PDE4A and neurofibromatosis: Many of these disorders are amenable to study in model systems such as mice or Drosophila. Neurofibromatosis is linked to the cAMP pathway through the regulation by neurofibromin of adenylate cyclase production of cAMP with neuronal apoptosis phenotypes in an NF1 mouse model shown to be rescued by a PDE4 inhibitor55.