title: Impaired mitochondrial glutamate transport in autosomal recessive neonatal myoclonic epilepsy.
abstract: Severe neonatal epilepsies with suppression-burst pattern are epileptic syndromes with either neonatal onset or onset during the first months of life. These disorders are characterized by a typical electroencephalogram pattern--namely, suppression burst, in which higher-voltage bursts of slow waves mixed with multifocal spikes alternate with isoelectric suppression phases. Here, we report the genetic mapping of an autosomal recessive form of this condition to chromosome 11p15.5 and the identification of a missense mutation (p.Pro206Leu) in the gene encoding one of the two mitochondrial glutamate/H(+) symporters (SLC25A22, also known as "GC1"). The mutation cosegregated with the disease and altered a highly conserved amino acid. Functional analyses showed that glutamate oxidation in cultured skin fibroblasts from patients was strongly defective. Further studies in reconstituted proteoliposomes showed defective [(14)C]glutamate uniport and [(14)C]glutamate/glutamate exchange by mutant protein. Moreover, expression studies showed that, during human development, SLC25A22 is specifically expressed in the brain, within territories proposed to contribute to the genesis and control of myoclonic seizures. These findings provide the first direct molecular link between glutamate mitochondrial metabolism and myoclonic epilepsy and suggest potential insights into the pathophysiological bases of severe neonatal epilepsies with suppression-burst pattern.
authors.affiliation: INSERM U393, Hopital Necker-Enfants Malades, Paris, France.
authors.forename: Florence
authors.initials: F
authors.lastname: Molinari
authors.forename: Annick
authors.initials: A
authors.lastname: Raas-Rothschild
authors.forename: Marlene
authors.initials: M
authors.lastname: Rio
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Fiermonte
authors.forename: Ferechte
authors.initials: F
authors.lastname: Encha-Razavi
authors.forename: Luigi
authors.initials: L
authors.lastname: Palmieri
authors.forename: Ferdinando
authors.initials: F
authors.lastname: Palmieri
authors.forename: Ziva
authors.initials: Z
authors.lastname: Ben-Neriah
authors.forename: Noman
authors.initials: N
authors.lastname: Kadhom
authors.forename: Michel
authors.initials: M
authors.lastname: Vekemans
authors.forename: Tania
authors.initials: T
authors.lastname: Attie-Bitach
authors.forename: Arnold
authors.initials: A
authors.lastname: Munnich
authors.forename: Pierre
authors.initials: P
authors.lastname: Rustin
authors.forename: Laurence
authors.initials: L
authors.lastname: Colleaux
mesh_terms: D027322:Amino Acid Transport System X-AG / Q000235:genetics*; D002675:Child, Preschool; D004569:Electroencephalography; D004831:Epilepsies, Myoclonic / Q000235:genetics*; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism* / Q000493:pharmacokinetics; D006801:Humans; D007621:Karyotyping; D008297:Male; D008928:Mitochondria / Q000235:genetics*
chemical_list: D027322:Amino Acid Transport System X-AG; D018698:Glutamic Acid