrum of mutations in patients with FAD has been investigated extensively in the Caucasian population but rarely in the Chinese population. Here, we performed whole-exome sequencing in a total of 15 unrelated Chinese patients with FAD. Among them, 12 were found to carry missense variants in APP, PSEN1, and PSEN2. Two novel variants (APP: p.D244G, p.K687Q), 3 variants not previously associated with FAD (APP: p.T297M, p.D332G; PSEN1: p.R157S), and 7 previously reported pathogenic variants (APP: p.V717I; PSEN1: p.M139I, p.T147I, p.L173W, p.F177S, p.R269H; PSEN2: p.V139M) were identified. The novel variant APP p.K687Q was classified as likely pathogenic, and the other 4 variants (APP: p.D244G, p.T297M, p.D332G; PSEN1: p.R157S) were classified as uncertain significance. Therefore, APP, PSEN1, and PSEN2 mutations account for 2 (25.0%), 5 (62.5%), and 1 (12.5%) of the genotyped cases positive for mutations, respectively. Furthermore, the genotype-phenotype correlations were described. Our findings broaden the genetic spectrum of FAD with APP, PSEN1, and PSEN2 variants.