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Published, Version of Record (VoR)Open Access Discount via Drexel Libraries Read and Publish Program 2026CC BY V4.0, Open
Journal article
Big Tau: Structure, Evolutionary Divergence, and Emerging Roles in Cytoskeletal Dynamics and Tauopathies
Cells (Basel, Switzerland), v 15(3), p241
27 Jan 2026
PMID: 41677608
Featured in Collection : Research Supported by Drexel Libraries' OA Programs
Abstract
Tau proteins are microtubule-associated proteins that regulate axonal structure, dynamics, and transport, and their dysregulation underlies several neurodegenerative diseases. The MAPT gene produces multiple tau isoforms through alternative splicing, including the high-molecular-weight isoform known as Big tau, which contains an insert of the large 4a exon of approximately 250 amino acids. Big tau is predominantly expressed in neurons of the peripheral nervous system (PNS), cranial motor nuclei, and select neurons of the central nervous system (CNS) such as the cerebellum and brainstem. Developmental expression studies indicate a switch from low-molecular-weight isoforms of tau to Big tau during axonal maturation, suggesting that Big tau optimizes cytoskeletal dynamics to accommodate long axonal projections. Comparative sequence and biophysical analyses show that the exon-4a insert is highly acidic, intrinsically disordered, and evolutionarily conserved in its length but not its primary sequence, implying a structural role. Emerging modeling and in vitro assays suggest that the extended projection domain provided by the exon-4a insert spatially and electrostatically shields the aggregation-prone PHF6 and PHF6* motifs in tau’s microtubule-binding domain, thereby reducing β-sheet driven aggregation. This mechanism may explain why tauopathies that involve aggregation of tau have little effect on the PNS and specific regions of the CNS such as the cerebellum, where Big tau predominates. Transcriptomic and proteomic data further suggest that alternative Big tau variants, including 4a-L, are expressed in certain cancerous tissues, indicating broader roles in cytoskeletal remodeling beyond neurons. Despite its putative anti-aggregation properties, the physiological regulation, interaction partners, and in vivo mechanisms of Big tau remain poorly defined. This review summarizes what is known about Big tau and what is missing toward a better understanding of how expansion via inclusion of exon 4a modifies tau’s structural and functional properties. Our purpose is to inspire future studies that could lead to novel therapeutic strategies to mitigate tau aggregation in neurodegenerative diseases.
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Details
- Title
- Big Tau: Structure, Evolutionary Divergence, and Emerging Roles in Cytoskeletal Dynamics and Tauopathies
- Creators
- Itzhak Fischer (Corresponding Author) - Drexel University, Neurobiology and AnatomyPeter W. Baas - Drexel University, Neurobiology and Anatomy
- Publication Details
- Cells (Basel, Switzerland), v 15(3), p241
- Publisher
- MDPI
- Number of pages
- 14
- Grant note
- USA National Institutes of Health: R21AG068597, R01NS28785 USA Department of Defense: W81XWH2110189
This work was supported by grants from the USA National Institutes of Health (R21AG068597 and R01NS28785) and the USA Department of Defense (W81XWH2110189) to PWB.
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Neurobiology and Anatomy; [Retired Faculty]
- Web of Science ID
- WOS:001687606800001
- Other Identifier
- 991022158567504721