This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiac disorders, Subject name: Pathology
Which protein is defective most commonly in dilated cardiomyopathy? 
Select and explain. 
A. Dystrophin, B. Tropomyosin, C. Titin, D. Troponin
C: Titin
Answer: C: Titin 
Explanation: In dilated cardiomyopathy, mutations in TTN, a gene that encodes titin (so-called because it is the largest protein expressed in humans), may account for approximately 20% of all cases of DCM. Additionally, mutations affecting the membrane-associated dystrophin protein that couples cytoskeleton to the extracellular matrix are also repoed.