Novel Misfolded Proteins in ADRD: Proteomics, Genetics, and Clinical-Pathological Correlations

There is a growing appreciation that dementia in old age is caused by many different underlying diseases, which are now referred to collectively as “Alzheimer’s disease and related dementias” (ADRD). Although we know of four proteins that are commonly misfolded in aged persons’ brains (Tau, TDP-43, Aß, a-Synuclein), there are likely to be more pathogenic protein species remaining to be discovered, which may be relevant to both diagnostic and therapeutic strategies. Our preliminary data provide strong evidence of this. The goals of this research project are to identify previously uncharacterized misfolded and aberrantly processed proteins and to resolve the genomic factors that modulate the severity and heterogeneity of ADRD. After characterizing the heterogeneous repertoire of misfolded proteins, we will establish, test, and apply a robust pipeline to elucidate the genetic risk factors for mixed-misfolding ADRD, and perform clinical-pathological correlation factoring in classic AD (plaques and tangles) and also known non-AD brain pathologies. We will execute the following Specific Aims: Specific Aim 1. Examine detergent-insoluble protein extracts from human amygdala (snapfrozen at autopsy) to investigate whether as yet uncharacterized misfolded proteins are detectable in ADRD. Polypeptides from the detergent-insoluble, urea-soluble protein fractions of amygdala will be interrogated using mass spectrometry. We have on-hand amygdalae from 40 cases that incorporate a spectrum of clinical and pathologic features. Additional studies will include detailed immunohistochemistry and biochemical studies to focus on the best candidate proteins for additional studies (Aims 2 and 3). Specific Aim 2. Construct a robust and harmonized database with exonic sequencing to localize genetic regions associated with novel misfolded proteins in ADRD. Genetics data augmented with rich NP endophenotypes and longitudinal clinical data will enable discovery and refinement of novel insights regarding the mechanisms driving dementia. Large-scale datasets (NACC, ADGC, ADSP) will be aggregated and harmonized to test the genetic drivers of clinical and NP-based endophenotypes, prioritizing subtype-specific candidate genetic regions. A focus of this work will be on rare, exonic genetic variants in genes that encode candidate misfolded proteins identified in Aim 1. Specific Aim 3. Establish the clinical-pathologic correlation for the novel misfolded proteinopathies in ADRD. Test the association between the potential novel proteinopathies (from Aim 1) with cognitive impairment, factoring in known markers tau, Aß, a-Synuclein, TDP-43, and cerebrovascular disease. We have 370 cases on-hand for analyses (both sexes) from the University of Kentucky AD Center biobank, which should be statistically powered to test our hypothesis that novel misfolding protein pathology/ies have independent correlation with antemortem cognitive status.