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: Anatomy
Holt Aram syndrome is caused by mutation of: 
Select and explain. 
A. TBX5, B. NKX2.5, C. Lefty, D. None of the above
A: TBX5
Answer: A: TBX5 
Explanation: Mutations in the TBX5 gene result in Holt-Oram syndrome, characterized by preaxial (radial) limb abnormalities and atrial septal defects.Ref: LANGMAN'S EMBRYOLOGY 11TH ED Chapter 12.