Differential cardiac proteins

NFAT proteins are expressed in skeletal, cardiac, and smooth muscle and play important roles in the regulation of the development and differentiation of these tissues. In skeletal muscle, NFAT isoforms are expressed at different stages of development and regulate progression from early muscle cell precursors to mature myocytes. NFAT proteins have also been shown to control the expression of the myosin heavy chain and positively regulate muscle growth [1, 2]. 

Sainte, Beuve C., Allen, P.D., Dambrin, G., et al., 1997, Cardiac calcium release channel (ryanodine receptor) in control and cardiomyopathic human hearts mRNA and protein contents are differentially regulated. J Mol Cell Cardiol., 29(4), pp 1237 16. 

Hamoir, G., Focant, B. and Dist che, M. (1972). Proteinic criteria of differentiation of white, cardiac and various red muscles in carp. Comparative Biochemistry and Physiology 41B, 665-674. 

Cell culture systems are ideal for detailed proteomic investigations of responses in protein expression to controlled stimuli. This is because they should provide defined systems with much lower inherent variability between samples, particularly if established cell lines are used. However, cells that are maintained in culture respond by alterations in their gene pattern, and consequently the protein expression, such that it can be quite different from that found in vivo. This process can occur quite rapidly in primary cultures of cells established from tissue samples and is even more profound in cells maintained long-term, particularly where transformation has been used to establish immortal cell lines. Cardiac myocytes can pose an even bigger challenge. While neonatal cardiac myocytes can be maintained and grown in vitro, adult cells are terminally differentiated and can be maintained for relatively short times in vitro but are not capable of cell division. 

Retinoic acid (RA), forskolin, and HDAC inhibitors have been shown/used to induce neuronal differentiation of hippocampal adult neural progenitor cells. However, these factors are either pleiotropic or of undefined physiologic relevance RA has neuronal subtype patterning activity and also been reported to induce cardiac differentiation (27) as well as pancreatic differentiation (28) HDAC inhibitors are nonspecific and forskolin activates protein kinase A and serves to increase the cellular levels of the general signaling molecule cAMP (29). 

Similarly, multiple genes, alternative RNA splicing, and posttranslational modifications result in multiple essential and regulatory light chains, tropomyosins, titins, and other myofibrillar proteins. Energy pathway enzymes are differentially expressed in various skeletal fiber types, in cardiac and smooth muscle, and at different stages of development. This also applies to Ca regulatory proteins such as the... 

Biochemical Studies The self-renewal of mES cells depends largely on LIF (leukemia inhibitory factor) and BMP (bone morphologic protein). However, SCI maintained an mES ability to self-renew for more than 10 passages in an undifferentiated/pluripotent state and showed relatively low cellular toxicity. The compound reversibly inhibited differentiation of mES cells induced by either FBS or retinoic acid treatment, and after washout SCI, mES cells were selectively induced to differentiate into neural/neuronal, cardiac muscle, and endodermal cells. 

Immunostaining studies of cells isolated from the contracting areas within the EBs confirmed the presence of cardiac-specific proteins (MHC, sarcomeric a-actinin, des-min, cTnf, ANP). These studies also demonstrated the presence of early-cardiac morphology with a typical early-striated staining pattern. The cells, however, did not exhibit immunoreactivify with anti-nebuhn monoclonal antibodies (mAbs), a specific skeletal muscle sarcomeric protein shown to be expressed early in skeletal myoblast differentiation. 

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