Identify the origin of de novo variants in TSC patients by ddPCR

Background Tuberous sclerosis complex (TSC), an inherited neurocutaneous disorder, is caused by variants in the TSC1 or TSC2 genes. The mosaic variants of TSC1 and TSC2 are scarcely detectable using the conventional next-generation sequencing (NGS). Therefore, this study aims to explore the detection and distribution of mosaic variants within affected families. Methods Through whole-exome sequencing (WES) or the TSC1 / TSC2 panel to detect the variants of the TSC1 and TSC2 genes, the reaction system of droplet digital PCR (ddPCR) was designed to detect the mosaicism of these variants in affected families. Results Genetic testing was carried out on 29 TSC patients via WES or the TSC1 / TSC2 panel. The results showed that 27 patients had positive results in the TSC gene variant tests. Fourteen cases were confirmed as de novo variants, and the asymptomatic fathers or mothers of 4 patients were identified as somatic mosaics by ddPCR, with mosaic proportions of 0.8%, 24.18%, 8.02%, and 0.33% respectively. Conclusions The ddPCR holds the potential to improve diagnostic accuracy, genetic risk assessment, and clinical diagnosis rates. Consequently, it could potentially be adopted as one of the modalities for prompt clinical diagnosis.