Conclusion of diagnostic odysseys due to inversions disruptingGLI3andFBN1
Pagnamenta AT., Yu J., Evans J., Twiss P., Offiah AC., Wafik M., Mehta SG., Javaid MK., Smithson SF., Taylor JC.
Many genetic testing methodologies are biased towards picking up structural variants (SVs) that alter copy number. Copy-neutral rearrangements such as inversions are therefore likely to suffer from underascertainment. In this study, manual review prompted by a virtual multidisciplinary team meeting and subsequent bioinformatic prioritisation of data from the 100K Genomes Project was performed across 43 genes linked to well-characterised skeletal disorders. Ten individuals from three independent families were found to harbour diagnostic inversions. In two families, inverted segments of 1.2/14.8 Mb unequivocally disruptedGLI3and segregated with skeletal features consistent with Greig cephalopolysyndactyly syndrome. For one family, phenotypic blending was due to the opposing breakpoint lying ~45 kb fromHOXA13. In the third family, long suspected to have Marfan syndrome, a 2.0 Mb inversion disruptingFBN1was identified. These findings resolved lengthy diagnostic odysseys of 9–20 years and highlight the importance of direct interaction between clinicians and data-analysts. These exemplars of a rare mutational class inform future SV prioritisation strategies within the NHS Genomic Medicine Service and similar genome sequencing initiatives. In over 30 years since these two disease-gene associations were identified, large inversions have yet to be described and so our results extend the mutational spectra linked to these conditions.