Human tau seeds trigger disease-specific shapes in mouse brains, new study finds

by Sanjukta Mondal, Medical Xpress

Sanjukta Mondal

Author

Meet our staff & contributors
Learn about our editorial standards

edited by Gaby Clark, reviewed by Robert Egan

Gaby Clark

Scientific Editor

Meet our editorial team
Behind our editorial process

Robert Egan

Senior Editor

Meet our editorial team
Behind our editorial process Editors' notes

This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility:

fact-checked

peer-reviewed publication

trusted source

proofread

The GIST Add as preferred source

Tau is a protein that occurs naturally in the brain. It is essential for proper neuron development and for how neurons communicate with each other. The same protein, however, when misshapen or misfolded, can act as a driver of neurodegenerative diseases. Abnormal buildup of tau is a hallmark of Alzheimer's disease, and scientists have also found an association between misfolded tau and more than 20 neurodegenerative diseases.

The prominent prion hypothesis proposes that misfolded proteins spread by forcing normally shaped proteins to copy their exact 3D structure. To test its validity, a recent study investigated at the atomic level how misfolded tau proteins spread and multiply through the brain.

Researchers injected tiny amounts of human tau seeds from Alzheimer's disease (AD) or corticobasal degeneration (CBD) into the brains of healthy mice. High-resolution microscopy that captured tau at the atomic level revealed that the mice's own tau had misfolded into exact 3D structural copies of the diseased original seeds. The human seeds vanished within a week, but not before setting off a chain reaction in which the mice's tau continued to form fibers with matching disease-specific folds and accumulate for the next nine to 12 months.

The findings are published in Nature.

How misfolds propagate

Misfolded forms of the protein called prion protein can form long, thread-like structures that cause brain degeneration in diseases such as kuru, bovine spongiform encephalopathy and chronic wasting disease. These misfolded proteins are thought to spread through templated seeding, a process in which small amounts of prion protein filaments cause normally folded prion proteins to misfold into filaments with the same structure.

Scientists have long suspected that abnormal tau spreads through the brain by forcing normal tau to copy its shape, a process called prion-like seeding. Tau is known to misfold into distinct shapes in different diseases and spread through the brain in neurodegenerative conditions. What previous studies had not shown directly was whether a misfolded tau seed makes normal tau reproduce its exact atomic structure as it spreads.

To observe the process at the molecular level, the researchers started by preparing the mice's brains. They obtained donated brain tissue from deceased individuals diagnosed with either Alzheimer's or corticobasal degeneration (CBD) and extracted the tau seeds.

After injecting the tau seeds into the mice's brains, the team examined the mice at set intervals from immediately after injection to nine and 12 months later, tracking tau buildup through tissue staining and protein analysis. At the 9- and 12-month marks, they collected brain tissue and isolated the newly formed mouse tau aggregates.

• Histological staining of wild-type mouse brains 9 months after injection with human AD tau seeds. Credit: Nature (2026). DOI: 10.1038/s41586-026-11061-x
• Histological staining of wild-type mouse brains 9 months after injection with human CBD. Credit: Nature (2026). DOI: 10.1038/s41586-026-11061-x

Seeds pass on the structure

High-resolution 3D images from cryo-electron microscopy revealed that the AD seeds made mouse tau adopt the exact Alzheimer's fold, known as the paired helical filament, while CBD seeds produced the exact CBD fold. These structures set off a cascade in which normal tau proteins continued to misfold in the same way.

The shape of the misfolded tau also determined which brain cells were affected. AD seeds produced tau clumps only inside nerve cells, whereas CBD seeds produced clumps in both neurons and supporting glial cells, similar to the cell loss pattern seen in people with CBD.

These findings provided structural evidence that distinct tau folds act as prion strains that retain their exact structural identity as they spread from cell to cell. Knowing how each tau fold forms and spreads could help researchers test treatments that aim to block tau seeding, and it could eventually lead to the development of new disease-specific diagnostic tools.

Written for you by our author Sanjukta Mondal, edited by Gaby Clark, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you.

Publication details

Sofia Lövestam et al, Prion-like transmission of human tau strains in the mouse brain, Nature (2026). DOI: 10.1038/s41586-026-11061-x

Journal information: Nature

Key medical concepts

Alzheimer's DiseaseCorticobasal DegenerationCryoelectron Microscopy

Clinical categories

Neurology Who's behind this story?

Sanjukta Mondal

Master's in Chemistry. Freelance science journalist and communicator. Published in Chemistry World, BioSpace, and The Hindu. Full profile →

Gaby Clark

MA in English, copy editor since 2021 with experience in higher education and health content. Dedicated to trustworthy science news. Full profile →

Robert Egan

Bachelor's in mathematical biology, Master's in creative writing. Well-traveled with unique perspectives on science and language. Full profile →

© 2026 Science X Network

Citation: Human tau seeds trigger disease-specific shapes in mouse brains, new study finds (2026, October 3) retrieved 3 October 2026 from https://medicalxpress.com/news/2026-10-human-tau-seeds-trigger-disease.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.