Differential expression of cardiac troponin T isoforms in normal and cardiac non-function mutant axolotl hearts

A recessive mutant gene, termed "c", for cardiac non-function in the Mexican axolotl, Ambystoma mexicanum, is responsible for the failure of myofibrillogenesis in cardiac nonfunction mutant embryonic hearts. Animals that are homozygous for the mutation (c/c) fail to develop beating hearts and consequently die. Thus, the Mexican axolotl has been a useful animal model to study embryonic heart development. Recently, the cardiac troponin T (cTnT) gene, along with three additional shorter isoforms of the gene, were cloned from normal embryonic hearts. These isoforms are believed to be the alternately spliced forms of the full length gene. One of the isoforms cloned is missing a cardiac-specific exon. Real-time PCR reveals that homozygous recessive mutant embryos (c/c) exhibit a lower transcription level of the cTnT gene than wildtype animals (+/+ or +/c). Expression levels of each of the isoforms are compared in normal and mutant hearts using quantitative real-time PCR.