In order to assess whether developmental compensation or lack of substantial aSyn expression/pathology in the mThy1-hSNCA mouse resulted in the lack of nigrostriatal degeneration in the presence of exacerbated aSyn pathology in the GBA1 D409V KI×mThy1-hSNCA line, we next decided to combine the GBA1 D409V mutation with a more pronounced PD model that demonstrates synuclein pathology and nigrostriatal dysfunction – the aSyn PFF model. Here, GBA1 is linked to Parkinson disease.