Scn7a, also known as Nax, encodes an atypical voltage-gated sodium channel. Unlike typical members of its family, it has evolved to function as a concentration-dependent sensor of extracellular sodium ions, playing a role in signal transduction. It is involved in tissue homeostasis, potentially detecting loss of homeostasis through extracellular sodium accumulation or endothelin signaling, and then inducing pro-inflammatory and pro-fibrotic responses [1].

Enhanced expression of Scn7a/Nax in dorsal root ganglion neurons contributes to bone cancer pain by increasing neuron excitability [4]. Post-ganglionic sympathetic neurons can directly sense raised extracellular Na+ via Scn7a/Nax, which may contribute to sympathetic-driven hypertension [5]. In esophageal squamous cell carcinoma, Scn7a is associated with prognosis, and in gastric cancer, it is a hub gene associated with tumor mutation burden, with low expression associated with better prognosis [2,3]. In temporal lobe epilepsy, increased and persistent expression of Scn7a/Na(x) is observed in the hippocampus of rats and humans [6]. In hepatocellular carcinoma, SCN7A has prognostic value and may be related to the PI3K pathway [7].

In conclusion, Scn7a functions as an extracellular sodium sensor and is involved in maintaining tissue homeostasis. Studies using various models have revealed its role in multiple disease conditions such as cancer, hypertension, and epilepsy. Understanding Scn7a's function provides insights into the pathophysiology of these diseases and may offer potential therapeutic targets.