Fig. 1

The effect of frameshift peptides on the properties of truncated FUS variants associated with ALS. a Diagrams showing FUS variants used in the study. Protein sequences of frameshift peptides attached to the respective FUS variant are also shown. Two types of tags were used, Flag and GFP. b Subcellular localisation of FUS variants with and without respective frameshift peptide tails when expressed as Flag fusions in SH-SY5Y cells. Cells were analysed 24 h post-transfection. Representative images are shown. Insets show fine granular aggregates (“small granules”) in the cytoplasm of cells expressing FUS(1–503)tail and FUS(1–514)tail variants. Scale bar, 10 μm. c Quantification of cytoplasmic aggregation of FUS variants with and without tail expressed as Flag fusions. Cells were analysed 24 h post-transfection. Between 166 and 201 cells were analysed per variant. * and ^# - p < 0.05, ^##p < 0.01, FUS(1–514) vs. FUS(1–514)tail and FUS(1–503) vs. FUS(1–503)tail (Mann-Whitney U test). d Increased nuclear retention of FUS(1–503) variant conferred by the attachment of the respective frameshift peptide. Representative images and quantification of nuclear/cytoplasmic (N/C) FUS ratio are shown. Forty cells were analysed per variant. ****p < 0.0001 (Student’s t test). Scale bar, 5 μm. e Increased stability of FUS variants with frameshift tails. Cells were transfected to express GFP-tagged FUS proteins, and 24 h post-transfection, cycloheximide (CHX) was added for 36 h. Protein levels were analysed by western blot with an anti-GFP antibody and results were quantified by densitometry (n = 4). Protein levels in CHX-treated samples were normalised to basal protein levels. *p < 0.05 (Mann-Whitney U test)