Autopsy-confirmed familial early-onset Alzheimer disease caused by the l153V presenilin 1 mutation

Mixed Pathologies in a Subject with a Novel PSEN1 G206R Mutation

BACKGROUND

There are more than 300 presenilin-1 (PSEN1) mutations identified but a thorough postmortem neuropathological assessment of the mutation carriers is seldom performed.

OBJECTIVE

To assess neuropathological changes (NC) in a 73-year-old subject with the novel PSEN1 G206R mutation suffering from cognitive decline in over 20 years. To compare these findings with an age- and gender-matched subject with sporadic Alzheimer's disease (sAD).

METHODS

The brains were assessed macro- and microscopically and the proteinopathies were staged according to current recommendations.

RESULTS

The AD neuropathological change (ADNC) was more extensive in the mutation carrier, although both individuals reached a high level of ADNC. The transactive DNA binding protein 43 pathology was at the end-stage in the index subject, a finding not previously described in familial AD. This pathology was moderate in the sAD subject. The PSEN1 G206R subject displayed full-blown alpha-synuclein pathology, while this proteinopathy was absent in the sAD case. Additionally, the mutation carrier displayed pronounced neuroinflammation, not previously described in association with PSEN1 mutations.

CONCLUSION

Our findings are exceptional, as the PSEN1 G206R subject displayed an end-stage pathology of every common proteinopathy. It is unclear whether the observed alterations are caused by the mutation or are related to a cross-seeding mechanisms. The pronounced neuroinflammation in the index patient can be reactive to the extensive NC or a contributing factor to the proteinopathies. Thorough postmortem neuropathological and genetic assessment of subjects with familial AD is warranted, for further understanding of a dementing illness.

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.

Genetic Markers of Alzheimer's Disease

Alzheimer's disease is a complex and heterogeneous, severe neurodegenerative disorder and the predominant form of dementia, characterized by cognitive disturbances, behavioral and psychotic symptoms, progressive cognitive decline, disorientation, behavioral changes, and death. Genetic background of Alzheimer's disease differs between early-onset familial Alzheimer's disease, other cases of early-onset Alzheimer's disease, and late-onset Alzheimer's disease. Rare cases of early-onset familial Alzheimer's diseases are caused by high-penetrant mutations in genes coding for amyloid precursor protein, presenilin 1, and presenilin 2. Late-onset Alzheimer's disease is multifactorial and associated with many different genetic risk loci (>20), with the apolipoprotein E ε4 allele being a major genetic risk factor for late-onset Alzheimer's disease. Genetic and genomic studies offer insight into many additional genetic risk loci involved in the genetically complex nature of late-onset Alzheimer's disease. This review highlights the contributions of individual loci to the pathogenesis of Alzheimer's disease and suggests that their exact contribution is still not clear. Therefore, the use of genetic markers of Alzheimer's disease, for monitoring development, time course, treatment response, and prognosis of Alzheimer's disease, is still far away from the clinical application, because the contribution of genetic variations to the relative risk of developing Alzheimer's disease is limited. In the light of prediction and prevention of Alzheimer's disease, a novel approach could be found in the form of additive genetic risk scores, which combine additive effects of numerous susceptibility loci.

Blood-Brain Barrier: From Physiology to Disease and Back

The blood-brain barrier (BBB) prevents neurotoxic plasma components, blood cells, and pathogens from entering the brain. At the same time, the BBB regulates transport of molecules into and out of the central nervous system (CNS), which maintains tightly controlled chemical composition of the neuronal milieu that is required for proper neuronal functioning. In this review, we first examine molecular and cellular mechanisms underlying the establishment of the BBB. Then, we focus on BBB transport physiology, endothelial and pericyte transporters, and perivascular and paravascular transport. Next, we discuss rare human monogenic neurological disorders with the primary genetic defect in BBB-associated cells demonstrating the link between BBB breakdown and neurodegeneration. Then, we review the effects of genes underlying inheritance and/or increased susceptibility for Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease, and amyotrophic lateral sclerosis (ALS) on BBB in relation to other pathologies and neurological deficits. We next examine how BBB dysfunction relates to neurological deficits and other pathologies in the majority of sporadic AD, PD, and ALS cases, multiple sclerosis, other neurodegenerative disorders, and acute CNS disorders such as stroke, traumatic brain injury, spinal cord injury, and epilepsy. Lastly, we discuss BBB-based therapeutic opportunities. We conclude with lessons learned and future directions, with emphasis on technological advances to investigate the BBB functions in the living human brain, and at the molecular and cellular level, and address key unanswered questions.

Clinical and molecular studies reveal a PSEN1 mutation (L153V) in a Peruvian family with early-onset Alzheimer's disease

Presenilin 1 (PSEN1) gene mutations are found in 30-70% of familial early-onset Alzheimer disease (EOAD) cases (onset <60 years). Prevalence of these mutations is highly variable including ethnic differences worldwide. No Peruvian kindred with familial AD (FAD) have been described. Standardized clinical evaluation and cognitive assessment were completed in a Peruvian family with severe EOAD. Clinical course was characterized by very early onset (before age 35 years), progressive cognitive impairment with early memory loss, spatial disorientation and executive dysfunction. We sequenced all exons of PSEN1 in the proband and identified a c.475C>G DNA change resulting in a p.L153V missense mutation in the transmembrane domain 2 of the gene. This mutation is also present in the three additional affected siblings but not in a non-affected family member consistent with segregation of this mutation with the disease. This is the first report of a Peruvian family affected with EOAD associated with a PSEN1 mutation. This same mutation has been reported previously in English and French families, but a novel variants very close to the mutation and ancestry informative markers analysis suggests the mutation might be of Amerindian or African origin in this Peruvian family.

Antioxidant therapies for Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disease featuring progressive impairments in memory, cognition, and behavior and ultimately leads to death. The histopathological changes of Alzheimer's disease include neuronal and synaptic loss, formation of extracellular senile plaques and intracellular neurofibrillary tangles in brain. Multiple lines of evidence indicate that oxidative stress not only strongly participates in an early stage of Alzheimer's disease prior to cytopathology, but plays an important role in inducing and activating multiple cell signaling pathways that contribute to the lesion formations of toxic substances and then promotes the development of Alzheimer's disease. Many years of studies show that antioxidant therapies have enjoyed general success in preclinical studies. Therefore, this paper mainly focuses on the recent developments of common used antioxidant therapies for Alzheimer's disease and thus provides indications for future potential antioxidant therapeutic strategies of neurodegenerative diseases.

A novel missense mutation in the transmembrane domain of neuregulin 1 is associated with schizophrenia

BACKGROUND

Although genetic factors are known to play an important role in schizophrenia, the identification of genes involved in this disorder has remained elusive. The neuregulin 1 gene is among the few candidate genes to have been implicated in schizophrenia susceptibility in several populations. However, no causal mutations within this gene have been identified.

METHODS

In attempts to identify polymorphisms within the neuregulin 1 gene, we performed DNA sequencing using 12 subjects with a history of psychosis from the Central Valley of Costa Rica. DNA genotyping and association studies were then performed in an extended cohort of 142 affected individuals and their relatives from the same population.

RESULTS

We identified a novel missense mutation (Val to Leu) in exon 11, which codes for the transmembrane region of the neuregulin 1 protein. Association analysis by the Family Based Association Test (FBAT) revealed that this mutation is associated with psychosis (p = .0049) and schizophrenia (p = .0191) in this population.

CONCLUSIONS

We report the finding of a missense mutation in the neuregulin 1 gene associated with schizophrenia. Additional analyses of an independent sample as well as detailed functional studies should be performed to determine the relevance of this novel polymorphism to the pathophysiology of schizophrenia.

Farber lipogranulomatosis: clinical and molecular genetic analysis reveals a novel mutation in an Indian family

Farber disease is a rare lysosomal storage disorder caused by a deficiency of the acid ceramidase enzyme, leading to the accumulation of ceramide in various tissues. It usually manifests within a few months after birth with a unique triad of symptoms, including painful and progressive deformed joints, progressive hoarseness and subcutaneous nodules. The disease is inherited as an autosomal recessive trait, and mutations in the N-acylsphingosine amidohydrolase (ASAH1) gene, which codes for the acid ceramidase enzyme, have been shown to cause the disease. In the current study, we report the identification of a novel disease-causing mutation in the ASAH1 gene that results in Farber disease in an Indian family. The mutation was identified in the eighth exon and is a missense mutation resulting in replacement of Valine by Leucine at codon 182. Two affected siblings harboured the identical mutation. The possible mechanism(s) of disease caused by this mutation are discussed.

Presenilin immunoreactivity in Alzheimer's disease

The role of presenilin (PS) mutations in familial Alzheimer's disease (AD) may be as a toxic gain of function, but in sporadic disease their contribution is more difficult to understand. In this study, we investigated PS proteins in sporadic AD by comparing the immunocytochemical profiles in sporadic AD with control brains using a quantitative immunocytochemical approach to both the N- and C-terminals of PS1 and PS2. Ten patients with pathologically proven AD (using modified Consortium to Establish a Registry for Alzheimer's Disease [CERAD] criteria) and 10 controls were age- and sex-matched. The immunocytochemical primary antibodies were affinity-purified goat polyclonal antibodies and the secondary antibodies were biotinylated donkey anti-goat to the N- and C-terminal of both PS1 and PS2. The number of PS-containing neurones was quantified manually and without the knowledge of the diagnosis. We found no significant differences in the number of PS1- and PS2-containing neurones in three anatomical regions for both N- and C-terminals between AD and controls. Our findings argue in favour of functional changes in PS molecules contributing to the pathogenesis of AD and are consistent with the hypothesis of dysfunction of the entire gamma-secretase complex, of which PS proteins are a constituent.

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.

Mapping the onset and progression of atrophy in familial frontotemporal lobar degeneration

BACKGROUND

Frontotemporal lobar degeneration (FTLD) may be inherited as an autosomal dominant disease. Studying patients "at risk" for developing FTLD can provide insights into the earliest onset and evolution of the disease.

METHOD

We carried out approximately annual clinical, MRI, and neuropsychological assessments on an asymptomatic 51 year old "at risk" family member from a family with FTLD associated with ubiquitin-positive and tau-negative inclusion bodies. We used non-linear (fluid) registration of serial MRI to determine areas undergoing significant regional atrophy at different stages of the disease.

RESULTS

Over the first 26 months of the study, the patient remained asymptomatic, but subsequently developed progressive speech production difficulties, and latterly severe orofacial dyspraxia, dyscalculia, frontal executive impairment, and limb dyspraxia. Regional atrophy was present prior to the onset of symptoms, and was initially centred on the left dorsolateral prefrontal cortex and the left middle frontal gyrus. Latterly, there was increasing asymmetric left frontal and parietal atrophy. Imaging revealed excess and increasing global atrophy throughout the study. Neuropsychological evaluation revealed mild intellectual impairment prior to the onset of these clinical symptoms; frontal executive and left parietal impairment subsequently emerged, culminating in widespread cognitive impairment. Fluid registered MRI allowed the emerging atrophy patterns to be delineated.

CONCLUSION

We have demonstrated the onset and progressive pattern of in vivo atrophy in familial FTLD using fluid registered MRI and correlated this with the clinical features. Fluid registered MRI may be a useful technique in assessing patterns of focal atrophy in vivo and demonstrating the progression of degenerative diseases.

Clinical, pathological, and biochemical spectrum of Alzheimer disease associated with PS-1 mutations

Three genes have been implicated in the etiology of early-onset autosomal-dominant Alzheimer disease (AD): the amyloid precursor protein, the presenilin-1, and presenilin-2 genes. Approximately half of autosomal-dominant AD cases are associated with mutations in the presenilin-1 (PS-1) gene on the long arm of Chromosome 14. Marked allelic heterogeneity characterizes families with PS-1 gene mutations; more than 100 different mutations have been found in independent families thus far. With the exception of age at onset, the clinical phenotype is similar to late-onset AD, although some rare specific phenotypes have been described. These mutations lead to enhanced deposition of total Abeta and Abeta42 (but not Abeta40) in the brain, compared with sporadic AD. There is a considerable heterogeneity in the histological profiles among brains from patients with different mutations, and although some lead to predominantly parenchymal deposition of Abeta in the form of diffuse and cored plaques, others show predominantly vascular deposition, with severe amyloid angiopathy. Only some mutations are associated with enhanced neurofibrillary tangle formation and increased neuronal loss compared with sporadic AD. However, there is an important clinical and pathological variability even among family members with the same mutation, which suggests the involvement of other genetic or environmental factors that modulate the clinical expression of the disease. This represents a valuable model for identifying such factors and has potential implications for the development of new therapeutic strategies for delaying disease onset.

A novel mutation (L250V) in the presenilin 1 gene in a Japanese familial Alzheimer's disease with myoclonus and generalized convulsion

This study reports a novel presenilin 1 (PS1) gene mutation in a Japanese family with Alzheimer's disease (AD). Two patients developed progressive memory disorder with disorientation around 50 years of age and showed myoclonus with frequent tonic-clonic seizures several years later. Direct sequencing of the proband's PS1 gene revealed a novel mis-sense mutation (leucine-to-valine at residue 250 (L250V)). This mutation was found in both patients, but not in a normal family member or normal Japanese control subjects. Thus, L250V is a novel PS1 gene mutation responsible for familial AD (FAD) in Japan.

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

The clinical, neuropsychological and neuropathological features of a patient with early-onset Alzheimer's disease as a result of the M139V presenilin-1 (PSEN-1) mutation are presented, and compared with previous reports of patients with the same mutation. Similarities, such as the age at onset and the relative preservation of naming skills, and differences, such as the significant basal ganglia, thalamic and cerebellar pathology, are noted. This clinical and pathological heterogeneity in patients with the same PSEN-1 mutation suggests phenotype modulation by genetic and/or epigenetic factors.