SPTAN1 encodes αII-spectrin, a cytoskeletal protein essential for cellular structure and neuronal function. As a key component of the spectrin-based membrane skeleton, SPTAN1 binds to actin filaments and plasma membrane proteins, providing structural support and proper localization of membrane components 1. The protein functions through a haploinsufficiency mechanism, as loss-of-function variants cause neurological disorders 1. SPTAN1 also acts as a cell density sensor by recruiting NUMB proteins when phosphorylated at high cell density, which activates Hippo signaling to prevent oncogenesis through contact inhibition 2. Pathogenic variants in SPTAN1 cause a broad spectrum of neurological disorders, including three distinct phenotypic groups: developmental epileptic encephalopathy, milder developmental delay with or without seizures, and pure or complex hereditary spastic paraplegia/ataxia 34. The protein is critical for neurodevelopment, and variants are associated with intellectual disability, autism, and motor neuropathies 15. Recent studies also reveal SPTAN1's role in cancer, where lactylation modifications promote hepatocellular carcinoma progression by activating NOTCH1/HES1 signaling and immune suppression 6. These findings establish SPTAN1 as both a crucial neuronal organizer and potential therapeutic target.