Wilson disease

Wilson disease (WD) is an autosomal recessive inherited disorder of copper metabolism, resulting in pathological accumulation of copper in many organs and tissues. The hallmarks of the disease are the presence of liver disease, neurologic symptoms, and Kayser-Fleischer corneal rings. The leading neurologic symptoms in WD are dysathria, dyspraxia, ataxia, and Parkinsonian-like extrapyramidal signs. Changes in the basal ganglia in brain magnetic resonance imaging (MRI) are characteristic features of the disease. In presence of liver cirrhosis, some features may resemble hepatic encephalopathy. Symptoms and MRI abnormalities may be fully reversible on treatment with zinc or copper chelators. Improvement can be monitored by serial recording of brain-stem-evoked responses. The basic defect is an impaired trafficking of copper in hepatocytes. ATP7B is the gene product of the WD gene located on chromosome 13 and resides in hepatocytes in the trans-Golgi network, transporting copper into the secretory pathway for incorporation into apoceruloplasmin and excretion into the bile. While about 40% of patients preset with neurologic symptoms, little is known about the role of copper and ATP7B in the central nervous system. In some brain areas, like in the pineal gland, ATP7B is expressed and functionally active. Increasing evidence supports an important role for metals in neurobiology. Two proteins related to neurodegeneration are copper-binding proteins (1) the amyloid precursor protein (APP), a protein related to Alzheimer's disease, and (2) the Prion protein, related to Creutzfeldt-Jakob disease. A major source of free-radical production in the brain derives from copper. To prevent metal-mediated oxidative stress, cells have evolved complex metal transport systems. APP is a major regulator of neuronal copper homeostasis and has a copper-binding domain (CuBD). The surface location of this site, structural homology of CuBD to copper chaperones, and the role of APP in neuronal copper homeostasis are consistent with the CuBD acting as a neuronal metallotransporter. There are several copper-containing enzymes in the brain, like dopamine beta hydroxylase or Cu/Zn superoxide dismutase (SOD1). Their function may be altered because of copper overload. WD appears to be associated with a dopaminergic deficit. Mutations in the SOD1gene cause familial amyotrophic lateral sclerosis. Survival of transgenic mice with a mutant SOD1 which fails to incorporate Cu((2+)) in its active si