Molecular analysis and diagnosis in Japanese patients with Wilson's disease

Background: Wilson's disease is characterized by the toxic accumulation of copper in the liver, brain, cornea and other organs. It is caused by both impaired excretion via the bile and impaired incorporation of copper into ceruloplasmin in the liver. The Wilson's disease gene (ATP7B) has been cloned as a putative copper-transporting P-type ATPase gene. We therefore analysed mutations of ATP7B in Japanese patients with Wilson's disease. Methods: Twenty-three Japanese patients with Wilson's disease were investigated. In all patients, the ATP7B coding sequence, including exon-intron junctions, was analysed by restriction endonuclease digestion, mutation detected enhancement gel electrophoresis and/or direct sequencing analysis of amplified fragments. Results: Thirteen mutations were identified, including seven missense mutations, four deletions, one insertion and one exon skipping in the coding region. The most common mutations were 2874deletion(del)C in exon 13 and arginine (Arg)778 leucine (Leu) in exon 8. Discussion: None of the observed mutations, except for 2302insertion(ins)C, have been previously detected in either European or North American patients. We conclude that the mutation spectrum of Wilson's disease may thus indicate a population-dependent pattern. Based on the population-dependent manner of the occurrence of ATP7B gene mutations, it may be possible to establish a molecular diagnosis system. A molecular diagnosis system is considered to be very effective for making a definitive diagnosis in very young patients and for also detecting carriers.