Long-read targeted sequencing uncovers clinicopathological associations for C9orf72-linked diseases

AbstractTo examine the length of a hexanucleotide expansion inC9orf72, which represents the most frequent genetic cause of frontotemporal lobar degeneration and motor neuron disease, we employed a targeted amplification-free long-read sequencing technology: No-Amp sequencing. In our cross-sectional study, we assessed cerebellar tissue from 28 well-characterizedC9orf72 expansion carriers. We obtained 3507 on-target circular consensus sequencing reads, of which 814 bridged theC9orf72 repeat expansion (23%). Importantly, we observed a significant correlation between expansion sizes obtained using No-Amp sequencing and Southern blotting (P  = 5.0  × 10−4). Interestingly, we also detected a significant survival advantage for individuals with smaller expansions (P  = 0.004). Additionally, we uncovered that smaller expansions were significantly associated with higher levels ofC9orf72 transcripts containing intron 1b (P  = 0.003), poly(GP) proteins (P  = 1.3  × 10− 5), and poly(GA) proteins (P  = 0.005). Thorough examination of the composition of the expansion revealed that its GC content was extremely high (median: 100%) and that it was mainly composed of GGGGCC repeats (median: 96%), suggesting that expandedC9orf72 repeats are quite pure. Taken together, our findings demonstrate that No-Amp sequencing is a powerful tool that enables the discovery of relevant clinicopathological associations, highlighting the important role played by the cerebella...
Source: Brain - Category: Neurology Source Type: research