2009 Vienna - European Society of Human Genetics

Genetic analysis, linkage ans association
nately, revealed results did not allow performing statistical analyses.
Since information involving SNPs heterozigosity in rats remains mainly
unknown, following experiments based on other polymorphic loci in
DRD2 and DAT1 genes are required.
P17.67
Febrile seizure or Darvet syndrome: A clinical and molecular
study of scN1A-related epilepsy in iranian families
A. Ebrahimi 1 , S. Zeinali 2 , H. Tonekaboni 3 , M. Fallah 1 , G. Modaber 1 , S. Seiedhassani
1 , M. Ataei 1 , r. alimohammadi 1 , M. Raeisi 4 , M. Houshmand 1 ;
1 NIGEB, Tehran, Islamic Republic of Iran, 2 Biotechnology Research Center
- Pasteur Institute, Tehran, Islamic Republic of Iran, 3 TUMS, Tehran, Islamic
Republic of Iran, 4 KBC,Kowsar Biotechnolgy Center, Tehran, Islamic Republic
of Iran.
Introduction:SCN1A-related seizure disorders encompass a spectrum
that ranges from simple febrile seizures (FS) and generalized epilepsy
with febrile seizures plus (GEFS+) at the mild end to Dravet syndrome
at the severe end. The phenotype can vary even within the same family.
Probands with autosomal dominant SCN1A-related seizure may
have a de novo mutation. Most SCN1A-related SMEI are the result of
a de novo heterozygous mutation. Early diagnosis prenatal diagnosis
for pregnancies at increased risk is possible if the disease causing
mutation in the family is known.
Material and methods: Classification of patients based on clinical
examination and genetic counseling were done. DNA was obtained
from 34 unrelated families with a spectrum of Idiopathic Epilepsy
(IE). In order to finding point mutations and SNPs, exons of SCNIA,
SCN1B and Mitochondrial common deletions, tRNA Lys tRNA Leu
in probands were Screened for any alteration using intronic primers
and were analyzed by Single Strand conformation Polymorphism gel
electrophoresis(SSCP) and any variation confirmed by direct sequencing.
Allele and genotype frequencies in the patients and in the control
groups were compared by χ2 analysis, Fisher’s exact test and logistic
regration analysis methods.
Conclusions: We could found new intronic and exonic variants in candidate
genes, in Iranian patients with IE subtypes. The high rate of
heterogeneity and consanguinity, large families with many affected
members in family as a social and healthy fact in Iranian populations
could be a golden gene pool for linkage analysis in common disease.
P17.68
Role of scN1B mutations in drug resistant in iranian epileptic
families
M. -. Moghaddasi 1 , M. Mamarabadi 2 , A. Ebrahimi 3 , M. S. Fallah 3 , H. Tonekaboni
4 , S. Zeinali 1 , H. Razjouyan 4 ;
1 IUMS;Iran University of Medical Sciences, Tehran, Islamic Republic of Iran,
2 Iran University of Medical Sciences, Tehran, Islamic Republic of Iran, 3 NIGEB;
National Institute of Genetic Engineering and Biotechnology, Tehran, Islamic
Republic of Iran, 4 TUMS;Tehran University of Medical Sciences, Tehran, Islamic
Republic of Iran.
Introduction: Many antiepileptic drugs (AEDs) prevent seizures by
blocking voltage-gated brain sodium channels such as SCN1A, SC-
N2A, and SCN1B. However, treatment is ineffective in 30% of epilepsy
patients, which might, at least in part, result from polymorphisms of
the sodium channel genes. The R85C and R85H mutations of the β1
subunitcause generalized epilepsy syndromes in humans and cause
an increase in excitability but the R85H mutation was more excitable.
We investigated the Role of SCN1B mutations in drug resistant in Iranian
epileptic families.
Material and methods: Diagnostic classification of patients followed the
proposal of the Commission on Classification and Terminology of the
International League Against Epilepsy (1989).Family History, Electroencephalography
(EEG) recordings and CT Scan were obtained from
most patients . Written consent was obtained from all participants.
DNA was obtained from 34 unrelated families with idiopathic generalized
epilepsy as index families. The all coding exons of SCN1B were
Screened for deletions and duplications by MLPA. In order to finding
point mutations and SNPs each exon individually amplified from genomic
DNA in PCR reactions using intronic primers and were analyzed
by Single Strand conformation Polymorphism gel electrophoresis
(SSCP) and conformation-sensitive gel electrophoresis(CSGE) and
so the PCR products with mobility variants were sequenced by ABI
sequencer.Allele and genotype frequencies in the patients and in the
control groups were compared by either χ2 analysis or Fisher’s exact
test.
Results: We have identified some new intronic variants in SCN1B and
new mutations too, in patients with IGE subtypes.
P17.69
Influence of SCN1A, SCN2A and SYN2 gene polymorphisms in
epilepsy susceptibility and therapeutic efficacy
B. Mittal, R. Lakhan, R. Shah, U. K. Misra;
Sanjay Gandhi Postgraduate Institute of Medical Sciences, LUCKNOW, India.
Epilepsy is a common multifactorial neurological disorder, with higher
prevalence in developing countries like India. Genetic variants of neuronal
sodium channels; like SCN1A, SCN2A, SCN3A and other neuronal
genes such as SYN2 have been implicated for their contribution
in epilepsy susceptibility and its therapy. To evaluate sodium channel
genes and synapsin vesicle associated gene SYN2 as candidates
for the epilepsy susceptibility and their role in therapeutic efficacy,
we screened two coding Single-nucleotide polymorphism of SCN1A
p.T1056A (rs2298771), SCN2A 56G>A (rs17183814) and rs3773364
A>G intronic polymorphism in SYN2 gene in north Indian epilepsy patients.
A total of 372 patients with epilepsy and 199 control individuals
were enrolled for the study. The genotyping was performed using
PCR-RFLP assay in all individuals. Therapeutic drug monitoring for
phenytoin, carbamazepine, phenobarbital, and valproate was also performed
in 20% of the patients to confirm compliance. Among all 372
patients with epilepsy, 118 were drug resistant and 254, were drug
responsive. AG genotype of SCN1A 3184 A>G polymorphism was significantly
higher and associated in epilepsy patients (P=0.005, OR =
1.764, 95% CI =1.192-2.611) while G variant of SCN2A was associated
with multiple drug resistance in north Indian patients with epilepsy
(P=0.037; OR 1.625 95% CI=1.030-2.564). The AG genotype of SYN2
gene also was significantly higher in patients with epilepsy versus control
subjects in north Indian population (P=0.02, OR = 1.55, 95% CI
=1.066-2.269). Overall results indicate these genes and their variants
have significant role in epilepsy susceptibility and could modulate drug
response behavior as well.
P17.70
two novel KcNQ2 mutations in Bulgarian patients with
idiopathic neonatal epilepsy
I. Yordanova 1,2 , Y. Gofman 3 , D. Hristova 4 , R. Ralcheva 5 , A. Lofgren 6 , P. De
Jonghe 6 , N. Ben-Tal 3 , I. Kremensky 1,2 , A. Jordanova 7,6 ;
1 National Genetics Laboratory, Sofia, Bulgaria, 2 Molecular Medicine Center,
Medical University, Sofia, Bulgaria, 3 Department of Biochemistry, Tel Aviv University,
Tel Aviv, Israel, 4 Department of Pediatrics, Medical University, Sofia,
Bulgaria, 5 Department of Pediatrics, Medical University, Varna, Bulgaria, 6 VIB
Department of Molecular Genetics, University of Antwerp, Antwerp, Belgium,
7 Department of Chemistry and Biochemistry, Medical University, Sofia, Bulgaria.
Mutations in the KCNQ2 gene, encoding the voltage-gated potassium
channel Kv7.2, have been identified as the underlying cause mainly
for benign familial neonatal convulsions (BFNC). They are located predominantly
in the pore region or the C-terminus of the Kv7.2 protein.
We performed a point mutation screening of KCNQ2 in patients with
idiopathic neonatal epilepsy, which included PCR analysis followed by
direct sequencing of all exons and exon-intron boundaries of the gene.
In addition, to determine the probable pathological effect of the mutations
we elaborated a computational model of the Kv7.2 channel structure,
using homology modeling. The predicted structure was based on
the known 3D structure of Kv1.2-Kv2.1 chimera.
In this study, one novel de novo missense mutation and one novel
familial nonsense mutation in KCNQ2 were found. The missense mutation
is located in the pore region of the Kv7.2 and disrupts the whole
channel structure. The mutation is arisen de novo in a girl with severe
intractable epilepsy and developmental delay. The nonsense mutation
is situated in the C-terminus of the channel and is predicted to cause
protein truncation. It was found in two sisters with BFNC and their father.
This is the first KCNQ2 study in Bulgarian epilepsy patients. Although
mutations in KCNQ2 are mostly considered to cause BFNC with AD inheritance,
we show that in rare cases they can contribute to the pathogenesis
of sporadic forms of severe neonatal epilepsy.
Acknowledgement to the Flanders fellowship!