Mutation analysis and the correlation between genotype and phenotype of Arg778Leu mutation in Chinese patients with Wilson disease

Background: The defective gene (ATP7B) that causes Wilson disease (WD) codes for a putative copper-transporting P-type adenosine triphosphatase. After cloning of ATP7B, the spectrum of mutations and their clinical consequences have been investigated in patients with WD in different ethnic populations. However, the spectrum of mutations and the correlation of genotype and phenotype in the Chinese population have not been extensively studied. Objective: To investigate the characterization of mutations of ATP7B and the correlation between genotype and phenotype in the Chinese population. Methods: We studied 60 unrelated healthy Chinese and 65 unrelated Chinese families, including 84 patients with WD and 126 parents. Genomic DNA was prepared from peripheral blood leukocytes using a salt-precipitation method. Polymerase chain reaction single-strand conformation polymorphism and subsequent direct sequencing were used to identify the mutations and polymorphisms of ATP7B. Statistical analysis was performed using t lest or chi (2) test. Results: We identified 18 mutations (7 novel) and 11 polymorphisms (3 novel). The novel mutations are -36C -->T, TrpB50ter, Gln914ter, 2810delT, Thr935Met, Arg1041Pro, and Glu1173Lys. The novel polymorphisms are 1168A -->G (Ile390Val), 2785A -->G (Ile929Val), and 3316G -->A (Val1106Ile). Two mutations, Arg778Leu and Thr935Met, are relatively frequent, representing 37.7% and 10.0% of patients, respectively. To our knowledge, we are the first to report the correlation between the genotype and phenotype of Arg778Leu. The result shows that Arg778Leu homozygotes are associated with the early onset of WD with hepatic presentation. Conclusions: The Arg778Leu and Thr935Met mutations are hot spots in the Chinese population. The features of mutations of ATP7B differ between the Chinese and Western ethnic populations. The Arg778Leu mutation has severe effects on the function of ATP7B. These findings are valuable for developing a fast and effective method to diagnose the presence of the WD gene.