CLDN20 (claudin 20) is a tight junction protein that plays a major role in obliterating the intercellular space through calcium-independent cell-cell adhesion activity. As a plasma membrane protein, CLDN20 mediates bicellular tight junction formation and maintains cell adhesion through protein binding interactions, functioning independently of calcium signaling. CLDN20 has emerged as a potential biomarker in multiple disease contexts. In a transcriptomic analysis comparing periodontitis and IgA nephropathy, CLDN20 was identified as one of seven critical crosstalk genes shared between these two conditions, suggesting a potential genetic link in their pathogenesis 1. Similarly, CLDN20 was identified among nine overlapping differentially expressed genes in ovarian cancer metastasis studies, although the specific functional role in cancer progression requires further investigation 2. In ischemic stroke research, CLDN20 was identified through multi-omics integration as a differentially expressed molecule in brain tissue at early stages of cerebral ischemia; however, when evaluated as a potential blood biomarker in acute stroke patients, CLDN20 showed less promise than other candidates like CTNND2 and GADD45G 3. These findings suggest CLDN20's expression is altered in multiple pathological conditions, though its specific mechanistic contributions beyond tight junction maintenance warrant further investigation.