Cardiac titin isoforms: Practice in interpreting results of electrophoretic analysis

The sarcomeric giant protein titin affects the passive elasticity of the heart muscle and is crucial for proper cardiac function, including diastolic relaxation of the left ventricle. A useful common method for studying titin is electrophoretic analysis which can be used to examine the distribution of its isoforms in the heart. There are 5 titin parameters that can be analyzed: the N2BA/N2B isoforms ratio, the T2/T1 bands ratio, Cronos isoform content, NT isoform content, the total titin-to-myosin heavy chain (TT/MHC) ratio. These parameters can only be assessed through electrophoresis of giant proteins. It is known that these parameters are related to various biomolecular processes in muscle cells, such as providing of elastic properties, turnover, contraction, and maintaining a highly ordered sarcomere structure. In this review, we discuss the diagnostic potential of electrophoretic visualization of cardiac titin changes in various human heart diseases and animal models of physiological adaptations or pathologies.