RNA analysis of consensus sequence splicing mutations: implications for thediagnosis of Wilson disease

Wilson disease (WD) is an autosomal recessive disorder caused by a defective function of the copper-transporting ATP7B protein. This results in progressive copper overload and consequent liver, brain, and kidney damage. Approximately 300 WD-causing mutations have been described to date. Missense mutations are largely prevalent, while splice-site mutations are rarer. Of these, only a minority are detected in splicing consensus sequences. Further, few splicing mutations have been studied at the RNA level. In this study we report the RNA molecular characterization of three consensus splice-site mutations identified by DNA analysis in WD patients. One of them, c.51 + 4 A --> T, resides in the consensus sequence of the donor splice site of intron 1; the second, c. 2121 + 3 A --> G, occurred in position + 3 of intron 7; and the c.2447 + 5 G --> A is localized in the consensus sequence of the donor splice site of intron 9. Analysis revealed predominantly abnormal splicing in the samples carrying mutations compared to the normal controls. These results strongly suggest that consensus sequence splice-site mutations result in disease by interfering with the production of the normal WD protein. Our data contribute to understanding the mutational spectrum that affect splicing and improve our capability in WD diagnosis

Acute gallbladder hydrops and arthritis: unusual initial manifestations of Wilson’s disease (WD)

Wilson disease (WD) is an autosomal recessive disorder, in which copper is deposited in the liver, brain, cornea and kidneys. The clinical presentation is variable, with fully expressed disease manifesting cirrhosis, neurologic damage and Kayser-Fleischer (K-F) ring on the cornea. A 24-year-old patient developed right upper quadrant pain with a palpable mass and a swelling of the right talocrural articulation. X-rays were uneventful, but the routine examination of hepatic enzymes discovered a 6–8 fold increase in SGPT, SGOT and AST. Antibodies for hepatitis B, C were normal, as well as the ANA, ANCA, antimytochondrial and anti-smooth muscle antibodies. Ultrasound of the abdomen revealed extremely dilated hepatic, cystic ducts as well as gallbladder. A large, oedematous gallbladder with yellow green bile was removed, the liver was found to be cirrhotic, but as the operative bleeding was abundant a biopsy was not done. Serum ceruloplasmin was low [0.160 g/l (normal 0.204–0.407)], serum copper 12.7 μmol/l (11.0–24.4), transaminasis: always very high, in the last months normal/slightly elevated. Urine copper: 1.0 μmol/24h (> 9.44). As first seen the proband had tremor, dysarthria, dystonia and KF ring on the cornea. After 10 months of treatment with penicillamine his transaminases normalized, the tremor, dysarthria, dystonia initially got worse and then ameliorated. The coagulation times are ameliorated, but not yet normalized. Mutational analysis has shown that the proband is homozygote for c.3207 C- > A, p.H1069Q while his parents are heterozygotes. His sister is a healthy non-carrier. In brief, we describe an unusual presentation of WD, with gallbladder hydrops and talocrural arthritis in a patient with complete clinical manifestations of the disease

The homozygosity index (HI) approach reveals high allele frequency for Wilson disease in the Sardinian population

Wilson disease (WD) is an autosomal recessive disorder resulting in pathological progressive copper accumulation in liver and other tissues. The worldwide prevalence (P) is about 30/million, while in Sardinia it is in the order of 1/10 000. However, all of these estimates are likely to suffer from an underdiagnosis bias. Indeed, a recent molecular neonatal screening in Sardinia reported a WD prevalence of 1:2707. In this study, we used a new approach that makes it possible to estimate the allelic frequency (q) of an autosomal recessive disorder if one knows the proportion between homozygous and compound heterozygous patients (the homozygosity index or HI) and the inbreeding coefficient (F) in a sample of affected individuals. We applied the method to a set of 178 Sardinian individuals (3 of whom born to consanguineous parents), each with a clinical and molecular diagnosis of WD. Taking into account the geographical provenance of the parents of every patient within Sardinia (to make F computation more precise), we obtained a q \ubc 0.0191 (F \ubc 7.8 10 4, HI \ubc 0.476) and a corresponding prevalence P \ubc 1:2732. This result confirms that the prevalence of WD is largely underestimated in Sardinia. On the other hand, the general reliability and applicability of the HI approach to other autosomal recessive disorders is confirmed, especially ifone is interested in the genetic epidemiology of populations with high frequency of consanguineous marriages

DNA and RNA studies for molecular characterization of a gross deletion detected in homozygosity in the NH2-terminal region of the ATP7B gene in a Wilson disease patient.

Wilson disease is an autosomal recessive disorder caused by defective function of the copper transporting protein ATP7B. Approximately 520 Wilson disease-causing mutations have been described to date. In this study we report the use of DNA and RNA analysis for molecular characterization of a gross deletion of the ATP7B gene detected in homozygosity in a Wilson disease patient. The c.51+384_1708-953del mutation spans an 8798 bp region of the ATP7B gene from exon 2 to intron 4. The results obtained suggest that the combination of DNA and RNA analyses can be used for molecular characterization of gross ATP7B deletions, thus improving genetic counselling and diagnosis of Wilson disease. Moreover these studies, help to better establish the molecular mechanisms producing Wilson disease

RNA analysis of consensus sequence splicing mutations: implications for the diagnosis of Wilson disease

Wilson disease (WD) is an autosomal recessive disorder caused by a defective function of the copper-transporting ATP7B protein. This results in progressive copper overload and consequent liver, brain, and kidney damage. Approximately 300 WD-causing mutations have been described to date. Missense mutations are largely prevalent, while splice-site mutations are rarer. Of these, only a minority are detected in splicing consensus sequences. Further, few splicing mutations have been studied at the RNA level. In this study we report the RNA molecular characterization of three consensus splice-site mutations identified by DNA analysis in WD patients. One of them, c.51 + 4 A --> T, resides in the consensus sequence of the donor splice site of intron 1; the second, c. 2121 + 3 A --> G, occurred in position + 3 of intron 7; and the c.2447 + 5 G --> A is localized in the consensus sequence of the donor splice site of intron 9. Analysis revealed predominantly abnormal splicing in the samples carrying mutations compared to the normal controls. These results strongly suggest that consensus sequence splice-site mutations result in disease by interfering with the production of the normal WD protein. Our data contribute to understanding the mutational spectrum that affect splicing and improve our capability in WD diagnosis

Mutation analysis of the ATP7B gene in a new group of Wilson's disease patients: Contribution to diagnosis.

Wilson's disease (WD), an autosomal recessive disorder of copper transport with a broad range of genotypic and phenotypic characteristics, results from mutations in the ATP7B gene. Herein we report the results of mutation analysis of the ATP7B gene in a group of 118 Wilson disease families (236 chromosomes) prevalently of Italian origin. Using DNA sequencing we identified 83 disease-causing mutations. Eleven were novel, while twenty one already described mutations were identified in new populations in this study. In particular, mutation analysis of 13 families of Romanian origin showed a high prevalence of the p.H1069Q mutation (50%). Detection of new mutations in the ATP7B gene in new populations increases our capability of molecular analysis that is essential for early diagnosis and treatment of WD

Twenty-four novel mutations in Wilson disease patients of predominantly Italian origin

Herein we report the results of mutation analysis of the ATP7B gene in a group of 134 Wilson disease (WD) families (268 chromosomes) prevalently of Italian origin. Using the SSCP and sequencing methods we identified 71 disease-causing mutations. Twenty-four were novel, while 19 more mutations already described, were identified in new populations in this study. A known mutation G591D showed a regional distribution, since it was only detected in 38.5% of the analyzed chromosomes in WD patients originating from Apulia, a region of South Italy. Detection of new mutations in the ATP7B gene increases our capability of molecular analysis that is essential for early diagnosis and treatment of WD