Targeted Ablation of the Murine alpha-Tropomyosin Gene

• Published in: Circulation research Vol. 81; no. 6; pp. 1005 - 1010
• Main Authors: Blanchard, Edward M, Iizuka, Kenji, Christe, Michael, Conner, David A, Geisterfer-Lowrance, Anja, Schoen, Frederick J, Maughan, David W, Seidman, Christine E, Seidman, J.G
• Format: Journal Article
• Language: English
• Published: Hagerstown, MD American Heart Association, Inc 01-12-1997; Lippincott; Lippincott Williams & Wilkins Ovid Technologies
• Subjects: Analytical, structural and metabolic biochemistry; Animals; Biological and medical sciences; Contractile proteins; Fundamental and applied biological sciences. Psychology; Gene Targeting; Holoproteins; Male; Mice; Mice, Knockout; Myocardium - pathology; Proteins; Tropomyosin - genetics; Tropomyosin - physiology; Embryo; Molecular form; Myofibril; Tropomyosin; Papillary muscle; Rodentia; Site directed mutagenesis; Contractile protein; Strain specificity; Striated muscle; Heterozygosity; Vertebrata; Mammalia; Mouse; Mutation; Performance
• ISSN: 0009-7330; 1524-4571
• DOI: 10.1161/01.RES.81.6.1005

We created a mouse that lacks a functional alpha-tropomyosin gene using gene targeting in embryonic stem cells and blastocyst-mediated transgenesis. Homozygous alpha-tropomyosin "knockout" mice die between embryonic day 9.5 and 13.5 and lack alpha-tropomyosin mRNA. Heterozygous alpha-tropomyosin knockout mice have [nearly =]50% as much cardiac alpha-tropomyosin mRNA as wild-type littermates but similar alpha-tropomyosin protein levels. Cardiac gross morphology, histology, and function (assessed by working heart preparations) of heterozygous alpha-tropomyosin knockout and wild-type mice were indistinguishable. Mechanical performance of skinned papillary muscle strips derived from mutant and wild-type hearts also revealed no differences. We conclude that haploinsufficiency of the alpha-tropomyosin gene produces little or no change in cardiac function or structure, whereas total alpha-tropomyosin deficiency is incompatible with life. These findings imply that in heterozygotes there is a regulatory mechanism that maintains the level of myofibrillar tropomyosin despite the reduction in alpha-tropomyosin mRNA. (Circ Res. 1997;81:1005-1010.)