UNRAVELLING THE MOLECULAR BASIS OF ALZHEIMER¿S DISEASE AND FRONTOTEMPORAL DEMENTIA: GENETIC AND EPIGENETIC APPROACH THROUGH NEXT GENERATION SEQUENCING AND OPENARRAY TECHNOLOGIES

Alzheimer’s disease (AD) and Frontotemporal dementia (FTD) are complex heterogeneous disorders with a strong genetic background, but the identification of a genetic cause is difficult given the multifactorial aetiology of the disorders. Epigenetic and environmental factors interplay to influence this complexity. The aim of the present project was to explore the two most common forms of dementia using genetic and epigenetic approaches. The first part focused on the genetic screening of 188 patients using a Next Generation Sequencing methodology. Different custom panels were designed to screen the most common genes involved in AD and FTD, common genetic risk factors and genes related to other neurodegenerative diseases causing dementia. Patients negative for the genetic screening of common causative genes but with strong family history for dementia and/or young onset of the symptoms were further investigated applying the SureSelect Custom Constitutional Panel 17Mb (CCP17), comprising more than 5000 genes associated to inherited diseases. The second part of the projects was based on the study of expression profile of miRNAs in genetic FTD patients, aiming to find a signature able to distinguish the genetic subgroups. The study was performed to test the expression levels of 754 miRNAs in 30 patients carrying mutations in C9ORF72, GRN and MAPT genes, and 10 control subjects, using OpenArray technology. Following the genetic study, a total of 35 variants were found in 36 over 188 patients screened. Some of these variants occurred in causative genes or in genetic risk factors associated to AD and FTD; other genes were classically associated to other phenotypes. Moreover, variants in genes unexpected in the clinical setting provide links to biological processes that need to be further explored. As resulted from the epigenetic study, a specific signature of miRNAs has been found for each group, which can distinguish patients from healthy subjects with high sensitivity and specificity and predict the underlying pathology. Targeted NGS confirms to be a highly efficient, cost-effective method able to unravel rare genetic variants whose significance need to be further explored. Studying epigenetic factors such as miRNA and their target genes would be helpful in gaining new insights into the pathogenic processes characteristic of dementias. This makes miRNAs interesting potential therapeutic targets.