Journal article
Tau pathology in the dorsal raphe may be a prodromal indicator of Alzheimer's disease
Molecular psychiatry, Vol.30(2), pp.532-546
02/2025
DOI: 10.1038/s41380-024-02664-9
PMCID: PMC12010729
PMID: 39143322
Abstract
Protein aggregation in brainstem nuclei is thought to occur in the early stages of Alzheimer's disease (AD), but its specific role in driving prodromal symptoms and disease progression is largely unknown. The dorsal raphe nucleus (DRN) contains a large population of serotonin (5-hydroxytryptamine; 5-HT) neurons that regulate mood, reward-related behavior, and sleep, which are all disrupted in AD. We report here that tau pathology is present in the DRN of individuals 25-80 years old without a known history of dementia, and its prevalence was comparable to the locus coeruleus (LC). By comparison, fewer cases were positive for other pathological proteins including α-synuclein, β-amyloid, and TDP-43. To evaluate how early tau pathology impacts behavior, we overexpressed human P301L-tau in the DRN of mice and observed depressive-like behaviors and hyperactivity without deficits in spatial memory. Tau pathology was predominantly found in neurons relative to glia and colocalized with a significant proportion of Tph2-expressing neurons in the DRN. 5-HT neurons were also hyperexcitable in P301L-tauDRN mice, and there was an increase in the amplitude of excitatory post-synaptic currents (EPSCs). Moreover, astrocytic density was elevated in the DRN and accompanied by an increase in IL-1α and Frk expression, which suggests increased inflammatory signaling. Additionally, tau pathology was detected in axonal processes in the thalamus, hypothalamus, amygdala, and caudate putamen. A significant proportion of this tau pathology colocalized with the serotonin reuptake transporter (SERT), suggesting that tau may spread in an anterograde manner to regions outside the DRN. Together these results indicate that tau pathology accumulates in the DRN in a subset of individuals over 50 years and may lead to behavioral dysregulation, 5-HT neuronal dysfunction, and activation of local astrocytes which may be prodromal indicators of AD.Protein aggregation in brainstem nuclei is thought to occur in the early stages of Alzheimer's disease (AD), but its specific role in driving prodromal symptoms and disease progression is largely unknown. The dorsal raphe nucleus (DRN) contains a large population of serotonin (5-hydroxytryptamine; 5-HT) neurons that regulate mood, reward-related behavior, and sleep, which are all disrupted in AD. We report here that tau pathology is present in the DRN of individuals 25-80 years old without a known history of dementia, and its prevalence was comparable to the locus coeruleus (LC). By comparison, fewer cases were positive for other pathological proteins including α-synuclein, β-amyloid, and TDP-43. To evaluate how early tau pathology impacts behavior, we overexpressed human P301L-tau in the DRN of mice and observed depressive-like behaviors and hyperactivity without deficits in spatial memory. Tau pathology was predominantly found in neurons relative to glia and colocalized with a significant proportion of Tph2-expressing neurons in the DRN. 5-HT neurons were also hyperexcitable in P301L-tauDRN mice, and there was an increase in the amplitude of excitatory post-synaptic currents (EPSCs). Moreover, astrocytic density was elevated in the DRN and accompanied by an increase in IL-1α and Frk expression, which suggests increased inflammatory signaling. Additionally, tau pathology was detected in axonal processes in the thalamus, hypothalamus, amygdala, and caudate putamen. A significant proportion of this tau pathology colocalized with the serotonin reuptake transporter (SERT), suggesting that tau may spread in an anterograde manner to regions outside the DRN. Together these results indicate that tau pathology accumulates in the DRN in a subset of individuals over 50 years and may lead to behavioral dysregulation, 5-HT neuronal dysfunction, and activation of local astrocytes which may be prodromal indicators of AD.
Details
- Title: Subtitle
- Tau pathology in the dorsal raphe may be a prodromal indicator of Alzheimer's disease
- Creators
- Samantha R Pierson - University of IowaKimberly L Fiock - University of IowaRuixiang Wang - University of IowaNagalakshmi Balasubramanian - University of IowaJessica Reinhardt - University of IowaKanza M Khan - Daemen CollegeThomas D James - University of IowaMikayla L HunterBenjamin J CooperHannah R Williamsen - University of IowaRyan Betters - University of IowaKaancan Deniz - University of IowaGloria Lee - University of IowaGeorgina Aldridge - University of IowaMarco M Hefti - University of IowaCatherine A Marcinkiewcz - University of Iowa
- Resource Type
- Journal article
- Publication Details
- Molecular psychiatry, Vol.30(2), pp.532-546
- DOI
- 10.1038/s41380-024-02664-9
- PMID
- 39143322
- PMCID
- PMC12010729
- NLM abbreviation
- Mol Psychiatry
- ISSN
- 1476-5578
- eISSN
- 1476-5578
- Publisher
- SPRINGERNATURE
- Grant note
We thank the Iowa Neurobank Core for providing human post-mortem tissues for this study, Mariah Leidinger of the Comparative Pathology Core at The University of Iowa for providing histology services for human and mouse tissues, and the personnel of the Department of Pathology's Immunohistochemistry Lab at The University of Iowa for performing TDP-43 staining. We additionally thank Ramasamy Thangavel for performing the alpha-syn-AT8-TH triple stain in human LC tissue.DAS:All data generated or analyzed during this study are included in this published article and its supplementary information files.
- Language
- English
- Electronic publication date
- 08/14/2024
- Date published
- 02/2025
- Academic Unit
- Neurology; Pathology; Iowa Neuroscience Institute; Neuroscience and Pharmacology; Immunology; Internal Medicine
- Record Identifier
- 9984696863902771
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