Analysis of Wilson disease mutations in copper binding domain of ATP7B gene

Abstract

Wilson's disease (WD) is an autosomal recessive disorder, resulting from variations in ATP7B gene. Clinical heterogeneity, including neuropsychiatric and hepatic manifestations over a large range of age groups make diagnosis difficult. Most of WD patients suffer severe disabilities and even die. So, overall goal of proposed study is the genetic and clinical characterization of Wilson's disease cases from Pakistani population. Clinical data was collected, and patients were investigated for variations in selected ATP7B exons using PCR based Sanger sequencing. Pathogenic effect predictions for detected variants were carried out using PROVEAN, MutationTaster2, and HSF software's. Clinical heterogeneity was observed in patients including reduced serum ceruloplasmin, signs of chronic liver damage and raised 24 h urinary copper excretion. Mean age of onset was 11.3 years. Kayser-Fleischer rings were present in 75% of cases. About 82.5% patients belonged to inbred families. Patients having neurological disorder were above 12 years of age. Total ten variants in analyzed region of ATP7B gene, including a reported variation (p. L227Yfs*35) were found in patients. The study also identified 4 putative novel synonymous variants (c.251A>C, c.15T>A, c.6T>C, c.238C>T) and 5 reported polymorphisms (c.83C>A, c.39_40insCGGCG, p.V456L, c.39_40insCGCCG and c.1544-53A>C). Reliable understanding of clinical presentations and genotype-phenotype correlation provide insight to function and structure of ATP7B and may assist in disease prognosis and family counseling. The study revealed clinical presentation of Pakistani WD cases and identification of sequence variants in screened region of ATP7B.

Fig 1

(A) Graph showing decreased serum ceruloplasmin level in all patients suffering from WD as compared to normal serum ceruloplasmin level among patients enrolled in this study and (B) Graph showing increased copper concentration in urine than normal 200μg/d in patients included in this study.

Fig 2

(A) Demonstrating younger age of onset of patients with initial liver disease, compared to patients with neurological manifestations in a Pakistani cohort (B) Pathogenic effect prediction output of HSF program for variation L227Yfs*35).

Fig 3

(A) Pedigree of family of Patient WD-1 and Chromatogram of variation found in exon2 of ATP7B and (B) Chromatograms for Novel Variants found in ATP7B gene.