Mutational analysis of ATP7B in Chinese Wilson disease patients

Wilson Disease (WD) is an inborn error of copper metabolism inherited in an autosomal recessive manner caused by the mutations in the P-type ATPase gene (ATP7B). In this study, we screen and detect the mutations of the ATP7B gene in unrelated Chinese WD patients. A total of 68 individuals from ten provinces of China with WD were recruited. Of them, 43 were males and 25 were females, and their onset ages were from 1 to 48 years with a median onset age of 22.2 years. All the exons and exon/intron boundaries of ATP7B gene of the patients were sequenced and aligned to the referred ATP7B gene sequence. The results suggested that 66 of the 68 patents carried with at least one mutation and 48 different mutations were identified including 34 missense, one synonymous, two nonsense, two splicing, and nine frameshift mutations (five insertion and four deletion). Among these mutations, c.2333G>T, c.2310C>G, c.2975C>T, and c.3443T>C were the most prevalent mutants and c.2310C>G always linked with c.2333G>T. The eighth, 11(th), and 18(th) exons carried more mutations (6/48, 5/48, and 5/48, respectively) than others. After comparing with the mutations reported previously, 22 out of the 48 mutations were identified as novel mutations. A popular algorithm, Polyphen-2, was used to predict the effects of the amino-acid substitution due to the mutations on the structure and function of ATP7B function and the predicted results indicated that all the missense mutations were unfavorable except c.121A>G and c.748G>A. Phenotype/genotype correlation analysis suggested that the patients with c.2975C>T or c.3809A>G often presented WD features before 12 years old while the patients with c.3443T>C almost presented WD after 12 years old. This is the first time to identify the common mutations contributing to early onset age in Chinese WD patients. Our study will broaden our knowledge about ATP7B mutations in WD patients.