Review Question - QID 109736

A 32-year-old man presents to his primary care provider reporting weakness. He recently noticed that he has difficulty letting go of a doorknob or releasing his hand after shaking hands with others. His past medical history is notable for diabetes, for which he takes metformin. He drinks 2-3 beers per day, uses marijuana occasionally, and works as a security guard. His family history is notable for an early cardiac death in his father. His temperature is 98.6°F (37°C), blood pressure is 130/85 mmHg, pulse is 85/min, and respirations are 18/min. On exam, there is notable muscle atrophy in his hands, feet, and neck. He has delayed hand grip release bilaterally and is slow to return from a smile to a neutral facial expression. His gait is normal, and Romberg's test is negative. He also has frontal balding. This patient’s condition is caused by a mutation in which of the following genes?