Maria Barbara Lepori

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=0.0191 (F=7.8 × 10−4, HI=0.476) and a corresponding prevalence P=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 if one is interested in the genetic epidemiology of populations with high frequency of consanguineous marriages.

The canine copper toxicosis gene MURR1 is not implicated in the pathogenesis of Wilson disease

BackgroundIt has recently been demonstrated that the Wilson disease (WD) protein directly interacts with the human homolog of the MURR1 protein in vitro and in vivo, and that this interaction is specific for the copper transporter. The aim of the present study was to clarify the role of MURR1 in the pathogenesis of WD as well as in other WD-like disorders of hepatic copper metabolism of unknown origin.MethodsUsing the single-strand conformation polymorphism (SSCP) method followed by sequencing, we analyzed the 5′ untranslated region (UTR) and three exons of the MURR1 gene in three groups of patients: 19 wd patients in whom no mutations were detected in the ATP7B gene, 53 wd patients in whom only one mutation in the ATP7B gene was found, and 34 patients in whom clinical and laboratory data suggested a WD-like disorder of hepatic copper metabolism of unknown origin.ResultsWe  detected in these patients six rare nucleotide substitutions, namely one splice-site consensus sequence and one missense and four silent nucleotide substitutions. All substitutions except one were found in the heterozygous state. No difference in the frequencies of the various substitutions was observed between patients and controls.ConclusionsThese data suggest that the MURR1 gene and its protein product are unlikely to play a primary role in the pathogenesis of Wilson disease. More extensive studies with larger numbers of clinically homogeneous patients should be carried out to establish whether nucleotide alterations in the MURR1 gene may have a role in causing WD or WD-like disorders or act as modifying factors in the phenotype variability in WD.

Analysis of the T1288R mutation of the wilson disease ATP7B gene in four generations of a family : Possible genotype-phenotype correlation with hepatic onset

Wilson disease, an autosomal recessive disorder due to mutations of the ATP7B gene, is characterized by copper accumulation and toxicity in the liver and subsequently in other organs, mainly the brain and cornea. A new missense mutation (T1288R) of the ATP7B gene has recently been discovered in a Wilson disease patient in our laboratory. The aim of the present study was to analyze clinical and genetic features of more generations of the family of the patient in which the new mutation T1288R was discovered. A total of 19 subjects were studied; in particular, four generations of the patient’s family were analyzed. The ATP7B gene was analyzed by single-strand conformational polymorphism followed by direct sequencing. Two brothers presented a clinical diagnosis of Wilson disease with an hepatic phenotype and a genotype characterized by the homozygotic mutation T1288R. The heterozygotic mutation T1288R was found in seven subjects belonging to all four generations. The present study represents the first screening for a Wilson disease mutation through four generations of a nonconsanguineous family. All the patients with the homozygotic T1288R mutation in the present pedigree presented an hepatic phenotype without a neurological presentation. Consequently, a genotype-phenotype correlation could be hypothesized, although further studies are necessary to clarify this topic.

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

Wilsons 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.

A new mutation of Wilson's disease P-type ATPase gene in a patient with cirrhosis and coombs-positive hemolytic anemia.

Wilson’s disease (WD) is an autosomal recessive disorder of hepatic copper metabolism with consequent copper accumulation and toxicity in the liver and in other tissues and with a prevalence of approximately 1:30,000 individuals (1). Liver disease, neurological and psychiatric disorders, and a combination of these are the most common clinical manifestations of WD (2, 3). A classic ocular involvement is represented by Kayser-Fleischer rings; less common clinical features include Fanconi syndrome, Coombs-negative hemolytic anemia, hypothyroidism, and hypoparathyroidism (2, 4). The most appropriate therapy, including the pharmacological approach and the orthotopic liver transplantation, remains controversial (5–9). The WD gene, ATP 7B, consisting of 21 exons, has been isolated on the long arm of chromosome 13 (13q14.1) (10– 12) and encodes a copper-transporting P-type adenosine triphosphatase (ATPase) (1). In hepatocytes, this ATPase resides in the trans-Golgi network transporting copper into the secretory pathway for incorporation into apoceruloplasmin and excretion of copper into the bile (8). Molecular analysis of patients and families with WD has demonstrated more than 200 unique mutations including missense and nonsense mutations, deletions, and inser-

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.

Development of TaqMan allelic specific discrimination assay for detection of the most common Sardinian Wilson's disease mutations. Implications for genetic screening

Wilsons disease (WD) is an autosomal recessive disorder caused by a defective function of the copper transporting ATP7B protein. Analysis of ATP7B gene in the Sardinian population revealed the presence of six common mutations that together account for 85% of WD chromosomes. We have developed an automated approach for the detection of these 6 common Sardinian mutations based on TaqMan technology. Ten DNA samples of WD patients carrying different combinations of the six most common Sardinian mutations and normal controls previously analysed were used in triplicate to set up the allelic discrimination assays. The system was validated in 96 samples obtained from WD patients carrying different combinations of the most common mutations under investigation. The results showed that allelic discrimination is a valid method that could be used for efficient diagnosis of single cases but also for a mass screening.

Wilson's disease caused by alternative splicing and Alu exonization due to a homozygous 3039-bp deletion spanning from intron 1 to exon 2 of the ATP7B gene.

We describe a case of Wilsons disease (WD) diagnosed at 5 years after routine biochemical test showed increased aminotransferases. Mutation analysis of the ATP7B gene revealed a 3039-bp deletion in the homozygous state spanning from the terminal part of intron 1 to nt position 368 of exon 2. This deletion results in the activation of 3 cryptic splice sites: an AG acceptor splice site in nt positions 578-579 producing a different breakpoint and removing the first 577 nts of exon 2, an acceptor and a donor splice site in nt positions 20363-4 and 20456-7, respectively, in intron 1, resulting in the activation of a 94-bp cryptic Alu exon being incorporated into the mature transcript. The resulting alternative transcript contains a TAG stop codon in the first amino acid position of the cryptic exon, likely producing a truncated, non-functional protein. This study shows that intron exonization can also occur in humans through naturally occurring gross deletions. The results suggest that the combination of DNA and RNA analyses can be used for molecular characterization of gross ATP7B deletions, thus improving genetic counseling and diagnosis of WD. Moreover these studies help to better establish new molecular mechanisms producing Wilsons disease.

“Acquired” hepatocerebral degeneration in a patient heterozygote carrier for a novel mutation in ATP7B gene

Acquired hepatocerebral degeneration (AHD) is a rare type of hepatic encephalopathy characterized by neuropsychiatric symptomatology, and peculiar neuroradiologic findings, without the clinical evidence of Wilson’s disease (WD). We studied a patient with AHD responsive to penicillamine who was heterozygote carrier for a novel mutation in the ATP7B gene, and discussed the possible role of the mutation in facilitating the appearance of the syndrome. A 37-year-old man with liver cirrhosis related to chronic hepatitis C was admitted because of progressive consciousness impairment. Family history was negative for WD. Ammoniemia was 176 lmol/L (NR, 9–33 lmol/L); total bilirubin 1.71 mg/dL (NR, 0.2–1.3 mg/dL); serum albumin 2.6 g/dL (NR, 3.3–5 g/dL); AST 62 U/L (NR, 10–45 U/L). Electroencephalogram disclosed diffuse slow wave activity. After rifaximin, lactulose, and branched chain amino acid infusion, his arousal state went back normal in about 12 hours, and ammonia levels decreased to 94 lmol/L.

Acute Liver Failure Because of Wilson Disease With Overlapping Autoimmune Hepatitis Features: The Coexistence of Two Diseases?

WCC, 10/L 6.2 8.5 4.5–13 Hb, g/dL 9.1 7.1 12–15.2 Hct, % 25 20.1 36–47 Reticulocyte, % 6.58 — 0.5–1.5 Haptoglobin, mg/dL <5.83 — 0–200 PLT, 10/L 73 38 150–450 TB, mg/dL 10.7 16.10 0.2–1.1 CB, mg/dL 4.4 7.6 0.1–0.3 A failure and death (1). Wilson disease (WD), an autosomal recessive disease of copper transport, is owing to mutation in ATP7B (2). Establishing the diagnosis of WD in the setting of ALF is critical because it allows treatment for prompt removal of serum copper and stabilization of the patient to facilitate lifesaving orthotopic liver transplantation (OLT). Autoimmune hepatitis (AIH) is a progressive inflammatory liver disorder characterized serologically by high levels of transaminases and immunoglobulin G, and presence of autoantibodies, and histologically by interface hepatitis in the absence of known etiology (3). Unlike patients with ALF owing to WD, patients presenting with ALF owing to AIH may respond better to medical treatment with immunosuppressive agents, therefore circumventing the need for liver transplantation. Herein we report a case of ALF caused by WD showing strong autoimmune features.