RANGRF (RAN guanine nucleotide release factor), encoding the MOG1 protein, functions as a critical regulator of RAN GTPase signaling and cardiac sodium channel trafficking. Mechanistically, RANGRF promotes guanine nucleotide release from RAN and prevents RCC1-mediated GTP binding, thereby regulating nuclear GTP-bound RAN levels 1. This activity regulates RAN-dependent mitotic spindle dynamics 1. Additionally, RANGRF enhances SCN5A (Nav1.5 sodium channel) expression at the cardiomyocyte cell membrane 2, with the wild-type protein markedly increasing sodium current in Nav1.5-expressing cells 2. Clinically, RANGRF mutations associate with inherited cardiac arrhythmias. A nonsense variant (p.E61X) eliminates MOG1's sodium current-enhancing effect, representing loss of function that may increase arrhythmia risk 2. This variant appears enriched in Brugada syndrome patients, though its pathogenic role remains uncertain 3. RANGRF mutations also occur in histiocytoid cardiomyopathy with accessory pathway-mediated arrhythmias 4. Beyond cardiac disease, elevated RANGRF expression associates with nodular parathyroid hyperplasia in end-stage renal disease, suggesting involvement in tissue growth regulation 5. miR-3144-5p negatively regulates RANGRF in cardiac myocytes, potentially modulating arrhythmogenesis 6.