Voltage sensor charge loss accounts for most cases of hypokalemic periodic paralysis

TLDR

Several missense mutations of CACNA1S and SCN4A occur in hypokalemic periodic paralysis, all targeting arginine residues in the S4 voltage‑sensor segments. We performed automated DNA sequencing of the S4 regions of CACNA1S and SCN4A in 83 cases, identifying known CACNA1S mutations in 64. Arginine mutations in S4 segments of CACNA1S and SCN4A explain 90 % of hypokalemic periodic paralysis cases, including 10 previously undefined cases with novel or domain‑specific mutations.

Abstract

Several missense mutations of CACNA1S and SCN4A genes occur in hypokalemic periodic paralysis. These mutations affect arginine residues in the S4 voltage sensors of the channel. Approximately 20% of cases remain genetically undefined.We undertook direct automated DNA sequencing of the S4 regions of CACNA1S and SCN4A in 83 cases of hypokalemic periodic paralysis.We identified reported CACNA1S mutations in 64 cases. In the remaining 19 cases, mutations in SCN4A or other CACNA1S S4 segments were found in 10, including three novel changes and the first mutations in channel domains I (SCN4A) and III (CACNA1S).All mutations affected arginine residues, consistent with the gating pore cation leak hypothesis of hypokalemic periodic paralysis. Arginine mutations in S4 segments underlie 90% of hypokalemic periodic paralysis cases.