High-plex Digital Spatial Profiling Identifies Subregion-Dependent Directed Proteome Changes Across Multiple Variants of Dementia

Frontotemporal lobar degeneration (FTLD) is the leading cause of dementia in patients under the age of 65. Even in a single anatomical region, there is variance within pathological protein deposition as a result of FTLD. This spectrum of pathology leads to difficulty in identification of the disease during its progression and consequential varied post mortem clinicopathological diagnoses. NanoString GeoMx™ Digital Spatial Profiling (DSP) is a novel method that leverages the ability to spatially multiplex protein biomarkers of interest. We utilized NanoString DSP to investigate the proteome geography at two levels of the cortex and the subcortical white matter in patients with various types of dementia (Alzheimer’s disease, FTLD-c9ALS, FTLD-17, FTLD-TDP, FTLD-GRN; n=6 per syndrome) and neurologically healthy controls (NHC). Analysis of 75 different protein biomarkers of interest revealed both a disease and cortical subregion specific biomarker profile. Layers II-V of the cortex from diseased individuals displayed the greatest protein dysregulation as compared to NHC. Additionally, out of all disease groups within cortical layer 1, II-V and white matter, the FTLD-17 group had the most significant protein dysregulation as compared to NHC--specifically associated with immune cell pathways. Traditional biomarkers of dementia, such as various phosphorylated tau proteins and amyloid-β 42 displayed dysregulation, however our data suggest spatial enrichment in distinct to cortical sublayers. In conclusion, we observed that depending on the variant of disease, specific protein deposits either span multiple levels of cortical geography or only a single layer. Thus, the specific localization of these deposits could potentially be used to elucidate region-specific pathologic biomarkers unique to individual variants of dementia. ### Competing Interest Statement JG and YR are employees of Nanostring Technologies, Inc. All other authors declare no conflicts of interests. * AD : Alzheimer’s disease Aβ : Amyloid-β ABC score : Activities of daily Living, Behavioral and psychological Symptoms of Dementia, and Cognitive Function AP-MS : quantitative affinity purification mass spectrometry APP : Amyloid precursor protein APEX : Ascorbic acid peroxidase ApoA1 : Apolipoprotein A1 ALS : Amyotrophic lateral sclerosis bvFTD : Behavioral variant frontotemporal dementia CERAD score : Consortium to Establish a Registry for Alzheimer’s Disease C9ORF72 : chromosome 9 open reading frame 72 DSP : Digital spatial profiling FDR : False discovery rate FTD : Frontotemporal dementia FTLD : Frontotemporal lobar degeneration GAPDH : glyceraldehyde-3-phosphate dehydrogenase GFAP : Glial fibrillary acidic protein GRN : progranulin mutation related frontotemporal lobar degeneration IBA1 : Ionized calcium binding adaptor molecule 1 IPSC : Induced pluripotent stem cell IQR : Interquartile range Lef1 : Lymphoid Enhancer Binding Factor 1 MAPT : microtubule associated protein tau Map2 : Microtubule associated protein 2 NEFL : Neurofilament light NHC : Neurologically healthy control NMDAR1 : Glutamate [NMDA] receptor subunit 1 Park5 (UCH-L1) : Ubiquitin carboxyl-terminal hydrolase isozyme L1 PD : Parkinson’s disease PGRN : Progranulin P2ry12 : Purinergic receptor P2Y12 P53 : Tumor protein 53 ROI : Region of interest S6 : Ribosomal protein S6 TARDBP : Transactive DNA-binding protein gene TDP-43 : Transactive response DNA binding protein of 43 kDa UBB : Ubiquitin