[Genetic analysis of two patients with adenosine deaminase (ADA)-deficiency: detection of three novel mutations and characterization of two paradoxical carriers].
Genetic basis of two patients (AT, MT) with ADA deficiency was studied. We identified three novel mutations (119 Q-->Stop, 235 R-->Q, one base deletion in Exon 4) from the patients. 119 Q-->Stop was detected in AT and her father. Deletion of one base in Exon 4 which would change the reading frame after codon 105 H, was detected in MT, her father and brother. There was no relation between the two families, however, 235 R-->Q was also detected in both the patients and their mothers. Extremely low ADA activity of PBMCs was revealed in healthy MT's mother and brother just as MT, although their dAXP levels of RBCs showed significantly lower than that of MT. We defined that they shared an additional mutation (310 M-->T) together with the mutation described above, respectively. EBV-transformed B-cell line (EBV-B) were established from the carriers. To our surprise, ADA activity of their lines was 1/10-1/5 of normal. The result of heat treatment studies using the EBV-B showed that the mutant ADA rapidly lose its enzyme activity without degradation of the protein. It suggests that 310 M-->T mutant ADA rapidly lost its enzyme activity due to conformational change of the catalytic site of ADA.
Oda
N
N
Department of Human Gene Therapy, Hokkaido University School of Medicine.
Ariga
T
T
Ono
S
S
Kobayashi
I
I
Kawamura
N
N
Okano
M
M
Kobayashi
Y
Y
Taniuchi
S
S
Terada
K
K
Kataoka
N
N
Sakiyama
Y
Y
D000243:Adenosine Deaminase / Q000172:deficiency* / Q000235:genetics*; D002648:Child; D005260:Female; D006579:Heterozygote; D006801:Humans; D009154:Mutation; D016511:Severe Combined Immunodeficiency / Q000201:enzymology / Q000235:genetics*
D000243:Adenosine Deaminase