Mutation analysis of the ATP7B gene and genotype–phenotype correlation in Chinese patients with Wilson disease

Abstract

Aim To discover the novel ATP7B mutations in 103 southern Chinese patients with Wilson disease (WD), and to determine the spectrum and frequency of mutations in the ATP7B gene and genotype–phenotype correlation in a large-scale sample of Chinese WD patients. Methods One hundred three WD patients from 101 unrelated families in southern China were enrolled in this study. Genomic DNA was extracted from the peripheral blood. Direct sequencing of all 21 exons within ATP7B was performed. Subsequently, an extensive study of the overall spectrum and frequency of ATP7B mutations and genotype–phenotype correlation was performed in all Chinese patients eligible from the literature, combined with the current southern group. Results In 103 patients with WD, we identified 48 different mutations (42 missense mutations, 4 nonsense mutations and 2 frameshifts). Of these, 3 mutations had not been previously reported: c.1510_1511insA, c.2233C>A (p.Leu745Met) and c.3824T>C (p.Leu1275Ser). The c.2333G>T (p.Arg778 Leu) at exon 8, was the most common mutation with an allelic frequency of 18.8%, followed by c.2975C>T (p.Pro992Leu) at exon 13, with an allelic frequency of 13.4%. In the comprehensive study, 233 distinct mutations were identified, including 154 missense mutations, 23 nonsense mutations and 56 frameshifts. Eighty-five variants were identified as novel mutations. The c.2333G>T (p.Arg778 Leu) and c.2975C>T (p.Pro992Leu) were the most common mutations, with allelic frequencies of 28.6% and 13.0%, respectively. Exons 8, 12, 13, 16 and 18 were recognised as hotspot exons. Phenotype–genotype correlation analysis suggested that c.2333G>T (p.Arg778 Leu) was significantly associated with lower levels of serum ceruloplasmin (P = 0.034). c.2975C>T (p.Pro992Leu) was correlated with earlier age of disease onset (P = 0.002). Additionally, we found that the c.3809A>G (p.Asn1270Ser) mutation significantly indicated younger onset age (P = 0.012), and the c.3884C>T (p.Ala1295Val) mutation at exon 18 was significantly associated with hepatic presentation (P = 0.048). Moreover, the patients with mixed presentation displayed the initial WD features at an older onset age than the groups with either liver disease or neurological presentation (P = 0.039, P = 0.015, respectively). No significant difference was observed in the presence of KF rings among the three groups with different clinical manifestations. Conclusion In this study, we identified three novel mutations in 103 WD patients from the southern part of China, which could enrich the previously established mutational spectrum of the ATP7B gene. Moreover, we tapped into a large-scale study of a Chinese WD cohort to characterise the overall phenotypic and genotypic spectra and assess the association between genotype and phenotype, which enhances the current knowledge about the population genetics of WD in China.

Clinical and genetic characterization of pediatric patients with Wilson’s disease from Yunnan province where ethnic minorities gather

“…The exons that were hotspots were examined in the 39 WD patients. The results showed that exons 8 and 18 harbored the highest percentage of mutations, which was not consistent with previous results that exons 8, 13 and 16 were the hotpot exons in the Chinese population ( Li et al, 2021 ). This result may be due to the differences between Han individuals and ethnic minorities.…”

“…The top five most common mutations in our study were c.2333G > T (p.R778L), c.2975C > T (p.P992L), c.2621C > T (p.A874V), c.3809A > G (p.N1270S) and c.2804C > T (p.T935M), which is not consistent with other reported studies (p.R778L, p.P992L, p.A874V, p.R919G and p.V1216M) ( Li et al, 2021 ). Mutation hotspots in ATP7B vary by geographic region, with a higher prevalence of specific mutations reported in certain populations ( Wallace and Dooley, 2020 ).…”

“…Three out of the six severely affected patients were from ethnic minorities. Several studies have shown that clinically asymptomatic patients have an earlier age of onset than patients with typical clinical manifestations ( Li et al, 2021 ; Zhang et al, 2022 ). In our study, most pediatric patients presented with abnormal liver enzymes, without symptoms.…”

Genetic studies discover novel coding and non‐coding mutations in patients with Wilson's disease in China

“… 28 , 29 Traditionally, the diagnosis of WD mainly depends on clinical manifestations and routine biochemical indexes, including hepatic copper content, 24‐hour elevated urinary copper, and decreased serum CP. 30 However, patients with mild symptoms may be misdiagnosed, resulting in delayed treatment. 20 Gene detection of ATP7B gene mutation may lead to reliable early diagnosis and treatment to prevent copper accumulation and tissue damage.…”

Role of serum ceruloplasmin in the diagnosis of Wilson's disease: A large Chinese study

“…Moreover, no significant difference was detected in ceruloplasmin levels in WD patients with or without K–F rings ( 6 ). In addition, some studies observed lower serum ceruloplasmin levels in patients with R778L homozygous mutations than in patients without R778L mutations ( 21 ). Another study reported that low serum ceruloplasmin levels were associated with truncating mutations in the ATP7B gene ( 22 ).…”