This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
[{'content': 'Protein deposited in familial amyloid neuropathy: \nSelect and explain. \nA. Mutated transthyretin, B. Normal transthyretin, C. Mutated β2, D. Normal β2', 'role': 'user'}, {'content': 'Answer: A \nExplanation: "Transthyretin (TTR) is a normal serum protein that binds and transports thyroxine and retinol, hence the\xa0name trans-thy-retin.\nA mutant form of transthyretin (and its fragments) is deposited in a group of\xa0genetically determined disorders referred to as familial amyloid polyneuropathies. Several mutations\xa0have been identified in the transthyretin protein that contributes to its deposition in tissues in the form of\xa0amyloid. Transthyretin is also deposited in the heart of aged individuals (senile systemic amyloidosis),\xa0but in such cases, the transthyretin molecule is structurally normal.\n\xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0Table: Classification of Amyloidosis', 'role': 'assistant'}]