Protein assemblies that appear in a neurodegenerative disorder caused by repeated blows to the head, such as sports injuries, are described online in Nature this week. Chronic traumatic encephalopathy (CTE) is characterized by the accumulation and aggregation of a protein called tau, similar to that seen in Alzheimer's disease. The new study shows that tau assemblies in CTE look slightly different from those in Alzheimer’s disease, even though it is the same tau protein that affects both. These findings demonstrate that subtle variations in the shape of tau assemblies define individual neurodegenerative diseases.

CTE affects participants of contact sports such as boxing and American football, ex-military personnel and people who have experienced physical abuse. Symptoms of CTE, such as problems with behaviour, mood, and thinking, typically do not start until long after the injuries, get worse over time and may result in dementia. Although tau protein assemblies have previously been identified as having a role in CTE progression, a detailed understanding of their structure has been lacking.

Sjors Scheres, Michel Goedert and colleagues determined the structures of tau protein from the brains of three individuals that had CTE: one American football player and two boxers. They find that the structures of the tau protein assemblies are identical in the three individuals, but differ from those seen in other neurodegenerative diseases associated with assemblies of tau protein, such as Alzheimer’s disease. The authors suggest that the newly described structure may aid in the design of diagnostic tests for CTE. The findings may improve our understanding of how brain trauma can lead to the formation of these tau proteins, which could inform the development of treatments to prevent tau accumulation in CTE.