Abstract
Abstract. The cardiac troponin complex, which is an important component of the contractile apparatus, is composed of the three subunits troponin I (TnI), troponin C (TnC) and troponin T (TnT). Troponin I is the inhibitory subunit and consists of three isoforms encoded by TNNI1, TNNI2 and TNNI3 genes, respectively. Due to the different types of cardiomyopathies caused by mutations in the TNNI3 gene and its fluorescence in situ hybridization (FISH) mapping on bovine chromosome 18q26, which was shown to be linked to the recessively inherited bovine dilated cardiomyopathy (BDCMP), bovine TNNI3 was considered as candidate gene for BDCMP. Real-time polymerase chain reaction (PCR) TNNI3 expression analysis resulted in a significant difference between BDCMP affected and unaffected animals when normalized to ACTB gene expression, but there was no significant difference in expression when normalized to GAPDH. Northen blotting experiment was in agreement with the expression analysis and did not reveal a significant difference between the group of BDCMP affected and unaffected animals. Sequencing of the bovine TNNI3 gene revealed a single nucleotide polymorphism in intron 6 (c.378+315G>A), but this single nucleotide polymorphism (SNP)was present regardless of the BDCMP status. In summary our data provide evidence to exclude the bovine TNNI3 gene as a candidate for BDCMP.
Highlights
The troponin complex is composed of the three subunits: troponin I (TnI), troponin C (TnC) and troponin T (TnT), which interact during muscle contraction and relaxation with actin via tropomyosin (GOMES et al 2002)
Two of them, coded by the genes TNNI1 and TNNI2, are present in slow-twitch and in fast-twitch skeletal muscles, and the third form coded by the TNNI3 gene is present in heart muscle (CUMMINS and PERRY 1978, TISO et al 1997)
The amino-acid sequences from the cardiac troponin I protein encoded by TNNI3 gene were compared between bovine
Summary
The troponin complex is composed of the three subunits: troponin I (TnI), troponin C (TnC) and troponin T (TnT), which interact during muscle contraction and relaxation with actin via tropomyosin (GOMES et al 2002). Human cardiac TnI protein has an animo-terminal extension with the RRRSS sequence. This sequence is present in rat and cattle counterparts (VALLINS et al 1990, MITTMANN et al 1992). Phosphorylation on both serines (S) results in a reduction of the interaction between troponin I and troponin C and this leads to an increase in heart contractility (LIAO et al 1992). Bovine dilated cardiomyopathy (BDCMP) is a severe and terminal heart disease. We present conclusive evidence that the bovine TNNI3 gene can be excluded as a candidate gene for BDCMP
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