[Functional analysis of a novel SCN5A mutation G1712C identified in Brugada syndrome].

OBJECTIVE: To elucidate the molecular and electrophysiological mechanisms of Brugada syndrome through functional analysis of a novel SCN5A gene mutation G1712C.
METHODS: A recombinant plasmid pRc<CMV-hH1 containing the mutant human cardiac sodium channel α subunit (hH1) cDNA was constructed using in vitro PCR-based site-directed mutagenesis technique. LipofectamineTM 3000 was used to transfect the plasmid DNA into HEK293 cell line to induce stable expression of Na+ channel β1-subunit, and the positive colonies were selected by screening with G418.The standard liposome method was used to transiently transfect HEK293 cells with either the wild-type or mutant Na+ channel subunits (hH1 and mhH1, respectively), and the macroscopic Na+ currents were recorded using whole-cell patch-clamp technique. Data acquisition and analysis, generation of voltage commands and curve fitting were accomplished with EPC-10, PatchMaster and IGOR Pro 6.0.
RESULTS: An HEK293 cell line that stably expressed Na+ channel β1-subunit was successfully established. After transient transfection with the WT subunit, large Na+ currents were recorded from the stable β1-cell line. Transient transfection with the G1712C subunit, however, did not elicit a Na+ current in the cells.
CONCLUSION: Compared with normal Na+ channel, the wild-type channel exhibits a similar sodium current. The characteristic kinetics of sodium channel of WT-hH1 was identical to that in normal cardiac muscle cell, and the missense mutation (G1712C) in the P-loop region of the domain IV may have caused the failure of sodium channel expression.