eP379: Optical genome mapping for high throughput analysis of repeat expansion disorders

Expansions and contractions of sequence repeats are associated with more than 40 diseases including Huntington’s disease, myotonic dystrophy Fragile X Syndrome, the most common heritable cause intellectual disability. Expanded unstable may expand during intergenerational transfer disorders tend to increase in severity each successive generation. syndrome is cognitive impairment Nearly all cases an expansion a CGG triplet repeat region FMR1 gene. Phenotype often correlated amount pathogenic expansion. Thus, accurate sizing crucial. Southern blotting gold standard for analyzing repeats. The repetitive polymorphic nature these regions presents difficulties both Polymerase chain reaction (PCR), where polymerase unable traverse through long repeats, sequencing based methods which face limitations on read lengths. Optical genome mapping (OGM) Saphyr system from Bionano Genomics has potential address shortcomings. images DNA molecules up megabases size, labeled at specific motifs nanochannel arrays. Molecules > 150kbp analyzed de novo assembly or aligned reference structural variant detection. OGM can detect germline SVs >500 bp size expansions/contractions, inversions, reciprocal translocations, absence heterozygosity (AOH). developed targeted analysis workflows related facioscapulohumeral muscular (FSHD) syndrome. To evaluate capability detecting expansions ranges consistent normal (<45 repeats), premutation (55-200 (>200 we variety samples. These include Coriell cell lines, as well lengths measured by normal, ranges, total 55 We also 20 phenotypically control subjects. In our annotated samples, observed expanded alleles annotation across entire range counts. Analytical sensitivity was 97% 100% PPV. largest detected almost 1,000 copies. samples counts below cutoff cases. Repeatability studies were carried out show analytical consistency establish minimum molecule quality requirements. Our EnFocus analyses report pass/ fail QC metrics input data analytic measurement using internal controls genome. performance here much higher dynamic compared PCR, NGS, precision blot. Genome Mapping effective tool exploring disease causing variations. particular, effectively assesses presence degree expansions. assessments precise. They remain so over large sizes, that confound other methods. Validation against methods, self-quality checks, repeatability experiments indicate this method robust. whole collected offer additional opportunities variants giving rise abnormal phenotypes.