SLCO6A1 encodes OATP6A1, a sodium-independent organic anion transporter localized to the basolateral plasma membrane with secondary active transmembrane transporter activity 1. The protein exhibits gonad-specific expression, particularly in testicular Sertoli cells, spermatogonia, and Leydig cells, with weak signals in epididymis and ovary 1. SLCO6A1 transports diverse substrates including taurocholic acid, dehydroepiandrosterone sulfate, and thyroid hormones (T3, T4), suggesting roles in sex steroid and thyroid hormone regulation during spermatogenesis 1. Beyond its normal gonadal function, SLCO6A1 is aberrantly expressed as a cancer/testis antigen in multiple malignancies: lung (5/10 tumors, 6/11 cell lines), bladder (5/12), and esophageal (5/12) cancers, as well as medulloblastoma (32% mRNA expression) 23. Psychiatric disease associations remain inconsistent; while a Swedish GWAS identified schizophrenia association with rs6878284, this was not replicated in Han Chinese populations 4. The rs7734060 variant showed marginal association with major depressive disorder in the Han Chinese population 4. Additionally, SLCO6A1 variants contribute to complex disease susceptibility: SNP-SNP interactions implicated it in Crohn's disease genetics 5, and a heterozygous deletion disrupting SLCO6A1 with missense variants suggested involvement in severe early-onset obesity 6. The gene's tissue-restricted expression and dual roles in normal physiology and cancer immunogenicity make it a potential target for therapeutic intervention.