Clinical Analysis And Gene Mutation Screening Of SCN1B And SCN1A In Generalized Epilepsy With Febrile Seizures Plus Families

Generalized epilepsy with febrile seizures plus(GEFS+) is a common epileptic syndrome which is described by families. It has significant phenotypic heterogeneity. The common phenotypes are FS and FS+.The unfrequent phenotypes include FS+ with absence seizure, FS+ with myoclonic seizure,FS+ with atonic seizure,and even severer syndromes such as myoclonic-astasic epilepsy and severe myoclonic epilepsy in infancy.GEFS+ is a kind of channelopathy. The ions are regulated by voltage-gated channels and ligand-gated channels when passing the cells.These channels are regulated by GABA,glutamic acid and many other neurotransmitters via different steps.GEFS+ also has genetic heterogeneity.Most of the cases show an autosomal dominant inheritance pattern.The current research indicates that the Na+ channel genes related to GEFS+ are SCN1B and SCN1A,which are coded byβ₁ andα₁ subunits of Na+ channel respectively.The abnormality of channel function and regulation is always resulted from the abnormal expression of these genes,which causes abnormal excitation of the neurons and the occurrence of seizures.Several mutation loci have been found in the foreign families,but the molecular biology research is rare in our country.In this experiment we made careful clinical analysis for the 15 GEFS+ families and summarized its phenotypes and genetic patterns.The mutation screening of SCN1B and SCN1A was made by direct sequencing of the polymerase chain reaction(PCR) products in order to find the characteristics of molecular biology. Materials and MethodsWe made careful inquries and physical examinations for the probands of the 15 pedigrees of GEFS+.Then we constructed the detailed family trees.Some patients also had EEG ,cranial CT or MRI scans.We attempted to classify epilepsy types and epilepsy syndromes according to the international classification. Finally clinical analysis was made according to the clinical data.The ages of the probands in these families ranged from 5 to 34 years and the average age was 15.3±9.1.These cases were followed by 3 months to 2 years. The phenotypes of 64 individuals(38 males and 26 females)conformed to GEFS+. We extracted the genome DNA and designed the primers. Destination genes were amplified by PCR,and agrose gel electrophoresis was done to check the PCR products. We made direct sequencing for the destination genes which were bright and pure. Finally we analyzed the results by the software.ResultsThe phenotypes included FS,FS+,FS+ with absence seizure,FS+ with myoclonic seizure,FS+ with focal seizure.The incidence between males and females had no significance (x²=0.701 P>0.05).Most of the parents were affected.Few parents were not,but at least 2 relatives were affected. Therefore it conformed to the characteristics of the autosomal dominant inheritance.We amplified all the exons of the SCN1B and SCN1A by PCR,and didn't find affirmative gene mutation in the 15 probands in contrast to genome DNA.Conclusions1. GEFS+ is a common epileptic syndrome in the childhood,with phenotypic heterogeneity. The common phenotypes are FS and FS+.The unfrequent phenotypes include FS+ with absence seizure, FS+ with myoclonic seizure,FS+ with focal seizure .2. GEFS+ also has genetic heterogeneity. If one of the parents is affected,the opportunity of his or her children to have this disease is almost equal no matter what gender is.lt conforms to the autosomal dominant inheritance.3. We made direct sequencing by PCR products in this study,and didn't find affimirtive mutations of SCN1B and SCN1A in all the probands.4. The 15 GEFS+ families we collected have complete clinical data and various phenotypes,which can establish the foundation for the research of molecular biology.