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Modulation of Tau Subcellular Localization as a Tool to Investigate the Expression of Disease-related Genes
Published on: December 20, 2019
Tangle evolution linked to differential 3- and 4-repeat tau isoform deposition: a double immunofluorolabeling study
Toshiki Uchihara1, Makoto Hara, Ayako Nakamura
1Laboratory of Structural Neuropathology, Tokyo Metropolitan Institute of Medical Science, Kamikitazawa, Setagaya, Tokyo, Japan. uchihara-ts@igakuken.or.jp
Abstract:
Double immunofluorolabeling for 3-repeat (3R) and 4-repeat (4R) tau was performed with two monoclonal antibodies, RD3 and RD4, after an additional pretreatment with potassium permanganate and oxalic acid to eliminate nonspecific 3R tau cytoplasmic staining. This method involves hyperdilution of one of the primary monoclonal antibodies (≥100-fold), making it undetectable by usual secondary antibodies. The hyperdiluted primary antibody can then only be detected after tyramide amplification. Subsequent application of the other monoclonal antibody at its usual concentration allows double immunofluorolabeling without cross-reaction. This novel method revealed that tau immunoreactivity (IR) in the hippocampal pyramidal neurons of Alzheimer's disease (AD) brains is heterogeneous in that pretangle neurons exhibit 4R-selective (3R-/4R+) IR, ghost tangles exhibit 3R-selective (3R+/4R-) IR, and neurofibrillary tangles exhibit both 3R and 4R (3R+/4R+) IR. Some nigral neurons exhibited RD3 IR in both AD and corticobasal degeneration/progressive supranuclear palsy (CBD/PSP) brains. However, in CBD/PSP cases, 3R IR was always superimposed on 4R IR, while 3R-selective neurons were present in AD cases. These differential isoform profiles may provide a pivotal molecular reference, closely related to the morphological evolution of tau-positive neurons, which may be variable according to disease (CBD/PSP vs. AD), lesion site (cerebral cortex and substantia nigra), or the stage of evolution (from pretangles to ghost tangles). These findings should provide a more comprehensive understanding of the histological differentiation of various tau deposits in human neurodegenerative disease.
Insights
A new double immunofluorescence method distinguishes tau protein isoforms in Alzheimer's disease (AD) and other neurodegenerative disorders. This technique reveals distinct tau profiles in different disease stages and types, aiding in understanding tau pathology evolution.
Area of Science:
- Neuroscience
- Immunohistochemistry
- Neurodegenerative Diseases
Background:
- Tau protein exists in different isoforms (3-repeat and 4-repeat) implicated in neurodegenerative diseases.
- Distinguishing these tau isoforms in specific neuronal populations and pathological structures is crucial for understanding disease mechanisms.
- Existing methods may lack the specificity to differentiate tau isoforms accurately in complex brain tissue.
Purpose of the Study:
- To develop and validate a novel double immunofluorescence method for precise detection of 3-repeat (3R) and 4-repeat (4R) tau.
- To investigate the differential expression and distribution of tau isoforms in Alzheimer's disease (AD) and corticobasal degeneration/progressive supranuclear palsy (CBD/PSP).
- To correlate tau isoform profiles with the morphological evolution of tau pathology and disease type.
Main Methods:
- Developed a double immunofluorescence technique using specific monoclonal antibodies (RD3 for 3R tau, RD4 for 4R tau).
- Employed a pretreatment with potassium permanganate and oxalic acid to reduce nonspecific staining.
- Utilized antibody hyperdilution and tyramide signal amplification to achieve specific and sensitive detection of both tau isoforms without cross-reactivity.
Main Results:
- Demonstrated heterogeneous tau immunoreactivity in hippocampal neurons of AD brains: pretangle neurons showed 4R-selective, ghost tangles showed 3R-selective, and neurofibrillary tangles showed both 3R and 4R tau.
- Observed distinct tau profiles in different neurodegenerative diseases: in CBD/PSP, 3R tau was superimposed on 4R tau, whereas AD cases exhibited 3R-selective neurons.
- Identified differential tau isoform expression in substantia nigra neurons across AD and CBD/PSP, with 3R-selective neurons present in AD.
Conclusions:
- The novel double immunofluorescence method accurately differentiates 3R and 4R tau deposits in neurodegenerative diseases.
- Differential tau isoform profiles are closely linked to the morphological changes and disease-specific evolution of tau pathology.
- These findings provide a molecular basis for understanding tau heterogeneity and its variation across different diseases, brain regions, and pathological stages.
