In one aspect, the present invention provides nucleic acid expression cassettes that are predominantly expressed in the mammalian liver. The present invention also provides vectors comprising a nucleic acid expression cassette that is predominantly expressed in the mammalian liver. The present invention also provides methods of ameliorating the symptoms of a disease, the methods including the steps of introducing into the liver of a mammalian subject a vector comprising a nucleic acid expression cassette that encodes a polypeptide, and expressing a therapeutic amount of the polypeptide in the liver.