Toxic milk (tx) is an autosomal recessive mutation which affects copper metabolism in the mouse. Mutant females produce offspring who exhibits an abnormal syndrome which includes juvenile lethality; the syndrome is attributable to copper deficiency established during gestation, exacerbated postnatally by copper-insufficient milk. Such infants can be rescued by copper supplementation. Survivors maintained on normal rations accumulate vast amounts of hepatic copper leading to copper toxicosis and severe liver damage. This mutation then provides animals which exhibit both a hypo- and hypercupric state. This project involves a study of the mechanisms and biochemical basis of the erroneous copper metabolism exhibited by toxic milk mice. The status of copper has grown rapidly in recent years with recognition of its practical importance in biology and medicine. The plasma copper protein ceruloplasmin, is involved in mobilization of plasma iron, the transport of copper and the regulation of biogenic amines; it has been implicated in the etiology of Parkinson's disease and Huntington's chorea. Another enzymatic cuproprotein, superoxide dismutase acts to protect cells against the deleterious effects of superoxide radicals, which alter macromolecules, damage membranes and have been implicated in pulmonary oxygen toxicity, photohemolysis, alcoholic liver cirrhosis. Two genetic diseases showing aberrant copper metabolism have been described: Menkes' steely hair syndrome, Wilson's disease. The tx mutation appears to act in the liver by affecting the balance between retention and release of copper. With the use of 67Cu, the kinetics of hepatic copper uptake and release will be defined; localization within the liver (particulate, cytosol) as well as the kinetics of copper incorporation into various hepatic cuproproteins (ceruloplasmin, superoxide dismutase, metallothionein) will be established. Hepatic cuproproteins from normal and mutant animals will be purified by column chromatography and gel filtration. They will be compared and characterized according to electrophoretic mobility, isoelectric point, metal and amino acid composition, molecular weight. Genotypes will also be compared with respect to activity and concentration of cuproproteins during development and maturation as well as under conditions of varying levels of copper intake.
| Rauch, H; Wells, A J (1995) The toxic milk mutation, tx, which results in a condition resembling Wilson disease in humans, is linked to mouse chromosome 8. Genomics 29:551-2 |
| Mercer, J F; Grimes, A; Danks, D M et al. (1991) Hepatic ceruloplasmin gene expression is unaltered in the toxic milk mouse. J Nutr 121:894-9 |
