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Genome-wide association study identifies four novel loci associated with Alzheimer's endophenotypes and disease modifiers.

ABSTRACT: More than 20 genetic loci have been associated with risk for Alzheimer's disease (AD), but reported genome-wide significant loci do not account for all the estimated heritability and provide little information about underlying biological mechanisms. Genetic studies using intermediate quantitative traits such as biomarkers, or endophenotypes, benefit from increased statistical power to identify variants that may not pass the stringent multiple test correction in case-control studies. Endophenotypes also contain additional information helpful for identifying variants and genes associated with other aspects of disease, such as rate of progression or onset, and provide context to interpret the results from genome-wide association studies (GWAS). We conducted GWAS of amyloid beta (A?42), tau, and phosphorylated tau (ptau181) levels in cerebrospinal fluid (CSF) from 3146 participants across nine studies to identify novel variants associated with AD. Five genome-wide significant loci (two novel) were associated with ptau181, including loci that have also been associated with AD risk or brain-related phenotypes. Two novel loci associated with A?42 near GLIS1 on 1p32.3 (? = -0.059, P = 2.08 × 10-8) and within SERPINB1 on 6p25 (? = -0.025, P = 1.72 × 10-8) were also associated with AD risk (GLIS1: OR = 1.105, P = 3.43 × 10-2), disease progression (GLIS1: ? = 0.277, P = 1.92 × 10-2), and age at onset (SERPINB1: ? = 0.043, P = 4.62 × 10-3). Bioinformatics indicate that the intronic SERPINB1 variant (rs316341) affects expression of SERPINB1 in various tissues, including the hippocampus, suggesting that SERPINB1 influences AD through an A?-associated mechanism. Analyses of known AD risk loci suggest CLU and FERMT2 may influence CSF A?42 (P = 0.001 and P = 0.009, respectively) and the INPP5D locus may affect ptau181 levels (P = 0.009); larger studies are necessary to verify these results. Together the findings from this study can be used to inform future AD studies.

SUBMITTER: Deming Y

PROVIDER: S-EPMC5613285 | biostudies-literature | 2017 May

REPOSITORIES: biostudies-literature

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Genome-wide association study identifies four novel loci associated with Alzheimer's endophenotypes and disease modifiers.

Deming Yuetiva Y Li Zeran Z Kapoor Manav M Harari Oscar O Del-Aguila Jorge L JL Black Kathleen K Carrell David D Cai Yefei Y Fernandez Maria Victoria MV Budde John J Ma Shengmei S Saef Benjamin B Howells Bill B Huang Kuan-Lin KL Bertelsen Sarah S Fagan Anne M AM Holtzman David M DM Morris John C JC Kim Sungeun S Saykin Andrew J AJ De Jager Philip L PL Albert Marilyn M Moghekar Abhay A O'Brien Richard R Riemenschneider Matthias M Petersen Ronald C RC Blennow Kaj K Zetterberg Henrik H Minthon Lennart L Van Deerlin Vivianna M VM Lee Virginia Man-Yee VM Shaw Leslie M LM Trojanowski John Q JQ Schellenberg Gerard G Haines Jonathan L JL Mayeux Richard R Pericak-Vance Margaret A MA Farrer Lindsay A LA Peskind Elaine R ER Li Ge G Di Narzo Antonio F AF Kauwe John S K JS Goate Alison M AM Cruchaga Carlos C

Acta neuropathologica 20170228 5

More than 20 genetic loci have been associated with risk for Alzheimer's disease (AD), but reported genome-wide significant loci do not account for all the estimated heritability and provide little information about underlying biological mechanisms. Genetic studies using intermediate quantitative traits such as biomarkers, or endophenotypes, benefit from increased statistical power to identify variants that may not pass the stringent multiple test correction in case-control studies. Endophenotyp ...[more]

PMID: 28247064

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Project description:Understanding how genomes encode complex cellular and organismal behaviors has become the outstanding challenge of modern genetics. Unlike classical screening methods, analysis of genetic variation that occurs naturally in wild populations can enable rapid, genome-scale mapping of genotype to phenotype with a medium-throughput experimental design. Here we describe the results of the first genome-wide association study (GWAS) used to identify novel loci underlying trait variation in a microbial eukaryote, harnessing wild isolates of the filamentous fungus Neurospora crassa. We genotyped each of a population of wild Louisiana strains at 1 million genetic loci genome-wide, and we used these genotypes to map genetic determinants of microbial communication. In N. crassa, germinated asexual spores (germlings) sense the presence of other germlings, grow toward them in a coordinated fashion, and fuse. We evaluated germlings of each strain for their ability to chemically sense, chemotropically seek, and undergo cell fusion, and we subjected these trait measurements to GWAS. This analysis identified one gene, NCU04379 (cse-1, encoding a homolog of a neuronal calcium sensor), at which inheritance was strongly associated with the efficiency of germling communication. Deletion of cse-1 significantly impaired germling communication and fusion, and two genes encoding predicted interaction partners of CSE1 were also required for the communication trait. Additionally, mining our association results for signaling and secretion genes with a potential role in germling communication, we validated six more previously unknown molecular players, including a secreted protease and two other genes whose deletion conferred a novel phenotype of increased communication and multi-germling fusion. Our results establish protein secretion as a linchpin of germling communication in N. crassa and shed light on the regulation of communication molecules in this fungus. Our study demonstrates the power of population-genetic analyses for the rapid identification of genes contributing to complex traits in microbial species.

Project description:Understanding how genomes encode complex cellular and organismal behaviors is an outstanding challenge of modern genetics. Unlike classical screening methods, analysis of the genetic variation that occurs naturally in wild populations can enable rapid, genome-scale trait mapping with a medium-throughput experimental design. Here we describe the results of the first genome-wide association analysis (GWAS) of a microbial eukaryote, using wild isolates of the filamentous fungus Neurospora crassa. We transcriptionally profiled each of 112 individuals collected in Louisiana and used RNA-seq data to genotype each strain at thousands of genetic loci genome-wide. We used these genotypes in a mapping analysis of microbial communication. In N. crassa, germinated asexual spores (germlings) sense the presence of other germlings, grow toward them in a coordinated fashion, and fuse. We evaluated germlings of each strain for their ability to chemically sense, chemotropically seek, and undergo cell fusion. GWAS identified one gene, NCU04379 (cse-1, encoding a homolog of neuronal calcium sensor), at which inheritance was strongly associated with the efficiency of germling communication. Deletion of cse-1 significantly lowered germling communication and fusion, and two genes encoding predicted binding partners of CSE-1 were also required for the communication trait. Additionally, mining our association results for signaling and secretion genes with a potential role in germling communication, we validated six more novel determinants of germling communication, including a secreted protease and two other genes whose deletion conferred a novel phenotype of increased communication and multi-germling fusion. These results establish protein secretion as a linchpin of germling communication in N. crassa and shed light on the regulation of communication molecules in this fungus. Our study demonstrates the power of population-genetic analyses for the rapid identification of genes contributing to complex traits in microbial species. 112 mycelial mRNA profiles of 16 hour wild type (WT) Neurospora crassa strains were generated by deep sequencing, using Illumina GAIIx.

Dataset Information

Genome-wide association study identifies four novel loci associated with Alzheimer's endophenotypes and disease modifiers.

Publications

Genome-wide association study identifies four novel loci associated with Alzheimer's endophenotypes and disease modifiers.

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