ATP7B is a copper-transporting P-type ATPase defective in the copper transport disorder, Wilson disease (WND). We have sequenced the 5' UTR and promoter region of ATP7B in 37 unrelated WND patients in whom partial sequencing of the coding region and intron/exon boundaries of the gene had failed to identify one or both disease-causing mutations. Three patients were found to be heterozygous for a 15 bp deletion between nucleotides -424 and -441. This deletion had been previously identified as the most common mutation in Sardinian WND patients. Two novel single-nucleotide changes were also identified within the 5' UTR and promoter of ATP7B; however, these were found at a similar frequency in control chromosomes and are apparently normal variants. These results suggest that mutations in regulatory elements of ATP7B are uncommon in patients of European ancestry, except in Sardinia.

Wilson disease (WND), an autosomal recessive disorder of copper transport, shows wide genotypic and phenotypic variability, with hepatic and/or neurological symptoms. The WND gene, ATP7B, encodes a copper transporting ATPase that is involved in the transport of copper into the plasma protein ceruloplasmin, and in the excretion of copper from the liver. ATP7B mutations result in copper storage in liver and brain. From 247 WND patients worldwide whose DNA has been sequenced in our laboratory, we have identified 24 new mutations. The origins of the patients were European white (one deletion, one nonsense, one splice site, and 18 missense), Chinese (one deletion, one missense) and Bangladeshi (one missense). Most of these had strong support as disease causing mutations, based on conservation between species, structural changes, and absence in controls. One missense mutation in a Chinese patient was considered uncertain because of its conservative nature and position in the protein. We also identified 15 nucleotide substitutions (11 of them new) causing silent or intronic changes, none of which produce an additional splice site that could lead to disease. Characterization of mutations, both disease-causing and normal variants, is essential for accurate molecular diagnosis of this condition.

ATOX1 is a cytoplasmic copper chaperone that interacts with the copper-binding domain of the membrane copper transporters ATP7A and ATP7B. ATOX1 has also been suggested to have a potential anti-oxidant activity. This study investigates the tissue-specific localization of the mouse homolog, Atox1, in mouse liver and kidney. Immunohistochemical studies in the liver localize the copper chaperone to hepatocytes surrounding both hepatic and central veins. In the kidney, Atox1 is localized to the cortex and the medulla. Cortex immunostaining is specific to glomeruli in both the juxtamedullary and cortical nephrons. Expression in the medulla appears to be associated with the loops of Henle. These data suggest that localized regions in the liver and kidney express Atox1 and have a role in copper homeostasis and/or anti-oxidant protection. Twenty-seven patients with Wilson disease-like phenotypes and two patients with Menkes disease-like phenotypes were screened for ATOX1 mutations with no alterations detected. The human phenotype resulting from mutations in ATOX1 remains unidentified.

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