Using mass spectrometry-based proteomics to identify candidate blood-based markers of cardiomyopathy in the southern sea otter (Enhydra lutris nereis)

Cardiomyopathy is a heart muscle disease and diagnosis relies on radiography and echocardiography, while blood-based markers are lacking. Development of a non-invasive test would be useful when imaging is not possible (e.g., prenatal diagnosis). In southern sea otters (Enhydra lutris nereis), cardiomyopathy is a prevalent cause of mortality and antemortem diagnosis is challenging. Sea otters requiring clinical care are at significant anesthetic risk if cardiomyopathy is present. A blood-based assay would improve triage decisions, case management, and treatment protocols to safeguard against co-morbidities. With support from the Oiled Wildlife Care Network, we analyzed undepleted sea otter serum using mass spectrometry-based proteomics. Though the larger sample set included 63 sera (that included a validation set of 22 sera with class labels blinded to the data collector), we a priori compared only samples from wild otters. Additionally, we generated proteomic data for four heat tissues with paired sera. These results demonstrate the utility of proteomic analysis, offer a glimpse into the sea otter proteome, and serve as a reference data set for relative protein abundance in sera and cardiac tissue.