MYO5B and heart disorder: Therefore, the aims of the present study were as follows: (i) to analyse the cardiac expression pattern of Class-5 myosins throughout the lifetime and under pathophysiological conditions; (ii) since MYO5b is the major Class-5 myosin expressed in the postnatal cardiomyocyte and in the adult heart, to analyse its role within the cardiomyocyte and the heart; (iii) to evaluate whether MYO5b is essential for cardiac function and homeostasis; and in particular (iv) to investigate whether MYO5B impairment has clinical implications in human cardiac diseases.