Phospholipase C beta 1 deficiency is associated with early-onset epileptic encephalopathy.
The epileptic encephalopathies of infancy and childhood are a collection of epilepsy disorders characterized by refractory, severe seizures and poor neurological outcome, in which the mechanism of disease is poorly understood. We report the clinical presentation and evolution of epileptic encephalopathy in a patient, associated with a loss-of-function mutation in the phospholipase C-β 1 gene. We ascertained a consanguineous family containing a male infant who presented with early-onset epileptic encephalopathy for detailed clinical phenotyping and molecular genetic investigation. In addition, a cohort of 12 consanguineous families of children with infantile spasms were analysed for linkage to the phospholipase C-β 1 gene locus. The male infant presented with tonic seizures in early infancy and subsequently developed infantile spasms. Over time, he developed drug-resistant epilepsy associated with severe neurological regression and failure to thrive. Molecular genetic investigation revealed a homozygous loss-of-function 0.5-Mb deletion, encompassing the promoter element and exons 1, 2 and 3 of phospholipase C-β 1 in the index case. Linkage to the phospholipase C-β 1 locus was excluded in the 12 other consanguineous families, consistent with genetic heterogeneity in this disorder. Although phospholipase C-β 1 deficiency has not previously been reported in humans, the Plcb1 homozygote knockout mouse displays early-onset severe tonic seizures and growth retardation, thus recapitulating the human phenotype. Phospholipase C-β 1 has important functions in both hippocampal muscarinic acetylcholine receptor signalling and in cortical development. Thus, the discovery of a phospholipase C-β 1 mutation allows us to propose a novel potential underlying mechanism in early-onset epileptic encephalopathy.
Kurian
Manju A
MA
Department of Medical and Molecular Genetics, University of Birmingham School of Medicine, Institute of Biomedical Research, Birmingham, UK.
Meyer
Esther
E
Vassallo
Grace
G
Morgan
Neil V
NV
Prakash
Nandhini
N
Pasha
Shanaz
S
Hai
Nebula A
NA
Shuib
Salwati
S
Rahman
Fatima
F
Wassmer
Evangeline
E
Cross
J Helen
JH
O'Callaghan
Finbar J
FJ
Osborne
John P
JP
Scheffer
Ingrid E
IE
Gissen
Paul
P
Maher
Eamonn R
ER
D004569:Electroencephalography; D004827:Epilepsy / Q000235:genetics* / Q000503:physiopathology; D005183:Failure to Thrive / Q000235:genetics* / Q000503:physiopathology; D017809:Fatal Outcome; D006801:Humans; D007223:Infant; D008297:Male; D009154:Mutation; D010641:Phenotype; D054799:Phospholipase C beta / Q000235:genetics*; D016133:Polymerase Chain Reaction
C518033:PLCB1 protein, human; D054799:Phospholipase C beta