Valentina Bessi

Autosomal Dominant Frontotemporal Lobar Degeneration Due to the C9ORF72 Hexanucleotide Repeat Expansion: Late-Onset Psychotic Clinical Presentation

BACKGROUND A hexanucleotide repeat expansion in the first intron of C9ORF72 has been shown to be responsible for a high number of familial cases of amyotrophic lateral sclerosis or frontotemporal lobar degeneration (FTLD). Atypical presentations have been described, particularly psychosis. METHODS We determined the frequency of the hexanucleotide repeat expansions in a population of 651 FTLD patients and compared the clinical characteristics of carriers and noncarriers. In addition, we genotyped 21 patients with corticobasal syndrome, 31 patients with progressive supranuclear palsy, and 222 control subjects. RESULTS The pathogenic repeat expansion was detected in 39 (6%) patients with FTLD (17 male and 22 female subjects); however, it was not detected in any corticobasal syndrome and progressive supranuclear palsy patients or controls. Twenty-four of 39 carriers had positive family history for dementia and/or amyotrophic lateral sclerosis (61.5%), whereas only 145 of 612 noncarriers had positive family history (23.7%; p<.000001). Clinical phenotypes of carriers included 29 patients with the behavioral variant frontotemporal dementia (bvFTD; 5.2% of all bvFTD cases), 8 with bvFTD/motor neuron disease (32% bvFTD/motor neuron disease cases), 2 with semantic dementia (5.9% of patients with semantic dementia), and none with progressive nonfluent aphasia. The presentation with late-onset psychosis (median age = 63 years) was more frequent in carriers than noncarriers (10/33 vs. 3/37, p = .029), as well as the presence of cognitive impairment at onset (15/33 vs. 5/37; p = .0039). CONCLUSIONS The repeat expansion in C9ORF72 is a common cause of FTLD and often presents with late-onset psychosis or memory impairment.

KIBRA gene variants are associated with episodic memory performance in subjective memory complaints.

The KIBRA gene encodes a cytoplasmatic protein, a member of the signal transduction protein family, expressed mainly in the brain. Recent studies have implicated the involvement of a genetic variation in the KIBRA gene (T allele) in human memory in normal subjects and in the risk of developing Alzheimers disease (AD). We report here the distribution of the KIBRA genetic variant and the Apolipoprotein E (ApoE) epsilon4 allele and their association with neuropsychological measures in older adults reporting problems with everyday memory (subjective memory complaints, SMC). We found that SMC subjects with the CT/TT genotype performed more poorly than those with the CC genotype on long-term memory tests. Thus, in our opinion, these data suggest that the KIBRA genotype could affect memory performance in a different way in those that complain of memory deficits compared to those that do not.

Association of IL10 promoter polymorphism in Italian Alzheimer's disease

Recent studies have reported a genetic association between single nucleotide polymorphisms (SNPs) in the promoter region of Interleukin (IL) 10 and Alzheimers disease (AD) with conflicting results. To further investigate the proposed association and to clarify the role of cytokines as a potential cause for AD susceptibility, we analyzed genotypes, allele distributions and haplotypes of IL10 promoter polymorphisms -1082 (rs1800896) and -819 (rs1800871) in an Italian sample of 222 sporadic AD patients and 179 normal controls. All 401 subjects were also genotyped for the Apolipoprotein E (ApoE) polymorphism. We reported a positive association between the -819T/C polymorphism and AD. Moreover, we found a significant difference for this SNP in the ApoE varepsilon4 non-carrier AD patients compared to the ApoE varepsilon4 non-carrier control group. For the -1082A genotype and allele distribution, no significant association was found in AD patients, although it was detected within the AT haplotype. Our results indicate that IL10 polymorphisms may be involved in the risk of developing AD.

Early structural changes in individuals at risk of familial Alzheimer’s disease: a volumetry and magnetization transfer MR imaging study

Presenilin 1 (PS1) mutation carriers provide the opportunity to asses early features of neurodegeneration in familial Alzheimer’s disease (AD). Gray matter (GM) regional volume loss and decrease of magnetization transfer ratio (MTR) consistent with microstructural changes have been reported in sporadic AD. We performed a regional volumetric and MTR analysis in carriers of PS1 mutations. Six non-demented mutated PS1 carriers (5 with memory deficits) and 14 healthy subjects were examined with high resolution T1-weighted images for volumetry and with T2* weighted images for MTR. Cortical GM volume and MTR values were derived. Compared to healthy controls, the GM volume of the left temporal and inferior parietal cortex and the MTR of the temporal cortex bilaterally were significantly decreased in PS1 gene carriers. In the latter, the temporal lobe MTR showed a trend for correlation with memory and executive function scores. Early neurodegeneration in non-demented subjects at risk for familial AD may be associated with atrophy and decreased MTR in the temporal cortex.

Association analysis of the paraoxonase-1 gene with Alzheimer's disease

Genetic variants in the paraoxonase (PON) gene cluster, particularly a single C/T promoter polymorphism (rs 705381) in the PON-1 gene, have recently been associated with Alzheimers disease (AD). The T allele, in particular, presents an increased risk for the development of AD. Here, we investigate the potential role of this polymorphism in an Italian case-control population consisting of 306 sporadic AD patients and 275 controls, and also evaluate a possible interaction with the ApoE genotype. No association between the PON-1 polymorphism and AD was observed. The T allele frequency was slightly over-represented in AD patients compared to the controls, but this was far from being statistically significant. Our sample was evaluated to have 97.3% power to detect an OR of 2.0 (64.3% power with OR=1.5) at an alpha level of 0.05. No evidence of an interaction between the T risk-allele and the ApoE epsilon4 allele status and no effect of the PON-1 polymorphism on age at onset was detected. Our results do not support other studies indicating that the PON-1 promoter polymorphism plays a major role in AD, suggesting that other large studies are necessary to further elucidate the effect of PON on the development of the disease in the general population.

Metabolic correlates of executive dysfunction. Different patterns in mild and very mild Alzheimer's disease.

This study was designed to examine the correlations between resting-state brain glucose metabolism (CMRglc), as measured with Positron Emission Tomography and performance on executive function tasks in Alzheimers disease (AD), while taking into account the severity of cognitive deterioration. We addressed this issue in 50 AD patients, classified as very mild (n = 22) and mild (n = 28) AD on the basis of an extensive neuropsychological battery. Thirteen healthy subjects were selected as controls for the neuropsychological measures. Statistical Parametric Mapping (SPM) was used to examine voxel-wise correlations between CMRglc and scores on selected cognitive tests of executive functions: the Stroop Test, the Trail Making Test, the Dual Task and the Phonemic Fluency, while correcting for age and global CMRglc. All analyses were done separately for the two AD subgroups. The very mild AD patients showed significant associations between Stroop and Trail Making Test scores and prefrontal regions metabolism, whereas the mild AD patients exhibited more widely distributed cognitive–metabolic correlations extending to the posterior brain regions. These data suggest that a large cortical network is implicated in executive dysfunction in AD, and that the pattern of cognitive–metabolic correlations varies according to disease severity.

Pattern and Progression of Cognitive Decline in Alzheimer’s Disease: Role of Premorbid Intelligence and ApoE Genotype

Background/Aims: Because of controversial results across studies, we evaluated the predictive value of premorbid intelligence and the apolipoprotein E (ApoE) genotype on baseline and progression of cognitive performance in Alzheimer’s disease (AD). Methods: Eighty-five mild AD cases, ApoE genotyped and included in a longitudinal cliniconeuropsychological-genetic study, underwent a premorbid intelligence test and up to 11 (average 5) neuropsychological assessments. We applied linear- and logistic-regression models for cross-sectional data and mixed models for longitudinal ones. Results: Higher premorbid intelligence was associated with higher global, executive and memory performance, while the ApoE Ε4 allele was specifically related to poorer memory performance. The premorbid intelligence-ApoE Ε4/Ε4 interaction was significant, with higher premorbid intelligence scores reducing the detrimental effect of ApoE Ε4 homozygosity on memory performance. Higher premorbid intelligence, but not the ApoE Ε4 allele, was related to faster memory deficit progression. Conclusion: The association of higher premorbid intelligence with better baseline cognitive performance and faster memory decline, as well as its interaction with the ApoE genotype, strengthens the role of cognitive reserve in shaping the disease’s clinical expression. Our findings confirm that the Ε4 allele affects memory deficit at baseline but does not exert any influence on the rate of cognitive decline.

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.

Do cholinesterase inhibitors act primarily on attention deficit? A naturalistic study in Alzheimer's disease patients.

Attention is the first non-memory domain affected in Alzheimers disease (AD), before deficits in language and visuo-spatial function, and it is claimed that attention deficits are responsible for the difficulties with daily living in early demented patients. The aim of this longitudinal study in a group of 121 Caucasian, community-dwelling, mild-to-moderate AD patients (Mini-Mental State Examination (MMSE) score >17) was to detect which cognitive domains were most affected by the disease and whether one year treatment with cholinesterase inhibitors was more effective in preserving attention than memory. All subjects were evaluated by a neuropsychological battery including global measurements (MMSE, Information-Memory-Concentration Test) and tasks exploring verbal long-term memory, language, attention, and executive functions. The comparison between two evaluations, made 12 months apart, shows statistically significant differences, indicating deterioration compared to baseline, in the following tests: MMSE (with no gender differences), Composite Memory Score, Short Story Delayed Recall, Trail-Making Test A, Semantic Fluency Test, and Token Test. Conversely, there were no differences in the two evaluations of the Digit Span, Corsi Tapping Test, Short Story Immediate Recall, and Phonemic Fluency Tests. It appears that the treatment specifically attenuated the decline in tests assessing attention and executive functions. A stabilization of the ability to pay attention, with the ensuing positive effects on executive functions, recent memory, and information acquisition which depend on attention, appears to be the main neuropsychological mechanism through which the activation of the cholinergic system, resulting from cholinesterase inhibition, exerts its effect on cognition.

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 Alzheimers 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 Alzheimers disease and LRRK2 p.R1514Q in 6 of 98 patients with Parkinsons 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.