Mitochondria and neonatal epileptic encephalopathies with suppression burst.

The mitochondrion is a key cellular structure involved in many metabolic functions such as ATP synthesis by oxidative phosphorylation, tricarboxylic acid cycle or fatty acid oxidation. These pathways are fundamental for biological processes such as cell proliferation or death. In the central nervous system, mitochondria dysfunctions have been involved in many neurological diseases and age-related neurodegenerative disorders, including epilepsy, Alzheimer's and Parkinson's diseases. Mitochondrial diseases are frequently caused by a disruption of the respiratory chain. Nevertheless, other mitochondrial functions, including organellar dynamics or metabolite transport, could also be involved in such pathologies. Here we described mitochondrial dysfunctions in a very severe, intractable and relatively rare neonatal epileptic encephalopathy, the Ohtahara syndrome. This condition is characterized by neonatal onset of seizures, interictal electroencephalogram with suppression burst pattern and a very poor outcome with very severe psychomotor retardation or death. The etiology of this disease remains elusive but seems to be very heterogeneous including brain malformations, metabolic errors, transcription factor and synaptic vesicle release defects. In this review, we discuss first the Ohtahara syndrome caused by mitochondrial respiratory chain damages, suggesting that these defects could be more common than previously thought. Then, we will adress the importance of the mitochondrial glutamate carrier SLC25A22 in these pathologies, since mutations of this gene were described in two distinct families. These findings suggest that glutamate metabolism should also be considered as an important cause of the Ohtahara syndrome.