Molecular pathways in the brain affected by the Alzheimer’s disease-related transcription factor REST

Abstract

Alzheimer’s disease (AD) is a neurodegenerative disease affecting primarily the older population and is becoming more and more relevant in an ageing society. AD patients experience severe neurological symptoms and progressive decline of neuronal functions. Despite active research on the disease and its origin, the effect of existing treatments is, to this day, relatively low in preventing further progression of the disease and cure the cumbersome effects of the disease on memory. The RE1-silencing transcription factor
(REST) is a protein that has been described as having a neuroprotective role in the brain, among other roles. The brain level of REST increases in old age, but not in AD patients. The exact role of REST in regulating molecular pathways in the brain remains largely understudied, and an innovative approach is to investigate the potential neuroprotective pathways associated with REST, with the objective to identify target points for future treatments against AD.

A mouse model genetically modified to lack neuronal REST at the adult stage, named conditional knockout (cKO), has previously been generated by the first supervisor of this project. This model is extremely valuable to study the action of REST on the brain, by comparing mice lacking REST to a healthy group of control mice. The aim of this project has been to comprehensively investigate the molecular and cellular pathways impacted by the REST protein in the brain, to possibly identify links to memory preservation or its decline in AD. For this approach, a wide combination of technologies was used, such as Western blot, proteomics, immunohistochemistry, RNA-seq and chromatin immunoprecipitation.

RNA-seq and proteomic analyses, including gene ontology, gene set enrichment and protein-protein interaction analyses indicate that the absence of REST decreases genes and proteins associated with neuronal and synaptic activity and protection processes (for instance decrease in postsynaptic neurotransmitter receptor activity and overall efficiency of the neuron connections in the cKO mice). Simultaneously it seems to up-regulate genes and proteins involved in immune/inflammatory responses in the brain, similarly to
observations made in the brain of AD patients. Indeed, the data points towards an increase in processes such as adaptive and humoral immune responses. In addition to these findings, data collected suggest the alteration of pathways related to learning and memory processes, protein/peptide clearance mechanisms in the cKO mouse brain (among others, clearance of amyloid-beta) and a dysfunctional mitochondrial activity. Certain of these findings were taken further and validated in western blot and immunohistochemistry experiments. These findings from the cKO model underline the importance of the role of REST in several brain functions with strong relevance to AD, especially the ones connected to memory and learning, as well as emphasis on the potential of this cKO model within research on AD. Further research about the REST protein can therefore have promising potentials for a better understanding of the memory decline in AD potentially contributing to future treatment strategies and complementing other treatments through the possible identification of new therapeutic targets.