Cardiac remodeling and arrhythmia in a mouse model of Depdc5 haploinsufficiency

Some ion channel genes linked to developmental and epileptic encephalopathy (DEE) are also linked to cardiac arrhythmia, leading to the hypothesis that predisposition to cardiac arrhythmias may contribute to the complex disease presentation of DEE and possibly to the mechanism of sudden unexpected death in epilepsy. However, channelopathies represent only ~25% of the genetic epilepsies. The remainder arise from variants in non-ion-channel genes, moving the disorder beyond channelopathies. Despite evidence that some non-ion-channel variants are linked to sudden cardiac death, we have little information on whether non-ion-channel DEE variants can also result in cardiac phenotypes.

Here, we investigated the DEE gene, DEPDC5, which is expressed in both brain and heart. We studied the cardiac phenotype of a Depdc5 haploinsufficient mouse model that genetically mimics DEPDC5 patients.

Depdc5^+/- mice showed increased susceptibility to ventricular arrhythmias, systolic dysfunction, and ventricular fibrosis, as well as shortened action potential duration, increased levels of sodium and potassium channel proteins, and increased sodium current and transient outward potassium current densities in acutely isolated ventricular myocytes. Thus, at least in mice, Depdc5 variants impact heart as well as brain excitability.

These data strengthen the hypothesis that cardiac arrhythmias may contribute to the complex presentation of DEE and expand our previous work showing cardiac arrhythmia in multiple mouse and human channelopathy models to include a model of a non-ion-channel variant. Although this work may have implications for DEPDC5 patients, critical differences between mouse and human cardiac physiology complicate the translation of mouse data to human disease. Essential next steps must include investigation of Depdc5 function in higher vertebrate models that more accurately mimic human physiology, as well as longitudinal patient natural history studies that monitor cardiovascular health, to test the hypothesis that DEE variants resulting in DEPDC5 haploinsufficiency may predispose patients to cardiac arrhythmias.