KCNN3 encodes a small conductance calcium-activated potassium channel located on chromosome 1 1. However, functional studies indicate that KCNN3 does not operate as a typical small conductance calcium-activated potassium channel but instead acts as a dominant-negative regulator by sequestering native KCNN3 proteins in intracellular compartments, thereby suppressing endogenous channel currents and reducing functional channels at the plasma membrane 1. This inhibitory effect extends to other SK subfamily members. The gene spans over 163.1 kb with eight exons and contains multiple transcription factor binding sites in its promoter region, suggesting complex transcriptional regulation 1. Clinically, KCNN3 variants are strongly associated with atrial fibrillation (AF) susceptibility. The SNP rs13376333 significantly increases AF risk (OR: 1.58 for lone AF; OR: 1.33 for total AF) 2, with the T allele conferring increased risk particularly in lone AF 3. KCNN3 is upregulated in AF patients 4 and associated with migraine susceptibility in genetic isolates 5. Recent evidence links KCNN3 to Sjögren's syndrome and recurrent pregnancy loss as a shared hub gene 6. Mutations in KCNN3 are associated with Zimmermann-Laband syndrome 3, establishing its role in genetic disease pathogenesis.