Of the variants linked to the development of biliary cirrhosis, ABCB4D243A has an expression profile that is indistinguishable statistically from that of the wild-type transporter, while ABCB4K435T and ABCB4G535D expressed to equally high levels in the presence and absence of ATP8B1/CDC50 and could not be distinguished statistically from the catalytically inactive ABCB4E558Q mutant. The gene discussed is ATP8B1; the disease is biliary liver cirrhosis.