PSAT1 and Parkinson disease: Of the shared proteins, phosphoserine aminotransferase 1 (PSAT1) and TNC (tenascin-C) were shared between AD and FXTAS, ring finger protein 214 (RNF214) was shared between PD and FXTAS, and only PSAT1 was shared between all three neurodegenerative diseases (Figure 5).