Anti-TMEM121B antibodies are used in the immunodetection of the protein transmembrane protein 121B. In humans, the canonical protein has a reported length of 578 amino acid residues and a mass of 58.4 kDa. Up to 2 different isoforms have been reported for this protein. It is reported to be widely expressed, especially in adult heart, brain, prostate, testes, peripherical blood leukocytes and fetal brain. It is a member of the TMEM121 protein family. Synonyms for this target antigen include cat eye syndrome chromosome region, candidate 6, cat eye syndrome critical region protein 6, and CECR6. TMEM121B gene orthologs have been reported in the mouse, rat, bovine, frog, zebrafish, chimpanzee and chicken species.