RNA sequencing of human fibroblasts after SUPT4H1 siRNA treatment

Asses the transcriptome-wide changes associated with depletion of transcription elongation factor, SUPT4H1, in human fibroblasts. An expanded hexanucleotide repeat in C9orf72 is the most common genetic cause of amyotrophic lateral sclerosis and frontotemporal dementia (c9FTD/ALS). Therapeutics (e.g., antisense oligonucleotides) are being developed to target RNAs containing the expanded repeat sequence (GGGGCC); however, this approach is complicated by the presence of antisense strand transcription of expanded GGCCCC repeats. We found that targeting the transcription elongation factor, Spt4, selectively decreased production of both sense and antisense expanded transcripts, as well as their translated dipeptide repeat (DPR) products, and also mitigated degeneration in animal models. Inhibition of SUPT4H1, the human ortholog of Spt4, similarly decreased production of sense and antisense RNA foci as well as DPR proteins in c9ALS patient fibroblasts and neurons from patient-derived induced pluripotent stem cells, consistent with our finding that cerebellar DPR protein levels correlate with SUPT4H1 expression in c9FTD/ALS patients. Therapeutic targeting of a single factor to eliminate pathological features of c9FTD/ALS offers advantages over approaches that require targeting sense and antisense repeats separately. 2 independent fibroblast lines: 2 replicate non-targeting siRNA treatments and 2 replicate SUPT4H1 siRNA treatments per line. Grouping by treatment for differential expression analysis (4 control siRNA samples and 4 SUPT4H1 siRNA samples)