Anti‐sense‐mediated inhibition of expression of the novel striated tropomyosin isoform TPM1κ disrupts myofibril organization in embryonic axolotl hearts

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Abstract
Striated muscle tropomyosin (TM) is described as containing ten exons; 1a, 2b, 3, 4, 5, 6b, 7, 8, and 9a/b. Exon 9a/b has critical troponin binding domains and is found in striated muscle isoforms. We have recently discovered a smooth (exon 2a)/striated (exons 9a/b) isoform expressed in amphibian, avian, and mammalian hearts, designated as an isoform of the TPM1 gene (TPM1κ). TPM1κ expression was blocked in whole embryonic axolotl heart by transfection of exon‐specific anti‐sense oligonucleotide. Reverse transcriptase polymerase chain reaction (RT‐PCR) confirmed lower transcript expression of TPM1κ and in vitro analysis confirmed the specificity of the TPM1κ anti‐sense oligonucleotide. Altered expression of the novel TM isoform disrupted myofibril structure and function in embryonic hearts.