CLGN (calmegin) is an endoplasmic reticulum chaperone protein primarily functioning in male reproductive biology. During spermatogenesis, CLGN acts as a molecular chaperone for client proteins essential for sperm-egg interaction, including those required for sperm adhesion to the zona pellucida and subsequent penetration 1. The gene is first expressed in primary spermatocytes during meiotic prophase, with transcriptional regulation involving the bHLH transcription factor Tcfl5 1. Beyond reproduction, CLGN demonstrates broader physiological roles: it associates with blood pressure regulation through sodium-gene interactions, with variants showing genome-wide significant associations with systolic and diastolic blood pressure 2. CLGN expression is also dysregulated in aldosterone-producing adenomas, where upregulation increases aldosterone levels via translational regulation of aldosterone synthase 3. In hepatocellular carcinoma pathogenesis, CLGN functions as an endoplasmic reticulum stress-related gene contributing to tumor development through immune modulation 4. Additionally, promoter DNA methylation changes affecting CLGN expression associate with progression from simple hepatic steatosis to advanced fibrosis and impact hepatocellular carcinoma survival outcomes 5. CLGN's calcium-binding capacity supports its chaperone function, while its involvement in multiple disease contexts suggests broader clinical relevance beyond reproductive function.