Abstracts

Rationale: In the developmental and epileptic encephalopathies (DEEs), early life seizures and intellectual disability are associated with complex syndromes of neurobehavioral impairment that feature disturbances in sleep, communication/social interactions, feeding and sensory integration. In many cases, behavioral symptoms persist despite effective seizure control (or spontaneous seizure remission). In this study, we apply instrumented homecage monitoring to characterize an encephalopathy-like syndrome in mice with constitutive deletions of Kcna1, a shaker-related voltage potassium channel subunit. Through label-free microscale proteomic profiling, we identify associated changes in proteomic landscapes of the hippocampus, where the cellular neurophysiological substrates of hyperexcitability may pleiotropically impact cognitive and emotional behaviors.

Methods: We studied three cohorts of WT and KO mice. First, we applied instrumented homecage monitoring (Noldus Phenotypers) to ~5 week old KO (n=13) and WT (n=19) littermates (~50% female). From the second cohort, we provided frozen whole hippocampal samples from a 3 mice/genotype to the BCM Proteomics Core facility. A third group of WT and KO mice were examined for histological (n=5-6/group) and ELISA-based confirmations (n=5-6/group) of proteomic results.

Results: In comparison to WT mice, KOs display intense nocturnal hyperactivity and profound insomnia, together with features of sensory over-responsivity, social withdrawal and fragmented patterns of licking and feeding behavior. KO hippocampi displayed significant upregulations in EGR3 (early growth response 3) and BDNF (brain-derived neurotrophic factor). Immunohistochemistry confirmed elevations in EGR3 across dorsal and ventral hippocampal regions, with concurrent elevations in gliosis (measured by GFAP staining) and without significant changes in cell number. BDNF elevations were confirmed by ELISA.

Conclusions: Our data support a working model by which early life seizures give rise to a vicious cycle of EGR3 upregulation and BDNF induction, which function to maintain seizure risk and encephalopathic behavior. In ongoing work, we are applying a blend of genetic and viral strategies to define the role of EGR3 in KCNA1-DEE.

Funding: V.K. receives support from the NIH (1K08NS110924-01), an AES Junior Investigator Award (2020-2021), The Mike Hogg Fund, and seed funding from Baylor College of Medicine’s Office of Research.