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Introduction: Patients with familial early-onset dementia (EOD) pose a unique opportunity for gene identification studies., Methods: We present the phenotype and whole-exome sequencing (WES) study of an autosomal dominant EOD family. Candidate genes were examined in a set of dementia cases and controls (n = 3712). Western blotting was conducted of the wild-type and mutant protein of the final candidate., Results: Age at disease onset was 60 years (range 56 to 63). The phenotype comprised mixed amnestic and behavioral features, and parkinsonism. Cerebrospinal fluid and plasma biomarkers, and a positron emission tomography amyloid study suggested Alzheimer's disease. WES and the segregation pattern pointed to a nonsense mutation in the TRIM25 gene (p.C168*), coding for an E3 ubiquitin ligase, which was absent in the cohorts studied. Protein studies supported a loss-of-function mechanism., Discussion: This study supports a new physiopathological mechanism for brain amyloidosis. Furthermore, it extends the role of E3 ubiquitin ligases dysfunction in the development of neurodegenerative diseases., Highlights: A TRIM25 nonsense mutation (p.C168*) is associated with autosomal dominant early-onset dementia and parkinsonism with biomarkers suggestive of Alzheimer's disease. TRIM25 protein studies support that the mutation exerts its effect through loss of function. TRIM25, an E3 ubiquitin ligase, is known for its role in the innate immune response but this is the first report of association with neurodegeneration. The role of TRIM25 dysfunction in development of amyloidosis and neurodegeneration merits a new line of research., (© 2022 The Authors. Alzheimer's & Dementia published by Wiley Periodicals LLC on behalf of Alzheimer's Association.)

ADAM10 is the main α-secretase acting in the non-amyloidogenic processing of APP. We hypothesized that certain rare ADAM10 variants could increase the risk for AD by conferring the age-related downregulation of α-secretase. The ADAM10 gene was sequenced in 103 AD cases (82% familial) and 96 cognitively preserved nonagenarians. We examined rare variants (MAF < 0.01) and determined their potential association in the AD group with lower CSF protein levels, as analyzed by means of ELISA, and Western blot (species of 50 kDa, 55 kDa, and 80 kDa). Rare variants were found in 15.5% of AD cases (23% early-onset, 8% late-onset) and in 12.5% of nonagenarians, and some were group-specific. All were intronic variants except Q170H, found in three AD cases and one nonagenarian. The 3'UTR rs74016945 (MAF = 0.01) was found in 6% of the nonagenarians (OR 0.146, p = 0.057). Altogether, ADAM10 total levels or specific species were not significantly different when comparing AD with controls or carriers of rare variants versus non-carriers (except a Q170H carrier exhibiting low levels of all species), and did not differ according to the age at onset or APOE genotype. We conclude that ADAM10 exonic variants are uncommon in AD cases, and the presence of rare intronic variants (more frequent in early-onset cases) is not associated with decreased protein levels in CSF.

Background: The disintegrin metalloproteinase 10 (ADAM10) is the main α-secretase acting in the non-amyloidogenic processing of APP. Some ADAM10 gene variants have been associated with higher susceptibility to develop late-onset AD, though clear clinical-genetic correlates remain elusive., Methods: Clinical-genetic and biomarker study of a first family with early- and late-onset AD associated with a nonsense ADAM10 mutation (p.Tyr167*). CSF analysis included AD core biomarkers, as well as Western blot of ADAM10 species and sAPPα and sAPPβ peptides. We evaluate variant's pathogenicity, pattern of segregation, and further screened for the p.Tyr167* mutation in 197 familial AD cases from the same cohort, 200 controls from the same background, and 274 AD cases from an independent Spanish cohort., Results: The mutation was absent from public databases and segregated with the disease. CSF Aβ42, total tau, and phosphorylated tau of affected siblings were consistent with AD. The predicted haploinsufficiency effect of the nonsense mutation was supported by (a) ADAM10 isoforms in CSF decreased around 50% and (b) 70% reduction of CSF sAPPα peptide, both compared to controls, while sAPPβ levels remained unchanged. Interestingly, sporadic AD cases had a similar decrease in CSF ADAM10 levels to that of mutants, though their sAPPα and sAPPβ levels resembled those of controls. Therefore, a decreased sAPPα/sAPPβ ratio was an exclusive feature of mutant ADAM10 siblings. The p.Tyr167* mutation was not found in any of the other AD cases or controls screened., Conclusions: This family illustrates the role of ADAM10 in the amyloidogenic process and the clinical development of the disease. Similarities between clinical and biomarker findings suggest that this family could represent a genetic model for sporadic late-onset AD due to age-related downregulation of α-secretase. This report encourages future research on ADAM10 enhancers.

The SORL1 gene encodes a protein involved in the amyloidogenic process, and its variants have been associated with Alzheimer's disease (AD) physiopathology. We screened for SORL1 variants in 124 familial (44 early- and 80 late-onset) dementia of Alzheimer type (DAT) cases. Nine potentially pathogenic changes (three not previously reported and six rare variants) were found in nine probands (7%). After screening the control population and siblings (presence in at least 1/200 controls and/or absence of segregation pattern), a causal relationship with the disease was considered unlikely in six variants and uncertain in one. The change Trp848Ter and a splice-site variant remained likely correlated with the disease. SORL1 mutations are present in 7% of our familial DAT cohort, though in most cases cannot be considered the direct cause of the disease.

We describe the clinical phenotype of nine kindred with presenile Alzheimer's disease (AD) caused by different presenilin 1 (PS1) point mutations, and compare them with reported families with mutations in the same codons. Mutations were in exon 4 (Phe105Val), exon 5 (Pro117Arg, Glu120Gly), exon 6 (His163Arg), exon 7 (Leu226Phe), exon 8 (Val261Leu, Val272Ala, Leu282Arg), and exon 12 (Ile439Ser). Three of these amino acid changes (Phe105Val, Glu120Gly, and Ile439Ser) had not been previously reported. Distinct clinical features, including age of onset, symptoms and signs associated with the cortical-type dementia and aggressiveness of the disease, characterized the different mutations and were quite homogeneous across family members. Age of onset fell within a consistent range: some mutations caused the disease in the thirties (P117R, L226F, V272A), other in the forties (E120G, H163R, V261L, L282R), and other in the fifties (F105V, I439S). Associated features also segregated with specific mutations: early epileptic activity (E120G), spastic paraparesis (V261L), subcortical dementia and parkinsonism (V272A), early language impairment, frontal signs, and myoclonus (L226F), and late myoclonus and seizures (H163R, L282R). Neurological deterioration was particularly aggressive in PS1 mutations with earlier age of onset such as P117R, L226F, and E120G. With few exceptions, a similar clinical phenotype was found in families reported to have either the same mutation or different amino acid changes in the same codons. This series points to a strong influence of the specific genetic defect in the development of the clinical phenotype.

Background: Variability of age at onset (AO) of Alzheimer disease (AD) among members of the same family is important as a biological clue and because of its clinical effects., Objective: To evaluate which clinical variables influence the discrepancy in AO among affected relatives with familial AD., Setting: Clinical genetic project of Spanish kindred with AD conducted by 4 academic hospitals in Madrid, Spain., Methods: Age at onset of AD in 162 families and discrepancy in AO in intragenerational and intergenerational affected pairs were analyzed in relation to age, sex, maternal or paternal transmission, pattern of inheritance, and apolipoprotein E genotype., Results: Maternal transmission of AD was significantly more frequent than paternal transmission (P < .001). In 27% of the affected individuals, AO occurred before the patient was 65 years old. Discrepancy in AO among siblings was within 5 years in 44% of the families, 6 to 10 years in 29%, and more than 10 years in 27% (range, 0-22). This discrepancy was independent of the sex of the sibling pairs and was significantly lower with maternal transmission of AD (P = .02). Segregation analysis showed no differences in the inheritance pattern between families with low (< or =5 years) or high (>5 years) AO discrepancy. Age at onset in carriers of the apolipoprotein E epsilon4 allele was slightly younger. However, among siblings, an extra apolipoprotein E epsilon4 allele was not consistently associated with earlier onset of AD. Eighty percent of patients, independent of sex or mode of transmission, were already affected at their parents' reported AO., Conclusions: There is a wide discrepancy in AO in affected siblings that is not clearly explained by a single clinical variable or apolipoprotein E genotype. The interaction of many factors probably determines AO in each affected individual. However, maternal transmission of AD seems to result in a similar AO in offspring, and the risk of developing dementia after the parent's reported AO decreases significantly.

Background: Most patients with dementia with Lewy bodies (DLB) exhibit diffuse plaque-only pathology with rare neocortical neurofibrillary tangles (NFTs), as opposed to the widespread cortical neurofibrillary-tau involvement in Alzheimer disease (AD). Another pathological difference is the astrocytic and microglial inflammatory responses, including release of interleukins (ILs), around the neuritic plaques and NFTs in AD brains that are absent or much lower in DLB. We analyzed cerebrospinal fluid (CSF) markers that reflect the pathological differences between AD and DLB., Objective: To determine CSF concentrations of tau, beta-amyloid, IL-1beta, and IL-6 as potential diagnostic clues to distinguish between AD and DLB., Methods: We measured total tau, beta-amyloid1-42, IL-1beta, and IL-6 levels in CSF samples of 33 patients with probable AD without parkinsonism, 25 patients with all the core features of DLB, and 46 age-matched controls., Results: Patients with AD had significantly higher levels of tau protein than patients with DLB and controls (P<.001). The most efficient cutoff value provided 76% specificity to distinguish AD and DLB cases. Patients with AD and DLB had lower, but not significantly so, beta-amyloid levels than controls. The combination of tau and beta-amyloid levels provided the best sensitivity (84%) and specificity (79%) to differentiate AD vs controls but was worse than tau values alone in discriminating between AD and DLB. Beta-amyloid levels had the best correlation with disease progression in both AD and DLB (P =.01). There were no significant differences in IL-1beta levels among patients with AD, patients with DLB, and controls. Patients with AD and DLB showed slightly, but not significantly, higher IL-6 levels than controls., Conclusions: The tau levels in CSF may contribute to the clinical distinction between AD and DLB. Beta-amyloid CSF levels are similar in both dementia disorders and reflect disease progression better than tau levels. Interleukin CSF concentrations do not distinguish between AD and DLB.