All issues > Volume 45(3); 2002

Original Article

J Korean Pediatr Soc. 2002;45(3):302-310. Published online March 15, 2002.

Characterization of Mutations in Bruton's Tyrosine Kinase(Btk) Gene from Unrelated 3 X-linked Agammaglobulinemia(XLA) Families in Korea

Chang-Hwa CH Song¹, Eun-Kyeong EK Jo¹, Jeong-Kyu JK Park¹, Jung-Soo JS Kim², Soo-Jong SJ Hong³, Jae-Ho JH Lee⁴

¹Department of Microbiology, College of Medicine, Chungnam National University, Taejon, Korea
²Department of Pediatrics, College of Medicine, Chungnam National University, Taejon, Korea
³Department of Pediatrics, College of Medicine, Chunbuk National University, Chunju, Korea
⁴Department of Pediatrics, Asan Medical Center, College of Medicine, Ulsan University, Seoul, Korea

Correspondence Jae-Ho JH Lee ,Email: immlee@cnu.ac.kr

Abstract

Purpose
: X-linked agammaglobulinemia(XLA) is an immunodeficiency caused by abnormalities in Bruton's tyrosine kinase(Btk), and is characterized by a deficiency of peripheral blood B cells. We studied cytoplasmic expression of Btk protein and analyzed the Btk gene in peripheral blood mononuclear cells(PBMC) from three XLA families in Korea.
Methods
: Heparinized venous blood samples were collected from four XLA patients and additional family members in three unrelated XLA families. Mononuclear cells were separated from their blood and the intracellular Btk protein was characterized by a flow cytometry. The mutation analysis was performed using direct sequencing.
Results
: Cytoplasmic expression of Btk protein in monocytes was not detected in the patients with XLA. We observed a novel deletion and two point mutations within introns(intron 1 and intron 18) resulting in alternative splicings. In XLA family 2, a 980 bp deletion(from intron 9＋191 T to intron 10-215 C) including exon 10 was found in patient P2. He was the only sporadic case in this study, because his mother and brother showed a normal Btk expression by flow cytometry.
Conclusion
: These identified genetic alterations support the molecular heterogeneity of Btk gene in XLA disease. Additionally, by means of flow cytometric analysis, we diagnosed three hypogammaglobulinemia patients as XLA. Advancements in diagnostic methods has facilitated a prompt and definite diagnosis of this disease.

Keywords :Bruton's tyrosine kinase, X-linked agammaglobulinemia, Direct sequencing, Flow cytometry, Carrier detection