PER2 C111G polymorphism, cognitive reserve and cognition in subjective cognitive decline and mild cognitive impairment: a 10-year follow-up study.

BACKGROUND AND PURPOSE: CLOCK and PER2 genes have been implicated in sleep-wake cycle alterations and neurodegenerative diseases. Our aim was to evaluate the effect of CLOCK T3111C and PER2 C111G on cognitive functioning in subjective cognitive decline (SCD) patients and mild cognitive impairment (MCI) patients at the baseline of a longitudinal study, and the effect of these two polymorphisms on the progression to Alzheimer's disease (AD) of the two groups. METHODS: Sixty-eight subjects (41 SCD and 27 MCI) who underwent clinical evaluation, neuropsychological assessment, CLOCK and PER2 genotyping at baseline and neuropsychological follow-up every 2 years for a mean time of 10 years were included. Subjects who developed AD (SCD-c and MCI-c) and non-converters (SCD-nc, MCI-nc) were considered. RESULTS: CLOCK T3111C was detected in 47% of cases (21 SCD, 11 MCI) and PER2 C111G in 19% of cases (eight SCD and five MCI). PER2 G carriers presented lower premorbid intelligence score (P = 0.049), fewer years of education (P = 0.007) and a lower frequency of family history of AD (P = 0.04) than G non-carriers. MCI PER2 G carriers had worse performance in tests assessing memory, executive function, language and visuospatial abilities at baseline. During follow-up, two SCD and 15 MCI subjects progressed to AD: both of the SCD-c subjects presented the PER2 G allele, while none of the SCD PER2 G non-carriers converted to AD (P = 0.003). CONCLUSION: PER2 seems to have a role in cognitive reserve and cognition in SCD and MCI patients. Nevertheless, further studies are needed to assess the role of PER2 C111G on the risk of progression to AD.

Incomplete penetrance in familial Alzheimer's disease with PSEN1 Ala260Gly mutation.

Presenilin1 (PSEN1) gene is the most common known genetic cause of early-onset familial Alzheimer's disease. We describe an Italian family with the known p.Ala260Gly mutation in PSEN1 gene. The presence of an asymptomatic 64-year-old male carrying the mutation provides evidence of a possible incomplete penetrance leading to a wider range of age at onset. In order to evaluate whether or not epigenetic modifications could contribute to the phenotypic heterogeneity, we assessed global DNA methylation levels which resulted significantly higher in the three females than in their presymptomatic brother. The study suggests that DNA methylation can contribute to slowing down or possibly protecting from the manifestation of symptoms even in monogenic diseases, emphasizing the great complexity of familial Alzheimer's disease.

Assessing the effectiveness of subjective cognitive decline plus criteria in predicting the progression to Alzheimer's disease: an 11-year follow-up study.

BACKGROUND AND PURPOSE: Subjective cognitive decline (SCD) is a self-experienced decline in cognitive capacity with normal performance on standardized cognitive tests and has been shown to increase the risk of Alzheimer's disease (AD). SCD could also be related to other conditions such as normal aging, psychiatric, neurological or medical disorders. The SCD Initiative proposed a set of features (SCD-plus) that increase the likelihood of preclinical AD in individuals with SCD. Our aim was to assess the effect of these features on the risk of conversion from SCD to AD. METHODS: In total 150 SCD subjects who underwent extensive neuropsychological investigation, assessment of cognitive complaints and apolipoprotein E (ApoE) genotyping at baseline and clinical-neuropsychological follow-up for a mean time of 11 years were included. RESULTS: During the follow-up, 20 subjects developed AD. Considering SCD-plus features, age at onset ≥60 years and ApoE ε4 significantly increased the risk of conversion from SCD to AD. When our sample was stratified into three groups (no risk factor, one risk factor, two risk factors), the proportion of conversion was statistically significantly different between the three groups. CONCLUSIONS: Our model allows the risk of AD to be stratified in patients experiencing SCD according to age at onset and ApoE genotype.

Genetics of Alzheimer's Disease and Frontotemporal Dementia.

The genetics of neurodegenerative diseases has an important role to clarify the pathogenetic mechanism, the diagnosis and finally the therapeutic and ethical implications. Moreover, the genetic approach to the study of the main clinical forms of dementia (Alzheimer's disease-AD and Frontotemporal Dementia-FTD) suggests clinical guidelines for helping families to navigate through these complexities. AD and FTD are multifactorial, genetically complex diseases involving many candidate genes. Mutations in three genes (i.e. Amyloid Precursor Protein, APP; presenilin 1, PSEN1; presenilin 2, PSEN2) have been linked to 50% of all familial forms of AD (FAD). Genome wide association studies (GWAS) have involved an increasing number of genes with a possible role in the disease pathogenesis. Up to now, the genetics of familial forms of FTD is related to 7 genes: the microtubule-associated protein tau (MAPT) progranulin (GRN), the valosin-containing protein (VCP), chromatin-modifying 2B (CHMP2B), the TARDNA binding protein 43 encoding gene (TARBDP), fused in sarcoma (FUS) and the last hexanucleotide expansion repeats in the open reading frame of chromosome 9 (C9orf72). Pre-test counseling and the identification of genetic defects are important in both patients and asymptomatic at risk family members.

Clinical heterogeneity in Italian patients with amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) is a rare and devastating neurodegenerative disorder. The majority of cases are sporadic ALS (SALS), with 5-10% being familial ALS (FALS), and are inherited mostly as autosomal dominant. Mutations in Cu/Zn superoxide dismutase (SOD1) and the TAR DNA-binding protein (TARDBP) gene are the most commonly known cause of ALS. We analyzed these genes in 61 Italian ALS patients using high-resolution melting analysis to confirm the role of SOD1 and TARDBP in the physiopathology of ALS. The screenings showed a single mutation in SOD1 (Asp109Tyr) and three in TARBDP (Ala382Thr, Gly295Ser, Gly294Val) in five unrelated ALS patients. This report enlarges the spectrum of clinical phenotypes associated with genetic mutations in SOD1 and TARDBP genes confirming the variability of phenotypes associated with the same mutation and emphasizes the importance of genetic analysis. The different genotype-phenotype correlations suggest the implication of other factors possibly influencing clinical manifestation of the disease, such as an epigenetic or epistatic effect with other genes not yet identified.