This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Diabetes Mellitus, Subject name: Medicine
[{'content': 'Which gene is involved in pathogenesis of Type 1 Diabetes mellitus? \nSelect and explain. \nA. CTLA-4, B. ABCD1, C. HNF-1 Alpha, D. HNF-4 Alpha', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Polymorphism in promoter region of insulin gene, CTLA-4 contributes to susceptibility to type 1 Diabetes mellitus. The most common cause of type 1 diabetes mellitus is autoimmunity. Most patients have DR3 and/ or DR4 haplotype.', 'role': 'assistant'}]