Late-onset Familial Alzheimer Research Articles

Alzheimer's polygenic risk scores are associated with cognitive phenotypes in Down syndrome.

This study aimed to investigate the influence of the overall Alzheimer's disease (AD) genetic architecture on Down syndrome (DS) status, cognitive measures, and cerebrospinal fluid (CSF) biomarkers. AD polygenic risk scores (PRS) were tested for association with DS-related traits. The AD risk PRS was associated with disease status in several cohorts of sporadic late- and early-onset and familial late-onset AD, but not in familial early-onset AD or DS. On the other hand, lower DS Mental Status Examination memory scores were associated with higher PRS, independent of intellectual disability and APOE (PRS including APOE, PRSAPOE , p=2.84×10-4 ; PRS excluding APOE, PRSnonAPOE , p=1.60×10-2 ). PRSAPOE exhibited significant associations with Aβ42, tTau, pTau, and Aβ42/40 ratio in DS. These data indicate that the AD genetic architecture influences cognitive and CSF phenotypes in DS adults, supporting common pathways that influence memory decline in both traits. Examination of the polygenic risk of AD in DS presented here is the first of its kind. AD PRS influences memory aspects in DS individuals, independently of APOE genotype. These results point to an overlap between the genes and pathways that leads to AD and those that influence dementia and memory decline in the DS population. APOE ε4 is linked to DS cognitive decline, expanding cognitive insights in adults.

E674Q (Shanghai APP mutant), a novel amyloid precursor protein mutation, in familial late-onset Alzheimer's disease

Identified as the pathogenic genes of Alzheimer's disease (AD), APP, PSEN1, and PSEN2 mainly lead to early-onset AD, whose course is more aggressive, and atypical symptoms are more common than sporadic AD. Here, a novel missense mutation, APP E674Q (also named “Shanghai APP”), was detected in a Chinese index patient with typical late-onset AD (LOAD) who developed memory decline in his mid-70s. The results from neuroimaging were consistent with AD, where widespread amyloid β deposition was demonstrated in 18F-florbetapir Positron Emission Tomography (PET). APP E674Q is close to the β-secretase cleavage site and the well-studied Swedish APP mutation (KM670/671NL), which was predicted to be pathogenic in silico. Molecular dynamics simulation indicated that the E674Q mutation resulted in a rearrangement of the interaction mode between APP and BACE1 and that the E674Q mutation was more prone to cleavage by BACE1. The in vitro results suggested that the E674Q mutation was pathogenic by facilitating the BACE1-mediated processing of APP and the production of Aβ. Furthermore, we applied an adeno-associated virus (AAV)-mediated transfer of the human E674Q mutant APP gene to the hippocampi of two-month-old C57Bl/6 J mice. AAV-E674Q-injected mice exhibited impaired learning behavior and increased pathological burden in the brain, implying that the E674Q mutation had a pathogenicity that bore a comparison with the classical Swedish mutation. Collectively, we report a strong amyloidogenic effect of the E674Q substitution in AD. To our knowledge, E674Q is the only pathogenic mutation within the amyloid processing sequence causing LOAD.

Human 8-cell embryos enable efficient induction of disease-preventive mutations without off-target effect by cytosine base editor.

Approximately 140 million people worldwide are homozygous carriers of APOE4 (ε4), a strong genetic risk factor for late onset familial and sporadic Alzheimer's disease (AD), 91% of whom will develop AD at earlier age than heterozygous carriers and noncarriers. Susceptibility to AD could be reduced by targeted editing of APOE4, but a technical basis for controlling the off-target effects of base editors is necessary to develop low-risk personalized gene therapies. Here, we first screened eight cytosine base editor variants at four injection stages (from 1- to 8-cell stage), and found that FNLS-YE1 variant in 8-cell embryos achieved the comparable base conversion rate (up to 100%) with the lowest bystander effects. In particular, 80% of AD-susceptible ε4 allele copies were converted to the AD-neutral ε3 allele in human ε4-carrying embryos. Stringent control measures combined with targeted deep sequencing, whole genome sequencing, and RNA sequencing showed no DNA or RNA off-target events in FNLS-YE1-treated human embryos or their derived stem cells. Furthermore, base editing with FNLS-YE1 showed no effects on embryo development to the blastocyst stage. Finally, we also demonstrated FNLS-YE1 could introduce known protective variants in human embryos to potentially reduce human susceptivity to systemic lupus erythematosus and familial hypercholesterolemia. Our study therefore suggests that base editing with FNLS-YE1 can efficiently and safely introduce known preventive variants in 8-cell human embryos, a potential approach for reducing human susceptibility to AD or other genetic diseases.

Genetic profiles of familial late-onset Alzheimer's disease in China: The Shanghai FLOAD study

Compared with early-onset familial AD (FAD), the heritability of most familial late-onset Alzheimer's disease (FLOAD) cases still remains unclear. However, there are few reported genetic profiles of FLOAD to date. In the present study, targeted sequencing of selected candidate genes was conducted for each of 90 probands with FLOAD and 101 unrelated matched normal controls among Chinese Han population. Results show a significantly lower rate of mutation in APP and PSENs, and APOE ε4 genetic risk is higher for FLOAD. Among the Chinese FLOAD population, the most frequent variant was CR1 rs116806486 [5.6%, 95% CI (1.8%, 12.5%)], followed by coding variants of TREM2 (4.4%, 95%CI (1.2%, 10.9%)) and novel mutations of ACE [3.3%, 95%CI (0.7%, 9.4%)]. Next, we found that novel pathogenic mutations in ACE including frame-shift and nonsense mutations were in association with FLOAD regardless of APOE ε4 status. Evidence from the Alzheimer's disease Neuroimaging Initiative (ADNI) database also supported this finding in different ethnicities. Results of in vitro analysis suggest that frame-shift and nonsense mutations in ACE may be involved in LOAD through decreased ACE protein levels without affecting direct processing of APP.

Single Point Mutation from E22-to-K in Aβ Initiates Early-Onset Alzheimer's Disease by Binding with Catalase.

Amyloid-beta (Aβ) is a critical etiological factor for late-onset familial Alzheimer's disease (AD). However, an early-onset AD has been found to be related with an Aβ mutation in glutamic acid 22-to-lysine (Italian type E22K). Why only one single point mutation at E22 residue induces AD remains unclear. Here, we report that a Chinese familial AD pedigree with E22K mutation was associated with higher levels of serum hydrogen peroxide (H2O2) and lower activity of catalase (a H2O2 degrading enzyme) than controls. Further, we found that E22K binding with catalase caused more severe H2O2 accumulation in the brains of E22K-injected rats than Aβ-injected rats. Unexpectedly, H2O2 bound with the mutation site 22K residue of E22K and elicited more rapid aggregation of E22K than Aβ in vitro. Moreover, H2O2 acted with E22K synergistically to induce higher cellular toxicity than with Aβ. Notably, intrahippocampal infusion of E22K led to more severe plaque deposition, neuron death, and more rapid memory decline than Aβ-injected rats. However, L-cysteine, a H2O2 scavenger, not only prevented self-aggregation of E22K but also reduced H2O2-promoted E22K assembly in vitro; subsequently, it alleviated Alzheimer-related phenotypes. Hence, E22K binding with catalase promotes the early onset of familial AD, and L-cys may reverse this disease.

Analysis of gene and imaging on a late onset Alzheimer's pedigree concomitant with presenilin 1 mutation

Objective To analyze the clinical manifestation, imaging data and genetics mutation variants of late onset familial Alzheimer's disease concomitant with a novel mutation of presenilin 1. Methods The clinical manifestations and auxiliary examination recordings of the pedigree were analyzed.DNA was extracted from peripheral blood samples of the proband and her sons.Mutational analysis was performed by the next-generation sequencing technology and the mutation event was confirmed by Sanger sequencing technology. Results Two patients of the family presenting as Alzheimer's dementia were late onset.MRI of the proband showed extensive cerebral microbleeds.The gene detection showed p. S289P mutation in the exon 8 of presenilin 1 of the proband. Conclusion Mutation of p. S289P in the presenilin 1 gene may contribute to late onset Alzheimer's disease accompanied by amyloid angiopathy. Key words: Alzheimer's disease; Presenilin 1; Cerebral microbleeds; Amyloid angiopathy

Mutation profile of APP, PSEN1, and PSEN2 in Chinese familial Alzheimer's disease

Causative mutations in the genes encoding amyloid precursor protein (APP), presenilin 1 (PSEN1), or presenilin 2 (PSEN2) account for a majority of cases of familial Alzheimer disease (FAD) inherited in an autosomal-dominant pattern. For the sake of characterizing mutations, index patients from 148 families with FAD were enrolled from mainland China. Sanger sequencing of the genes APP, PSEN1, and PSEN2 was performed to characterize the mutation spectrum of the Chinese population. Thirteen of 148 (8.8%) individuals had possible pathogenic APP, PSEN1, or PSEN2 variants, including 2 (15.4%) APP variants, 8 (61.5%) PSEN1 variants, and 3 (23.1%) PSEN2 variants. PSEN1 variants represented the largest proportion in Chinese FAD, and PSEN2 variants are responsible for late-onset FAD in China. Analysis of genetic-clinical correlations permitted the conclusion that FAD phenotypes were mainly influenced by specific genetic defects.

A rare missense variant of CASP7 is associated with familial late-onset Alzheimer's disease

IntroductionThe genetic architecture of Alzheimer's disease (AD) is only partially understood. MethodsWe 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. ResultsWe 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). DiscussionOur 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.

A rare loss-of-function variant of ADAM17 is associated with late-onset familial Alzheimer disease

Common variants of about 20 genes contributing to AD risk have so far been identified through genome-wide association studies (GWAS). However, there is still a large proportion of heritability that might be explained by rare but functionally important variants. One of the so far identified genes with rare AD causing variants is ADAM10. Using whole-genome sequencing we now identified a single rare nonsynonymous variant (SNV) rs142946965 [p.R215I] in ADAM17 co-segregating with an autosomal-dominant pattern of late-onset AD in one family. Subsequent genotyping and analysis of available whole-exome sequencing data of additional case/control samples from Germany, UK, and USA identified five variant carriers among AD patients only. The mutation inhibits pro-protein cleavage and the formation of the active enzyme, thus leading to loss-of-function of ADAM17 alpha-secretase. Further, we identified a strong negative correlation between ADAM17 and APP gene expression in human brain and present in vitro evidence that ADAM17 negatively controls the expression of APP. As a consequence, p.R215I mutation of ADAM17 leads to elevated Aß formation in vitro. Together our data supports a causative association of the identified ADAM17 variant in the pathogenesis of AD.

Evaluation of Gene-Based Family-Based Methods to Detect Novel Genes Associated With Familial Late Onset Alzheimer Disease.

Gene-based tests to study the combined effect of rare variants on a particular phenotype have been widely developed for case-control studies, but their evolution and adaptation for family-based studies, especially studies of complex incomplete families, has been slower. In this study, we have performed a practical examination of all the latest gene-based methods available for family-based study designs using both simulated and real datasets. We examined the performance of several collapsing, variance-component, and transmission disequilibrium tests across eight different software packages and 22 models utilizing a cohort of 285 families (N = 1,235) with late-onset Alzheimer disease (LOAD). After a thorough examination of each of these tests, we propose a methodological approach to identify, with high confidence, genes associated with the tested phenotype and we provide recommendations to select the best software and model for family-based gene-based analyses. Additionally, in our dataset, we identified PTK2B, a GWAS candidate gene for sporadic AD, along with six novel genes (CHRD, CLCN2, HDLBP, CPAMD8, NLRP9, and MAS1L) as candidate genes for familial LOAD.

Rare ABCA7 variants in 2 German families with Alzheimer disease.

ObjectiveThe aim of this study was to identify variants associated with familial late-onset Alzheimer disease (AD) using whole-genome sequencing.MethodsSeveral families with an autosomal dominant inheritance pattern of AD were analyzed by whole-genome sequencing. Variants were prioritized for rare, likely pathogenic variants in genes already known to be associated with AD and confirmed by Sanger sequencing using standard protocols.ResultsWe identified 2 rare ABCA7 variants (rs143718918 and rs538591288) with varying penetrance in 2 independent German AD families, respectively. The single nucleotide variant (SNV) rs143718918 causes a missense mutation, and the deletion rs538591288 causes a frameshift mutation of ABCA7. Both variants have previously been reported in larger cohorts but with incomplete segregation information. ABCA7 is one of more than 20 AD risk loci that have so far been identified by genome-wide association studies, and both common and rare variants of ABCA7 have previously been described in different populations with higher frequencies in AD cases than in controls and varying penetrance. Furthermore, ABCA7 is known to be involved in several AD-relevant pathways.ConclusionsWe conclude that both SNVs might contribute to the development of AD in the examined family members. Together with previous findings, our data confirm ABCA7 as one of the most relevant AD risk genes.

Polygenic risk scores in familial Alzheimer disease.

To investigate the association between a genetic risk score (GRS) and familial late-onset Alzheimer disease (LOAD) and its predictive value in families multiply affected by the disease. Using data from the National Institute on Aging Genetics Initiative for Late-Onset Alzheimer Disease (National Institute on Aging-Late-Onset Alzheimer's Disease Family Study), mixed regression models tested the association of familial LOAD with a GRS based on single nucleotide polymorphisms (SNPs) previously associated with LOAD. We modeled associations using unweighted and weighted scores with estimates derived from the literature. In secondary models, we adjusted subsequent models for presence of the APOE ε4 allele and further tested the interaction between APOE ε4 and the GRS. We constructed a similar GRS in a cohort of Caribbean Hispanic families multiply affected by LOAD by selecting the SNP with the strongest p value within the same regions. In the NIA-LOAD families, the GRS was significantly associated with LOAD (odds ratio [OR] 1.29; 95% confidence interval 1.21-1.37). The results did not change after adjusting for APOE ε4. In Caribbean Hispanic families, the GRS also significantly predicted LOAD (OR 1.73; 1.57-1.93). Higher scores were associated with lower age at onset in both cohorts. High GRS increases the risk of familial LOAD and lowers the age at onset, regardless of ethnic group.

Silencing of the Drosophila ortholog of SOX5 leads to abnormal neuronal development and behavioral impairment.

SOX5 encodes a transcription factor that is expressed in multiple tissues including heart, lung and brain. Mutations in SOX5 have been previously found in patients with amyotrophic lateral sclerosis (ALS) and developmental delay, intellectual disability and dysmorphic features. To characterize the neuronal role of SOX5, we silenced the Drosophila ortholog of SOX5, Sox102F, by RNAi in various neuronal subtypes in Drosophila. Silencing of Sox102F led to misorientated and disorganized michrochaetes, neurons with shorter dendritic arborization (DA) and reduced complexity, diminished larval peristaltic contractions, loss of neuromuscular junction bouton structures, impaired olfactory perception, and severe neurodegeneration in brain. Silencing of SOX5 in human SH-SY5Y neuroblastoma cells resulted in a significant repression of WNT signaling activity and altered expression of WNT-related genes. Genetic association and meta-analyses of the results in several large family-based and case-control late-onset familial Alzheimer's disease (LOAD) samples of SOX5 variants revealed several variants that show significant association with AD disease status. In addition, analysis for rare and highly penetrate functional variants revealed four novel variants/mutations in SOX5, which taken together with functional prediction analysis, suggests a strong role of SOX5 causing AD in the carrier families. Collectively, these findings indicate that SOX5 is a novel candidate gene for LOAD with an important role in neuronal function. The genetic findings warrant further studies to identify and characterize SOX5 variants that confer risk for AD, ALS and intellectual disability.

The Role of Cardiovascular Risk Factors and Stroke in Familial Alzheimer Disease.

The contribution of cardiovascular disease (CV) and cerebrovascular disease to the risk for late-onset Alzheimer disease (LOAD) has been long debated. Investigations have shown that antecedent CV risk factors increase the risk for LOAD, although other investigations have failed to validate this association. To study the contribution of CV risk factors (type 2 diabetes, hypertension, and heart disease) and the history of stroke to LOAD in a data set of large families multiply affected by LOAD. The National Institute on Aging Late-Onset Alzheimer Disease/National Cell Repository for Alzheimer Disease family study (hereinafter referred to as NIA-LOAD study) is a longitudinal study of families with multiple members affected with LOAD. A multiethnic community-based longitudinal study (Washington Heights-Inwood Columbia Aging Project [WHICAP]) was used to replicate findings. The 6553 participants in the NIA-LOAD study were recruited from 23 US Alzheimer disease centers with ongoing data collection since 2003; the 5972 WHICAP participants were recruited at Columbia University with ongoing data collection since 1992. Data analysis was performed from 2003 to 2015. Generalized mixed logistic regression models tested the association of CV risk factors (primary association) with LOAD. History of stroke was used for the secondary association. A secondary model adjusted for the presence of an apolipoprotein E (APOE) ε4 allele. A genetic risk score, based on common variants associated with LOAD, was used to account for LOAD genetic risk beyond the APOE ε4 effect. Mediation analyses evaluated stroke as a mediating factor between the primary association and LOAD. A total of 6553 NIA-LOAD participants were included in the analyses (4044 women [61.7%]; 2509 men [38.3%]; mean [SD] age, 77.0 [9] years), with 5972 individuals from the WHICAP study included in the replication sample (4072 women [68.2%]; 1900 men [31.8%]; mean [SD] age, 76.5 [7.0] years). Hypertension was associated with decreased LOAD risk (odds ratio [OR], 0.63; 95% CI, 0.55-0.72); type 2 diabetes and heart disease were not. History of stroke conferred greater than 2-fold increased risk for LOAD (OR, 2.23; 95% CI, 1.75-2.83). Adjustment for APOE ε4 did not alter results. The genetic risk score was associated with LOAD (OR, 2.85; 95% CI, 2.05-3.97) but did not change the independent association of LOAD with hypertension or stroke. In the WHICAP sample, hypertension was not associated with LOAD (OR, 0.99; 95% CI, 0.88-1.11), whereas history of stroke increased the risk for LOAD (OR, 1.96; 95% CI, 1.56-2.46). The effect of hypertension on LOAD risk was also mediated by stroke in the NIA-LOAD and the WHICAP samples. In familial and sporadic LOAD, a history of stroke was significantly associated with increased disease risk and mediated the association between selected CV risk factors and LOAD, which appears to be independent of the LOAD-related genetic background.

SORL1 variants across Alzheimer’s disease European American cohorts

The accumulation of the toxic Aβ peptide in Alzheimer's disease (AD) largely relies upon an efficient recycling of amyloid precursor protein (APP). Recent genetic association studies have described rare variants in SORL1 with putative pathogenic consequences in the recycling of APP. In this work, we examine the presence of rare coding variants in SORL1 in three different European American cohorts: early-onset, late-onset AD (LOAD) and familial LOAD.

Novel PSEN1 mutations (H214N and R220P) associated with familial Alzheimer's disease identified by targeted exome sequencing

Autosomal dominant Alzheimer's disease (AD) is caused by mutations in amyloid precursor protein, presenilin 1 (PSEN1), and presenilin 2 genes and is mostly associated with early-onset form of AD (EOAD), whereas very few mutations were also found in late-onset AD (LOAD) cases. Because of the clinical overlapping between AD and other degenerative dementias such as frontotemporal dementias, a wide-spectrum genetic analysis should be envisaged in the differential diagnosis of this group of disorders. We used next-generation sequencing techniques to analyze 10 genes involved in dementia on a cohort of 20 EOAD and 20 LOAD cases. We found 5 rare coding variants (frequency <1%). PSEN1 H214N mutation, identified in a case of familial EOAD and PSEN1 R220P, found in a case of familial LOAD, are predicted to be pathogenic. These findings confirm the contribution of PSEN1 genetic variants also to LOAD, underlining the need of extending the genetic screening of presenilin mutations to LOAD patients. Two variants in microtubule-associated protein tau and 1 in progranulin appeared to be benign polymorphisms, showing no major contribution of these genes to AD.

Linkage analyses in Caribbean Hispanic families identify novel loci associated with familial late-onset Alzheimer's disease

IntroductionWe performed linkage analyses in Caribbean Hispanic families with multiple late-onset Alzheimer's disease (LOAD) cases to identify regions that may contain disease causative variants. MethodsWe selected 67 LOAD families to perform genome-wide linkage scan. Analysis of the linked regions was repeated using the entire sample of 282 families. Validated chromosomal regions were analyzed using joint linkage and association. ResultsWe identified 26 regions linked to LOAD (HLOD ≥3.6). We validated 13 of the regions (HLOD ≥2.5) using the entire family sample. The strongest signal was at 11q12.3 (rs2232932: HLODmax = 4.7, Pjoint = 6.6 × 10−6), a locus located ∼2 Mb upstream of the membrane-spanning 4A gene cluster. We additionally identified a locus at 7p14.3 (rs10255835: HLODmax = 4.9, Pjoint = 1.2 × 10−5), a region harboring genes associated with the nervous system (GARS, GHRHR, and NEUROD6). DiscussionFuture sequencing efforts should focus on these regions because they may harbor familial LOAD causative mutations.

Genome-wide linkage analyses of non-Hispanic white families identify novel loci for familial late-onset Alzheimer's disease

IntroductionFew high penetrance variants that explain risk in late-onset Alzheimer's disease (LOAD) families have been found. MethodsWe performed genome-wide linkage and identity-by-descent (IBD) analyses on 41 non-Hispanic white families exhibiting likely dominant inheritance of LOAD, and having no mutations at known familial Alzheimer's disease (AD) loci, and a low burden of APOE ε4 alleles. ResultsTwo-point parametric linkage analysis identified 14 significantly linked regions, including three novel linkage regions for LOAD (5q32, 11q12.2–11q14.1, and 14q13.3), one of which replicates a genome-wide association LOAD locus, the MS4A6A-MS4A4E gene cluster at 11q12.2. Five of the 14 regions (3q25.31, 4q34.1, 8q22.3, 11q12.2–14.1, and 19q13.41) are supported by strong multipoint results (logarithm of odds [LOD*] ≥1.5). Nonparametric multipoint analyses produced an additional significant locus at 14q32.2 (LOD* = 4.18). The 1-LOD confidence interval for this region contains one gene, C14orf177, and the microRNA Mir_320, whereas IBD analyses implicates an additional gene BCL11B, a regulator of brain-derived neurotrophic signaling, a pathway associated with pathogenesis of several neurodegenerative diseases. DiscussionExamination of these regions after whole-genome sequencing may identify highly penetrant variants for familial LOAD.

Familial late-onset Alzheimer’s disease: description of an Italian family with four affected siblings and one case of early-onset dementia in the preceding generation

We describe a family composed of six siblings, four of which affected by late-onset Alzheimer's disease (LOAD). We constructed the family pedigree, evaluated mutations usually associated with early-onset Alzheimer's disease (APP, PSEN1, PSEN2), and assessed polymorphisms in the apolipoprotein E (APOE) gene and in cytokine genes that we had previously found to be associated with a higher risk of LOAD (IL-10, IL-6, TNF-α). Results showed that all subjects carried one ε4 allele of the APOE gene and those with the earliest age of onset exhibited the AA (-1082) IL-10 and the CC (-174) IL-6 genotypes. The only male had a genetic profile which also included the A (-308) TNF-α allele. These data confirm the role of the APOE gene as genetic risk factor in LOAD, and suggest that the risk of developing AD may be governed by a "susceptibility profile" involving polymorphisms in inflammatory genes.

Coding mutations in SORL1 and Alzheimer disease.

Common single nucleotide polymorphisms in the SORL1 gene have been associated with late onset Alzheimer disease (LOAD), but causal variants have not been fully characterized nor has the mechanism been established. The study was undertaken to identify functional SORL1 mutations in patients with LOAD. This was a family- and cohort-based genetic association study. Caribbean Hispanics with familial and sporadic LOAD and similarly aged controls were recruited from the United States and the Dominican Republic, and patients with sporadic disease of Northern European origin were recruited from Canada. Prioritized coding variants in SORL1 were detected by targeted resequencing and validated by genotyping in additional family members and unrelated healthy controls. Variants transfected into human embryonic kidney 293 cell lines were tested for Aβ40 and Aβ42 secretion, and the amount of the amyloid precursor protein (APP) secreted at the cell surface was determined. Seventeen coding exonic variants were significantly associated with disease. Two rare variants (rs117260922-E270K and rs143571823-T947M) with minor allele frequency (MAF) < 1% and 1 common variant (rs2298813-A528T) with MAF = 14.9% segregated within families and were deemed deleterious to the coding protein. Transfected cell lines showed increased Aβ40 and Aβ42 secretion for the rare variants (E270K and T947M) and increased Aβ42 secretion for the common variant (A528T). All mutants increased the amount of APP at the cell surface, although in slightly different ways, thereby failing to direct full-length APP into the retromer-recycling endosome pathway. Common and rare variants in SORL1 elevate the risk of LOAD by directly affecting APP processing, which in turn can result in increased Aβ40 and Aβ42 secretion.