Genomic DNA extracted from the blood samples of 123 medico-legal autopsy-negative SUNDS cases and 104 sex-, age- and ethnic-matched controls from Southern China underwent comprehensive amino acid coding region mutational analysis for the BrS associated genes SCN5A, SCN1B, SCN2B, SCN3B, SCN4B, MOG1, and GPD1-L using PCR and direct sequencing.
The Val110Ile mutation of SCN3B is a relatively common cause of SCN5A-negative BrS in Japan, which has a reduced sodium current because of the loss of cell surface expression of Nav1.5.
A missense mutation (L10P) was detected in exon 1 of SCN3B, the beta 3 subunit of the cardiac sodium channel, but not in any other gene known to be associated with Brugada syndrome or in 296 controls.