Background
The Genome Center for Alzheimer’s Disease (GCAD) coordinates the integration and meta‐analysis of all available Alzheimer’s disease (AD) relevant whole genome sequencing (WGS) data with ...the goal of identifying AD risk or protective genetic variants and eventual therapeutic targets. The WGS datasets are generated via the collaboration of scientists from the Alzheimer’s Disease Sequencing Project (ADSP) and GCAD. With the vision to minimize data heterogeneity, introduced by different sequencing protocols and machines, GCAD processes all samples using identical pipelines and performs quality assurance (QA) checks.
Methods
Raw sequencing data (FASTQs or BAMs) were aligned to GRCh38/hg38 by BWA, and variant calling and joint genotyping were done by GATK. Furthermore, Smoove, Manta and Streka were applied to generate structural variant (SV) calls per sample. QA checks including sex, contamination and genotype concordance as well as the ADSP QC protocol were performed to evaluate the quality of samples and variants. To facilitate the access and usage of the big joint‐genotyped VCF files, we introduced a compact version for storing variant info and sample genotypes only.
Results
We dropped 235 (1.3%) samples of poor coverage (<20x) or that failed QA checks, and we flagged 173 (1.0%) samples that were of borderline quality. As a result, the dataset (ADSP Release 3, 2021) includes 16,905 genomes from 17 diverse cohorts with 3 major ethnicities: 10,651 Non‐Hispanic Whites, 3,212 Hispanics and 2,874 African Americans. Data are deeply sequenced (average genome coverage: >30x). All samples’ CRAMs, gVCFs from GATK, and VCFs from the three SV callers were deposited into NIAGADS Data Sharing Service (DSS) (https://dss.niagads.org/) for public distribution. In addition, joint‐genotype VCFs are available in both compact and QC versions. This joint‐genotype VCF contains >206M bi‐allelic single‐nucleotide variants, 16M bi‐allelic indels and 28M multi‐allelic variants, with 96% of variants remaining after stringent QC.
Conclusion
The ADSP and GCAD generate high quality genotype calls and SV calls. Currently the project is processing ∼37,000 WGS samples sequenced primarily through the ADSP Follow‐Up Study, which will contain a more ancestrally diverse set of populations. We anticipate this 2022 release will continue to benefit the research community studying AD genetics.
The aim of this study was to explore whether variants in LRP10, recently associated with Parkinson's disease and dementia with Lewy bodies, are observed in 2 large cohorts (discovery and validation ...cohort) of patients with progressive supranuclear palsy (PSP). A total of 950 patients with PSP were enrolled: 246 patients with PSP (n = 85 possible (35%), n = 128 probable (52%), n = 33 definite (13%)) in the discovery cohort and 704 patients with definite PSP in the validation cohort. Sanger sequencing of all LRP10 exons and exon-intron boundaries was performed in the discovery cohort, and whole-exome sequencing was performed in the validation cohort. Two patients from the discovery cohort and 8 patients from the validation cohort carried a rare, heterozygous, and possibly pathogenic LRP10 variant (p.Gly326Asp, p.Asp389Asn, and p.Arg158His, p.Cys220Tyr, p.Thr278Ala, p.Gly306Asp, p.Glu486Asp, p.Arg554∗, p.Arg661Cys). In conclusion, possibly pathogenic LRP10 variants occur in a small fraction of patients with PSP and may be overrepresented in these patients compared with controls. This suggests that possibly pathogenic LRP10 variants may play a role in the development of PSP.
•Exploration of LRP10 variants in progressive supranuclear palsy (PSP).•Ten of 950 patients were carriers of a possibly pathogenic LRP10 variant.•First study to show that LRP10 variants occur in a small fraction of patients with PSP.•LRP10 variants may be overrepresented in patients with PSP compared with controls.•LRP10 variants may play a role in the development of PSP.
Abstract INTRODUCTION Despite a two‐fold risk, individuals of African ancestry have been underrepresented in Alzheimer's disease (AD) genomics efforts. METHODS Genome‐wide association studies (GWAS) ...of 2,903 AD cases and 6,265 controls of African ancestry. Within‐dataset results were meta‐analyzed, followed by functional genomics analyses. RESULTS A novel AD‐risk locus was identified in MPDZ on chromosome (chr) 9p23 (rs141610415, MAF = 0.002, P = 3.68×10 −9 ). Two additional novel common and nine rare loci were identified with suggestive associations ( P < 9×10 −7 ). Comparison of association and linkage disequilibrium (LD) patterns between datasets with higher and lower degrees of African ancestry showed differential association patterns at chr12q23.2 ( ASCL1 ), suggesting that this association is modulated by regional origin of local African ancestry. DISCUSSION These analyses identified novel AD‐associated loci in individuals of African ancestry and suggest that degree of African ancestry modulates some associations. Increased sample sets covering as much African genetic diversity as possible will be critical to identify additional loci and deconvolute local genetic ancestry effects. Highlights Genetic ancestry significantly impacts risk of Alzheimer's Disease (AD). Although individuals of African ancestry are twice as likely to develop AD, they are vastly underrepresented in AD genomics studies. The Alzheimer's Disease Genetics Consortium has previously identified 16 common and rare genetic loci associated with AD in African American individuals. The current analyses significantly expand this effort by increasing the sample size and extending ancestral diversity by including populations from continental Africa. Single variant meta‐analysis identified a novel genome‐wide significant AD‐risk locus in individuals of African ancestry at the MPDZ gene, and 11 additional novel loci with suggestive genome‐wide significance at P < 9×10−7. Comparison of African American datasets with samples of higher degree of African ancestry demonstrated differing patterns of association and linkage disequilibrium at one of these loci, suggesting that degree and/or geographic origin of African ancestry modulates the effect at this locus. These findings illustrate the importance of increasing number and ancestral diversity of African ancestry samples in AD genomics studies to fully disentangle the genetic architecture underlying AD, and yield more effective ancestry‐informed genetic screening tools and therapeutic interventions.
The genetic architecture of Alzheimer's disease (AD) is only partially understood.
We conducted an association study for AD using whole sequence data from 507 genetically enriched AD cases (i.e., ...cases having close relatives affected by AD) and 4917 cognitively healthy controls of European ancestry (EA) and 172 enriched cases and 179 controls of Caribbean Hispanic ancestry. Confirmation of top findings from stage 1 was sought in two family-based genome-wide association study data sets and in a whole genome–sequencing data set comprising members from 42 EA and 115 Caribbean Hispanic families.
We identified associations in EAs with variants in 12 novel loci. The most robust finding is a rare CASP7 missense variant (rs116437863; P = 2.44 × 10−10) which improved when combined with results from stage 2 data sets (P = 1.92 × 10−10).
Our study demonstrated that an enriched case design can strengthen genetic signals, thus allowing detection of associations that would otherwise be missed in a traditional case-control study.
Abstract The Alzheimer’s Disease Sequencing Project (ADSP) undertook whole exome sequencing in 5,740 late-onset Alzheimer disease (AD) cases and 5,096 cognitively normal controls primarily of ...European ancestry (EA), among whom 218 cases and 177 controls were Caribbean Hispanic (CH). An age-, sex- and APOE based risk score and family history were used to select cases most likely to harbor novel AD risk variants and controls least likely to develop AD by age 85 years. We tested ~1.5 million single nucleotide variants (SNVs) and 50,000 insertion-deletion polymorphisms (indels) for association to AD, using multiple models considering individual variants as well as gene-based tests aggregating rare, predicted functional, and loss of function variants. Sixteen single variants and 19 genes that met criteria for significant or suggestive associations after multiple-testing correction were evaluated for replication in four independent samples; three with whole exome sequencing (2,778 cases, 7,262 controls) and one with genome-wide genotyping imputed to the Haplotype Reference Consortium panel (9,343 cases, 11,527 controls). The top findings in the discovery sample were also followed-up in the ADSP whole-genome sequenced family-based dataset (197 members of 42 EA families and 501 members of 157 CH families). We identified novel and predicted functional genetic variants in genes previously associated with AD. We also detected associations in three novel genes: IGHG3 (p = 9.8 × 10 −7 ), an immunoglobulin gene whose antibodies interact with β-amyloid, a long non-coding RNA AC099552.4 (p = 1.2 × 10 −7 ), and a zinc-finger protein ZNF655 (gene-based p = 5.0 × 10 −6 ). The latter two suggest an important role for transcriptional regulation in AD pathogenesis.
Some of the unexplained heritability of Alzheimer disease (AD) may be due to rare variants whose effects are not captured in genome-wide association studies because very large samples are needed to ...observe statistically significant associations.
To identify genetic variants associated with AD risk using a nonstatistical approach.
Genetic association study in which rare variants were identified by whole-exome sequencing in unrelated individuals of European ancestry from the Alzheimer's Disease Sequencing Project (ADSP). Data were analyzed between March 2017 and September 2018.
Minor alleles genome-wide and in 95 genes previously associated with AD, AD-related traits, or other dementias were tabulated and filtered for predicted functional impact and occurrence in participants with AD but not controls. Support for several findings was sought in a whole-exome sequencing data set comprising 19 affected relative pairs from Utah high-risk pedigrees and whole-genome sequencing data sets from the ADSP and Alzheimer's Disease Neuroimaging Initiative.
Among 5617 participants with AD (3202 57.0% women; mean SD age, 76.4 9.3 years) and 4594 controls (2719 59.0% women; mean SD age, 86.5 4.5 years), a total of 24 variants with moderate or high functional impact from 19 genes were observed in 10 or more participants with AD but not in controls. These variants included a missense mutation (rs149307620 p.A284T, n = 10) in NOTCH3, a gene in which coding mutations are associated with cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), that was also identified in 1 participant with AD and 1 participant with mild cognitive impairment in the whole genome sequencing data sets. Four participants with AD carried the TREM2 rs104894002 (p.Q33X) high-impact mutation that, in homozygous form, causes Nasu-Hakola disease, a rare disorder characterized by early-onset dementia and multifocal bone cysts, suggesting an intermediate inheritance model for the mutation. Compared with controls, participants with AD had a significantly higher burden of deleterious rare coding variants in dementia-associated genes (2314 vs 3354 cumulative variants, respectively; P = .006).
Different mutations in the same gene or variable dose of a mutation may be associated with result in distinct dementias. These findings suggest that minor differences in the structure or amount of protein may be associated with in different clinical outcomes. Understanding these genotype-phenotype associations may provide further insight into the pathogenic nature of the mutations, as well as offer clues for developing new therapeutic targets.
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