Severe epilepsy as the major symptom of new mutations in the mitochondrial tRNA(Phe) gene.
OBJECTIVE
To present 2 families with maternally inherited severe epilepsy as the main symptom of mitochondrial disease due to point mutations at position 616 in the mitochondrial tRNA(Phe) (MT-TF) gene.


METHODS
Histologic stainings were performed on skeletal muscle slices from the 2 index patients. Oxidative phosphorylation activity was measured by oxygraphic and spectrophotometric methods. The patients' complete mitochondrial DNA (mtDNA) and the relevant mtDNA region in maternal relatives were sequenced.


RESULTS
Muscle histology showed only decreased overall COX staining, while a combined respiratory chain defect, most severely affecting complex IV, was noted in both patients' skeletal muscle. Sequencing of the mtDNA revealed in both patients a mutation at position 616 in the MT-TF gene (T>C or T>G). These mutations disrupt a base pair in the anticodon stem at a highly conserved position. They were apparently homoplasmic in both patients, and had different heteroplasmy levels in the investigated maternal relatives.


CONCLUSIONS
Deleterious mutations in the mitochondrial tRNA(Phe) may solely manifest with epilepsy when segregating to homoplasmy. They may be overlooked in the absence of lactate accumulation and typical mosaic mitochondrial defects in muscle.
Department of Epileptology and Life & Brain Center, University of Bonn, Bonn, Germany.
G
G
Zsurka
K G
KG
Hampel
I
I
Nelson
C
C
Jardel
S R
SR
Mirandola
R
R
Sassen
C
C
Kornblum
P
P
Marcorelles
S
S
Lavoué
A
A
Lombès
W S
WS
Kunz
D000293:Adolescent; D000927:Anticonvulsants / Q000627:therapeutic use; D004272:DNA, Mitochondrial / Q000235:genetics*; D003576:Electron Transport Complex IV / Q000378:metabolism; D004827:Epilepsy / Q000150:complications / Q000188:drug therapy / Q000235:genetics*; D005192:Family Health; D005260:Female; D006801:Humans; D008297:Male; D028361:Mitochondrial Diseases / Q000235:genetics* / Q000503:physiopathology*; D018482:Muscle, Skeletal / Q000473:pathology; D009154:Mutation / Q000235:genetics*; D012150:Polymorphism, Restriction Fragment Length; D012360:RNA, Transfer, Phe / Q000235:genetics*; D013385:Succinate Dehydrogenase / Q000378:metabolism; D055815:Young Adult
D000927:Anticonvulsants; D004272:DNA, Mitochondrial; D012360:RNA, Transfer, Phe; D013385:Succinate Dehydrogenase; D003576:Electron Transport Complex IV