Heart-specific targeting of firefly luciferase by the myosin light chain-2 promoter and developmental regulation in transgenic mice.
Based on hybridization studies indicating constitutive expression levels of the endogenous myosin light chain-2 (MLC-2) gene in embryonic, fetal, and adult myocardium, a model system for selective targeting of genes to the heart of transgenic mice has been developed. A 2.1-kb DNA fragment of the 5' flanking region of the rat cardiac MLC-2 gene was fused to the firefly luciferase reporter gene and introduced into fertilized mouse oocytes. In four independent transgenic mouse lines, the expression of the MLC-2-luciferase fusion gene was found exclusively in heart muscle. In contrast to the endogenous MLC-2 gene, no luciferase activity was detectable in slow-twitch skeletal muscle or any other tissue of transgenic mice. This result suggests that the 2.1-kb DNA fragment of the 5' flanking region of the cardiac MLC-2 gene contains the regulatory elements required for selective gene expression in cardiac myocytes in vivo. In contrast to the endogenous steady-state MLC-2 expression during development, transgenic luciferase activity was 10-fold higher during embryogenesis, when formation of the ventricular loop and septum takes place. The enhanced luciferase activity in early heart development may suggest a growth-dependent control mechanism, involving either transcriptional or posttranscriptional regulation. In conclusion, this model system with the 2.1-kb ventricle-specific MLC-2 promoter sequence should facilitate the overexpression of gene products in the developing and mature heart muscle and further elucidate molecular mechanisms of myocardial diseases such as cardiomyopathies.
Franz
W M
WM
Department of Virus Research, Max-Planck-Institut für Biochemie, Martinsried, FRG.
Breves
D
D
Klingel
K
K
Brem
G
G
Hofschneider
P H
PH
Kandolf
R
R
D000818:Animals; D000831:Animals, Newborn; D001483:Base Sequence; D001517:Coleoptera; D005318:Fetal Heart / Q000378:metabolism; D005786:Gene Expression Regulation; D006321:Heart / Q000196:embryology / Q000254:growth & development; D008156:Luciferases / Q000235:genetics*; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009206:Myocardium / Q000378:metabolism*; D009218:Myosins / Q000235:genetics*; D009928:Organ Specificity; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000032:analysis
D012333:RNA, Messenger; D008156:Luciferases; D009218:Myosins