A cloned cDNA for duck malic enzyme detects abnormally large malic enzyme mRNAs in a strain of mice (Mod-1n) that does not express malic enzyme protein

• Published in: Biochemistry (Easton) Vol. 23; no. 15; pp. 3454 - 3459
• Main Authors: Glynias, Manuel J, Morris, Sidney M, Fantozzi, Dominic A, Winberry, Larry K, Back, Donald W, Fisch, Judith E, Goodridge, Alan G
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 17.07.1984
• Subjects: Animals; Biological and medical sciences; Cloning, Molecular; Crosses, Genetic; DNA - metabolism; Ducks - genetics; Fundamental and applied biological sciences. Psychology; Genes. Genome; Liver - enzymology; Malate Dehydrogenase - genetics; Mice; Mice, Inbred Strains; Mice, Mutant Strains - genetics; Molecular and cellular biology; Molecular genetics; Molecular Weight; RNA, Messenger - genetics; Species Specificity; Enzyme; Liver; Rodentia; Gene expression; Vertebrata; Mammalia; Messenger RNA; Gene; Diet; Mouse; Malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+); Mutation; Molecular cloning; Localization
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00310a011

Sensitive immunochemical assays were used to measure the mass and rate of synthesis of malic enzyme protein in wild-type and Mod-1n mutant mice fed a high carbohydrate/low fat diet supplemented with thyroid hormone. Malic enzyme activity in the fed, wild-type mice was 100-fold higher than in starved, wild-type mice. Neither activity, mass, nor synthesis of malic enzyme could be detected in fed, mutant mice. However, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase responded to these dietary manipulations with normal or supranormal increases in activities, respectively, in mutant mice. A cDNA clone containing an almost complete copy of the mRNA for malic enzyme from duck liver was used to analyze poly(A+) RNA from C57BL/6J-DBA/2J hybrid mice that had been fasted and refed a high carbohydrate/low fat diet supplemented with thyroid hormone. The 32P-cDNA probe hybridized to two RNAs of 2250 and 2950 nucleotides. The same two RNAs were detected in RNA from starved mice except at much lower concentrations. A similar analysis of RNA from Mod-1n mice fed the high carbohydrate-thyroid diet also revealed two hybridizing RNAs but each was 700-800 nucleotides longer than its counterpart in wild-type mice. The abundance of malic enzyme mRNA in the fed, mutant mice was about the same as that in fed, wild-type mice. The mutant malic enzyme mRNAs also were present in RNA from starved mice but at much lower concentrations. These results suggest that the mutation responsible for the Mod-1n phenotype is in the structural gene for malic enzyme.