MALATTIA DI ALZHEIMER E DEGENERAZIONE LOBARE FRONTOTEMPORALE: RICERCA DI MUTAZIONI AUTOSOMICHE DOMINANTI E ANALISI GENETICA E FUNZIONALE DI GENI CANDIDATI

This PhD study is intended to perform a genetic screening on a population of AD and FTLD patients in order to identify pathogenetic causal mutations (PSEN1, PSEN2 and APP for AD; MAPT, GRN and the GGGGCC repeat expansion one the C9orf72 gene for FTLD) and to investigate the role of several candidate genes (GRN,TMEM106b and OLR1) considered to be risk factors for the two disease. Eighteen patients were carriers of pathogenetic causal mutations: 1 carrier of Ala260Val (g.49964C>T) situated in exon 8 of PSEN1,16 carriers of GRN gene mutations and 1 carrier of a new variant, Gly304Ser (g.123789G>A), located in exon 10 of MAPT gene. The presence of GGGGCC repeat expansion, positioned on the first intron of C9orf72 gene, was analyzed in a larger population (651 FTLD patients, 21 CBD and 31 PSP patients). Thirty nine patients with FTLD were carriers of pathogenetic repeat expansion, whereas none of CBD and PSP patients as well as 222 controls carried the mutation. Several associations studies were performed in the remaining sporadic population of AD and FTLD patients. Regarding the influence of GRN genetic variability on susceptibility to AD, two SNPs rs9897526G>A and rs5848 were investigated. A tendency to an increased frequency of rs5848T allele was found in AD patients as compared with controls, whereas for the rs9897526 SNP, in patients carrying the rs9897526A variant was observed a significant earlier age at disease onset compared with patients carrying the G allele. The case-control study carried out on a populations of FTLD patients was focused on four Tagging SNPs (rs2879096, rs3785817, rs4792938 and rs9897526) as well as on rs5848 SNP, localized in the 3\u2019UTR of GRN gene. A statistically significant association of the rs4792938 CC genotype was observed in FTLD patients compared with healthy controls. Concerning the role of TMEM106b gene on susceptibility to AD, an association analysis was performed on three SNP, rs1020004 A/G, rs6966915 C/T and rs1990622 A/G, but no significant differences in allelic and genotype frequencies were found for all polymorphisms between AD patients and controls. The possible functional importance of genetic variability associated with this gene was tested by plasmatic ELISA detection of GRN on eighty AD patients. Stratifying the results according to rs1990622 SNP status, no significant differences in progranulin plasma levels were found in AD patients. Regarding OLR1, in particular it was analyzed the SNP rs1050283 T/C, located in 3\u2019UTR of the gene. Logistic regression analysis, adjusted for gender and ApoE status, showed a statistically significant association of OLR1 rs1050283 under the assumption of a dominant and a genotypic model. Therefore this SNP could be considered a susceptibility factor for sporadic AD. Given that the SNP rs1050283 is also located in a predicted binding site of the miRNA has-miR369-3p, a preliminary expression analysis was performed on the two transcripts in the PBMC in order to clarify a possible functional role of individual genetic variability on the expression of OLR1 gene. Stratifying the results according to the presence of rs1050283C allele, a significant decrease of relative expression levels of OLR1 was observed in patients carrying at least one polymorphic C allele, despite the normal expression levels of has-miR369-3p. These data suggest that the presence of the polymorphic allele could influence the binding of has-miR369-3p to its 3\u2019UTR consensus sequence, in which the SNP is located

Exosome determinants of physiological aging and age-related neurodegenerative diseases

Aging is consistently reported as the most important independent risk factor for neurodegenerative diseases. As life expectancy has significantly increased during the last decades, neurodegenerative diseases became one of the most critical public health problem in our society. The most investigated neurodegenerative diseases during aging are Alzheimer disease (AD), Frontotemporal Dementia (FTD) and Parkinson disease (PD). The search for biomarkers has been focused so far on cerebrospinal fluid (CSF) and blood. Recently, exosomes emerged as novel biological source with increasing interest for age-related neurodegenerative disease biomarkers. Exosomes are tiny Extracellular vesicles (EVs; 30\u2013100 nm in size) released by all cell types which originate from the endosomal compartment. They constitute important vesicles for the release and transfer of multiple (signaling, toxic, and regulatory) molecules among cells. Initially considered with merely waste disposal function, instead exosomes have been recently recognized as fundamental mediators of intercellular communication. They can move from the site of release by diffusion and be retrieved in several body fluids, where they may dynamically reflect pathological changes of cells present in inaccessible sites such as the brain. Multiple evidence has implicated exosomes in age-associated neurodegenerative processes, which lead to cognitive impairment in later life. Critically, consolidated evidence indicates that pathological protein aggregates, including A\u3b2, tau, and \u3b1-synuclein are released from brain cells in association with exosomes. Importantly, exosomes act as vehicles between cells not only of proteins but also of nucleic acids [DNA, mRNA transcripts, miRNA, and non-coding RNAs (ncRNAs)] thus potentially influencing gene expression in target cells. In this framework, exosomes could contribute to elucidate the molecular mechanisms underneath neurodegenerative diseases and could represent a promising source of biomarkers. Despite the involvement of exosomes in age-associated neurodegeneration, the study of exosomes and their genetic cargo in physiological aging and in neurodegenerative diseases is still in its infancy. Here, we review, the current knowledge on protein and ncRNAs cargo of exosomes in normal aging and in age-related neurodegenerative diseases

Size dependent etching of nanodiamond seeds in the early stages of CVD diamond growth

We present an experimental study on the etching of detonation nanodiamond (DND) seeds during typical microwave chemical vapor deposition (MWCVD) conditions leading to ultra-thin diamond film formation, which is fundamental for many technological applications. The temporal evolution of the surface density of seeds on Si(100) substrate has been assessed by scanning electron microscopy (SEM). The resulting kinetics have been explained in the framework of a model based on the effect of particle size, according to the Young-Laplace equation, on both chemical potential of carbon atoms in DND and activation energy of reaction. We found that seeds with size smaller than a critical radius, r*, are etched away while those greater than r* can grow. Finally, the model allows to estimate the rate coefficients for growth and etching from the experimental kinetics.Comment: 28 pages; 15 Figures, 3 Table

Role of Genetics and Epigenetics in the Pathogenesis of Alzheimer's Disease and Frontotemporal Dementia

Alzheimer's disease (AD) and frontotemporal dementia (FTD) represent the first cause of dementia in senile and pre-senile population, respectively. A percentage of cases have a genetic cause, inherited with an autosomal dominant pattern of transmission. The majority of cases, however, derive from complex interactions between a number of genetic and environmental factors. Gene variants may act as risk or protective factors. Their combination with a variety of environmental exposures may result in increased susceptibility to these diseases or may influence their course. The scenario is even more complicated considering the effect of epigenetics, which encompasses mechanisms able to alter the expression of genes without altering the DNA sequence. In this review, an overview of the current genetic and epigenetic progresses in AD and FTD will be provided, with particular focus on 1) causative genes, 2) genetic risk factors and disease modifiers, and 3) epigenetics, including methylation, non-coding RNAs and chromatin remodeling

Etching kinetics of nanodiamond seeds in the early stages of CVD diamond growth

We present an experimental study on the etching of detonation nanodiamond (DND) seeds during typical microwave chemical vapor deposition (MWCVD)conditions leading to ultra-thin diamond film formation, which is fundamental for many technological applications. The temporal evolution of the surface density of seeds on the Si(100) substrate has been assessed by scanning electron microscopy (SEM). The resulting kinetics have been explained in the framework of a model based on the effect of the particle size, according to the Young-Laplace equation,on both chemical potential of carbon atoms in DND and activation energy of the reaction with atomic hydrogen. The model describes the experimental kinetics of seeds' disappearance by assuming that nanodiamond particles with a size smaller than a "critical radius", r*, are etched away while those greater than r* can grow. Finally, the model allows to estimate the rate coefficients for growth and etching from the experimental kinetics

Femtosecond-laser nanostructuring of black diamond films under different gas environments

Irradiation of diamond with femtosecond (fs) laser pulses in ultra-high vacuum (UHV) conditions results in the formation of surface periodic nanostructures able to strongly interact with visible and infrared light. As a result, native transparent diamond turns into a completely different material, namely “black” diamond, with outstanding absorptance properties in the solar radiation wavelength range, which can be efficiently exploited in innovative solar energy converters. Of course, even if extremely effective, the use of UHV strongly complicates the fabrication process. In this work, in order to pave the way to an easier and more cost-effective manufacturing workflow of black diamond, we demonstrate that it is possible to ensure the same optical properties as those of UHV-fabricated films by performing an fs-laser nanostructuring at ambient conditions (i.e., room temperature and atmospheric pressure) under a constant He flow, as inferred from the combined use of scanning electron microscopy, Raman spectroscopy, and spectrophotometry analysis. Conversely, if the laser treatment is performed under a compressed air flow, or a N2 flow, the optical properties of black diamond films are not comparable to those of their UHV-fabricated counterparts

The geometrical nature of optical resonances : from a sphere to fused dimer nanoparticles

We study the electromagnetic response of smooth gold nanoparticles with shapes varying from a single sphere to two ellipsoids joined smoothly at their vertices. We show that the plasmonic resonance visible in the extinction and absorption cross sections shifts to longer wavelengths and eventually disappears as the mid-plane waist of the composite particle becomes narrower. This process corresponds to an increase of the numbers of internal and scattering modes that are mainly confined to the surface and coupled to the incident field. These modes strongly affect the near field, and therefore are of great importance in surface spectroscopy, but are almost undetectable in the far field

Improving the performance of printable carbon electrodes by femtosecond laser treatment

Low-cost carbon-conductive films were screen-printed on a Plexiglas® substrate, and then, after a standard annealing procedure, subjected to femtosecond (fs) laser treatments at different values of total accumulated laser fluence ΦA. Four-point probe measurements showed that, if ΦA > 0.3 kJ/cm2, the sheet resistance of laser-treated films can be reduced down to about 15 Ω/sq, which is a value more than 20% lower than that measured on as-annealed untreated films. Furthermore, as pointed out by a comprehensive Raman spectroscopy analysis, it was found that sheet resistance decreases linearly with ΦA, due to a progressively higher degree of crystallinity and stacking order of the graphitic phase. Results therefore highlight that fs-laser treatment can be profitably used as an additional process for improving the performance of printable carbon electrodes, which have been recently proposed as a valid alternative to metal electrodes for stable and up-scalable perovskite solar cells

Aluminum (Oxy)nitride thin films grown by fs-PLD as electron emitters for thermionic applications

Thin films based on aluminum nitride were obtained by fs-laser assisted Pulsed Laser Deposition (fs-PLD) at room temperature on tantalum substrates for studying the electron emission performance in the temperature range 700- 1600 °C, so to investigate the possibility of their exploitation as thermionic cathodes. Results of structural, chemical and morphological analyses show the growth of nanostructured thin films with a significant oxygen contamination, forming a mixture of crystalline aluminum nitride and aluminum oxide as well as metallic aluminum inclusions. Despite the considerable presence of oxygen, the developed cathodes demonstrate to possess promising thermionic emission characteristics, with a work function of 3.15 eV, a valuable Richardson constant of 20.25 A/(cm²K²), and a highly thermo-electronic stability up to operating temperatures of 1600 °C