GJA4 encodes connexin 37, a gap junction protein essential for cell-to-cell communication through low molecular weight material diffusion 1. In normal physiology, GJA4 mediates intercellular signaling and is critical for lymphatic valvulogenesis and vascular development 2. The protein functions as both gap junction channels and hemichannels in the vascular endothelium 3. GJA4 mutations have emerged as significant modifiers of human disease. A common SNP (rs41266431) acts as a clinical disease severity modifier in cystic fibrosis, with homozygous G-variant carriers showing reduced pulmonary function and lower survival to end-stage lung disease compared to other carriers 1. Somatic gain-of-function mutations, particularly c.121G>T (p.Gly41Cys), are identified in 75-96% of orbital cavernous venous malformations (OCVM) and 42.5% of intracranial angioleiomyomas, where they form hyperactive hemichannels causing endothelial cell integrity loss 3, 4. This mutation is also found in extra-axial cavernous hemangiomas alongside GNAQ/GNA14 variants 5. Biallelic germline variants are associated with fetal lymphatic dysfunction and abnormal vascular development 2. GJA4 is implicated in nonsyndromic primary ovarian insufficiency through involvement in meiosis and ovarian development pathways 6. These findings establish GJA4 as a critical regulator of vascular integrity and lymphatic development with distinct roles in vascular malformations and systemic diseases.