Neural correlates of altered insight in frontotemporal dementia: a systematic review.

Altered insight into disease or specific symptoms is a prominent clinical feature of frontotemporal dementia (FTD). Understanding the neural bases of insight is crucial to help improve FTD diagnosis, classification and management. A systematic review to explore the neural correlates of altered insight in FTD and associated syndromes was conducted. Insight was fractionated to examine whether altered insight into different neuropsychological/behavioural objects is underpinned by different or compatible neural correlates. 6 databases (Medline, Embase, PsycINFO, Web of Science, BIOSIS and ProQuest Dissertations & Theses Global) were interrogated between 1980 and August 2019. 15 relevant papers were found out of 660 titles screened. The studies included suggest that different objects of altered insight are associated with distinctive brain areas in FTD. For example, disease unawareness appears to predominantly correlate with right frontal involvement. In contrast, altered insight into social cognition potentially involves, in addition to frontal areas, the temporal gyrus, insula, parahippocampus and amygdala. Impaired insight into memory problems appears to be related to the frontal lobes, postcentral gyrus, parietal cortex and posterior cingulate. These results reflect to a certain extent those observed in other neurodegenerative conditions like Alzheimer's disease (AD) and also other brain disorders. Nevertheless, they should be cautiously interpreted due to variability in the methodological aspects used to reach those conclusions. Future work should triangulate different insight assessment approaches and brain imaging techniques to increase the understanding of this highly relevant clinical phenomenon in dementia.

Association of the New Variant Tyr424Asp at TBK1 Gene with Amyotrophic Lateral Sclerosis and Cognitive Decline.

A new risk gene associated with amyotrophic lateral sclerosis (ALS) has recently been identified: the Tank-binding kinase 1 (TBK1) gene. Up to now, 90 TBK1 variants have been described in ALS patients with or without frontotemporal dementia (FTD), thus making TBK1 the third or fourth most frequent genetic cause of ALS and FTD. A point mutation analysis in a cohort of 69 Italian ALS patients was performed in order to analyze the frequency of TBK1 mutations and the correlation with clinical phenotypes. The analysis identified the novel variant p.Tyr424Asp in a patient with a rapid progression of the disease. Our data supports the implication of TBK1 in ALS pathogenesis in Italy.

The novel PSEN1 M84V mutation associated to frontal dysexecutive syndrome, spastic paraparesis, and cerebellar atrophy in a dominant Alzheimer's disease family.

We identified the novel PSEN1 pathogenic mutation M84V in 3 patients belonging to a large kindred affected by autosomal dominant Alzheimer's disease (AD). The clinical phenotype was characterized by early onset dementia in 14 affected subjects over 3 generations. Detailed clinical, imaging and genetic assessment was performed. We highlighted the presence of unusual symptoms such as frontal executive syndrome, psychosis and spastic paraparesis in these patients. Spastic paraparesis has been reported in other PSEN1 mutations in adjacent codons, suggesting that the position of the genetic defect may affect the clinical expression, although this phenotype can occur in mutations throughout the whole PSEN1 gene. Brain magnetic resonance imaging showed diffuse cortical atrophy, but also atrophy of cerebellar lobules, mainly involving Crus I, in 2 patients without cerebellar motor deficits. These neuroimaging results were consistent with recent findings about the association between sporadic AD and distinct and circumscribed cerebellar atrophy. The present work acknowledged the novel PSEN1 pathogenic mutation M84V and might contribute to the ongoing debate about the involvement of cerebellum in AD.

Low Florbetapir PET Uptake and Normal Aß1-42 Cerebrospinal Fluid in an APP Ala713Thr Mutation Carrier.

According to the literature, the APP Ala713Thr mutation is associated with Alzheimer's disease and cerebral amyloid angiopathy. We describe a case of dementia clinically compatible with frontotemporal dementia in an APP Ala713Thr mutation carrier in which both [18F]Florbetapir PET uptake and Aß1-42 cerebrospinal fluid levels were normal. Further evidences are required to establish if this association is only incidental.

Analyses of the role of the glucocorticoid receptor gene polymorphism (rs41423247) as a potential moderator in the association between childhood overweight, psychopathology, and clinical outcomes in Eating Disorders patients: A 6 years follow up study.

Childhood overweight and the SNP rs41423247 of the glucocorticoid receptor gene (GR) were reported to represent predisposing factors for Eating Disorders (EDs). The distribution of the polymorphism was evaluated in 202 EDs patients, and in 116 healthy subjects. The Structured Clinical Interview for the DSM-IV and self-reported questionnaires were administered at the admission to the clinic and at 3 time points (end of a cognitive behavioral therapy, 3 and 6 years follow up). G-allele was associated with childhood overweight, depressive disorder comorbidity, and diagnostic instability. G-allele carriers reporting childhood overweight showed greater frequency of subjective binge eating and emotional eating.

Novel presenilin 1 mutation (Ile408Thr) in an Italian family with late-onset Alzheimer's disease.

Alzheimer's disease (AD) is a neurodegenerative disease affecting over 20 million people worldwide, mainly adult subjects in advanced age. Over 240 different fully penetrant autosomal dominant mutations in 532 families around the world have been described in three genes [i.e., amyloid precursor protein (APP), and presenilins (PSEN1 and PSEN2)] causing 50% of all Familial AD. We report a new mutation (p.Ile408Thr, c. 1223T>C) in the PSEN1 gene in one autosomal dominant Late Onset AD patient. The genetic variation occurred in a conserved domain of the protein and was present in the proband and in the younger sister who is likely to be prodromal AD. Thus, we suggest that this variant will have probably a pathogenic effect, hypothesizing a possible key role of this new mutation in the pathogenesis of Alzheimer's disease for this family.

Epigenetic modifications in Alzheimer's disease: cause or effect?

Alzheimer's disease (AD) is a multifactorial disorder induced by a combination of genetic and environmental factors, and epigenetic modifications could be the key to understand the pathogenesis of AD. We performed a methylation study of the promoter regions of the three AD principal causative genes in 60 late-onset AD patients and 60 controls. The studied regions in the three causative genes were strongly unmethylated in both groups, but in AD patients the methylation resulted significantly increased. Our study adds new insights to previous ones by showing the involvement of epigenetic changes in AD, which influence the pathogenesis of the disease.

Mutation analysis of patients with neurodegenerative disorders using NeuroX array.

Genetic analyses of patients with neurodegenerative disorders have identified multiple genes that need to be investigated for the presence of damaging variants. However, mutation analysis by Sanger sequencing is costly and time consuming. We tested the utility of a recently designed semi-custom genome-wide array (NeuroX; Illumina, Inc) tailored to study neurodegenerative diseases (e.g., mutation screening). We investigated 192 patients with 4 different neurodegenerative disorders for the presence of rare damaging variations in 77 genes implicated in these diseases. Several causative mutations were identified and confirmed by Sanger sequencing, including PSEN1 p.M233T responsible for Alzheimer's disease in a large Italian family, as well as SOD1 p.A4V and p.I113T in patients with amyotrophic lateral sclerosis. In total, we identified 78 potentially damaging rare variants (frequency <1%), including ABCA7 p.L400V in a family with Alzheimer's disease and LRRK2 p.R1514Q in 6 of 98 patients with Parkinson's disease (6.1%). In conclusion, NeuroX appears to be helpful for rapid and accurate mutation screening, although further development may be still required to improve some current caveats.

Association of the variant Cys139Arg at GRN gene to the clinical spectrum of frontotemporal lobar degeneration.

BACKGROUND: Progranulin protein (PGRN) is a cysteine-rich growth factor encoded by the progranulin gene (GRN). PGRN mutations were identified in patients with frontotemporal lobar degeneration (FTLD) and recently its role as risk factor has been described in patients with probable Alzheimer's disease (AD). To date, more than 100 genetic variants in GRN gene have been described and the pathogenic nature is still unclear for almost 36% of them. OBJECTIVE: Here, we describe three clinical cases carrying the PGRN variation Cys139Arg in order to increase the knowledge on the association of this variant to the clinical spectrum of FTLD. METHODS: The genetic analysis was performed using high resolution melting analysis. The Human Progranulin ELISA Kit was used in order to determine PGRN expression levels in the plasma samples. RESULTS: The three patients carrying the genetic variation showed three final different clinical diagnosis, respectively behavioral frontotemporal dementia, semantic dementia, and corticobasal syndrome, thus underlining the clinical heterogeneity typically associated with GRN mutations. All cases shared similar plasma PGRN levels that resulted intermediate between those measured in controls and in GRN null mutation carriers, showing a partial reduction of the protein in plasma. Moreover, according to the bioinformatics software, the Cys139Arg variation causes a decreased stability of the structure of the protein. CONCLUSION: We describe three new patients affected by neurological syndromes included in the clinical spectrum of FTLD carrying the Cys139Arg genetic variant, thus suggesting a possible implication in the pathogenesis of FTLD.

Imaging and cognitive reserve studies predict dementia in presymptomatic Alzheimer's disease subjects.

There is strong evidence that Alzheimer's disease (AD) pathology starts decades before clinical onset. Cognitive reserve (CR) and brain reserve can be a good predictive model for AD development. Neuroimaging can help in describing cerebral reserves, as well as in detecting AD brain pathology before the onset of clinical dementia. Education and occupation act as proxies for CR and are associated with a lower risk of AD and delayed onset of symptoms. The apolipoprotein E (ApoE)-ε4 allele is a strong risk factor for AD and is associated with lower hippocampal volume even in normal aging. A fluorodeoxyglucose positron emission tomography study of brain metabolism shows different metabolic phenotypes among subjects with different educational levels and ApoE genotypes. More highly educated subjects reach a clinical level when the cerebral areas involved in coping with network disruption are seriously impaired, and the AD-ε4 carriers show more global metabolic brain impairment compared with non-ε4 carriers. Thus, CR can counteract a genetically unfavorable background, suggesting a possible preventive strategy. AD research findings have already produced results, since recent epidemiological studies report a decreasing incidence of AD in the last years.

TOMM40 polymorphisms in Italian Alzheimer's disease and frontotemporal dementia patients.

Chromosome 19 is one of the several prominent chromosomes related to the risk of developing late-onset Alzheimer's disease (LOAD) and frontotemporal lobar degeneration (FTLD). However, only Apolipoprotein E (APOE) has been confirmed as a risk factor for both disorders. The aim of this study was to investigate a set of polymorphisms in the translocase of the outer mitochondrial membrane 40 (TOMM40) gene, located in close proximity to APOE, to clarify if the TOMM40 gene may be considered a risk factor for AD and FTLD, independently of APOE status. We performed a case-control study in a dataset of Italian LOAD and FTLD patients, analyzing the following three single-nucleotide polymorphisms (SNPs): rs157580, rs2075650 and rs157581. The analysis was made in 710 Italian subjects: 282 LOAD patients, 156 FTLD patients and 272 healthy subjects. Our results confirm the presence of an association between TOMM40 SNPs and LOAD in our Italian population, suggesting that genetic variations proximate to APOE contributes to the LOAD risk. Genotype and allele distribution of the TOMM40 polymorphisms between the FTLD group and controls did not show any statistical difference. When we analyzed haplotype distribution of the SNPs, taking into account the presence of the APOE allele, we observed a strong association between the ε4 allele and the GAC haplotype both in LOAD and FTLD patients. In contrast, this association did not hold for ε3/GAC. These results demonstrate that the TOMM40 gene does not have an APOE-independent role in the risk of developing LOAD and FTLD.

Ataxia-telangiectasia mutated (ATM) genetic variant in Italian centenarians.

Lifespan is attributable to genetic factors and some studies have attempted to identify putative genes implicated in human longevity. Several genetic loci have been associated with longevity, but some of these are not replicable, probably due to the vast differences among ethnicities. We analyzed in 128 Italian long-lived individuals and 150 unrelated healthy subjects, the recently reported association between rs189037 in the ataxia-telangiectasia mutated gene promoter and longevity in Chinese nonagenarians/centenarians. Our study confirms the association between the rs189037 C/T genotype and longevity in Italian centenarians, with an odds ratio of 1.85 (95 % CI 0.99-3.45). To understand the genetic basis for longevity is an extraordinarily difficult task, and therefore it is important to replicate any positive findings, especially if detected in other ethnic groups, in order to reach reliable conclusions on the real effect that candidate genes have on longevity.

DAPK1 is associated with FTD and not with Alzheimer's disease.

Apoptosis is correlated with various forms of dementia. Death-associated protein kinase 1 (DAPK1) plays an important role in neuronal apoptosis and could influence the pathology of late-onset Alzheimer's disease (LOAD) and frontotemporal dementia (FTD). It has been reported that two common polymorphisms (rs4878104 and rs4877365) are associated with LOAD, thus we examined the genotype and allele distributions of the above polymorphisms in 681 Italian subjects, including patients with LOAD and FTD. We showed a positive association between rs4878104 and FTD, suggesting a possible implication of the DAPK1 genetic variant in the susceptibility to FTD.

Suitability of neuropsychological tests in patients with vascular dementia (VaD).

The concept of vascular dementia (VaD) has evolved with the introduction of vascular cognitive impairment (VCI). VaD patients show predominantly frontal cognitive deficits. The executive area is particularly affected, while memory deficits are less frequent in patients with VaD than patients with AD. Several neuropsychological tests are available for the diagnosis and differentiation of dementias, but there are currently no tests developed specifically for VaD. We proposed to evaluate various neuropsychological tests, on the basis of evidence from different studies, in order to clarify the utility of the neuropsychological assessment in vascular dementia.

Progranulin genetic screening in frontotemporal lobar degeneration patients from central Italy.

Recently, mutations in the progranulin gene (GRN) were reported to account for the vast majority of Frontotemporal lobar Degeneration (FTLD) and a growing number of reports describe the implication of this gene in the development of the FTLD pathology with a significant variation in clinical features. To better clarify the contribution of GRN mutations to Italian FTLD, we screened 381 subjects: 171 cases and 210 healthy subjects, all from Central Italy, particularly of Tuscan origins. GRN gene was analyzed using High Resolution Melting Analysis and automated Genetic Analyzer. Human Progranulin ELISA Kit was employed to determine the plasma progranulin levels. The screening showed a total of six genetic variants in the GRN gene: 3 pathogenic and 3 non pathogenic in 13 out of 171 patients. The rare intronic variant IVS2 +7 G > A was found in one patient. The pathogenetic mutation, p.T272SfsX10, is confirmed as the most common GRN mutation in Italian FTLD patients with a frequency in our study of 2.32%. Moreover, we identified the first Italian patient with the p.R493X mutation, to date described in 43 families worldwide. Our data report, for the first time, the occurrence of GRN mutations in Tuscany, Central Italy, confirming that genetic variations in this gene could be a considerable genetic cause of FTLD and that genetic screening might be useful both in familial and sporadic FTLD patients.

Association Study of Genetic Variants in CDKN2A/CDKN2B Genes/Loci with Late-Onset Alzheimer's Disease.

Alzheimer's disease (AD) is the most common form of dementia clinically characterized by progressive impairment of memory and other cognitive functions. Many genetic researches in AD identified one common genetic variant (ε4) in Apolipoprotein E (APOE) gene as a risk factor for the disease. Two independent genome-wide studies demonstrated a new locus on chromosome 9p21.3 implicated in Late-Onset Alzheimer's Disease (LOAD) susceptibility in Caucasians. In the present study, we investigated the role of three SNP's in the CDKN2A gene (rs15515, rs3731246, and rs3731211) and one in the CDKN2B gene (rs598664) located in 9p21.3 using an association case-control study carried out in a group of Caucasian subjects including 238 LOAD cases and 250 controls. The role of CDKN2A and CDKN2B genetic variants in AD is not confirmed in our LOAD patients, and further studies are needed to elucidate the role of these genes in the susceptibility of AD.

Implication of a genetic variant at PICALM in Alzheimer's disease patients and centenarians.

A common polymorphism (rs3851179) in the PICALM (phosphatidylinositol-binding clathrin assembly protein) gene has been recently associated with reduced risk of developing late-onset Alzheimer's disease (LOAD). We analyzed the genotype and allele distributions of the PICALM polymorphism in 813 Italian subjects, including LOAD patients and centenarians. The segregation of the PICALM rs3851179 showed no statistically significant difference between LOAD cases and controls. The implication of a genetic variant at PICALM is confirmed for the first time, in centenarians, thus suggesting a possible role in longevity.

Implication of serotonin-transporter (5-HTT) gene polymorphism in subjective memory complaints and mild cognitive impairment (MCI).

Serotonin-transporter-linked polymorphism (5-HTTLPR) is involved in neuropsychiatric diseases and recently the S-isoform has been correlated with a higher risk of developing emotion-induced retrograde amnesia. In order to better clarify the possible role of the 5-HTT S/L polymorphism and its effects on cognitive ability, especially on memory skills, we report here the distributions of the 5-HTT genetic variant and the Apolipoprotein E (ApoE) ɛ-4 allele and their association with neuropsychological measures in older adults reporting problems with everyday memory. Moreover, we verified the presence of a possible association between the S-allele with depression and the personal trait of neuroticism. Our results indicate an association between the 5-HTTLPR S-allele and the risk of developing MCI. No association was found in the other three groups. We found a positive dose-dependent association between the S-allele and the Rey-Osterrieth complex figure test (recall) score. Finally, our data did not find an association between the same allele and depression or neuroticism. This data, in our opinion shows a slight, non-established influence of 5-HTTLPR on memory skills exhibited in challenging memory tests but no influence on other extra-mnesic cognitive abilities.

Semantic dementia associated with mutation V363I in the tau gene.

A 46-year-old woman who presented with prosopagnosia was clinically evaluated. Results of neuropsychological measures showed severe impairment in oral naming with anomia and a marked deficit in naming and recognition of famous faces. The clinical diagnosis was semantic dementia (SD). Genetic testing revealed a missense mutation V363I in exon 12 of the microtubule-associated protein tau (MAPT) gene. This is the description of an association between a mutation in the MAPT gene and a case of SD. The same mutation was recently described in a case of progressive non-fluent aphasia, but the prominent presenting feature in tau gene mutation cases is the behavioral variant of frontotemporal dementia, with typical symmetrical frontotemporal atrophy.