Frontotemporal dementias are neuropathologically characterized by frontotemporal lobar degeneration (FTLD). Intraneuronal inclusions of transactive response DNA-binding protein 43 kDa (TDP-43) are the defining pathologic hallmark of approximately half of the FTLD cases, being referred to as FTLD-TDP. The classification of FTLD-TDP into five subtypes (Type A to Type E) is based on pathologic phenotypes; however, the molecular determinants underpinning the phenotypic heterogeneity of FTLD-TDP are not well known. It is currently undetermined whether TDP-43 post-translational modifications (PTMs) may be related to the phenotypic diversity of the FTLDs. Thus, the investigation of FTLD-TDP Type A and Type B, associated with GRN and C9orf72 mutations, becomes an essential step.
Immunohistochemistry was used to identify and map the intraneuronal inclusions. Sarkosyl-insoluble TDP-43 was extracted from brains of GRN and C9orf72 carriers post-mortem and studied by western blot analysis, immunoelectron microscopy and mass spectrometry.
Filaments of TDP-43 were present in all FTLD-TDP preparations. PTM profiling identified multiple phosphorylated, N-terminal acetylated, or otherwise modified residues, several of which have been identified for the first time as related to sarkosyl-insoluble TDP-43. Several PTMs were specific for either Type A or Type B, while others were identified in both types.
The current results provide evidence that the intraneuronal inclusions in the two genetic diseases contain TDP-43 filaments. The discovery of novel, potentially Type-specific TDP-43 PTMs emphasizes the need to determine the mechanisms leading to filament formation and PTMs, and the necessity of exploring the validity and occupancy of PTMs in a prognostic/diagnostic setting.
[doi:10.25345/C5599Z54B]
[dataset license: CC0 1.0 Universal (CC0 1.0)]
Keywords: mass spectrometry ; neurodegeneration ; FTLD ; TDP-43 ; phosphorylation ; GRN
Principal Investigators: (in alphabetical order) |
Bernardino Ghetti, Indiana University School of Medicine, USA Kathy Newell, Indiana University School of Medicine, USA Laura Cracco, Indiana University School of Medicine, USA |
Submitting User: | edoud |
Cracco L, Doud EH, Hallinan GI, Garringer HJ, Jacobsen MH, Richardson R, Buratti E, Vidal R, Ghetti B, Newell KL.
Distinguishing post-translational modifications in dominantly inherited FTD: FTLD-TDP Type A (GRN) versus Type B (C9orf72).
Neuropathol Appl Neurobiol. Epub 2022 Jul 14.
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