METALLOTHIONEIN SYNTHESIS AND DEGRADATION IN INDIAN CHILDHOOD CIRRHOSIS FIBROBLASTS

Indian childhood cirrhosis (ICC) is a fatal liver disease characterize d by the accumulation of copper-sulfur aggregates. We demonstrated tha t cultured fibroblasts from a patient with ICC contain vesicular aggre gates, fibrillar whorls, and crystalloids along with dilated rough end oplasmic reticulum filled with flocculent material. Although the coppe r content of the fibroblasts was normal, both basal and metal-induced metallothionein (MT) synthesis was reduced in the ICC cells. The lower MT synthesis in ICC cells was seen at copper concentrations of 100, 2 00, and 400 mu M, zinc concentrations of 50 and 100 mu M, and a cadmiu m concentration of 2 mu M. The lower MT synthesis in ICC cells was not due to failure of the cells to take up copper because Cu-67 uptake ki netics were normal is the mutant cells. MT degradation was also normal in the ICC cells. The size of human MT IIA mRNA was normal in the ICC cells, but its amount was reduced under both basal and metal-induced conditions. The MT IIA gene, which is the predominant MT gene in human beings, showed no sequence alterations in any of its exons, introns, or promoter region in the ICC cells compared with normal cells. These studies demonstrate that this case of ICC represents a genetic disease with some level of expression in cultured fibroblasts; the basic defe ct may involve insufficient MT mRNA and protein-synthesis for the copp er load present. However, it remains to be determined whether reduced MT synthesis is a primary or secondary phenomenon.