The understanding of mutations of motor or regulatory muscle proteins that lead to cardiac insufficiency and skeletal muscle deficiency helps to design better strategies to overcome such abnormalities. Zebrafish has been used as an animal model for diverse human cardiac diseases; however, most studies focused on molecular and biochemical aspects, neglecting the function, especially the relevance of motor and regulatory proteins in force production.

The in vitro motility assay (IVMA) is the most suitable technique to measure the maximum sliding speed of labeled actin filaments moved by working strokes of the heads of immobilized myosin molecules under optimal ATP-concentration. Thus, IVMA is a useful tool to investigate interactions and mechanical properties of the actomyosin motor and the consequences of specific mutations at the molecular level, but so far it has not been used to study function of actomyosin from zebrafish cardiac and skeletal muscle.

We established an isolation protocol for myosin and polymerizable actin from zebrafish skeletal muscle. Cardiac and skeletal motor and regulatory muscle proteins from adult wild type zebrafish extracts were confirmed by SDS-PAGE and western blot and their activity by IVMA. Functional cardiac myosin was extracted from 1/3 - 1/5 of single zebrafish hearts directly into the IVMA flow cells. The established extraction protocols are suitable for zebrafish cardiac and skeletal muscle and the resulting motor proteins are functional, in high quality and reproducible for IVMA.