Odorant-binding protein amyloidosis in tigers ( Panthera tigris )

Systemic amyloidosis in felids is predominantly associated with amyloid A amyloidosis, whereas other forms remain poorly characterized. In this study, we describe a previously unrecognized form of amyloidosis in 6 genetically unrelated tigers ( Panthera tigris ) with involvement of the heart, synovium, kidneys, and spleen. Liquid chromatography–tandem mass spectrometry and immunohistochemistry identified odorant-binding protein (OBP), a lipocalin family protein, as the major amyloid precursor protein. Proteomic mapping of OBP-derived peptides together with in silico structural prediction suggested that low-complexity domains within the N-terminal region of tiger OBP may contribute to amyloid formation. Sequence analysis of OBP revealed no mutations shared among affected tigers, and no familial relationships were identified, suggesting that this disease may be associated with advanced age. These findings identify OBP amyloidosis as a novel amyloidosis with features suggestive of systemic distribution in tigers and provide insight into the potential role of N-terminal low-complexity domains in amyloid formation.