A pattern to rule them all: tracing a human brain map of molecular aspects shared by Alzheimer's disease and dementia with Lewy bodies.

Alzheimer's disease (AD) and dementia with Lewy bodies (LBD) are the most widespread forms of degenerative dementia. However, little is known about the molecular aspects that link these conditions with each other and with aging itself. Whole transcriptome analysis and Gene Set Enrichment Analysis (GSEA) have been carried out on brain samples from hippocampus (HI), temporal and parietal cortex (TC, PC), cingulate cortex (CG), and substantia nigra (SN) of subjects with a neuropathological diagnosis of AD or LBD. According to the Abbiategrasso Brain Bank (ABB) protocol, the neuropathological diagnosis was based on a complete histological characterization, including all the main proteinopathies and vascular scoring. Transcriptomic results show major differences in the number of differentially expressed genes (DEGs) between the two pathologies. In AD, gene expression is more affected compared to LBD. DEGs have peculiar spatial distribution: HI and TC show transcriptomic changes related to synapses, while in CG, SN, and PC, changes are related to proteostasis; in LBD, DEGs are predominant in SN and PC affecting proteostasis, oxidative stress, and inflammation. In AD, GSEA shows that different regions cluster by shared biological processes. AD appears much more complex, and different forms of AD do exist. Nonetheless, the molecular signature of same regions across the two pathologies can be interestingly overlapped. Exploring the molecular processes that occur before the deposition of pathological lesions may reveal individual neurodegeneration trajectory to achieve personalized therapies, which could be much more effective than the mere immunological removal of protein deposits.