GRN Missense Variants and Familial Alzheimer's Disease: Two Case Reports.

BACKGROUND: Progranulin protein (GRN) is a growth factor, encoded by the GRN (Granulin precursor) gene, involved in several functions including inflammation, wound repair, signal transduction, proliferation, and tumorigenesis. Mutations in GRN gene are usually the genetic etiology of frontotemporal dementia (FTD), but different studies reported GRN mutations in Alzheimer 's disease (AD) patients. OBJECTIVE: Here, we analyzed FTD linked gene GRN in 23 patients with a clinical diagnosis of AD and a family history of AD (FAD), not carrying mutations in AD candidate genes (PSEN 1, PSEN 2, and APP). In addition, Microtubule-associated protein tau (MAPT) gene was studied too. All patients underwent an extensive neuropsychological battery. METHODS: Genetic analyses were performed thought PCR assay and sequencing. Variants were annotated with ANNOVAR and allele frequency was checked on population databases. In silico prediction tools were consulted to check nonsynonymous variants and their effect on protein function and structure. The clinical data were retrospectively collected from medical records. RESULTS: Genetic screening of MAPT and GRN in 23 FAD patients highlighted two rare different variants in two probands (2/23 = 8,7%) located in GRN gene: R433W (p.Arg433Trp) and C521Y (p.Cys521Tyr). The R433W and C521Y are variants with uncertain significant, that are predicted to affect GRN protein structure and function, with a possible damaging effect. CONCLUSIONS: Our data provide evidence of the importance of GRN genetic analysis also in the study of familial AD.

Proteomic analysis across patient iPSC-based models and human post-mortem hippocampal tissue reveals early cellular dysfunction and progression of Alzheimer's disease pathogenesis.

The hippocampus is a primary region affected in Alzheimer's disease (AD). Because AD postmortem brain tissue is not available prior to symptomatic stage, we lack understanding of early cellular pathogenic mechanisms. To address this issue, we examined the cellular origin and progression of AD pathogenesis by comparing patient-based model systems including iPSC-derived brain cells transplanted into the mouse brain hippocampus. Proteomic analysis of the graft enabled the identification of pathways and network dysfunction in AD patient brain cells, associated with increased levels of Aß-42 and ß-sheet structures. Interestingly, the host cells surrounding the AD graft also presented alterations in cellular biological pathways. Furthermore, proteomic analysis across human iPSC-based models and human post-mortem hippocampal tissue projected coherent longitudinal cellular changes indicative of early to end stage AD cellular pathogenesis. Our data showcase patient-based models to study the cell autonomous origin and progression of AD pathogenesis.

Genetic variation in APOE, GRN, and TP53 are phenotype modifiers in frontotemporal dementia.

Frontotemporal dementia (FTD) is a clinical, genetic, and pathologic heterogeneous group of neurodegenerative diseases. In this study, we investigated the role of APOƐ4, rs5848 in GRN, and rs1042522 in TP53 gene as disease risk factors and/or phenotype modifiers in 440 FTD patients, including 175 C9orf72 expansion carriers. We found that the C9orf72 expansion carriers showing an earlier age at onset (p < 0.001). Among the clinical groups, the FTD-MND (motoneuron disease) showed the lowest survival (hazard ratio [HR] = 4.12), and the progressive nonfluent aphasia group showed the highest onset age (p = 0.03). In our cohort, the rs1042522 in TP53 was associated with disease onset (p = 0.02) and survival (HR = 1.73) and rs5848 GRN with a significantly shorter survival in CC homozygous patients (HR = 1.98). The frequency of APOƐ4 carriers was significantly increased in the C9orf72 noncarriers (p = 0.022). Although validation of our findings is necessary, our results suggest that TP53, GRN, and APOE genes may act as phenotype modifiers in FTD and should be considered in future clinical trials.

Notch4 and mhc class II polymorphisms are associated with hcv-related benign and malignant lymphoproliferative diseases.

Mixed cryoglobulinemia (MC), is a HCV-related, clinically benign, lymphoproliferative disorder (LPD) that may evolve into a non Hodgkin's lymphoma (NHL). Significant associations were found between two single nucleotide polymorphisms near NOTCH4 (rs2071286) and the HLA class II (rs9461776) genes and HCV-related MC syndrome (MCS). We analyzed NOTCH4 rs2071286 and HLA-II rs9461776 in 3 HCV-related LPD groups (asymptomatic MC, MCS, NHL) with HCV infection without lymphoproliferative disorders. We found a positive relationship between NOTCH4 rs207186 T minor allele frequency (MAF) and patients with HCV-related LPDs at risk of NHL (Chi-square test for trend = 14.84 p = 0.0001), in accordance with an over-dominant model in the NHL group (CT vs CC + TT, OR=1.88, 95% CI 1.24-2.83, p = 0.0026). Regarding HLA II rs9461776, G MAF increased in patients with HCV-related LPDs at risk of NHL (Chi-square test for trend = 8.40 p = 0.0038), in accordance with a recessive genotypic model in the NHL group (G/G vs A/A + A/G, OR = 11.07, 95% CI 2.37-51.64, p = 0.0022). Both NOTCH4 rs2071286 and HLA-II rs9461776 were present on chromosome 6 and showed D' and r values of linkage disequilibrium (LD) of about 0.5 values, thereby suggesting there is no extensive LD in the HCV+ population. This data shows that the previously demonstrated association between NOTCH4 rs2071286 and HLA-II rs9461776 polymorphisms and HCV-related MCS could be extended to overall patients with HCV-related LPDs. The significant relationship between rs2071286 and rs9461776 MAF and the increased risk for NHL, suggests their use as non-invasive markers to categorize patients at risk of lymphoma.

Plasma membrane injury depends on bilayer lipid composition in Alzheimer's disease.

Increasing evidence indicates that interaction of amyloid-ß peptide (Aß) with the cell membrane is a primary step in Alzheimer's disease (AD) neurotoxicity. In particular, it has been demonstrated that lipid rafts are key sites of Aß production, aggregation, and interaction with the cell membrane. In this study we show that Aß42 oligomers are recruited to lipid rafts, leading to plasma membrane perturbation and Ca2+ dyshomeostasis in primary fibroblasts from familial AD patients bearing APPVal717Ile, PS-1Leu392Val, or PS-1Met146Leu gene mutations. In contrast, a moderate increase in membrane cholesterol content precluded the interaction of Aß42 oligomers with the plasma membrane and resulting cell damage. Moreover, the recruitment of amyloid assemblies to lipid raft domains of cholesterol-depleted fibroblasts was significantly increased, thus triggering an earlier and sharper increase in intracellular Ca2+ levels and plasma membrane permeabilization. Our findings suggest a protective role for raft cholesterol against amyloid toxicity in AD.

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.

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.

Lipid rafts are primary mediators of amyloid oxidative attack on plasma membrane.

Increasing evidence indicates that cell surfaces are early interaction sites for Abeta-derived diffusible ligands (ADDLs) and neurons in Alzheimer's disease (AD) pathogenesis. Our previous data showed significant oxidative damage at the plasma membrane in fibroblasts from familial AD patients with enhanced Abeta production. Here, we report that lipid rafts, ordered membrane microdomains, are chronic mediators of Abeta-induced lipid peroxidation in SH-SY5Y human neuroblastoma cells overexpressing amyloid precursor protein (APPwt) and APPV717G genes and in fibroblasts bearing the APPV717I gene mutation. Confocal microscope analysis showed that Abeta-oxidised rafts recruit more ADDLs than corresponding domains in control cells, triggering a further increase in membrane lipid peroxidation and loss of membrane integrity. Moreover, amyloid pickup at the oxidative-damaged domains was prevented by enhanced cholesterol levels, anti-ganglioside (GM1) antibodies, the B subunit of cholera toxin and lipid raft structure alteration. An enhanced structural rigidity of the detergent-resistant domains, isolated from APPwt and APPV717G cells and exposed to ADDLs, indicates a specific perturbation of raft physicochemical features in cells facing increased amyloid assembly at the membrane surface. These data identify lipid rafts as key mediators of oxidative damage as a result of their ability to recruit aggregates to the cell surface.

Lack of association between TNF-alpha polymorphisms and Alzheimer's disease in an Italian cohort.

Tumor necrosis factor-alpha (TNF-alpha) is a pro-inflammatory cytokine that plays an important role in the inflammatory process that can be observed in Alzheimer's disease (AD) brain. Different functional promoter polymorphisms within genes modulating inflammation have been demonstrated to elevate the AD risk; thus, we studied five common variations within the promoter region of the TNF-alpha gene in 609 subjects (253 AD patients and 356 controls). No positive associations were found, confirming the greater part of previous studies. Moreover, we also investigated the combined haplotypes of the five different polymorphisms without finding a positive association. Thus, the present investigation does not support the proposal that common nucleotide variations in the TNF-alpha gene can influence the development of AD at least in Italian population.

Protective effect of new S-acylglutathione derivatives against amyloid-induced oxidative stress.

Recent data support the role of oxidative stress in the pathogenesis of Alzheimer disease (AD). In particular, glutathione (GSH) metabolism is altered and its levels are decreased in affected brain regions and peripheral cells from AD patients and in experimental models of AD. In the past decade, interest in the protective effects of various antioxidants aimed at increasing intracellular GSH content has been growing. Because much experimental evidence suggests a possible protective role of unsaturated fatty acids in age-related diseases, we designed the synthesis of new S-acylglutathione (acyl-SG) thioesters. S-Lauroylglutathione (lauroyl-SG) and S-palmitoleoylglutathione (palmitoleoyl-SG) were easily internalized into the cells and they significantly reduced Abeta42-induced oxidative stress in human neurotypic SH-SY5Y cells. In particular, acyl-SG thioesters can prevent the impairment of intracellular ROS scavengers, intracellular ROS accumulation, lipid peroxidation, and apoptotic pathway activation. Palmitoleoyl-SG seemed more effective in cellular protection against Abeta-induced oxidative damage than lauroyl-SG, suggesting a valuable role for the monounsaturated fatty acid. In this study, we demonstrate that acyl-SG derivatives completely avoid the sharp lipoperoxidation in primary fibroblasts from familial AD patients occurring after exposure to Abeta42 aggregates. Hence, we put forward these derivatives as new antioxidant compounds which could be excellent candidates for therapeutic treatment of AD and other oxidative stress-related diseases.

Cystatin C and apoe polymorphisms in Italian Alzheimer's disease.

Recent studies have reported a genetic association between the 73 G/A polymorphism within exon 1 of the cystatin C gene and Alzheimer's disease (AD) with conflicting results. To further investigate the proposed association and to clarify the role of CST3 as risk factor for AD, we analyzed the genotype and allele frequency distribution of CST3 G73A and apolipoprotein (ApoE) gene polymorphisms in 243 Italian patients with AD and 186 controls. Patients with AD were consecutively collected among the outpatients from the Neurology Department at the University of Florence. All 429 subjects were genotyped for CST3 and ApoE polymorphisms. After stratification according to age, the GG frequency resulted slightly higher in younger (<65 years) cases, but far from statistically significant. There was also no evidence of a statistical interaction between CST3 and ApoE polymorphisms. In conclusion, our data suggest that the CST3 genetic variant is not a susceptibility factor in AD, nor mitigate the effect of the ApoE varepsilon4 allele in the risk of developing AD.