RT-PCR of 28 normal tissues detected CTAGE1 expression only in testis. RT-PCR detected CTAGE1 expression in 35% of the CTCL tissues examined and in all 4 CTCL cell lines examined, but not in any leukemia or melanoma cell lines tested. CTAGE1 was detected by 5 of 15 sera of mycosis fungoides patients and by 2 of 3 sera of Sezary syndrome patients, but not by any control sera.By 5-prime RACE of a testis cDNA library, Usener et al. (2003) identified a longer (4.4 kb) CTAGE1 variant, which they designated CTAGE2. The deduced 86-kD protein is translated from a different open reading frame than that encoding the CTAGE1 protein. Usener et al. (2003) also identified 3 other splice variants related to the major CTAGE1 and CTAGE2 variants. Some of the CTAGE1 and CTAGE2 variants were expressed only in testis, while others were expressed in a wide range of adult and fetal tissues.