Analysis of the upstream regions governing expression of the chicken cardiac troponin T gene in embryonic cardiac and skeletal muscle cells.

Abstract

Abstract. The chicken gene encoding cardiac troponin T (cTNT) is expressed in both cardiac and skeletal muscle during early embryonic development, but is specifically repressed in skeletal muscle during fetal development. To determine if the cis-acting sequences governing transcription of a single gene in these two related cell types are the same, we have transfected promoter/upstream segments of the cTNT gene coupled to the bacterial chloramphenicol acetyltransferase gene into primary cultures of early embryonic cardiac and skeletal muscle cells. Using this assay system, chloramphenicol acetyltransferase activity directed by the cTNT promoter/upstream region was between two and three orders of magnitude higher in cardiac or skeletal muscle cells than in fibroblast cells, indicating that cis elements responsible for cell-specific expression reside in this region of the cTNT gene. Deletion experiments showed that a 67-nucleotide DNA segment residing between 268 and 201 nucleotides upstream of the cTNT transcription initiation site is required for cTNT promoter activity in embryonic cardiac cells. This region is not required in embryonic skeletal muscle cells because a cTNT promoter construction containing only 129 upstream nucleotides is transcriptionally active in these cells. These results demonstrate that different cis-acting sequences are required for cTNT expression in early embryonic cardiac and skeletal muscle cells. Nonessential regions residing farther upstream, on the other hand, affected the level of expression of these minimum regions in a similar manner in both cell types. The data from these experiments indicate, therefore, that transcription of the cTNT promoter in early embryonic cardiac and skeletal muscle cells is governed both by common and divergent regulatory elements in cis and in trans.

Differential Effects of Protein Kinase C, Ras, and Raf-1 Kinase on the Induction of the Cardiac B-type Natriuretic Peptide Gene through a Critical Promoter-proximal M-CAT Element

“…Although M-CAT elements have not been previously shown to mediate Ras inducibility, a large body of information supports a role for M-CAT sequences as determinants of cardiac and skeletal muscle-specific gene expression (35,57,58). Cardiac and striated muscle tissues are particularly enriched in M-CAT binding factors; however, they are also found in many other cell-and tissue types (39, 59 -61).…”

Divergent transcriptional enhancer factor-1 regulates the cardiac troponin T promoter

“…To study the transcriptional mechanisms that operate during myogenesis, we use the avian cTnT gene as a model of cardiac gene expression (21)(22)(23)(24). The avian cTnT gene is expressed in embryonic cardiac and skeletal muscle and is restricted to cardiac muscle later in development (22).…”

Developmental Changes of Cardiac and Slow Skeletal Muscle Troponin T Expression in Chicken Cardiac and Skeletal Muscles

“…Development of the cardiac muscle is triggered by transcriptional regulatory factors, dHAND, eHAND, and Nkx 2.5 (Schwartz and Olson, 1999), but skeletal muscle development by the MyoD family (Olson, 1992). The 247 bp upstream sequence from the transcription initiation site in the chicken cTnT gene is necessary for the gene expression in the cardiac muscle, while only 129 bp is needed for its expression in the skeletal muscle (Mar et al, 1988). Our results also showed cTnT transition from highmolecular-weight to low-molecular-weight isoforms in the avian and mammalian hearts, but not at all in the chicken skeletal muscles and less strikingly in the mouse leg muscle.…”