ATP1A3-related Disorders: Identification of mutation specific pathomechanisms in human neurons and animal models as basis for novel therapeutic approaches.

• Applicant: Professor Dr. Hendrik Rosewich
• Subject Area: Pediatric and Adolescent Medicine
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 496916190

Alternating hemiplegia of childhood (AHC) is a rare neurological disorder that is associated with transient episodes of hemiplegia in conjunction with other paroxysmal symptoms such as dystonia, nystagmus, autonomic dysfunction, and cerebral seizures. The non-paroxysmal symptoms of AHC include various levels of psychomotor development disorder, including cognitive impairment, ranging from learning to intellectual disability. In 2012, using a trio-whole exome sequencing strategy, we were able to show that the AHC, which has been clinically defined for over 40 years, is caused by heterozygous de novo mutations in the ATP1A3 gene. Interestingly, it has been known since 2004 that mutations in this gene are also responsible for a rare movement disorder in adulthood, namely Rapid-Onset Dystonia-Parkinsonism (RDP, DYT12). RDP is characterized by a sudden onset of dystonia with signs of Parkinsonism (primarily bradykinesia and postural instability). Through our precise genetic and clinical characterization, we were able to show that AHC and RDP represent clinical entities within a clinical continuum with overlapping core neurological symptoms. Patients with AHC show rather severe symptoms while patients with RDP tend to be milder.In recent years, other diseases with mutations in the ATP1A3 gene have been identified which display a large number of the known neurological core symptoms, but which are each differentiated by their own characteristic neurological symptoms. These include in particular the CAPOS syndrome (cerebellar ataxia, areflexia, pes cavus, optic atrophy, sensorineural hearing loss), early infantile epileptic encephalopathy (EIEE), childhood rapid onset ataxia (CROA) and relapsing encephalopathy with rapid onset cerebellar ataxia (RECA).Despite intensive research, the pathomechanisms that underlie the wide clinical spectrum of ATP1A3-dependent diseases are largely unknown. The aim of our project is therefore the identification of mutation-specific pathomechanisms. For this purpose, we will use an autaptic culture system human neurons to analyze the distribution of ATP1A3 and validate the protein-protein-interactions known from animal models by means of co-immunolabeling. Moreover, we will analyze the electrophysiological properties of ATP1A3-deficient human neurons compared to wild-type human neurons comprehensively. In addition, using complexome profiling with nanoLC-MS/MS analysis, we will investigate mutation-specific changes in the protein-protein interaction and the protein complex formation of ATP1A3 in the mouse model and verify them in human cell systems.The results will provide a better understanding of the high phenotypic variability within the individual ATP1A3-dependent disease. Moreover, they will elucidate the pathomechnisms that underlie the specific clinical symptoms of the different ATP1A3-related disorders and thus form the basis for the establishment of therapeutic approaches.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Jeong Seop Rhee