Correlation of ATP7B genotype with phenotype in Chinese patients with Wilson disease

Abstract

Aim: To determine the mutational characterization of P-type ATP7B gene and to explore the correlation of ATP7B genotype to phenotype in Chinese patients with Wilson disease (WD).

Methods: Seventy-five patients with WD from 72 no-kinship families, 44 males and 31 females, were enrolled in this study. The age of onset ranged from 4 to 39 years, <=18 years in 72 patients. Some exons of ATP7B gene mutations were analyzed in patients with WD by using biochemical methods, polymerase chain reaction-single strand configuration polymorphism (PCR-SSCP) and DNA sequence analysis. A total of 778 coding regions were identified with restriction enzyme Msp I. The activity of Cu-ATPase was assessed by measuring inorganic phosphorus.

Results: Sixty-six of 75 patients (88%) had with hepatic manifestations, 39 of them had only hepatic manifestations, 27 patients had hepatic and neurological manifestations or other symptoms at the same time (16 patients had associated neurological manifestation, 3 patients had osteopathy, 8 patients had other symptoms). Eight of the 75 patients (10.7%) had only neurological symptoms, one patient (5 years old) had no symptom. Twelve changing patterns were detected in ATP7B gene by DNA sequencing, including seven mutations (R778L, C656X, G943D, V1140A, V1106I V1216M and 1384del17), six polymorphisms (IVS4-5t/c, A2495G, C2310G, IVS18+6c/t and IVS20+5a/g). R778L occurred in 49/66 patients (74%) with hepatic manifestations, homozygosis of R778L in 16 patients, heterozygosity of R778L in 33 patients. V1106I mutation of ATP7B gene occurred in 2 patients with delaying onset of clinical symptoms. Cu-ATPase activity of three patients with known mutations (R778L/V1106I/A2495G, R778L/V1216M and R778L/R778L) were determined, and the activity of Cu-ATPase was decreased by 44.55%, 88.23% and 69.49% respectively.

Conclusion: 1384del17bp is a novel mutation found in WD patients. R778L is the most common mutation of ATP7B gene. There is a correlation between R778L and hepatic manifestations in WD patient.

Figure 1

Family analysis of patient 038. A: Patients father carrying 1384Del17bp (ATP7B genes position 1384-1400 bp deletion). B: Msp I digested PCR product of ATP7B gene exon 8 of patients mother shows that she was R778L carrier. C and D: Patients genotypes are R778L/1384Del17 bp, 1384Del17 bp from his father and R778L from his mother.

Figure 2

Nucleic acid sequence of PCR products of WD gene. A: Gly943Asp(G943D) heterlozygous for a G-A mutation at position 2828, B: Val1140Ala (V1140A) heterlozygous for a T-C mutation at position3419, C: Val1106Ile (V1106I) heterlozygous for aG-A mutation at position3316, D: Val1216Met (V1216M) heterlozygous for a G-A mutation at position 3646.E. and F: Arg778 Leu (R778L) homolozygous and heterzygous for a G-T mutation at position 2333.