CACNA1C variants associated with focal epilepsy and their correlations with arrhythmias and developmental disorders.

Purpose

CACNA1C variants have been identified in cardiac arrhythmias and developmental disorders (DD). Here, we aimed to explore the association between CACNA1C and epilepsy and the mechanism underlying phenotypic heterogeneity.

Methods

Trio-based whole-exome sequencing was performed in patients with focal epilepsy. Genes with recurrently identified variants were selected for further studies.

Results

Three de novo CACNA1C variants were identified in three patients with focal epilepsy. All variants presented no minor allele frequency in the Genome Aggregation Database, which was significantly lower than that of benign variants in the ClinVar database. The three de novo variants were evaluated as pathogenic or likely pathogenic variants according to the updated American College of Medical Genetics and Genomics (ACMG) classification. Two patients experienced infrequent seizures and became seizure free. The other patient had refractory epilepsy with DD and arrhythmia. Previously, 138 CACNA1C variants were reported to be associated with arrhythmias, of which 39 were classified as pathogenic or likely pathogenic; 30 variants were associated with DD, 19 of which were classified as pathogenic or likely pathogenic according to the updated ACMG classification. Further analysis indicated that null variants were more common in DD than in epilepsy (p=1.39×10-3) and arrhythmias (p=6.31×10-7). The epilepsy-associated variants were predominantly located in the voltage sensor region (p=9.03×10-3), whereas the arrhythmia-associated variants were mostly located in the linker region (p=2.13×10-4). There was a greater percentage of de novo variants in patients with epilepsy and DD than in those with arrhythmias (p=6.02×10-3; p=2.47×10-2).

Conclusion

CACNA1C is potentially a candidate causative gene of focal epilepsy. The genotype-phenotype correlation of CACNA1C helps explain phenotypic heterogeneity.