In a recent PSP GWAS [27], four loci near MAPT, STX6, EIF2AK3, and MOBP conferred significant risk, in addition to three suggestive loci at 1q41 intergenic locus, BMS1 and SLCO1A2. We assessed these seven strongest PSP risk loci in our eGWAS in the ADs, non–ADs and combined datasets, as well as the PSP subset of non–ADs (Table 5, Supplementary Table 16 in Dataset S1). We found novel, significant rs11568563 minor allele associations with reduced brain SLCO1A2 levels (pCer = 2.33×10−8; pTCx = 4.36×10−2–9.14×10−18), which confers increased PSP risk [27]. SLCO1A2 encodes solute carrier organic anion transporter family member 1a2 and is a drug transporter into the CNS [46]. Fine-mapping of the SLCO1A2 region revealed rs11568563 to be the strongest cisSNP influencing brain levels of this gene (Figure S5). This SNP was also identified as the top PSP-associating variant at this locus [27]. All other cisSNPs that associate with brain SLCO1A2 levels have weaker effects that appear to be due to their LD with s11568563, which is a missense coding mutation within SLCO1A2. Whether rs11568563 is merely tagging the functional variant(s)
