Leigh syndrome (LS) is the most common pediatric mitochondrial disease, manifesting in the first year of life and leading to early death due to a lack of proven therapies. Like other mitochondrial diseases, LS is caused by gene mutations impacting proteins essential for the mitochondrial respiratory chain, including all complexes. Mutations in NDUFS4, a gene that encodes a subunit critical for structure and stability of complex I, have been linked to LS. Mice with the whole-body NDUFS4 KO exhibit major LS symptoms, particularly epilepsy, along with psychomotor deterioration, progressive neurodegeneration and premature lethality (~P60). Our earlier findings showed that mice with Ndufs4 KO specifically in GABAergic interneurons (Gad2-Ndufs4-KO) exhibit the severe epilepsy and sudden death observed in the global KO mice. These mice represent an excellent model of LS epilepsy, isolated from other clinical manifestations of the disease. LS related epilepsy is often very difficult to treat and indicative of poor disease prognosis. Chronic hypoxia therapy (CHT) has previously shown promise in improving survival and reversing neurodegeneration in LS mice. Yet its impact on seizures remains unknown. In this study, we investigated the efficacy of CHT in ameliorating the epileptic phenotype. Mice with LS epilepsy demonstrated a longer lifespan when exposed to  normobaric 11% O2 than normoxia from postnatal day 35 to day 70. Upon return to normoxic conditions, mice kept in chronic hypoxia die within days. In addition, preliminary thermal seizure tests show an increased thermal seizure threshold in hypoxic mice compared to normoxic ones.  Future studies will evaluate CHT impact on spontaneous seizures using video EEG technique. Our study will aid in the development of a novel therapeutic approach for seizures and related death in Leigh syndrome.

Dravet Syndrome (DS) is a severe developmental epileptic encephalopathy often associated with SCN1A mutations. DS is predominantly caused by a heterozygous loss-of-function mutation in the SCN1A gene, which codes for the pore-forming alpha subunit of the Na_v1.1 voltage-gated sodium channel. The disease is marked by seizures that are resistant to treatment, ataxia, developmental delays, cognitive impairment, and higher rates of premature mortality, primarily due to sudden unexpected death in epilepsy (SUDEP). At this time however, there is no effective intervention against these devastating outcomes. Anecdotal evidence from family members of children with DS suggests that sensory stimulation during these seizures might reduce their severity and duration. This study investigates whether sensory stimulation can reduce SUDEP in DS using a preclinical mouse model with the SCN1A knocked out. We created a closed-loop responsive system that detects seizure onset and triggers sensory stimulation in real time by utilizing piezoelectric sensors, a Teensy microcontroller, and a 12V computer fan to deliver airflow-based stimulation as a response to spontaneous seizures. Using the modified Racine scale, the system successfully identified scale 4 seizures (generalized tonic-clonic while lying on the belly), as well as scale 6 seizures (generalized tonic-clonic with tonic extension). However, it was unable to detect scale 5 seizures (by sudden, erratic jumping movements). Particularly, for scale 6 seizures, typically fatal in all cases, activating the fan completely prevented SUDEP, resulting in zero mortality. In contrast, for scale 5 seizures that went undetected and did not trigger the fan, mortality remained at 100%. These findings emphasize the potential of airflow-based sensory stimulation as a promising, non-invasive intervention for SUDEP. Future research will focus on improving seizure detection algorithms to enhance sensitivity across a wider range of seizure types.

Leigh Syndrome (LS) is a neurodegenerative disease due to the dysfunction of mitochondria. This disease usually begins in infancy and affects approximately 1 in 40,000 individuals, with children experiencing a progressive decline in their cognitive and motor functions often accompanied by severe treatment-resistant epileptic seizures. Mutations in Ndufs4, the gene that encodes a subunit of mitochondrial complex I have been linked to LS. Using mouse models, our lab has previously demonstrated that GABAergic interneurons play an important role in the pathophysiology of LS. Specifically, mice with Ndufs4 knockout (KO) in GABAergic neurons located across all brain regions exhibit seizures. However, seizures in epilepsy patients and animal models typically originate from forebrain structures. In this project, we examined whether inactivation of Ndufs4 in GABAergic neurons of the forebrain alone is sufficient to cause seizures in mice. To inactivate the Ndufs4 gene in the interneurons of the forebrain, homozygotes floxed Ndfus4 (Ndufs4flx/flx) mice were crossed with Dlx56Cre+ mice. Ndufs4flx/flx; Dlx56Cre+ mice obtained from this cross were used as experimental mice. We hypothesized that mice carrying the gene KO in this region will exhibit seizures and related mortality. Thermal seizure testing was conducted on 9 experimental mice and 10 control mice. Our results show that mice with Dlx56Cre KO exhibit a high seizure susceptibility to both spontaneous and thermally induced seizures. In addition, these mice exhibit a very reduced life span with nearly all mice dying by age P60. These findings indicate that inactivation of Ndufs4 in GABAergic neurons of the forebrain is sufficient to induce seizures and mortality in mice.