Figure 6.

Specificity of commercial dipeptide repeat protein antibodies on MSD immunoassay. (A) Schematic of sense and antisense RNAs carrying the repeat expansion and of their translation through non-canonical repeat-associated non-AUG (RAN) translation. RAN translation is expected to produce 5 different dipeptide repeat proteins (DPRs): poly-GA and polyGR from the sense strand, poly-PA and poly-PR from the antisense strand and poly-GP from both the sense and antisense strands. (B) Ten DPR antibodies were tested on MSD immunoassay in 3 sample types: Human C9-ALS/FTD post-mortem cerebellum versus non-mutant neurologically unaffected post-mortem cerebellum, C9orf72 mutant transgenic mouse striatum versus WT mouse striatum, and 2-week-old C9-ALS/FTD patient iPSC-derived motor neurons (MNs) versus isogenic 2-week-old C9orf72 KO iPSC-MNs. Further information on tissues used are provided in Table S3. Electrochemiluminescence signals were normalized to background signals from negative controls of the same sample type, producing signal ratios shown on the y-axis. Raw signals are reported in Table S4. Poly-GA antibody MABN889 and lots A-I 0756 and A-I 0757 of poly-GP antibody TALS828.179 selectively recognized poly-GA and poly-GP respectively in all sample types assessed. Dotted line = ratio of 1, i.e. no change compared to control. N = 2 technical replicates. Error bars = SD.