Identification of a testis-expressed creatine transporter gene at 16p11.2 and confirmation of the X-linked locus to Xq28.

Creatine and creatine phosphate act as a buffer system for the regeneration of ATP in tissues with fluctuating energy demands. Following reports of the cloning of a creatine transporter in rat, rabbit, and human, we cloned and sequenced a creatine transporter from a human intestinal cDNA library. PCR amplification of genomic DNAs from somatic cell hybrid panels localized two creatine transporter (CT) genes: CT1 to Xq26-q28 and CT2 to 16p11.2. Refinement of CT1 to Xq28 was confirmed by FISH. Identification of CT2 sequences in YACs and cosmid contigs that had been ordered on human chromosome 16 enabled its assignment to the proximal end of 16p11.2. Sequencing of the CT2 gene identified sequence differences between CT1 and CT2 transcripts that were utilized to determine that CT2 is expressed in testis only. CT2 is the most proximally identified gene on chromosome 16p to date. The existence of an autosomal, testis-specific form of the human creatine transporter gene suggests that creatine transporter activity is critical for normal function of spermatazoa following meiosis.