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Segregation of Cardiac and Skeletal Muscle-Specific Regulatory Elements of the β-Myosin Heavy Chain Gene
Hansjorg Rindt, Stephanie Knotts and Jeffrey Robbins
Proceedings of the National Academy of Sciences of the United States of America
Vol. 92, No. 5 (Feb. 28, 1995), pp. 1540-1544
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/2366818
Page Count: 5
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The β-myosin heavy chain (β-MyHC) gene is expressed in cardiac and slow skeletal muscles. To examine the regulatory sequences that are required for the gene's expression in the two compartments in vivo, we analyzed the expression pattern of a transgene consisting of the β-MyHC gene 5' upstream region linked to the chloramphenicol acetyl-transferase reporter gene. By using 5600 bp of 5' upstream region, the transgene was expressed at high levels in the slow skeletal muscles. Decreased levels of thyroid hormone led to the up-regulation of the transgene in both cardiac and skeletal muscles, mimicking the behavior of the endogenous β-MyHC gene. After deleting the distal 5000 bp, the level of reporter gene expression was strongly reduced. However, decreased levels of thyroid hormone led to an 80-fold skeletal muscle-specific increase in transgene expression, even upon the ablation of a conserved cis-regulatory element termed MCAT, which under normal (euthyroid) conditions abolishes muscle-specific expression. In contrast, cardiac-specific induction was not detected with the deletion construct. These observations indicate that the cardiac and skeletal muscle regulatory elements can be functionally segregated on the β-MyHC gene promoter.
Proceedings of the National Academy of Sciences of the United States of America © 1995 National Academy of Sciences