ATP6V0C variants impair V-ATPase function causing a neurodevelopmental disorder often associated with epilepsy.

The vacuolar H+-ATPase is an enzymatic complex that functions in an ATP-dependent manner to pump protons across membranes and acidify organelles, thereby creating the proton/pH gradient required for membrane trafficking by several different types of transporters. We describe heterozygous point variants in ATP6V0C, encoding the c-subunit in the membrane bound integral domain of the vacuolar H+-ATPase, in 27 patients with neurodevelopmental abnormalities with or without epilepsy. Corpus callosum hypoplasia and cardiac abnormalities were also present in some patients. In silico modelling suggested that the patient variants interfere with the interactions between the ATP6V0C and ATP6V0A subunits during ATP hydrolysis. Consistent with decreased vacuolar H+-ATPase activity, functional analyses conducted in Saccharomyces cerevisiae revealed reduced LysoSensor fluorescence and reduced growth in media containing varying concentrations of CaCl2. Knockdown of ATP6V0C in Drosophila resulted in increased duration of seizure-like behaviour, and the expression of selected patient variants in Caenorhabditis elegans led to reduced growth, motor dysfunction and reduced lifespan. In summary, this study establishes ATP6V0C as an important disease gene, describes the clinical features of the associated neurodevelopmental disorder and provides insight into disease mechanisms.

Targeting firing rate neuronal homeostasis can prevent seizures.

Manipulating firing-rate neuronal homeostasis, which enables neurons to regulate their intrinsic excitability, offers an attractive opportunity to prevent seizures. However, to date, no drug-based interventions have been reported that manipulate this type of neuronal homeostatic mechanism. Here, we used a combination of Drosophila and mouse, and, in the latter, both a pentylenetetrazole (PTZ)-induced seizure model and an electrically induced seizure model for refractory seizures to evaluate the anticonvulsant efficacy of a novel class of anticonvulsant compounds, based on 4-tert-butyl-benzaldehyde (4-TBB). The mode of action included increased expression of the firing rate homeostatic regulator Pumilio (PUM). Knockdown of pum expression, in Drosophila, blocked anticonvulsive effects of 4-TBB, while analysis of validated PUM targets in mouse brain revealed significant reductions following exposure to this compound. A structure-activity study identified the active parts of the molecule and, further, showed that the pyrazole analogue demonstrates highest efficacy, being active against both PTZ-induced and electrically induced seizures. This study provides a proof of principle that anticonvulsant effects can be achieved through regulation of firing rate neuronal homeostasis and identifies a possible chemical compound for future development.