Gene panel sequencing performed in the probands of family B, C, D, and E did not identify other rare variants in known epilepsy genes targeted in our panel. None of the GABRG2 mutations of this study were reported in the Exome Aggregation Consortium (ExAC) database, which includes the 1000 Genomes project database and the 6,503 exomes listed in the exome variant server. Although we acknowledge that the p value might be overestimated because of a lower coverage of exons 3 and 6 in ExAC control individuals, we observed a significant enrichment of rare nonsynonymous GABRG2 variants in our cohort of patients (6/108, 5.6%) compared with individuals of European ancestry from the ExAC browser (73/33,370 (0.22%), p < 2.2 × 10−7). To further demonstrate the causality of the GABRG2 variants in the FS phenotype by linkage analysis, we calculated 2-point LOD scores in the 6 families. The sum of the maximal pairwise LOD scores was 3.02, indicating significant likelihood that the GABRG2 variants are causal.
