Gene expression analysis in absence epilepsy using a monozygotic twin design.
OBJECTIVE
To identify genes involved in idiopathic absence epilepsies by analyzing gene expression using a monozygotic (MZ) twin design.


METHODS
Genome-wide gene expression in lymphoblastoid cell lines (LCLs) was determined using microarrays derived from five discordant and four concordant MZ twin pairs with idiopathic absence epilepsies and five unaffected MZ twin pairs. Gene expression was analyzed using three strategies: discordant MZ twins were compared as matched pairs, MZ twins concordant for epilepsy were compared to control MZ twins, and a singleton design of affected versus unaffected MZ twin individuals was used irrespective of twin pairing. An overlapping gene list was generated from these analyses. Dysregulation of genes recognized from the microarray experiment was validated using quantitative real time PCR (qRT-PCR) in the twin sample and in an independent sample of 18 sporadic absence cases and 24 healthy controls.


RESULTS
Sixty-five probe sets were identified from the three combined microarray analysis strategies. Sixteen genes were chosen for validation and nine of these genes confirmed by qRT-PCR in the twin sample. Differential expression for EGR1 (an immediate early gene) and RCN2 (coding for the calcium-binding protein Reticulocalbin 2) were reconfirmed by qRT-PCR in the independent sample.


CONCLUSIONS
Using a unique sample of discordant MZ twins, our study identified genes with altered expression, which suggests novel mechanisms in idiopathic absence epilepsy. Dysregulation of EGR1 and RCN2 is implicated in idiopathic absence epilepsy.
Helbig
Ingo
I
Department of Medicine, Epilepsy Research Centre, University of Melbourne, Austin Health, Australia.
Matigian
Nicholas A
NA
Vadlamudi
Lata
L
Lawrence
Kate M
KM
Bayly
Marta A
MA
Bain
Sharon M
SM
Diyagama
Dileepa
D
Scheffer
Ingrid E
IE
Mulley
John C
JC
Holloway
Andrew J
AJ
Dibbens
Leanne M
LM
Berkovic
Samuel F
SF
Hayward
Nicholas K
NK
D000328:Adult; D000927:Anticonvulsants / Q000627:therapeutic use; D002135:Calcium-Binding Proteins / Q000235:genetics*; D045744:Cell Line, Tumor / Q000473:pathology; D051766:Early Growth Response Protein 1 / Q000235:genetics*; D004832:Epilepsy, Absence / Q000175:diagnosis* / Q000188:drug therapy / Q000235:genetics*; D005260:Female; D015870:Gene Expression / Q000235:genetics*; D006801:Humans; D008297:Male; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000473:pathology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014430:Twins, Monozygotic / Q000235:genetics*; D014635:Valproic Acid / Q000627:therapeutic use
D000927:Anticonvulsants; D002135:Calcium-Binding Proteins; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; C088393:RCN2 protein, human; D014635:Valproic Acid