The Research Of RET Proto-oncogene Mutation In An MEN 2A Pedigree

[Object]Medullary thyroid carcinoma（MTC）is a kind of rare aggressive endocrine tumor arising from parafollicular C cells that produce calcitonin,and it exists in sporadic and hereditary forms.Hereditary medullary thyroid carcinoma（HMTC）is divided into 3 subtypes:multiple endocrine neoplasia type 2A（MEN 2A;55-60%）,multiple endocrine neoplasia type 2B（MEN 2B;5-10%）and familial MTC（35-40%）.It has been confirmed that germline mutations of RET proto-oncogene are the molecular pathogenesis basis of MEN 2A.Herein,we detected the germline mutations of RET proto-oncogene in an MEN 2A pedigree from Eastern China,not only can we understand the characteristics of mutations in this pedigree,but also screen out the individuals that carrying RET gene mutations,in order to guide them to get an early diagnosis and treatment as soon as possible.By studying the correlation between the mutations and disease,it can provide references for the early diagnosis of disease in this pedigree,and also we expect proper clinical management significance of MEN 2A patients.[Methods]In this study,subjects are MEN 2A patients and their relatives from the department of Otolaryngology Head and Neck Surgery of Jining Medical University Affiliated Hospital during the period between 2013 and 2015.Subjects were confirmed as MEN 2A patients by taking history,laboratory diagnosis and imaging examination.We collected basic information of the 46 subjects,extracted their peripheral blood genomic DNA,all the 21 exons in RET proto-oncogene were amplified by using polymerase chain reaction,the products were purified and then directly two-way sequenced.And we also analyzed all the mutations of RET gene,explored the relationship between these mutations and MEN 2A in this pedigree by linkage disequilibrium analysis and logistic regression analysis.[Result]（1）13 types of RET gene mutations were detected in this pedigree（p.A45Ap.F285S、C.854₈55CA、p.A432A、p.G691S、p.D707E、p.L769L、p.V778I、p.S904S、C.*15T>C、C.*167T>A、C.*731T>C、C.*1506G>A）.Of these,p.F285S in exon 4,c.854 855CA in exon 4 and p.D707E in exon 11 are reported for the first time in our study.（2）Both linkage disequilibrium analysis and logistic regression analysis showed a significant correlation between mutation p.D707E and MTC（LOD=3.69,OR=4.413,p=0.000167）,indicating that this mutation was a risk factor for MTC.（3）Single nucleotide polymorphisms（SNPs）G691S in exon 11 and S904S in exon 15（D’=1.0,r2=1.0,LOD=12.83）,rs2075912 and rs2565200 in 3’-untranslated region（UTR）of RET gene are in complete linkage disequilibrium（D’=1.0,r2=1.0,LOD=20.23）,no correlation of these SNPs and MTC were observed in this pedigree.（4）No hotspot mutations of RET gene were detected in this pedigree.[Conclusion]（1）Heterozygous non-synonymous mutation p.D707E in RET gene is rare,but a risk factor for MTC.