USP7 and Parkinson disease: Finally, we investigated the effect of USP7 on three familial PD-associated pathological mutants of FBXO7: two point-mutants of FBXO7 in which the Thr-22 or Arg-378 residues are substituted with Met and Gly, respectively (FBXO7-T22M and FBXO7-R378G), and a nonsense mutant at Arg-498 (FBXO7-R498X) (Fig 7A).