Knockout of kcnj16 (kir5.1) in Dahl salt-sensitive rats produces seizure phenotype

Kir5.1 is a member of an inwardly rectifying potassium (Kir) channel family notably present in the kidney and brain. We previously established that a knockout rat model of Kcnj16 (gene encoding Kir5.1) on a Dahl salt-sensitive background (SSKcnj16-/-) exhibits a severe cardiovascular phenotype (Palygin et al., JCI Insight, 2017). Mutations in ion channel genes can alter neuronal excitability and mutations in Kir genes have been linked to seizure disorders in humans. Since Kir5.1 is known to be expressed in the brain and may contribute to neuronal membrane potential and spatial potassium buffering, we hypothesized that in addition to cardiovascular and renal dysfunction, neurological phenotypes, including seizures, would be prevalent in the SSKcnj16-/-rats. We found that SSKcnj16-/- rats (but not control SS rats) experience tonic-clonic seizures when exposed to a 10 kHz tone (86 dB for 2 min), whereas other frequencies (0.1 or 1 kHz) did not elicit seizures. When exposed to the seizure-inducing acoustic stimulus once/day for 10 days, we noted that SSKcnj16-/- rats experienced a seizure in response to 92% of stimuli. SSKcnj16-/- rats also showed spontaneous mortality within hours after a stimulus with a survival rate of 67% (N=21) for the duration of the 10 day protocol. Control rats (N=10) had no incidence of seizure or death during the 10 days of acoustic stimulation. We found no difference among male and female SSKcnj16-/- rats, where both sexes had a similar audiogenic seizure response and reduced survival. Behavioral tests including a modified Irwin screen and open field test revealed that before and after seizure stimulation SSKcnj16-/- rats tended to have altered activity levels, gait, piloerection, and respiration rates. Analysis of blood electrolytes revealed critically low serum potassium levels in SSKcnj16-/- compared to SS controls, a difference that appeared to be exacerbated by repeated seizures. We hypothesize that seizures may be intensifying potassium imbalance and disrupting the homeostasis that is particularly essential for excitable cells such as neurons. We conclude that knockout of Kir5.1 leads to distinct neurological phenotypes including a seizure disorder and subsequent spontaneous death, which may have relevance to channelopathies associated with seizure disorders in humans