<P> Research concerns on nuclear actin are usually focused on isoform beta . However the use of antibodies directed against different actin isoforms allows identifying not only the cytoplasmic beta in the cell nucleus, but also: </P> <Ul> <Li> gamma actin in the cell nuclei of human melanoma, </Li> <Li> alpha skeletal muscle actin in the nuclei of mouse myoblasts, </Li> <Li> cytoplasmic gamma actin and also alpha smooth muscle actin in the nucleus of the foetal mouse fibroblast </Li> </Ul> <Li> gamma actin in the cell nuclei of human melanoma, </Li> <Li> alpha skeletal muscle actin in the nuclei of mouse myoblasts, </Li>

Which of these is not one of the primary functions of muscle