Since, as compared with controls, the levels of ERK1/2 were greatly increased in the CSF of patients with AD but far less so in the CSF of patients with MCI, and TGF-β is normal in MCI but greatly reduced in AD, one may infer that the rise in ERK1/2 resulted from the low level of TGF-β and should not worsen by raising that level. The gene discussed is MAPK3; the disease is Alzheimer disease.