Human cardiac troponin T: identification of fetal isoforms and assignment of the TNNT2 locus to chromosome 1q.

The troponin complex is located on the thin filament of striated muscle and is composed of three component polypeptides: troponin T, troponin I, and troponin C. Three troponin T genes have been described on the basis of molecular cloning in humans and other vertebrates. These are expressed in a tissue-specific manner and encode the troponin T isoforms expressed in cardiac muscle, slow skeletal muscle, and fast skeletal muscle, respectively. Each of these genes is subject to alternative splicing, resulting in the production of multiple tissue-specific isoforms. We have cloned cDNAs encoding human cardiac troponin T from adult heart and have used these to demonstrate that multiple cardiac troponin T mRNAs are present in the human fetal heart, resulting from alternative splicing in the 5' coding region of the gene. Hybridization of the cloned cDNAs to genomic DNA identifies a single-copy gene, and using somatic cell hybrid analysis, we have mapped the corresponding gene locus (designated TNNT2) to the long arm of chromosome 1 (1cen-qter).