Novel mutations in ATP1A3 associated with catastrophic early life epilepsy, episodic prolonged apnea, and postnatal microcephaly

Objective: Mutations of ATP1A3 have been associated with rapid onset dystonia-parkinsonism and more recently with alternating hemiplegia of childhood. Here we report onechild with catastrophic early life epilepsy and shortened survival, and another with epilepsy, episodic prolonged apnea, postnatal microcephaly, and severe developmental disability. Novel heterozygous mutations (p.Gly358Val and p.Ile363Asn) were identified in ATP1A3in these children. Methods: Subjects underwent next-generation sequencing under a research protocol. Clinical data were collected retrospectively. The biochemical effects of the mutations on ATP1A3 protein function were investigated. Postmortem neuropathologic specimens from control and affected subjects were studied. Results: The mutations localized to the P domain of the Na, K-ATPase alpha 3 protein, and resulted in significant reduction of Na, K-ATPase activity in vitro. We demonstrate in both control human brain tissue and that from the subject with the p.Gly358Val mutation that ATP1A3 immunofluorescence is prominently associated with interneurons in the cortex, which may provide some insight into the pathogenesis of the disease. Significance: The findings indicate these mutations cause severe phenotypes of ATP1A3-related disorder spectrum that include catastrophic early life epilepsy, episodic apnea, and postnatal microcephaly.