Wednesday, February 5, 2025
2/5/2025
In many neurological diseases, specific subsets of neurons are more sensitive to dysfunction and degeneration than others. In Alzheimer’s disease (AD), excitatory (EX) neurons are preferentially vulnerable to tau pathology which defines the pathogenesis and progression of dysfunction in AD. Understanding the molecular origins of selective neuronal vulnerability is of fundamental importance for all of the neurodegenerative diseases including AD. Using single-nucleus RNA-seq dataset analysis and weighted gene co-expression network analysis of the transcriptomic signatures of different cell types from non-AD cases, we identified novel subproteome gene signatures in EX neurons that may serve as potential master regulators of selective neuronal and regional vulnerability to tau pathology in early AD. The ectodermal-neural cortex 1 (ENC1) is one such potential master regulator. Although the role of ENC1 in AD has not been thoroughly investigated, if it functions as a master regulator as predicted by bioinformatics analysis, it may be possible to regulate ENC1 levels to control tau pathology and thwart the onset or progression of AD. Preliminary analysis of human entorhinal cortex from AD and control brain specimens has revealed that ENC1 is enriched in the nucleus of EX neurons in control brains, while cytoplasmic ENC1 levels are elevated within neurons that show accumulated pathological tau species in AD specimens. The interaction between ENC1 and tau correlates directly with levels of pathological tau. Furthermore, forced overexpression of ENC1 mainly in the cytoplasm increases tau aggregation and seeding activity, whereas knockdown of ENC1 reduces these pathological changes. ENC1 has been shown to increase the neurotoxicity of mutant huntingtin under ER stress through the interaction with p62 and the inhibition of autophagy flux. Our new data also show ENC1 overexpression increases pathological tau accumulation, p62 puncta formation and autophagy dysfunction, implicating impairment of p62-mediated autophagy as a mechanism underlying the cytoplasmic accumulation of ENC1 and pathological tau in neurons. Based on these preliminary data, we hypothesize that cytoplasmic ENC1 contributes to the vulnerability of EX neurons to tau pathology, and that reducing ENC1 in EX neurons will enhance the autophagy pathway thereby protecting these EX neurons from selective neurodegeneration in AD. To test this hypothesis, this proposal will (1) determine the effect of ENC1 on tau aggregation and propagation in human cerebral organoids; (2) investigate the role of ENC1 in autophagy pathway and if this pathway is involved in ENC1-induced tau aggregation and propagation in vitro; and (3) determine if cell-type specific manipulation of ENC1 affects neuronal autophagy, AD pathology and cognition in vivo. The proposed studies will provide mechanistic insight into the role of ENC1 as a master regulator of tau homeostasis and will also provide greater insight for developing novel therapeutics targeting ENC1-dependent pathways to prevent, treat or delay the neurodegeneration in AD. Furthermore, this work will elucidate novel mechanisms underlying selective neuronal vulnerability in AD.
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