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.