These candidate genes were prioritized in this study based on (1) GBA1’s role as a major lysosomal driver of PD pathogenesis; (2) functional convergence of TMEM175, SCARB2, and CTSB with GCase activity and lysosomal function—either through direct interaction (SCARB2)9, pH regulation (TMEM175)10,11, or cathepsin B(CTSB) in mediating prosaposin cleavage to form saposin C, the lysosomal coactivator of GCase12,13. Here, PSAP is linked to Parkinson disease.