© 1999 by The Society for Integrative and Comparative Biology
Regulation of Muscle Growth and Sarcomeric Protein Gene Expression over the Intermolt Cycle1
School of Postgraduate Medicine, Keele University Hartshill, Stoke on Trent ST4 7QB, UK Tel: (0)1792 554605, Fax: (0)1782 747319
Correspondence: 2E-mail: beal7{at}bemp.keele.ac.uk
Crustacean muscle growth is associated with a hormonally mediated cyclical molt stage. The mechanisms by which fibre lengthening and hypertrophy occur in Crustaceans over the molt has been the subject of our and other researchers' investigations using histological, biochemical and molecular approaches. In this paper, we review our studies and present evidence for the different molecular mechanisms by which sarcomeric proteins are upregulated to achieve muscle sarcomere addition in lobsters during the molt.
Synthesis of the sarcomeric proteins has been shown to increase during the premolt and postmolt phases in the leg and abdominal muscles coinciding with the addition of sarcomeres over ecdysis. This is in contrast to research on claw muscle demonstrating premolt atrophy. Our work and others' have investigated the factors which modulate this growth and turnover of muscle tissue in crustaceans. These changes in muscle turnover correspond with an elevated titre of circulating ecdysteroids and the role of these molting hormones in regulating sarcomeric mRNA and protein levels during cyclical muscle growth is discussed.
Our results suggest that sarcomeric proteins may be controlled via both transcriptional and translational mechanisms during the molt interval and these findings are discussed in relation to previous research investigating muscle growth in Crustacea.