Maria Gabriella Muraca

Worldwide distribution of PSEN1 Met146Leu mutation. A large variability for a founder mutation

Objective: Large kindreds segregating familial Alzheimer disease (FAD) offer the opportunity of studying clinical variability as observed for presenilin 1 (PSEN1) mutations. Two early-onset FAD (EOFAD) Calabrian families with PSEN1 Met146Leu (ATG/CTG) mutation constitute a unique population descending from a remote common ancestor. Recently, several other EOFAD families with the same mutation have been described worldwide. Methods: We searched for a common founder of the PSEN1 Met146Leu mutation in families with different geographic origins by genealogic and molecular analyses. We also investigated the phenotypic variability at onset in a group of 50 patients (mean age at onset 40.0 ± 4.8 years) by clinical, neuropsychological, and molecular methodologies. Results: EOFAD Met146Leu families from around the world resulted to be related and constitute a single kindred originating from Southern Italy before the 17th century. Phenotypic variability at onset is broad: 4 different clinical presentations may be recognized, 2 classic for AD (memory deficits and spatial and temporal disorientation), whereas the others are expressions of frontal impairment. The apathetic and dysexecutive subgroups could be related to orbital-medial prefrontal cortex and dorsolateral prefrontal cortex dysfunction. Conclusions: Genealogic and molecular findings provided evidence that the PSEN1 Met146Leu families from around the world analyzed in this study are related and represent a single kindred originating from Southern Italy. The marked phenotypic variability might reflect early involvement by the pathologic process of different cortical areas. Although the clinical phenotype is quite variable, the neuropathologic and biochemical characteristics of the lesions account for neurodegenerative processes unmistakably of Alzheimer nature.

Presenilin 2 Ser130Leu mutation in a case of late-onset “sporadic” Alzheimer’s disease

Sirs: Presenilin 2 gene (PS2) mutations are a rare cause of Familial Alzheimer’s Disease (FAD) [1] showing an older and variable age at onset (range 45–88 years) and a quite longer disease duration [2]. Although Presenilins mutations unequivocally identify FAD, a few cases of early onset apparently sporadic AD have been recently reported [3–6]. However, to date, no pathogenic mutations of these genes have been described in late onset apparently sporadic AD cases. The PS2 Ser130Leu mutation, signalled as pathogenic and causative in a patient from a dominant FAD family [7], has recently been interpreted, after in vitro experimental procedures, as a rare polymorphism or a no pathogenic mutation [8]. We report the PS2 Ser130Leu mutation in a patient with an apparently sporadic late onset AD. The patient was the owner of a bakery till retirement age at 70. At 81, his wife noted progressive memory impairment and episodes of spatial disorientation while driving. His mood and personality changed. He started to shun social contact, losing interest in friends and in leisure activities, he developed delusions. Familial history reported two first degree relatives with a ‘‘Parkinson’s disease’’ without cognitive impairment (Fig. 1). On examination the patient was depressed, apathetic and evidenced moderate impairment of cognition (MMSE 22.1). CDR was 0.5. Psychometric testing were performed and the findings are shown in Table 1. Neurological examination was normal. CT revealed a mid temporal atrophy without vascular lesions. Blood chemistry investigations were normal. A diagnosis of AD was considered. Six months later the patient showed worsened memory functions; he was disoriented as to time and space and became unable to perform Raven Progressive Matrices (Table 1). MMSE was 16.1. He rapidly developed language deficits, agitation, delusions and hallucinations. One year later the patient was untestable (MMSE 5/30) amnesic, agnosic, aphasic, and showed mild bradikinesia. CDR was 4. No evidence of fluctuating course was reported by the family. Although not usual, the family asked for molecular screening of the known FAD genes. Informed consent was obtained for molecular genetic purposes. DNA of the proband, of the II10 unaffected brother (the only one available out of 10 siblings) and of his 3 healthy children was extracted from peripheral leukocytes. Sequence analysis of PS2 gene coding exons (3–12) [9] showed in the proband a C-to-T transition at the second position of codon 130 in exon 5 predicting a serine-toleucine substitution (Ser130Leu). This mutation was present also in two out of three children and absent in 110 age-matched healthy controls (age, 70.6 ± 4.7) and in 100 FAD patients (age, 71.9 ± 7.4) that we screened. APOE genotype was 3/3. We found a PS2 Ser130Leu mutation in an apparently sporadic late onset AD case in which two siblings were referred as having a so-called ‘‘parkinson’s’’ disease. Neither a de novo nor an inherited mutation can be ruled out because DNA from parents was unavailable. Moreover, we cannot consider this substitution as a common polymorphism because we did not find it in 220 subjects. Mutation at codon 130 do not map in any transmembrane domain, differently from other known mutations that, disrupting a-helical conformation, produce more Ab42 [10]. These findings are in agreement with the study C. Tomaino Æ L. Bernardi Æ M. Anfossi A. Costanzo Æ F. Ferrise Æ M. Gallo S. Geracitano Æ R. Maletta S. AM Curcio Æ M. Mirabelli Æ R. Colao F. Frangipane Æ G. Puccio C. Calignano Æ M. G. Muraca A. Paonessa Æ N. Smirne Æ A.C. Bruni (&) Regional Neurogenetic Centre AS6 6 Viale A. Perugini 88046 Lamezia Terme CZ, Italy Tel.: +39-0968 208080 Fax: +39-0968 208032 E-Mail: bruni@arn.it

Homozygous carriers of APP A713T mutation in an autosomal dominant Alzheimer disease family

Objective: To report, for the first time, a large autosomal dominant Alzheimer disease (AD) family in which the APP A713T mutation is present in the homozygous and heterozygous state. To date, the mutation has been reported as dominant, and in the heterozygous state associated with familial AD and cerebrovascular lesions. Methods: The family described here has been genealogically reconstructed over 6 generations dating back to the 19th century. Plasma β-amyloid peptide was measured. Sequencing of causative AD genes was performed. Results: Twenty-one individuals, all but 1 born from 2 consanguineous unions, were studied: 8 were described as affected through history, 5 were studied clinically and genetically, and 8 were asymptomatic at-risk subjects. The A713T mutation was detected in the homozygous state in 3 patients and in the heterozygous state in 8 subjects (6 asymptomatic and 2 affected). Conclusions: Our findings, also supported by the β-amyloid plasma assay, confirm (1) the pathogenic role of the APP A713T mutation, (2) the specific phenotype (AD with cerebrovascular lesions) associated with this mutation, and (3) the large span of age at onset, not influenced by APOE, TOMM40, and TREM2 genes. No substantial differences concerning clinical phenotype were evidenced between heterozygous and homozygous patients, in line with the classic definition of dominance. Therefore, in this study, AD followed the classic definition of a dominant disease, contrary to that reported in a previously described AD family with recessive APP mutation. This confirms that genetic AD may be considered a disease with dominant and recessive traits of inheritance.

Role of Niemann-Pick Type C Disease Mutations in Dementia

BACKGROUND Several neurological and systemic diseases can cause dementia, beyond Alzheimers disease. Rare genetic causes are often responsible for dementia with atypical features. Recently, mutations causative for Niemann-Pick type C disease (NPC) have also been implicated in neurodegenerative diseases. NPC is an autosomal recessive lipid storage disorder caused by mutations in NPC1 and NPC2 genes. In adults, clinical presentation mimicking other neurodegenerative diseases makes diagnosis difficult. Recent evidence suggests that heterozygous mutations in NPC genes may take on etiological significance. OBJECTIVE To investigate the presence of NPC1 and NPC2 mutations in adults affected by neurodegenerative dementia plus. METHODS We performed a genetic screening on 50 patients using a wide clinical and biochemical approach to characterize the phenotype of mutated patients. RESULTS Sequencing analysis revealed four different and known heterozygous mutations in NPC1 and NPC2 genes. Patient 1 carried the p. F284LfsX26 in NPC1 and was affected by progressive supranuclear palsy-like syndrome. The remaining three patients showed a corticobasal syndrome and harbored the c.441+1G>A variant of NPC2 (patient 2), the missense p.N222 S mutation associated with the c.1947+8G>C variant in the splice region of intron 12 in NPC1 (patient 3), and the p.V30M mutation in NPC2 (patient 4), respectively. Filipin staining was abnormal in patients 1 and 2. mRNA analysis revealed an altered splicing of the NPC2 gene in patient 2. CONCLUSIONS Heterozygous mutations of NPC1 and NPC2 genes could contribute to dementia plus, at least in a subset of patients. We highlight the occurrence of NPC1 and NPC2 heterozygous variants in dementia-plus as pathological event.

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 Alzheimers 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.

Frequency of Cardiovascular Genetic Risk Factors in a Calabrian Population and Their Effects on Dementia

BACKGROUND Several genetic variants playing a key role in cholesterol levels, blood pressure, and vascular dysfunction influence the risk of Alzheimers disease (AD) and vascular dementia (VaD). The many meta-analysis studies carried out on large numbers of samples in different populations have not provided clear results to date, because a trans-ethnic shift of risk genotypes in different populations is often observed. OBJECTIVES To determine genotypes allele frequencies of the polymorphisms most frequently identified to be correlated with cardio-cerebrovascular disease and AD in a Southern Italy population and to investigate their possible association with dementia. METHODS The genotype and allele frequencies of 13 cardio-cerebrovascular risk polymorphisms were assessed and their possible association with dementia was investigated in a case-control study, including 221 consecutive unrelated subjects diagnosed with dementia (120 subjects affected by AD, 55 by frontotemporal dementia, and 33 by vascular dementia) and 218 matched controls of Calabrian origin. RESULTS Carriers of at least one APOEɛ4 allele resulted to be at higher risk of AD [OR(95% CI) = 2.721(1.477-5.011)] and VaD [OR(95% CI) = 6.205(2.356-16.342)] compared to non-carriers. Individuals with the IV genotype of the CETP polymorphism were more likely to have AD [OR(95% CI) = 2.427(1.364-4.319)] and VaD [OR(95% CI) = 3.649(1.455-9.152)] compared to subjects with the II-VV genotypes. CONCLUSION CETP I405V polymorphism is likely a risk factor for AD and VaD in our cohort, independent of APOEɛ4 status. Unmodifiable genetic risk factors should be taken into account to promote a healthy lifestyle to prevent dementia.

P3-277: TAU V363I mutation: Pathogenic or not?

both with and without adjustment for genomic control (GC) as well as empirical p values. We also compared our LOAD GWAS results with the Braak GWAS results. Results: After stringent quality control based on Hardy-Weinberg disequilibrium, missing genotypes and minor allele frequencies, high quality genotypes were obtained for 306,672 SNPs. We analyzed the AD cases and controls separately to avoid stratification bias. None of the SNPs had genome-wide significance after Bonferroni correction. In the AD cases, there were 79 SNPs with GC adjusted p 0.0002. In the controls, there were 81 such SNPs. These represent an excess of 17-27 SNPs under the null hypothesis of no association. The unadjusted, GC adjusted and empirical p values were highly correlated. There were SNPs with evidence of Braak NFT stage association in both the cases and controls. There were SNPs with evidence of association with both AD and Braak stage. Linear regression analysis of Braak NFT stage in the ADs, after including age, sex and ApoE as covariates, led to the identification of 78 SNPs with p 0.0002. Conclusions: These results suggest the presence of variants in the human genome that may be associated with both risk of AD and brain NFT pathology. Given that the Braak GWAS is performed in only a subset of our total series, constituting 12-16% of the subjects from our LOAD GWAS, use of Braak stage endophenotype deserves further exploration as a methodology to detect susceptibility variants for late onset Alzheimer’s disease. (*) Equal contribution.

P3-286: Subcortical ischemic vascular dementia: A search for APP gene mutations

Prism 7000 Sequence Detection System. TaqMan SNP genotyping products and assays. Multinomial regression models were used to determine the risk of AD and MCI-AT. Results: The T and C alleles were not independent risk factors for AD and MCI-AT ( OR 1.22; CI95%, 0.35-4.21, OR 1.04; CI95%, 0.29-3.76, respectively). This was also the case for the TT, TC and CC genotypes. Neither UBQLN1 alleles nor genotypes were independent risk factors for AD or MCI-AT. Once adjusted for sex and the presence of apolipoprotein E4 (APOE4), our results did not reveal an association between UBQLN1 polymorphism and either AMCI-AT or AD. Conclusions: This is the first Spanish’s study which evaluates the role of UBQLN1 polymorphism in cognitive impairment. UBQLN1 polymorphism is not an independent risk factor for AD or MCI-AT.