Tingting Xiao

Polygenic Analysis of Late-Onset Alzheimer's Disease from Mainland China.

Recently, a number of single nucleotide polymorphisms (SNPs) were identified to be associated with late-onset Alzheimer disease (LOAD) through genome-wide association study data. Identification of SNP-SNP interaction played an important role in better understanding genetic basis of LOAD. In this study, fifty-eight SNPs were screened in a cohort of 229 LOAD cases and 318 controls from mainland China, and their interaction was evaluated by a series of analysis methods. Seven risk SNPs and six protective SNPs were identified to be associated with LOAD. Risk SNPs included rs9331888 (CLU), rs6691117 (CR1), rs4938933 (MS4A), rs9349407 (CD2AP), rs1160985 (TOMM40), rs4945261 (GAB2) and rs5984894 (PCDH11X); Protective SNPs consisted of rs744373 (BIN1), rs1562990 (MS4A), rs597668 (EXOC3L2), rs9271192 (HLA-DRB5/DRB1), rs157581 and rs11556505 (TOMM40). Among positive SNPs presented above, we found the interaction between rs4938933 (risk) and rs1562990 (protective) in MS4A weakened their each effect for LOAD; for three significant SNPs in TOMM40, their cumulative interaction induced the two protective SNPs effects lost and made the risk SNP effect aggravate for LOAD. Finally, we found rs6656401-rs3865444 (CR1-CD33) pairs were significantly associated with decreasing LOAD risk, while rs28834970-rs6656401 (PTK2B-CR1), and rs28834970-rs6656401 (PTK2B-CD33) were associated with increasing LOAD risk. In a word, our study indicates that SNP-SNP interaction existed in the same gene or cross different genes, which could weaken or aggravate their initial single effects for LOAD.

The role of exosomes in the pathogenesis of Alzheimer’ disease

Exosomes are small vesicles secreted by most cell types including neurons that function in intercellular communication through transfer of their cargo or encapsulate and eliminate unnecessary cellular components and therefore have a broad impact on nerve development, activation and regeneration. In addition, exosomes have been observed to be involved in spreading pathological misfolded proteins, thereby leading to the onset and propagation of disease. Alzheimer disease (AD) is the most common form of dementia and characterized by two types of lesions: amyloid plaques and neurofibrillary tangles. Accumulating evidence has demonstrated that exosomes are associated with amyloid precursor (APP) and Tau proteins and play a controversial role in Alzheimer’s disease process. In this review, we will discuss the role of exosomes in the metabolism and secretion of APP and Tau proteins and their subsequent impact on AD pathogenesis.

Reply: High prevalence of CHCHD10 mutations in patients with frontotemporal dementia from China

Sir, Data recently published in Brain indicate that the CHCHD10 gene (NM_213720.2) plays an important role in frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) (Bannwarth et al. , 2014; Johnson et al. , 2014; Muller et al. , 2014; Dols-Icardo et al. , 2015; Marroquin et al. , 2015). The CHCHD10 gene is located on chromosome 22q.11.23 and encodes a protein enriched at cristae junctions in mitochondria. Mutations in this gene cause mitochondrial dysfunction, which leads to disease. The study is the first report proposing that mitochondrial dysfunction contributes to the pathogenesis of ALS and FTD. The prevalence of the CHCHD10 mutation has been reported in a number of nationalities, including German (2.3%), French (2.6%), Spanish (0.68%) and Italian (1%) populations (Chaussenot et al. , 2014; Muller et al. , 2014; Chio et al. , 2015; Dols-Icardo et al. , 2015). However, no mutation analysis has been performed in Asian populations, and most variants have been on the ALS or ALS-FTD spectrum. Here, we present data showing that the CHCHD10 mutation is common in patients with the pure FTD phenotype in China. Patients with ALS ( n = 165) and FTD ( n = 65) were recruited at the outpatient clinic of Xiangya Hospital, China. The patients with ALS did not have mutations in SOD1 , FUS , C9orf72 and TARDBP . Additionally, the patients with FTD did not have any variants of MAPT , GRN and C9orf72 . We screened all of the exons in the CHCHD10 gene using Sanger sequencing. The analyses also included 500 unaffected individuals with matched geographical ancestry as healthy controls. This study was approved by the ethics committee of Xiangya Hospital, Central South University in China. …

Identification of CHCHD10 Mutation in Chinese Patients with Alzheimer Disease

CHCHD10 gene has been identified to be associated with frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). Considering the clinical phenotype and pathology characterization were overlapped between FTD and Alzheimer disease (AD), and so far, no systematic analysis of CHCHD10 mutation was conducted in patients with AD in Asian population. Therefore, we screened of all exons in CHCHD10 in a cohort of 484 AD patients (60 with family history) from Mainland China. A heterozygous variant p.A35D (c.104C>A), previously reported in a patient with FTD in Italian population, was identified in a female patient with sporadic LOAD. The age at onset of mutation carrier was 86, presented as typical amnestic dementia. The mutation was found to be deleterious according to in silico predictions and excluded in 500 ethnically and geographically matched controls. Our finding revealed the clinical manifestations of variant p.A35D (c.104C>A) in a LOAD case and indicated that CHCHD10 mutation was presented in different types of dementia.

Screening of SOD1 , FUS and TARDBP genes in patients with amyotrophic lateral sclerosis in central-southern China

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease affecting motor neurons of the brain, brainstem and spinal cord. To date, mutations in more than 30 genes have been linked to the pathogenesis of ALS. Among them, SOD1, FUS and TARDBP are ranked as the three most common genes associated with ALS. However, no mutation analysis has been reported in central-southern China. In this study, we sequenced SOD1, FUS and TARDBP in a central-southern Chinese cohort of 173 patients with ALS (15 familial ALS and 158 sporadic ALS) to detect mutations. As a result, five missense mutations in SOD1, namely, p.D101N, p.D101G, p.C111Y, p.N86S and p.V87A, were identified in three unrelated familial probands and three sporadic cases; two mutations in FUS were found in two unrelated familial probands, including an insertion mutation (p.P525_Y526insY) and a missense mutation (p.R521H); no variants of TARDBP were observed in patients. Therefore, SOD1 mutations were present in 20.0% of familial ALS patients and 1.9% of sporadic ALS patients, while FUS mutations were responsible for 13.3% of familial ALS cases, and TARDBP mutations were rare in either familial or sporadic ALS cases. This study broadens the known mutational spectrum in patients with ALS and further demonstrates the necessity for genetic screening in ALS patients from central-southern China.

Mutations of CCNF gene is rare in patients with amyotrophic lateral sclerosis and frontotemporal dementia from Mainland China

Abstract Objective: Mutations of the cyclin F (CCNF) gene were recently identified to be associated with amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) in Western and Japanese populations. The rare protein-altering variants frequency is 0.6 to 3.3% in ALS and FTD from these diverse geographic populations while no systematic analysis of CCNF variants were conducted in the Chinese population. Methods: We screened all exons of CCNF in a cohort of 269 cases (including 181 ALS and 88 FTD) from Mainland China using Sanger sequencing. Results: A rare heterozygous variant (c.481G > A, p.G161R) was detected in a sporadic ALS case with a frequency of 0.6%, while no mutation was identified in patients with FTD. The same variant was also found in a sporadic ALS patient from America. Conclusions: Our result indicates that the mutation of CCNF is rare in patients with ALS and FTD from Mainland China.

Mutation analysis of the TIA1 gene in Chinese patients with amyotrophic lateral sclerosis and frontotemporal dementia

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the progressive loss of motor neurons in the brain and spinal cord. Frontotemporal dementia (FTD) is a group of dementia syndromes characterized by the progressive deterioration of behaviors, executive dysfunction, and verbal impairment. Increasing evidence indicates that these 2 diseases share a common genetic etiology and pathophysiological mechanism. Recently, rare mutations in the low-complexity domain of the RNA-binding protein T-cell-restricted intracellular antigen-1 (TIA1) gene were identified in Caucasian ALS and ALS-FTD patients. However, no comprehensive mutation analysis of the TIA1 gene has been performed in Chinese patients with ALS and FTD. In this study, we screened the low-complexity domain of TIA1 in a cohort of 241 ALS and 51 FTD patients in mainland China. As a result, 2 novel missense mutations (p.P352L and p.I300T) were identified in 2 sporadic patients with ALS, while no mutation was found in FTD cases. To the best of our knowledge, this report presented the first mutation analysis of the TIA1 gene in patients with ALS and FTD in Chinese population. Our findings broaden the known mutational spectrum in patients with ALS and further confirm TIA1 as a novel causative gene of ALS.

Mutational analysis of PRNP in Alzheimer’s disease and frontotemporal dementia in China

The prion protein (PRNP) gene is associated with prion diseases, whereas variants of the PRNP gene may also explain some cases of Alzheimer disease (AD) and frontotemporal dementia (FTD) in Caucasian populations. To determine the prevalence of the PRNP gene in patients with AD and FTD in China, we screened all exons of the PRNP gene in a cohort of 683 cases (606 AD and 77 FTD) in the Chinese Han population and we detected a novel missense mutation p.S17G in a late-onset AD (LOAD) patient. Furthermore, we analyzed the PRNP M/V polymorphism at codon 129, which was previously reported as a risk factor. However, there were no significant differences in genotype and allele frequency either in AD (OR = 0.75[0.378–1.49], P = 0.492), or FTD patients (OR = 2.046[0.265–15.783], P = 0.707). To our knowledge, this is the first study to reveal a correlation between the PRNP gene and Chinese AD and FTD patients in a large cohort. This study reports a novel p.S17G mutation in a clinically diagnosed LOAD patient, suggesting that the PRNP mutation is present in Chinese AD patients, whereas, M129V polymorphism is not a risk factor for AD or FTD in the Chinese Han population.