Enzyme changes associated with mitoichondrial malic enzyme deficiency in mice

Evidence for regulatory genes on mouse chromosome 7 that affect the quantitative expression of proteins in the fetal and newborn liver

A series of deletions around the albino locus on mouse chromosome 7 is believed to include one or more regulatory genes that control the activities of a cluster of liver enzymes. To further characterize the functions of this region of the mouse genome, we have used quantitative two-dimensional electrophoresis to analyze the effects of two of these deletions, c3H and c14CoS, on the expression of liver proteins. More than 400 distinct protein gene products were quantitated in livers from fetal and newborn wild-type homozygous (cch/cch), heterozygous (cch/c3H or cch/c14CoS), and deletion homozygous (c3H/c3H or c14CoS/c14CoS) mice. Livers of fetal and newborn c3H heterozygotes and homozygous wild-type littermates produced qualitatively identical protein patterns after two-dimensional electrophoresis. In livers of c3H homozygous fetuses, however, abnormal amounts (either increased or decreased relative to homozygous wild-type and heterozygous littermates) of 29 proteins were found. Twenty-eight of these 29 protein anomalies were also found in livers of newborn c3H homozygotes. Livers of fetal and newborn mice homozygous for the c14CoS deletion, which overlaps the c3H deletion and produces a similar phenotype, expressed normal amounts of these proteins. One of the 29 proteins (MSN807) has an amino-terminal sequence similar to a 23-kDa translationally controlled protein abundant in mouse erythroleukemia and sarcoma-180 cells. These results suggest that normal chromosome 7 contains genes, located within the region of the c3H but not the c14CoS deletion, that regulate the abundance of specific proteins in the liver. These proteins cannot be related to the phenotypic alterations shared by the c3H and c14CoS deletions.

Mice homozygous for chromosomal deletions at the albino locus region lack specific polypeptides in two-dimensional gels

Radiation-induced chromosomal deletions involving the albino locus region of the mouse result, when homozygous, in abnormalities ranging from sterility to lethality at various stages of development. We have utilized two-dimensional electrophoresis to search for polypeptide alterations in livers from newborn mice homozygous for the c14CoS and c3H deletions and also from c3H/c6H compound heterozygote mice. Five-hundred polypeptide spots detectable in normal mouse liver gels were scored. Alterations involving five polypeptides were observed in the various overlapping deletions. A spot corresponding to a polypeptide with a 38,000 Mr was missing from mice homozygous for the short c14CoS and the longer overlapping c3H deletions. Another polypeptide with a 29,000 Mr was missing from c3H homozygotes and c3H/c6H heterozygotes. A third polypeptide with a 62,000 Mr was missing only from c3H homozygotes. Two additional polypeptides were markedly increased in amount in c14CoS and c3H homozygotes. The partial overlap between the three deletions analyzed allows provisional genetic mapping of previously unknown loci for three of the five electrophoretically identifiable polypeptides expressed in newborn mouse livers. The results obtained provide a basis for studying radiation-induced deletions with two-dimensional electrophoresis gels.

Inherited metabolic disease in laboratory animals: a review

Research on the screening for and study of animal models of inherited metabolic disease is reviewed. It is emphasized that an animal model, to be of value, must be an inherited deficiency of the same enzyme as the one deficient in the human syndrome. If this criterion is adhered to there is a remarkable identity in aetiology between animal and man. Specific examples of inherited metabolic disease in laboratory animals are described for: amino acid metabolism; lysosomal storage diseases, carbohydrate metabolism, transport disorders and trace element metabolism; the mutants found in mice being the easiest to manipulate biochemically and genetically. There is still a lack of adequate screening programmes for animal homologues of the more serious human inborn errors (such as lysosomal storage diseases) where laboratory studies could provide significant advances in therapy.