ESPE Abstracts

Objective: X-linked agammaglobulinemia (XLA) is a kind of primary immunodeficiency disease caused by mutations in the gene encoding Bruton agammaglobulinemia tyrosine kinase (BTK). This study, we identified a novel in frame deletion mutation in exon11, c.902 _ c.904 delAAG(p.e301 _ g302 delinsG) in BTK gene and evaluated the function of BTK.

Methods: A five-year-old boy presented with recurrent respiratory tract infections. His height was 110.3 cm (M), his body weight was 17.5 kg, white blood cell count, immunoglobulin (IgG, IgA, IgM), immunoglobulin subtypes (Ig G1, Ig G2, Ig G3, Ig G4) and CD3, CD4, CD8 were detected. BTK gene exons of the patient and his parents were sequenced. Mutation and wild type recombinant plasmid (pEGFP-N1 vector) were constructed respectively, 293T cell and COS7 cell line were transfected, qPCR and western blot were detected.

Results: Agammaglobulinemia was detected as Ig G was 20.0 mg/dl (800–1800 mg/dl) and Ig G subtypes (G1, G2, G3, G4) were all very low. A novel in frame deletion mutation of BTK gene c.902 _ c.904 delAAG(p.E301 _ G302 delinsG) in a child was detected and no mutations of BTK in his parents were founded. In pEGFP-N1 vector, EGFP is the downstream gene of BTK gene. Fluorescence signal can be used to measure transcription level. The expression was no difference between BTK normal group and deletion group from the fluorescence intensity. By the result of western blot, The protein volume of normal type was higher than deletion type.

Conclusion: A novel in frame deletion mutation of BTK gene, c.902 _ c.904 delAAG (p.E301 _ G302 delinsG) of BTK gene was identified and it affects the protein stability after BTK translation, result to the typical clinical manifestation of XLA.