Pathogenic Neurofibromatosis type 1 (NF1) RNA-splicing resolved by targeted RNAseq

PurposeNeurofibromatosis type 1 (NF1) is caused by loss-of-function variants in the NF1 gene. Approximately 10% of these variants affect RNA splicing and are either missed by conventional DNA diagnostics or are misinterpreted by in silico splicing predictions. A targeted RNAseq-based approach was designed to detect pathogenic RNA splicing and associated pathogenic DNA variants. MethodsRNA was extracted from lymphocytes, followed by targeted NF1 RNAseq. An in-house developed tool (QURNAS) was used to calculate the enrichment score (ERS) for each splicing event. ResultsThis method was thoroughly tested using two different patient cohorts with known pathogenic splice-variants. In both cohorts all 56 normal reference transcript exon splice junctions, 24 previously described and 45 novel non-reference splicing events were detected. Additionally, all expected pathogenic splice-variants were detected. Eleven patients with NF1 symptoms were subsequently tested, three of which have a known NF1 DNA variant with a putative effect on RNA splicing. This effect could be confirmed for all 3. The other eight patients were previously without any molecular confirmation of their NF1-diagnosis. A deep-intronic pathogenic splice variant could now be identified for two of them (25%). ConclusionTargeted NF1 RNAseq can be successfully used to detect pathogenic RNA splicing variants, complementary to DNA based diagnostics.