Cerebral amyloid angiopathy and comparative analysis of amyloid-β protein in birds

Abstract

Senile plaques and cerebral amyloid angiopathy (CAA) are well-documented in various mammals, and several species even exhibit neurofibrillary tangle (NFT). However, we know far less about whether such symptoms are present in birds. Therefore, here we clarified the occurrence and pathogenesis of avian a{beta}-related lesions, analyzing the a{beta} amino-acid sequence across 28 birds at multiple life stages, representing 15 species, 14 genera, and 9 nine families. We also determined the expected a{beta} amino-acid sequence after comparing data from the brains of nine birds (seven species) with publicly available NCBI data. We observed CAA and senile plaque-like deposition only in a female Amazon parrot, estimated to be around 30-40 years old. We identified two A{beta} depositions (40 and 42) in the same location that correspond to A{beta} 6-42. Additionally, we observed severe A{beta} deposition, accompanied by severe hemorrhaging, in blood vessels of the superficial and deep portions of the brain. These lesions were directly related to the cause of death. Of 40 bird species, 36 exhibited type 1 A{beta} amino-acid sequences, similar to humans. Given that all of these birds were old, our results suggest that A{beta} is deposited primarily as CAA as the animals age. This report is the first clinically based description of CAA in birds. Interspecific variation likely exists because we identified species that did not exhibit A{beta} deposition even when the birds are old enough. However, even birds of the same taxonomic status differed in whether they possessed or lacked A{beta} deposition. Thus, other factors besides A{beta} amino-acid sequence could influence this symptom.