BTK Gene Mutation Analysis Of Agammaglobulinemia English

Background:X-linked (Bruton’s) agammaglobulinemia (XLA) is a rare immunodeficiency caused by a block in B-cell development by mutations in the Bruton’s tyrosine kinase (BTK) gene. Typical presentations of XLA have been reported, and no clear genotype-phenotype correlation has been established in XLA.Objective:We sought to contribute to the understanding of the mutation features in Chinese patients of X-linked agammagloblinemia through tne BTK gene mutation analysis of a cohort of clinical diagnosed XLA patients. We also sought to contribute to the understanding of the phenotype-genotype correlation of XLA through characterization of the area distribution, clinical and immunological phenotype.Methods:1. To measure the serum concentration of immunoglobuline and percentage peripheral blood B lymphocytes.2. Using anti-BTK monoclone antibody to measure the expression level of BTK protein by flowcytometry.3. The BTK mutations in XLA patients were detected using PCR and direct sequencing. Results were analyzed and blasted with data in the Genebank of Japan GenomeNet.Results:1. Fifty patients were diagnosed as XLA by clinical manifestation and laboratory findings.All of these patients had recurrent bacterial infections and low levels of serum immunoglobuline and peripheral blood B lymphocytes. The patients in this study mainly came from Shanghai, JiangSu, ZheJiang, JiangXi and HeNan Province.2. In our study,40 patients were identified to have BTK gene mutation including 16 cases of missense mutation,13 casesof nonsense mutation,4 cases of frame-shift insertion,4 cases of frame-shift deletion and 3 cases of splice-site mutation. These gene mutations distribute over the five protein domains and mainly locate in TK domain. Among these mutations,14 cases were new muatation types which had not been reported in international Btk database (http://bioinf.uta.fi/BTKbase).8 cases of missense mutations were occurred at CpG sites.26 mothers of the patients were confirmed be carriers of mutations.3. The average age of diagnosis of the XLA patients in our study is 5.5 years old. 50% of patients were diagnosed before age 6 and missense mutation maybe related to older age of dignosis. Although there seems no obvious relationship among different mutation types,numbers of circulating B cells and levels of immunoglobulines in serum, patients with some types of missense mutation tend to have relatively high levels of immunoglobulines and B cells comparing to other mutation types.Conclusions:There’s no clear genotype-phenotype correlation in Chinese XLA patients. Missense and nonsense mtation is the most frequent type of mutation in Chinesse XLA patients. Some types of missnese mutation may be related to relatively high levels of immunoglobulines and expression level of BTK protein. Polymorphic variant (2031T>C) in Exon 18 may partly contribute to the clinical phenotype of arthritis...