Structural and molecular homogeneity of ATTRv-T60A amyloid fibrils across patients and organs.

Transthyretin amyloidosis is a systemic protein misfolding disorder with diverse clinical phenotypes, including cardiomyopathy, polyneuropathy, or a combination of both. While structural polymorphism of amyloid fibrils has been linked to disease heterogeneity in neurodegenerative disorders, its role in transthyretin amyloidosis remains unclear. Here, we used cryo-electron microscopy to analyze ex vivo fibrils extracted from the hearts of three patients carrying the T60A mutation, a variant associated with mixed cardiac and neuropathic symptoms. In one patient, we additionally examined fibrils from the thyroid, kidney, and liver. All fibrils across patients and tissues adopted a single morphology previously associated with cardiomyopathy. Complementary molecular analyses revealed high compositional homogeneity. Notably, we extracted fibrils from the liver, an organ considered fibril-free, with seeding capacity in vitro. These findings suggest structural homogeneity as a hallmark of cardiac and mixed phenotypes, and provide a mechanistic rationale for the transmission of amyloidosis following domino liver transplantation.