Mutation Analysis Of TSC1 And TSC2 Gene In Patients With Tuberous Sclerosis Complex

Background: Tuberous sclerosis complex is an autosomal dominant genetic disease,characterized by facial angiofibromas,epilepsy,intellectual disability and development of hamartomas in several organs.Hamartomas developed in the heart,kidney,brain,and other systems,and mostly were benign tumor,rarely were malignance.The disease was caused by mutations in one of two genes,TSC1 or TSC2 gene,which were located in 9q34 and 16p13.3 and encoded the proteins hamartin and tuberin,respectively.These two kinds of protein widely expressed in the organization in the body and form a heterodimer which lies at the crossroad of many signalling pathways.If mutations happened in either TSC1 or TSC2 gene,it would result in dysregulated mTOR activation,leading to the occurrence of tuberous sclerosis complex.Currently TSC1 and TSC2 gene mutations were reported frequently,which not only enrich the TSC1 and TSC2 gene mutation spectrum,but also lay a theoretical foundation for the study of the correlation between genotype and phenotype.In the study,we collected the clinical data from three families and two sporadic cases of tuberous sclerosis complex of Han nationality in Sichuan Province,China.For proband and sporadic cases,mutation analyses of TSC1 and TSC2 gene were performed by direct sequencing.Objective: To identify pathogenic mutations of TSC1 and TSC2 gene in three families and two sporadic cases with tuberous sclerosis complex(TSC)of Han nationality in Sichuan Province,China.Methods: We collected blood samples and clinical data from three families and two sporadic cases.Genomic DNA was extracted from peripheral blood of the proband and the sporadic cases.Polymerase chain reaction(PCR)was used to amplify all the exons and exon-intron flanking sequences of TSC1 and TSC2 genes,and the products were analyzed by direct sequencing.Finally the results were analysed by Chromas 2.0 to identify new pathogenic mutations.Results: One novel missense mutation c.1964C>T(P.S655F)from the first familial case was detected in the exon 19 of the TSC2 gene,leading to 1964 th nucleotide C was substituted by T(655th amino acid serine was substituted by phenylalanine);One novel mutation c.1119-1120insA(p.S374KfsX2)from the first sporadic case was detected in the exon 11 of the TSC1 gene leading to a early stop codon TAA behind the 2th amino acids;One repeat deletion mutation c.5238-5255delCATCAAGCGGCTCCGCCA(p.his1746GlnfsX56)from the second sporadic case was detected in the exon 40 of the TSC2 gene leading to a early stop codon TGA behind the 56 th amino acids.Conclusion: The novel missense mutation c.1964 C>T(P.S655F)and the novel insertion mutation c.1119-1120insA(p.S374KfsX2)may be the underlying cause of the first familial and the first sporadic case with TSC respectively.The deletion mutation 5238-5255 delCATCAAGCGGCTCCG CCA(p.his1746GlnfsX56)of TSC2 may be the underlying cause of the second sporadic case with TSC.