Recessive DES cardio/myopathy without myofibrillar aggregates: intronic splice variant silences one allele leaving only missense L190P-desmin.

TitleRecessive DES cardio/myopathy without myofibrillar aggregates: intronic splice variant silences one allele leaving only missense L190P-desmin.
Publication TypeJournal Article
Year of Publication2019
AuthorsRiley, LG, Waddell, LB, Ghaoui, R, Evesson, FJ, Cummings, BB, Bryen, SJ, Joshi, H, Wang, M-X, Brammah, S, Kritharides, L, Corbett, A, MacArthur, DG, Cooper, ST
JournalEur J Hum Genet
Date Published2019 Apr 25
ISSN1476-5438
Abstract

We establish autosomal recessive DES variants p.(Leu190Pro) and a deep intronic splice variant causing inclusion of a frameshift-inducing artificial exon/intronic fragment, as the likely cause of myopathy with cardiac involvement in female siblings. Both sisters presented in their twenties with slowly progressive limb girdle weakness, severe systolic dysfunction, and progressive, severe respiratory weakness. Desmin is an intermediate filament protein typically associated with autosomal dominant myofibrillar myopathy with cardiac involvement. However a few rare cases of autosomal recessive desminopathy are reported. In this family, a paternal missense p.(Leu190Pro) variant was viewed unlikely to be causative of autosomal dominant desminopathy, as the father and brothers carrying this variant were clinically unaffected. Clinical fit with a DES-related myopathy encouraged closer scrutiny of all DES variants, identifying a maternal deep intronic variant within intron-7, predicted to create a cryptic splice site, which segregated with disease. RNA sequencing and studies of muscle cDNA confirmed the deep intronic variant caused aberrant splicing of an artificial exon/intronic fragment into maternal DES mRNA transcripts, encoding a premature termination codon, and potently activating nonsense-mediate decay (92% paternal DES transcripts, 8% maternal). Western blot showed 60-75% reduction in desmin levels, likely comprised only of missense p.(Leu190Pro) desmin. Biopsy showed fibre size variation with increased central nuclei. Electron microscopy showed extensive myofibrillar disarray, duplication of the basal lamina, but no inclusions or aggregates. This study expands the phenotypic spectrum of recessive DES cardio/myopathy, and emphasizes the continuing importance of muscle biopsy for functional genomics pursuit of 'tricky' variants in neuromuscular conditions.

DOI10.1038/s41431-019-0393-6
Alternate JournalEur. J. Hum. Genet.
PubMed ID31024060
Grant ListAPP1080587 / / Department of Health | National Health and Medical Research Council (NHMRC) /
APP1136197 / / Department of Health | National Health and Medical Research Council (NHMRC) /
HG008900 / / U.S. Department of Health & Human Services | NIH | National Human Genome Research Institute (NHGRI) /
UM1 HG008900 / / U.S. Department of Health & Human Services | NIH | National Human Genome Research Institute (NHGRI) /
UM1 HG008900 / / U.S. Department of Health & Human Services | NIH | National Human Genome Research Institute (NHGRI) /