Concordance of whole-genome long-read sequencing with standard clinical testing for Prader-Willi and Angelman syndromes

Current clinical testing approaches for individuals with suspected imprinting disorders are complex, often requiring multiple tests performed in a stepwise fashion to make a precise molecular diagnosis. We investigated whether whole-genome long-read sequencing (LRS) could be used as a single data source to simultaneously evaluate copy number variants (CNVs), single nucleotide variants (SNVs), structural variants (SVs), and differences in methylation in a cohort of individuals known to have either Prader-Willi or Angelman syndrome. We evaluated 25 individuals sequenced to an average depth of coverage of 36x on an Oxford Nanopore PromethION. A custom one-page report was generated that could be used to assess copy number, SNVs, and methylation patterns at select CpG sites within the 15q11.2-q13.1 region and prioritize candidate pathogenic variants in UBE3A . After training with three positive controls, three analysts blinded to the known clinical diagnosis arrived at the correct molecular diagnosis for 22 out of 22 cases (20 true positive, 2 negative controls). Our findings demonstrate the utility of LRS as a single, comprehensive data source for complex clinical testing, offering potential benefits such as reduced testing costs, increased diagnostic yield, and shorter turnaround times in the clinical laboratory.