Mapping The Gene For BFIC Pedigrees

Objective: Benign familial infantile convulsion (BFIC) is a kind of idiopathic epilepsy syndrome following Mendelian inheritance. It is advisable to map the gene for BFIC pedigrees by linkage analysis. In our study, six short tandem repeat (STR) loci including D19S245 and D19S250 on chromosome 19ql2-ql3.1, D16S3131 and D16S3133 on chromosome 16pl2-ql2, D2S399 and D2S2330 on chromosome 2q24 were chosen as DNA markers for linkage analysis. This study can bring some important information to find the gene for BFIC patient in China and to discover the gene mechanism in the future.Methods: The subjects were five BFIC pedigrees, 70 members in totall, including 28 patients and 42 non-patients, from four districts including Xinxiang, Nanyang, Zhoukou and Hebi in Henan province. Genomic DNA was extracted from peripheral blood by means of phenol/chloroform followed by alcohol precipitation. 5ml peripheral blood was extracted from BFIC family member. 2%NaiEDTA was added in each sample to prevent from solidifying. DNA was dissolved in deionized water and served as template.Amplification fragment length polymorphism analysis (AFLP) was conducted at the six STR loci to judge the individal's genetype. The primer sequences are from the Genome Database. The volume is 25ul for each PCR. PCR products were separated by constant temperature and constant power (48 , 20W) electrophoresis on 5% denaturating polyacrylamide gels for 2-3 hours and followed by silver staining. The allele ladder is used in judging the ampilified fragment lengths.Linkage analysis was performed by MLINK program from LINKAGE software package (versions. 1). Two-point LOD score were calculated at recombination rates ( 9 )from 0.000 to 0.5 assuming the male and the female has equal recombination rates. An autosomal domimant model was used with 90%, 80%, 70%, 60%, 50% penetrance assuming frequency of disease gene for BFIC to be 0.001. According to the LOD scores, the linkage relations between STR markers and the gene for BFIC was judged. The test for heterogeneity was carried out for the results of pairwise analysis with positive loci. It was preformed by the genetic analysis program HOMOGM.Results: The results produced by MLINK program are as follows: In three pedigrees including HY-01, CY-01 and CY-02, the maximum sum two-point LOD score of 2.151 for D16S3131 was obtained at recombination rates of 0.000 under autosomal dominant model with 90% penetrance. The LOD score of 2.151, which over 1 and under 3, suggested that D16S3131 maybe linked to the disease gene for BFIC. In pedigrees XY-01 and QX-01, the two-point LOD score was negative at recombination rates between 0.000 and 0.2 under autosomal dominant model.For D19S250, the maximum sum two-point LOD score of 1.056 and 1.155 were obtained at recombination rates of 0.085 under autosomal dominant model with 70% and 60% penetrance in two pedigrees including HY-01 and CY-01. Another maximum sum two-point LOD score of 1.227 was obtained at recombination rates of 0.080 under autosomal dominant model with 50% penetrance in these two pedigrees. The LOD score of 1.056, 1.155 and 1.227, which over 1 and under 3, suggested that D19S250 maybe linked to the disease gene for BFIC. In pedigrees CY-02, XY-01 and QX-01, the two-point LOD score was negative at recombination rates between 0.000 and 0.1 under autosomal dominant model. These tesults suggested there were locus heterogeneity among these BFIC pedigrees.For the other DNA markers, including D2S399, D2S2330, D16S3133 and D19S245, there were no evidence can support linkage.The results produced by HOMOGM program showed thait there were locus heterogeneity in BFIC. Among these five pedigrees, a proportion of 39.8% families was probably linked to D16S3131, a proportion of 41.3% families was probably linked to D19S250, a proportion of 18.8% families was probably unlinked to any of the two loci.Conclusion: According to these results, three conclusion can be drawn. Firstly, thedisease gene for some BFIC pedigrees maybe linked to D16S3131...