Mutation Identification And Functional Analysis Of Disease Gene In Three Chinese Families With Mendelian Susceptibility To Mycobacterial Disease

Mendelian Susceptibility to Mycobacterial Diseases（MSMD）is a rare immunodeficiency disease which is predisposition to clinical disease by weakly virulent mycobacteria,such as BCG and nontuberculous mycobacteria.In this study,we do the genetic analysis on three chinese families with MSMD.We identified the disease gene in these families and decipher the molecular mechanism of the disease by molecular biological methods.By DNA sequencing of the disease genes of MSMD,we identified three novel compound heterozygous mutations in IL12RB1 gene: The first proband carry a missense mutation（c.635 G > A,p.R212Q）and a deletion（c.764delG）in IL12RB1gene;The second proband was found a missense mutation（c.632 G > C,p.R211P）and a nonsense mutation（c.847 C > T,p.R283X）in IL12RB1 gene;The third proband was found a missense mutation（c.64 G > A,p.A22T）and a gene insertion（c.1673₁674insGAGCTTC CTGAG）in IL12RB1 gene.To study the effect of IL12RB1 gene mutations,we check the protein expression levels and localization of the mutant and wild-type IL12Rβ1 protein in HEK293 T and Hela cell lines.The results reveal that the mutation of IL12RB1 gene affected the protein expression and the protein location to cell membrane.There are no IL12Rβ1 protein expression when the cells transfected with mutant IL12RB1 gene（R283X,c.764 delG,c.1673₁674insGAGCTTCCTGAG）respectively.While three missense mutations reduce the expression level of IL12Rβ1in the cell and cell membrane.In this study,we identified three novel compound heterozygous mutations,R283 X,c.764 delG and c.1673₁674insGAGCTTCCTGAG mutations affected the expression of IL12Rβ1,R211 P,R212Q and A22 T mutations reduce the expression level of IL12Rβ1 in the cell and cell membrane,reduced IL12Rβ1 expression in the cell will decrease the expression level of INF-γ upon the Mycobacterial infection.The decrease of IFN-γ will leads the Susceptibility to Mycobacterial Diseases.