A de novo nonsense variant in the DMD gene associated with X-linked dystrophin-deficient muscular dystrophy in a cat

BackgroundX-linked dystrophin-deficient muscular dystrophy (MD) is a form of MD caused by variants in the DMD gene. It is a fatal disease characterized by progressive weakness and degeneration of skeletal muscles. Hypothesis/ObjectivesIdentify deleterious genetic variants in DMD by whole-genome sequencing (WGS) using a next-generation sequencer. AnimalsOne MD-affected cat, its parents, and 354 cats from a breeding colony. MethodsWe compared the WGS data of the affected cat with data available in the National Center for Biotechnology Information database and searched for candidate high-impact variants by in silico analyses. Next, we confirmed the candidate variants by Sanger sequencing using samples from the parents and cats from the breeding colony. We used 2 genome assemblies, the standard felCat9 (from an Abyssinian cat) and the novel AnAms1.0 (from an American Shorthair cat), to evaluate genome assembly differences. ResultsWe found 2 novel high-impact variants: a 1-bp deletion in felCat9 and an identical nonsense variant in felCat9 and AnAms1.0. Whole genome and Sanger sequencing validation showed that the deletion in felCat9 was a false positive because of misassembly. Among the 357 cats, the nonsense variant was only found in the affected cat, which indicated it was a de novo variant. Conclusion and Clinical ImportanceWe identified a de novo variant in the affected cat and next-generation sequencing-based genotyping of the whole DMD gene was determined to be necessary for affected cats because the parents of the affected cat did not have the risk variant.