PRKAR2A and Parkinson disease: The functional module “cAMP” included all dysregulated “PD Beginning” (blue) genes, including downregulation of cAMP homeostasis genes (Adcy5, Pde7b, and Pde10a) and reduced protein levels of the cAMP target Prkar2a/protein kinase A (PKA) in all S1/S2-expressing PD conditions.