Cloning, mapping and expression analysis of the sheep Wilson disease gene homologue

Copper homeostasis in mammals is maintained by the balance of dietary intak e and copper excretion via the bile. Sheep have a variant copper phenotype and do not efficiently excrete copper by this mechanism, often resulting in excessive copper accumulation in the liver. The Wilson disease protein (AT P7B) is a copper transporting P-type ATPase that is responsible for the eff lux of hepatic copper into the bile. To investigate the role of ATP7B in th e sheep copper accumulation phenotype, the cDNA encoding the ovine homologu e of ATP7B was isolated and sequenced and the gene was localised by fluores cence in situ hybridisation to chromosome 10. The 6.3 kb cDNA encoded a pre dicted protein of 1444 amino acids which included all of the functional dom ains characteristic of copper transporting P-type ATPases. ATP7B mRNA was e xpressed primarily in the liver with lower levels present in the intestine, hypothalamus and ovary. A splice variant of ATP7B mRNA, which was expresse d in the liver and comprised approximately 10% of the total ATP7B mRNA pool , also was isolated. The results suggest that ATP7B is produced in the shee p and that the tendency to accumulate copper in the liver is not due to a g ross alteration in the structure or expression of ATP7B. (C) 2000 Elsevier Science B.V. All rights reserved.