Clinical, imaging, pathological, and biochemical characterization of a novel presenilin 1 mutation (N135Y) causing Alzheimer's disease.
ABSTRACT: We present 2 cases of early-onset Alzheimer's disease due to a novel N135Y mutation in PSEN1. The proband presented with memory and other cognitive symptoms at age 32. Detailed clinical characterization revealed initial deficits in memory with associated dysarthria, progressing to involve executive dysfunction, spastic gait, and episodic confusion with polyspike discharges on long-term electroencephalography. Amyloid- and FDG-PET scans showed typical results of Alzheimer's disease. By history, the proband's father had developed cognitive symptoms at age 42 and died at age 48. Neuropathological evaluation confirmed Alzheimer's disease, with moderate to severe amyloid angiopathy. Skeletal muscle showed type 2 fiber-predominant atrophy with pale central clearing. Genetic testing of the proband revealed an N135Y missense mutation in PSEN1. This mutation was predicted to be pathogenic by in silico analysis. Biochemical analysis confirmed that the mutation caused an increased A?42/A?40 ratio, consistent with other PSEN1 mutations and with a loss of presenilin function.
Project description:Presenilins play essential roles in memory formation, synaptic function, and neuronal survival. Mutations in the Presenilin-1 (PSEN1) gene are the major cause of familial Alzheimer's disease (FAD). How PSEN1 mutations cause FAD is unclear, and pathogenic mechanisms based on gain or loss of function have been proposed. Here, we generated Psen1 knockin (KI) mice carrying the FAD mutation L435F or C410Y. Remarkably, KI mice homozygous for either mutation recapitulate the phenotypes of Psen1(-/-) mice. Neither mutation altered Psen1 mRNA expression, but both abolished ?-secretase activity. Heterozygosity for the KI mutation decreased production of A?40 and A?42, increased the A?42/A?40 ratio, and exacerbated A? deposition. Furthermore, the L435F mutation impairs hippocampal synaptic plasticity and memory and causes age-dependent neurodegeneration in the aging cerebral cortex. Collectively, our findings reveal that FAD mutations can cause complete loss of Presenilin-1 function in vivo, suggesting that clinical PSEN mutations produce FAD through a loss-of-function mechanism.
Project description:A pathogenic mutation in PSEN1 p.Glu184Gly was discovered in a Thai family with early onset Alzheimer's disease (EOAD) as the first case in Asia. Proband patient presented memory impairment and anxiety at the age of 41 years. Family history was positive, since several family members were also diagnosed with dementia (father and grandfather). MRI in the patient revealed global cortical atrophy without specific lesions or lacuna infarctions. Extensive genetic profiling for 50 neurodegenerative disease related genes was performed by next generation sequencing (NGS) on the patient. PSEN1 Glu184Gly was previously reported in French families with frontal variant Alzheimer's disease (AD). Interestingly, this mutation is located near the splicing site and could possibly result in abnormal cleavage of PSEN1 transcript. Furthermore, 3D models from protein structural predictions revealed significant structural changes, since glycine may result in increased flexibility of TM-III helix. Inter/intra-helical interactions could also be altered. In the future, functional studies should be performed to verify the probable role PSEN1 Glu184Gly in amyloid beta processing and pathogenicity.
Project description:Alzheimer's disease (AD) is hypothesized to be caused by an overproduction or reduced clearance of amyloid-? (A?) peptide. Autosomal dominant AD (ADAD) caused by mutations in the presenilin (PSEN) gene have been postulated to result from increased production of A?42 compared to A?40 in the central nervous system (CNS). This has been demonstrated in rodent models of ADAD but not in human mutation carriers. We used compartmental modeling of stable isotope labeling kinetic (SILK) studies in human carriers of PSEN mutations and related noncarriers to evaluate the pathophysiological effects of PSEN1 and PSEN2 mutations on the production and turnover of A? isoforms. We compared these findings by mutation status and amount of fibrillar amyloid deposition as measured by positron emission tomography (PET) using the amyloid tracer Pittsburgh compound B (PIB). CNS A?42 to A?40 production rates were 24% higher in mutation carriers compared to noncarriers, and this was independent of fibrillar amyloid deposits quantified by PET PIB imaging. The fractional turnover rate of soluble A?42 relative to A?40 was 65% faster in mutation carriers and correlated with amyloid deposition, consistent with increased deposition of A?42 into plaques, leading to reduced recovery of A?42 in cerebrospinal fluid (CSF). Reversible exchange of A?42 peptides with preexisting unlabeled peptide was observed in the presence of plaques. These findings support the hypothesis that A?42 is overproduced in the CNS of humans with PSEN mutations that cause AD, and demonstrate that soluble A?42 turnover and exchange processes are altered in the presence of amyloid plaques, causing a reduction in A?42 concentrations in the CSF.
Project description:Mutations in presenilin-1 (PSEN1), encoding the catalytic subunit of the amyloid precursor protein-processing enzyme ?-secretase, cause familial Alzheimer's disease. However, the mechanism of disease is yet to be fully understood and it remains contentious whether mutations exert their effects predominantly through gain or loss of function. To address this question, we generated an isogenic allelic series for the PSEN1 mutation intron 4 deletion; represented by control, heterozygous and homozygous mutant induced pluripotent stem cells in addition to a presenilin-1 knockout line. Induced pluripotent stem cell-derived cortical neurons reveal reduced, yet detectable amyloid-beta levels in the presenilin-1 knockout line, and a mutant gene dosage-dependent defect in amyloid precursor protein processing in PSEN1 intron 4 deletion lines, consistent with reduced processivity of ?-secretase. The different effects of presenilin-1 knockout and the PSEN1 intron 4 deletion mutation on amyloid precursor protein-C99 fragment accumulation, nicastrin maturation and amyloid-beta peptide generation support distinct consequences of familial Alzheimer's diseaseassociated mutations and knockout of presenilin-1 on the function of ?-secretase.
Project description:BACKGROUND:Presenilin-1 (PSEN1) is one of the causative genes for early onset Alzheimer's disease (EOAD). Recently, emerging studies reported several novel PSEN1 mutations among Asian. We describe a male with EOAD had a pathogenic PSEN1 mutation. CASE PRESENTATION:A 53-year-old male presented with memory decline, followed by difficulty in finding ways. Patient had positive family history, since his mother and one of his brother was also affected with dementia. Brain magnetic resonance imaging (MRI) scan showed mild degree of atrophy of bilateral hippocampus and parietal lobe. 18F-Florbetaben-PET (FBB-PET) revealed increased amyloid deposition in bilateral frontal, parietal, temporal lobe and precuneus. Whole exome analysis revealed a heterozygous, probably pathogenic PSEN1 (c.695G?>?T, p.W165C) mutation. Interestingly, Trp165Cys mutation is located in trans membrane (TM)-III region, which is conserved between PSEN1/PSEN2. In vitro studies revealed that PSEN1 Trp165Cys could result in disturbances in amyloid metabolism. This prediction was confirmed by structure predictions and previous in vitro studies that the p.Trp165Cys could result in decreased A?42/A?40 ratios. CONCLUSION:We report a case of EOAD having a pathogenic PSEN1 (Trp165Cys) confirmed with in silico and in vitro predictions.
Project description:Mutations in APP (amyloid precursor protein), PSEN1 (presenilin 1) or PSEN2 (presenilin 2) are the main cause of early-onset familial forms of Alzheimer's disease (autosomal dominant AD or ADAD). These genes affect ?-secretase-dependent generation of Amyloid ? (A?) peptides, the main constituent of amyloid plaques and one of the pathological hallmarks of AD. Evaluation of patients with ADAD includes assessment of family history, clinical presentation, biomarkers, neuropathology when available and DNA sequencing data. These analyses frequently uncover novel variants of unknown significance in ADAD genes. This presents a barrier to recruitment of such individuals into clinical trials, unless a biochemical test can demonstrate that a novel mutation results in altered APP processing in a manner consistent with pathogenicity. Here we describe generation and characterization of a novel presenilin 1 and 2 double knock-out in N2A mouse neuroblastoma cells using CRISPR/Cas9, which results in complete ablation of A? production, decreased Pen-2 expression and Nicastrin glycosylation. Because of the absence of background A? secretion from endogenous ?-secretases, these cells can be used for validation of PSEN1 and PSEN2 variant effects on production of A? or other ?-secretase substrates and for biochemical studies of ?-secretase function using novel variants. We examined several PSEN1 and PSEN2 mutations of known and unknown pathogenicity. Known mutants increased A?42/A?40 ratio with varying effect on A?40, A?42, total A? levels and Pen-2 expression, which aligns with previous work on these mutants. Our data on novel PSEN1 V142F, G206V and G206D mutations suggest that these mutations underlie the reported clinical observations in ADAD patients. We believe our novel cell line will be valuable for the scientific community for reliable validation of presenilin mutations and helpful in defining their pathogenicity to improve and facilitate evaluation of ADAD patients, particularly in the context of enrollment in clinical trials.
Project description:We have previously characterised functional brain abnormalities in young adults at genetic risk for late-onset Alzheimer's disease. To gain further knowledge on the preclinical phase of Alzheimer's disease, we sought to characterise structural and functional MRI, CSF, and plasma biomarkers in a cohort of young adults carrying a high-penetrance autosomal dominant mutation that causes early-onset Alzheimer's disease.Between January and August, 2010, 18-26-year-old presenilin 1 (PSEN1) E280A mutation carriers and non-carriers from the Colombian Alzheimer's Prevention Initiative Registry in Medellín Antioquia, Colombia, had structural MRI, functional MRI during associative memory encoding and novel viewing and control tasks, and cognitive assessments. Consenting participants also had lumbar punctures and venepunctures. Outcome measures were task-dependent hippocampal or parahippocampal activations and precuneus or posterior cingulate deactivations, regional grey matter reductions, CSF A?(1-42), total tau and phospho-tau(181) concentrations, and plasma A?(1-42) concentrations and A?(1-42):A?(1-40) ratios. Structural and functional MRI data were compared using automated brain mapping algorithms and search regions related to Alzheimer's disease. Cognitive and fluid biomarkers were compared using Mann-Whitney tests.44 participants were included: 20 PSEN1 E280A mutation carriers and 24 non-carriers. The carrier and non-carrier groups did not differ significantly in their dementia ratings, neuropsychological test scores, or proportion of apolipoprotein E (APOE) ?4 carriers. Compared with non-carriers, carriers had greater right hippocampal and parahippocampal activation (p=0·001 and p<0·014, respectively, after correction for multiple comparisons), less precuneus and posterior cingulate deactivation (all p<0·010 after correction), and less grey matter in several parietal regions (all p<0·002 uncorrected and corrected p=0·009 in the right parietal search region). In the 20 participants (ten PSEN1 E280A mutation carriers and ten non-carriers) who had lumbar punctures and venepunctures, mutation carriers had higher CSF A?(1-42) concentrations (p=0·008) and plasma A?(1-42) concentrations (p=0·01) than non-carriers.Young adults at genetic risk for autosomal dominant Alzheimer's disease have functional and structural MRI findings and CSF and plasma biomarker findings consistent with A?(1-42) overproduction. Although the extent to which the underlying brain changes are either neurodegenerative or developmental remain to be determined, this study shows the earliest known biomarker changes in cognitively normal people at genetic risk for autosomal dominant Alzheimer's disease.Banner Alzheimer's Foundation, Nomis Foundation, Anonymous Foundation, Forget Me Not Initiative, Boston University Department of Psychology, Colciencias, National Institute on Aging, National Institute of Neurological Disorders and Stroke, and the State of Arizona.
Project description:We report a probable pathogenic Thr119Ile mutation in presenilin-1 (PSEN1) in two unrelated Korean patients, diagnosed with early onset Alzheimer's disease (EOAD). The first patient presented with memory decline when she was 64 years old. Magnetic resonance imaging (MRI) scans showed diffuse atrophy in the fronto-parietal regions. In addition, 18F-fludeoxyglucose positron emission tomography (FDG-PET) showed reduced tracer uptake in the parietal and temporal cortices, bilaterally. The second patient developed memory dysfunction at the age of 49, and his mother was also affected. Amyloid positron emission tomography (PET) was positive, but MRI scans did not reveal any atrophy. Targeted NGS and Sanger sequencing identified a heterozygous C to T exchange in PSEN1 exon 5 (c.356C>T), resulting in a p.Thr119Ile mutation. The mutation is located in the conserved HL-I loop, where several Alzheimer's disease (AD) related mutations have been described. Structure analyses suggested that Thr119Ile mutation may result in a significant change inside conservative loop. Additional in vitro studies are needed to estimate the role of the PSEN1 Thr119Ile in AD disease progression.
Project description:Fibrillar amyloid-? (A?) is thought to begin accumulating in the brain many years before the onset of clinical impairment in patients with Alzheimer's disease. By assessing the accumulation of A? in people at risk of genetic forms of Alzheimer's disease, we can identify how early preclinical changes start in individuals certain to develop dementia later in life. We sought to characterise the age-related accumulation of A? deposition in presenilin 1 (PSEN1) E280A mutation carriers across the spectrum of preclinical disease.Between Aug 1 and Dec 6, 2011, members of the familial Alzheimer's disease Colombian kindred aged 18-60 years were recruited from the Alzheimer's Prevention Initiative's registry at the University of Antioquia, Medellín, Colombia. Cross-sectional assessment using florbetapir PET was done in symptomatic mutation carriers with mild cognitive impairment or mild dementia, asymptomatic carriers, and asymptomatic non-carriers. These assessments were done at the Banner Alzheimer's Institute in Phoenix, AZ, USA. A cortical grey matter mask consisting of six predefined regions.was used to measure mean cortical florbetapir PET binding. Cortical-to-pontine standard-uptake value ratios were used to characterise the cross-sectional accumulation of fibrillar A? deposition in carriers and non-carriers with regression analysis and to estimate the trajectories of fibrillar A? deposition.We enrolled a cohort of 11 symptomatic individuals, 19 presymptomatic mutation carriers, and 20 asymptomatic non-carriers, ranging in age from 20 to 56 years. There was greater florbetapir binding in asymptomatic PSEN1 E280A mutation carriers than in age matched non-carriers. Fibrillar A? began to accumulate in PSEN 1E280A mutation carriers at a mean age of 28·2 years (95% CI 27·3-33·4), about 16 years and 21 years before the predicted median ages at mild cognitive impairment and dementia onset, respectively. (18)F florbetapir binding rose steeply over the next 9·4 years and plateaued at a mean age of 37·6 years (95% CI 35·3-40·2), about 6 and 11 years before the expected respective median ages at mild cognitive impairment and dementia onset. Prominent florbetapir binding was seen in the anterior and posterior cingulate, precuneus, and parietotemporal and frontal grey matter, as well as in the basal ganglia. Binding in the basal ganglia was not seen earlier or more prominently than in other regions.These findings contribute to the understanding of preclinical familial Alzheimer's disease and help set the stage for assessment of amyloid-modifying treatments in the prevention of familial Alzheimer's disease.Avid Radiopharmaceuticals, Banner Alzheimer's Foundation, Nomis Foundation, Anonymous Foundation, Forget Me Not Initiative, Colciencias, National Institute on Aging, and the State of Arizona.
Project description:The presenilin 1 (PSEN1) L271V mutation causes early-onset familial Alzheimer's disease by disrupting the alternative splicing of the PSEN1 gene, producing some transcripts harboring the L271V point mutation and other transcripts lacking exon 8 (PS1(?exon8)). We previously reported that PS1 L271V increased amyloid beta (A?) 42/40 ratios, while PS1(?exon8) reduced A?42/40 ratios, indicating that the former and not the exon 8 deletion transcript is amyloidogenic. Also, PS1(?exon8) did not rescue A? generation in PS1/2 double knockout cells indicating its identity as a severe loss-of-function splice form. PS1(?exon8) is generated physiologically raising the possibility that we had identified the first physiological inactive PS1 isoform. We studied PS1(?exon8) in vivo by crossing PS1(?exon8) transgenics with either PS1-null or Dutch APP(E693Q) mice. As a control, we crossed APP(E693Q) with mice expressing a deletion in an adjacent exon (PS1(?exon9)). PS1(?exon8) did not rescue embryonic lethality or Notch-deficient phenotypes of PS1-null mice displaying severe loss of function in vivo. We also demonstrate that this splice form can interact with wildtype PS1 using cultured cells and co-immunoprecipitation (co-IP)/bimolecular fluorescence complementation. Further co-IP demonstrates that PS1(?exon8) interacts with nicastrin, participating in the ?-secretase complex formation. These data support that catalytically inactive PS1(?exon8) is generated physiologically and participates in protein-protein interactions.