Another risk gene for PSP was suggested by experiments that went beyond common GWAS studies since this gene (possibly C4A) had to be identified in a gene-dense region of the human genome, the RCCX locus and surrounding areas within the HLA class III region on 6p21.33 (https://www.genecards.org/cgi-bin/carddisp.pl?gene=WHR1). Here, C4A is linked to supranuclear palsy, progressive, 1.