Klinische und experimentelle Kardiologie
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Recent Advances on the TPM4 Gene Expression in Humans

Dipak K Dube*, Syamalima Dube, Lynn Abbott, and Bernard J Poiesz

Tropomyosin, a coiled-coil dimeric protein, is a component of thin filaments that constitute myofibrils, the contractile apparatus of striated muscles. It is also a component of the actin filament network in non-muscle cells. In vertebrates, except for fish, there are four known TPM genes (TPM1, TPM2, TPM3, and TPM4) each of which can generate a number of TPM isoforms via alternative splicing and/or using alternate promoters. In humans, except for TPM4, the sarcomeric TPM isoform (s) for each TPM gene have been known for long time. Recently, we have cloned and sequenced the sarcomric isoform of the TPM4 gene designated as TPM4a. In addition, using qRT-PCR we have reported the expression of TPM4a in human striated muscles. Also, using 2D Western blot analyses followed by Mass spectra, we have reported the potential TPM4a protein expression in human cardiac tissues. However, much of the role of TPM4a in muscle contraction in human is yet to be elucidated. Although the role of the TPM4 gene in human diseases in not well documented, new information is emerging in this regard. For example, of the TPM4 isoforms TPM4g has been reported as a non-invasive biomarker in prenatal diagnosis of congenital heart defects; mutations in TPM4 have been implicated in Macrothombocytopenia in humans; differential expression of two TPM isoforms TPM4b and TPM4g in human breast cancer cells. However, the role of TPM4-ALK oncogenes in inflammatory myofibroblastic tumors in humans is well documented.