Bionano Publishes on Using OGM for Detection of Repeat Expansions in CANVAS and Adult-Onset Ataxia

 Bionano Genomics, Inc. (Nasdaq: BNGO) today announced the publication of the first study to evaluate the utility of optical genome mapping (OGM) in the analysis of repeat expansion disorders. Repeat expansion disorders are a class of disorders that impact approximately 1 in 3,000 people and are caused by expansions of short tandem DNA repeats.

Researchers in this study describe how OGM can be adopted as an alternative to Southern blot analysis for the identification of repeat expansions in the RFC1 gene that lead to cerebellar ataxia with neuropathy and bilateral vestibular areflexia syndrome (CANVAS) and adult-onset ataxia in multiple populations. Individuals with RFC1 (AAGGG)n repeat expansion disorder may present with a spectrum of features including cerebellar ataxia, neuropathy, and vestibular areflexia. Specifically, ataxias are a group of neurodegenerative repeat expansion disorders, characterized by atrophy of the cerebellum that leads to the inability to control balance and coordination. Even though there are many known cerebellar ataxia–causing genes and variations, some adult patients with adult-onset ataxia remain genetically undiagnosed, and studies to identify genetic causes are ongoing.

In the study, researchers screened 626 samples for the presence of (AAGGG)n repeat expansions in the RFC1 gene using a combination of PCR to detect repeat sequences, and OGM, to determine the size of the repeat expansions. OGM confirmed the presence of expanded RFC1 alleles in all cases where it was used as part of the workflow. Repeats identified using OGM were in the range of 800–1299 repeat units. OGM is well-suited for analyzing large repeat expansion disorders that require the measurement of long, intact DNA molecules for accurate sizing, as was observed in this study. The study noted the successful use of OGM to replace the labor intensive and time-consuming Southern blot, which has been the “gold” standard for sizing repeat expansions up to now.

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