Early-onset Alzheimer's disease with presenilin-1 M139V mutation: clinical, neuropsychological and neuropathological study

Genetics, Functions, and Clinical Impact of Presenilin-1 (PSEN1) Gene

Presenilin-1 (PSEN1) has been verified as an important causative factor for early onset Alzheimer's disease (EOAD). PSEN1 is a part of γ-secretase, and in addition to amyloid precursor protein (APP) cleavage, it can also affect other processes, such as Notch signaling, β-cadherin processing, and calcium metabolism. Several motifs and residues have been identified in PSEN1, which may play a significant role in γ-secretase mechanisms, such as the WNF, GxGD, and PALP motifs. More than 300 mutations have been described in PSEN1; however, the clinical phenotypes related to these mutations may be diverse. In addition to classical EOAD, patients with PSEN1 mutations regularly present with atypical phenotypic symptoms, such as spasticity, seizures, and visual impairment. In vivo and in vitro studies were performed to verify the effect of PSEN1 mutations on EOAD. The pathogenic nature of PSEN1 mutations can be categorized according to the ACMG-AMP guidelines; however, some mutations could not be categorized because they were detected only in a single case, and their presence could not be confirmed in family members. Genetic modifiers, therefore, may play a critical role in the age of disease onset and clinical phenotypes of PSEN1 mutations. This review introduces the role of PSEN1 in γ-secretase, the clinical phenotypes related to its mutations, and possible significant residues of the protein.

Presenilin 1 Gene Mutation (M139V) in a German Family with Early-Onset Alzheimer's Disease: A Case Report

OBJECTIVE

This study describes a 44-year-old German male with early-onset Alzheimer's disease as a result of a M139V presenilin 1 mutation. The patient has at least seven affected family members, spanning at least four generations.

METHOD

We performed a complete demographic, genetic, neuropsychological, neuropsychiatric, neuroradiological, and neuropathological characterizations of this patient. The findings were compared with previous reports of patients with the same mutation. Demographic, neuropsychological, neuropsychiatric, neuroradiological, and neuropathological data from several affected members of the patient's family were also addressed.

RESULTS

We describe similarities shared with other cases, including age at onset, rapid disease progression, severe deficits in arithmetic and visuo-constructive abilities with relative preservation of naming skills, and the presence of predominant frontal behavioral symptoms. Differences with respect to previously described cases, including the absence of positive neurological or radiological findings, psychotic symptoms, or a depressive disorder, are also identified and discussed.

CONCLUSIONS

Heterogeneity in symptoms between affected patients from the same or from different families suggests that individual, genetic, or epigenetic factors most likely modulate the phenotype of patients carrying the M139V mutation.

A Case of Early-Onset Alzheimer's Disease Mimicking Schizophrenia in a Patient with Presenilin 1 Mutation (S170P)

Atypical psychological symptoms frequently occur in early-onset Alzheimer's disease (EOAD), which makes it difficult to differentiate it from other psychiatric disorders. We report the case of a 28-year-old woman with EOAD, carrying a presenilin-1 mutation (S170P), who was initially misdiagnosed with schizophrenia because of prominent psychiatric symptoms in the first 1-2 years of the disease. Amyloid-β positron emission tomography (PET) showed remarkably high tracer uptake in the striatum and thalamus. Tau PET showed widespread cortical uptake and relatively low uptake in the subcortical and medial temporal regions. Our case advocates for considering EOAD diagnosis for young patients with psychiatric and atypical cognitive symptoms.

A Novel PSEN1 M139L Mutation Found in a Chinese Pedigree with Early-Onset Alzheimer's Disease Increases Aβ42/Aβ40 ratio

BACKGROUND

Presenilin1 (PSEN1) is the most common gene related to familial Alzheimer's disease (AD). Only several mutation types from Chinese have been reported, with less biological function research conducted.

OBJECTIVES

We explore the pathological function of PSEN1 M139L, a mutation located at α-helix of PSEN1 transmembrane 2, using predictive programs and in vitro study and compare its effects on Aβ production to those of an artificial PSEN1 S141G located at non α-helix mutation face.

METHODS

APP, PSEN1, and PSEN2 genes were screened for mutations using Sanger sequencing in the DNA samples of the proband and additional available family members. Disease-mutation cosegregation analysis and three software programs were performed to predict the mutation's pathogenicity. In vitro, we investigated the impact of these mutations on Aβ production in HEK293-APPswe cells using lentiviral vectors harboring PSEN1 WT, PSEN1 M139L, the positive control (PSEN1 M139V) and the non α-helical mutation (PSEN1 S141G). In addition, we co-transfected PSEN1 and tau into cells to determine the mutations' impact on tau phosphorylation.

RESULTS

PSEN1 M139L mutation was discovered in the index patient and four affected siblings. Cosegregation analysis and silicon prediction suggested the mutation was probably disease causing. In vitro studies demonstrated that both PSEN1 M139L and PSEN1 S141G caused elevated ratios of Aβ42/Aβ40, but changes of tau phosphorylation were not detected.

CONCLUSION

The novel PSEN1 M139L mutation found in familial AD increases the Aβ42/Aβ40 ratio significantly. Mutations at non α-helical mutation face of PSEN1 TM2 can affect Aβ production and the region may play a key role in PSEN1 function.

Phenotypic Variability in Autosomal Dominant Familial Alzheimer Disease due to the S170F Mutation of Presenilin-1

BACKGROUND

In rare cases, patients with Alzheimer disease (AD) present at an early age and with a family history suggestive of an autosomal dominant mode of inheritance. Mutations of the presenilin-1 (PSEN1) gene are the most common causes of dementia in these patients. Early-onset and particularly familial AD patients frequently present with variable non-amnestic cognitive symptoms such as visual, language or behavioural changes as well as non-cognitive, e.g. motor, symptoms.

OBJECTIVE

To investigate the phenotypic variability in carriers of the PSEN1 S170F mutation.

METHODS

We report a family with 4 patients carrying the S170F mutation of whom 2 underwent detailed clinical examinations. We discuss our current findings in the context of previously reported S170F cases.

RESULTS

The clinical phenotype was consistent regarding initial memory impairment and early onset in the late twenties found in all S170F patients. There were frequent non-amnestic cognitive changes and, at early stages of the disease, indications of a more pronounced disturbance of visuospatial abilities as compared to face and object recognition. Non-cognitive symptoms most often included myoclonus and cerebellar ataxia. A review of the available case reports indicates some phenotypic variability associated with the S170F mutation including different constellations of symptoms such as parkinsonism and delusions.

CONCLUSION

The variable clinical findings associated with the S170F mutation highlight the relevance of atypical phenotypes in the context of research and under a clinical perspective. CSF sampling and detection of Aβ species may be essential to indicate AD pathology in unclear cases presenting with cognitive and motor symptoms at a younger age.

Corticobasal Syndrome in a Family with Early-Onset Alzheimer's Disease Linked to a Presenilin-1 Gene Mutation

BACKGROUND

Alzheimer's disease (AD) is the second-most frequent cause underlying corticobasal syndrome (CBS). However, a reliable diagnosis using clinical, neuropsychological, or neuroimaging approaches has not yet been achieved.

METHODS

Clinical, neuropsychological, imaging, and neuropathology studies were undertaken in a large Spanish family with early-onset familial AD (EOFAD) carrying a Met233Leu mutation linked to presenilin-1 gene (PSEN-1).

RESULTS

Two of three examined members of this family presented with the usual amnestic pattern. At the age of 47 years, a third family member, in whom pathology was later confirmed, developed prominent CBS combined with severe neuropsychiatric and behavioral disturbances resembling those often found in EOFAD.

CONCLUSION

Although CBS in EOFAD appears to be rare, demonstration of a linkage to PSEN-1 gene mutations may permit in vivo diagnosis.

Previously not recognized deletion in presenilin-1 (p.Leu174del.) in a patient with early-onset familial Alzheimer's disease

We report on a previously not recognized mutation in exon 6 of presenilin-1 (PSEN1) (c.520_522delCTG) in a male patient with early onset familial Alzheimer disease. The mutation results in the deletion of a leucine at amino acid position 174 of the protein. The index patient presented with progressive memory loss at 50 years of age. Initially, depression was the only ancillary symptom. At age 53 clinical diagnosis of early Alzheimer disease was made based on neuropsychological, neuroimaging, and CSF findings. The patient's father and his paternal grandmother also suffered from memory loss and cognitive decline. The clinical findings in the patient are similar to signs and symptoms in previously reported patients with missense mutations at codon 174 of PSEN1.

Atypical presentation of a novel Presenilin 1 R377W mutation: sporadic, late-onset Alzheimer disease with epilepsy and frontotemporal atrophy

Mutations within Presenilin 1 (PSEN1) represent the most common cause of monogenic Alzheimer Disease (AD). The clinical phenotype is highly variable, even if early onset disease with an autosomal dominant pattern of inheritance and presenting memory deficits usually occur. In the present work, we described the case of a late-onset AD patient, without any positive family history for dementia, and associated with seizures and behavioural symptoms. Structural and functional neuroimaging showed frontotemporal changes without posterior biparietal brain abnormalities. Cerebrospinal analysis was consistent with AD pattern, with decreased Aβ42 and increased Tau and phospho-Tau. A novel pathogenetic mutation within PSEN1 gene was detected within exon 8, leading to a substitution from arginine to tryptophan (AGG > TGG: R377W), affecting a splice junction and protein function. The case herein reported further confirms the heterogeneity of PSEN1 mutations and the need to take into account genetic screening in those cases with atypical presentation.

Familial Alzheimer's disease mutations in presenilins: effects on endoplasmic reticulum calcium homeostasis and correlation with clinical phenotypes

Mutations in presenilins 1 and 2 (PS1 and PS2) are responsible for approximately 40% of all early onset familial Alzheimer's disease (FAD) monogenic cases. Presenilins (PSs) function as the catalytic subunit of γ-secretase and support cleavage of the amyloid-β protein precursor (AβPP). We previously discovered that PSs also function as passive endoplasmic reticulum (ER) calcium (Ca2+) leak channels and that most FAD mutations in PSs affected their ER Ca2+ leak function. To further validate the relevance of our findings to human disease, we here performed Ca2+ imaging experiments with lymphoblasts established from FAD patients. We discovered that most FAD mutations in PSs disrupted ER Ca2+ leak function and resulted in increased ER Ca2+ pool in human lymphoblasts. However, we found that a subset of PS1 FAD mutants supported ER Ca2+ leak activity, as ER Ca2+ pool was unaffected in lymphoblasts. Most of the "functional" mutations for ER Ca2+ leak were clustered in the exon 8-9 area of PSEN1 gene and segregated with the cotton wool plaques and spastic paraparesis clinical phenotype occasionally observed in PS1 FAD patients. Our findings with the "functional" and "non-functional" PS1 FAD mutants were confirmed in Ca2+ rescue experiments with PS double-knockout mouse embryonic fibroblasts. Based on the combined effects of the PS1 FAD mutations on ER Ca2+ leak and γ-secretase activities we propose a model that explains the heterogeneity observed in FAD. The proposed model has implications for understanding the pathogenesis of both familial and sporadic AD.

Carbon-11-Pittsburgh compound B positron emission tomography imaging of amyloid deposition in presenilin 1 mutation carriers

(11)Carbon-Pittsburgh compound B positron emission tomography studies have suggested early and prominent amyloid deposition in the striatum in presenilin 1 mutation carriers. This cross-sectional study examines the (11)Carbon-Pittsburgh compound B positron emission tomography imaging profiles of presymptomatic and mildly affected (mini-mental state examination ≥ 20) carriers of seven presenilin 1 mutations, comparing them with groups of controls and symptomatic sporadic Alzheimer's disease cases. Parametric ratio images representing (11)Carbon-Pittsburgh compound B retention from 60 to 90 min were created using the pons as a reference region and nine regions of interest were studied. We confirmed that increased amyloid load may be detected in presymptomatic presenilin 1 mutation carriers with (11)Carbon-Pittsburgh compound B positron emission tomography and that the pattern of retention is heterogeneous. Comparison of presenilin 1 and sporadic Alzheimer's disease groups revealed significantly greater thalamic retention in the presenilin 1 group and significantly greater frontotemporal retention in the sporadic Alzheimer's disease group. A few individuals with presenilin 1 mutations showed increased cerebellar (11)Carbon-Pittsburgh compound B retention suggesting that this region may not be as suitable a reference region in familial Alzheimer's disease.

Presenilin 1 gene mutation (M139I) in a patient with an early-onset Alzheimer's disease: clinical characteristics and genetic identification

Mutations in the presenilin 1 (PSEN1) gene are more commonly identified as genetic causes of early-onset familial Alzheimer's disease than mutations in the amyloid precursor protein (APP) and the presenilin 2 (PSEN2) genes. More than 100 different mutations in the PSEN1 gene have been detected, and the clinical phenotypes have been described in the literature. This paper reports the case of a 38-year-old female showing early memory impairment and having a base pair mutation from guanine (G) to cytosine (C) at codon 139 of PSEN1, which leads to the substitution of a methionine with an isoleucine.

Monogenic Mendelian disorders in general neurological practice

An observational study of monogenic Mendelian disorders seen in general neurology outpatient clinics over a 6-year period was undertaken. Fifty-three patients with 16 different diagnoses were identified, the commonest being Huntington's disease and neurofibromatosis type 1. This low frequency of monogenic Mendelian disorders has implications for both continuing medical education and for neurological training. All such patients are probably best referred to specialist clinics where expertise in diagnosis, genetic counselling and testing, and management has been developed.

The topography of grey matter involvement in early and late onset Alzheimer's disease

Clinical observations have suggested that the neuropsychological profile of early and late onset forms of Alzheimer's disease (EOAD and LOAD) differ in that neocortical functions are more affected in the former and learning in the latter, suggesting that they might be different diseases. The aim of this study is to assess the brain structural basis of these observations, and test whether neocortical areas are more heavily affected in EOAD and medial temporal areas in LOAD. Fifteen patients with EOAD and 15 with LOAD (onset before and after age 65; Mini Mental State Examination 19.8, SD 4.0 and 20.7, SD 4.2) were assessed with a neuropsychological battery and high-resolution MRI together with 1:1 age- and sex-matched controls. Cortical atrophy was assessed with cortical pattern matching, and hippocampal atrophy with region-of-interest-based analysis. EOAD patients performed more poorly than LOAD on visuospatial, frontal-executive and learning tests. EOAD patients had the largest atrophy in the occipital [25% grey matter (GM) loss in the left and 24% in the right hemisphere] and parietal lobes (23% loss on both sides), while LOAD patients were remarkably atrophic in the hippocampus (21 and 22% loss). Hippocampal GM loss of EOAD (9 and 16% to the left and right) and occipital (12 and 14%) and parietal (13 and 12%) loss of LOAD patients were less marked. In EOAD, GM loss of 25% or more was mapped to large neocortical areas and affected all lobes, with relative sparing of primary sensory, motor, and visual cortex, and anterior cingulate and orbital cortex. In LOAD, GM loss was diffusely milder (below 15%); losses of 15-20% were confined to temporoparietal and retrosplenial cortex, and reached 25% in restricted areas of the medial temporal lobe and right superior temporal gyrus. These findings indicate that EOAD and LOAD differ in their typical topographic patterns of brain atrophy, suggesting different predisposing or aetiological factors.

Prevalence and causes of seizures at the time of diagnosis of probable Alzheimer's disease

BACKGROUND/AIMS

To investigate the frequency of epilepsy at the time of diagnosis of Alzheimer's disease (AD).

METHODS

Observational study, Cognitive Function Clinic population, over a 6-year period (2000-2005 inclusive).

RESULTS

In a cohort of 177 patients with newly diagnosed clinically probable AD, 12 (6.8%) had a history of seizure disorder and/or were using anti-epileptic medications at the time of diagnosis. In 6 of these cases (3.4%), seizure onset was approximately concurrent with the onset of cognitive decline, and no symptomatic or provoking factor for seizures other than AD was identified.

CONCLUSION

Although epileptic seizures are more common later in the course of AD, nonetheless they may accompany the onset of, and be symptomatic of, the disease, perhaps reflecting a shared pathogenesis.

Clinical phenotypic heterogeneity of Alzheimer's disease associated with mutations of the presenilin-1 gene

It is now 10 years since the first report of mutations in the presenilin genes that were deterministic for familial autosomal dominant Alzheimer's disease. The most common of these mutations occurs in the presenilin-1 gene (PSEN1) located on chromosome 14. In the ensuing decade, more than 100 PSEN1 mutations have been described. The emphasis of these reports has largely been on the novelty of the mutations and their potential pathogenic consequences rather than detailed clinical, neuropsychological, neuroimaging and neuropathological accounts of patients with the mutation. This article reviews the clinical phenotypes of reported PSEN1 mutations, emphasizing their heterogeneity, and suggesting that other factors, both genetic and epigenetic,must contribute to disease phenotype.

"Frontal variant Alzheimer's disease": a reappraisal

Two cases of clinically diagnosed sporadic Alzheimer's disease with early and prominent behavioural features (social disinhibition, emotional blunting, stereotyped verbal utterances) sufficient to prompt an initial diagnosis of frontotemporal dementia are presented. It is suggested that the term "frontal variant AD" be used for this clinically defined phenotype, which has also been described in cases of inherited AD associated with certain presenilin-1 gene mutations. This differs from previous usage of the term "frontal variant AD" to describe AD with predominant frontal lobe neuropathological change (although the clinical phenotype may reflect regional distribution of pathology), but parallels the clinical definition of visual agnosic, aphasic and apraxic presentations of AD. The proposed usage would also emphasise differential diagnosis.

Getting it wrong: the clinical misdiagnosis of Alzheimer's disease

Two patients whose diagnosis of Alzheimer's disease proved to be incorrect on follow-up are presented. Factors which contributed to the misdiagnosis included failure to obtain collateral history, failure to apply widely accepted diagnostic criteria, over-reliance on structural brain imaging and lack of longitudinal follow-up. Analysis of diagnostic errors may permit avoidance of similar pitfalls in future.