We have also reported that, in the presence of the PARK5-linked ubiquitin carboxy-terminal hydrolase-L1 (UCH-L1) I93M mutant in mice, the AAV-αSyn-induced accumulation of αSyn and apoptotic DA cell death was enhanced, but not influenced in the absence of wild-type UCH-L1, indicating that PARK5-linked PD might be caused by gain-of-function mutation in UCH-L1 [166]. This evidence concerns the gene UCHL1 and Parkinson disease.