COX8C encodes cytochrome c oxidase subunit 8C, a testis-enriched component of mitochondrial complex IV (cytochrome c oxidase), the terminal enzyme of the electron transport chain 1. This gene represents a third isoform of cytochrome c oxidase subunit VIII that arose through gene duplication and is present across Eutherian mammals, with evidence of mitochondrial targeting and sequence conservation suggesting functional significance 1. COX8C is specifically expressed in testicular germ cells and shows stage-specific expression during spermatogenesis 2. Despite its testis-enriched expression pattern, knockout studies demonstrate that COX8C is not essential for male fertility or sperm mitochondrial function, as Cox8c knockout mice show normal fertility and sperm motility 3. The gene is differentially expressed during Barrett's esophagus disease progression, suggesting potential involvement in metabolic reprogramming during tumorigenesis 4. COX8C expression can be induced by estradiol/ERα signaling in osteoblasts as part of mitochondrial bioenergetic enhancement 5. While other COX8 isoforms like COX8A are essential for complex IV stability and human health, COX8C appears to have a more specialized but non-critical role in testicular energy metabolism.