CTSB and Parkinson disease: For instance, Chang and colleagues performed a Genome-Wide Association Study (GWAS) of 6476 subjects from the 23 and Me PD cohort (PDWBS (Web-Based Study of Parkinson’s Disease)) and 302,042 controls genotyped on custom Illumina arrays [15], identifying that common variations in the CTSB gene, which encodes Cathepsin B, have been linked to an elevated PD risk.