A 20-year-old woman with Hirschsprung disease presents with acute leg pain. The patient had a glioma resected 3 years ago. An X-ray film of the leg reveals a fracture of the left tibia. Laboratory studies show elevated serum levels of calcium and PTH. A CT scan of the patient's neck demonstrates a solitary parathyroid mass. Two years later, the patient presents with hypeension, and a CT scan of the abdomen displays a 4-cm mass in the right adrenal. Genetic studies conducted on this patient would likely reveal germline mutations in which of the following protooncogenes?