As an additional staining, Gallyas-Braak was performed for selected sections. For immunohistochemistry, the following primary antibodies were used: mouse monoclonal anti-phosphorylated neurofilament protein (p-NFP) (Clone SMI31; diluted 1:5000; Covanse, Princeton, NJ, USA), rabbit polyclonal anti-ubiquitin (diluted 1:400; Sigma-Aldrich, St. Louis, MO, USA), rabbit polyclonal anti-Cu/Zn SOD (SOD1) (diluted 1:2000; Stressgen Bioreagents, check details Victoria,

Canada), mouse monoclonal anti-phosphorylated tau protein (p-tau) (clone AT8; diluted 1:1000; Innogenetics, Ghent, Belgium), mouse monoclonal anti-tau protein 3-repeat isoform RD3 (Clone 8E6/C 11-05-803; diluted 1:2000; Millipore, Billerica, MA, USA), mouse monoclonal anti-tau protein 4-repeat

isoform RD4 (Clone 1E1A6-05-804; diluted 1:100; Millipore, Billerica, MA, USA), mouse monoclonal anti-transactivation response DNA-binding protein of 43 kDa (TDP-43) (Clone 60019-2-Ig; Epitope amino acids 203–209; diluted 1:4000; Proteintech Group, Chicago, IL, USA), mouse monoclonal anti-TDP-43 (Clone K1B8; Epitope amino acids 1–260; diluted 1:3000; LifeSpan Biosciences, Seattle, WA, USA), mouse monoclonal anti-TDP-43 phosphorylated at 403/404 codons (p-TDP43) (Clone 11-9; diluted 1:3000; Cosmo Bio, Tokyo, Japan), and rabbit polyclonal anti-fusion, TLS, translocated in liposarcoma protein, pigpen, POMp75 (FUS) (Clone polyclonal; Epitope amino acids 1–50; diluted 1:200; Sigma-Aldrich, St. Louis, MO, USA). Prior to staining for SOD1, RD3, RD4, TDP-43, BGB324 mouse Cell press p-TDP43 and FUS, sections were pretreated by microwaving in 10 mmol/L citrate buffer, pH 6.0 (800 W, 95°C, 5 min). These primary antibodies were diluted with phosphate-buffered saline (PBS), pH 7.5 containing 5% bovine serum albumin. All sections were incubated at 4°C overnight. Following secondary antibody administration, the sections were washed and incubated with the avidin-biotinylated enzyme complex using the respective Vectastain Elite ABC kits (Vector Laboratories, Peterborough, UK), and immunoreactive product deposits were finally visualized with 0.5 mg/mL 3,3′-diaminobenzidine tetrahydrochloride as the chromogen (Sigma-Aldrich, Dorset,

UK) mixed with 0.05% hydrogen peroxidase in PBS. After taking microphotographs of HE-stained abnormal structures, the sections were decolored in 70% ethanol containing 1% hydrogen chloride, washed in distilled water, quenched with hydrogen peroxide, rinsed in PBS, and incubated with the antibodies as described above to identify immunohistochemical localization of the antigens. Genomic DNA was extracted from frozen brain tissue by standard methods. The entire coding region of the SOD1 gene (MIM 147450) was amplified by performing PCR, and sequenced with an Applied Biosystems 3130 DNA sequencer (Life Technologies, Carlsbad, CA, USA). The research procedure was approved by the ethics committees of Hiroshima University and Kansai Medical University.