Brain tau isoform mRNA and protein correlation in PSP brain

Monoaminergic neuropathology in Alzheimer's disease

None of the proposed mechanisms of Alzheimer's disease (AD) fully explains the distribution patterns of the neuropathological changes at the cellular and regional levels, and their clinical correlates. One aspect of this problem lies in the complex genetic, epigenetic, and environmental landscape of AD: early-onset AD is often familial with autosomal dominant inheritance, while the vast majority of AD cases are late-onset, with the ε4 variant of the gene encoding apolipoprotein E (APOE) known to confer a 5-20 fold increased risk with partial penetrance. Mechanisms by which genetic variants and environmental factors influence the development of AD pathological changes, especially neurofibrillary degeneration, are not yet known. Here we review current knowledge of the involvement of the monoaminergic systems in AD. The changes in the serotonergic, noradrenergic, dopaminergic, histaminergic, and melatonergic systems in AD are briefly described. We also summarize the possibilities for monoamine-based treatment in AD. Besides neuropathologic AD criteria that include the noradrenergic locus coeruleus (LC), special emphasis is given to the serotonergic dorsal raphe nucleus (DRN). Both of these brainstem nuclei are among the first to be affected by tau protein abnormalities in the course of sporadic AD, causing behavioral and cognitive symptoms of variable severity. The possibility that most of the tangle-bearing neurons of the LC and DRN may release amyloid β as well as soluble monomeric or oligomeric tau protein trans-synaptically by their diffuse projections to the cerebral cortex emphasizes their selective vulnerability and warrants further investigations of the monoaminergic systems in AD.

Tau gene promoter rs242557 and allele-specific protein binding

The H1 haplotype clade of the tau gene (MAPT) is associated with increased risk of the sporadic disorders, progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) and to a lesser extent, Parkinson’s disease (PD). The H1c sub-haplotype drives this association in PSP and CBD, and is also weakly associated with Alzheimer’s disease (AD), suggesting involvement in common pathogenic pathway(s). The rs242557 single-nucleotide polymorphism (SNP) that defines H1c resides in a highly conserved repressor domain in the MAPT promoter. Previously, in cellular reporter assays, we showed significant rs242557 allele-specific differences in transcriptional repression, with the H1c-specific rs242557/A allele contributing a significantly higher MAPT promoter activity compared to the non-H1c rs242557/G allele. With evidence of allele-specific differences in protein binding to this repressor domain, we set out to identify those proteins that bind to this region. Electrophoretic mobility shift assay (EMSA) analysis strongly suggested allele-specific differences in protein affinities. In order to identify nuclear proteins that differentially bind to this repressor domain, we carried out a promoter-trap assay and analysed the bound proteins by SDS-PAGE and HPLC ESI-QTOF mass spectrometry. We identified 37 proteins and used bioinformatic tools such as STRING and Reactome to analyse and stratify the results. These included U2AF65, hnRNPU, PTBP1, hnRNPD0, U5 snRNP 116, ALY, HMGB2, H1 and actin and provide the basis for further studies of the role of the MAPT repressor domain and the binding proteins in regulating MAPT gene transcription and splicing.