Abstract
ABSTRACT Muscle differentiation requires the assembly of high-order structures called myofibrils, composed of sarcomeres. Even though the molecular organization of sarcomeres is well known, the mechanisms underlying myofibrillogenesis are poorly understood. It has been proposed that integrin-dependent adhesion nucleates myofibrils at the periphery of the muscle cell to sustain sarcomere assembly. Here, we report a role for the gene perdido ( perd , also known as kon-tiki , a transmembrane chondroitin proteoglycan) in myofibrillogenesis. Expression of perd RNAi in muscles, prior to adult myogenesis, can induce misorientation and detachment of Drosophila adult abdominal muscles. In comparison to controls, perd -depleted muscles contain fewer myofibrils, which are localized at the cell periphery. These myofibrils are detached from each other and display a defective sarcomeric structure. Our results demonstrate that the extracellular matrix receptor Perd has a specific role in the assembly of myofibrils and in sarcomeric organization. We suggest that Perd acts downstream or in parallel to integrins to enable the connection of nascent myofibrils to the Z-bands. Our work identifies the Drosophila adult abdominal muscles as a model to investigate in vivo the mechanisms behind myofibrillogenesis.
Highlights
The study of muscle development and maintenance is crucial for better understanding the basis of myopathies
We found that the expression of either of the perd RNA interference (RNAi) lines in myoblasts from the larval period onwards prevented the eclosion of young adults from the pupal cage
Consistent with this, persistent larval muscles (PLMs) from Mef2-GAL4.UAS-perd RNAi abdomens were always detached and formed myospheres (Fig. 1E,F). This mutant phenotype was less conspicuous in the dorsal abdominal muscles, which required the co-expression of perd RNAi lines with Dicer to induce muscle detachment
Summary
The study of muscle development and maintenance is crucial for better understanding the basis of myopathies. Muscle development is a multistep process that is conserved across the animal kingdom. It starts with the specification of muscle precursor cells, the myoblasts, which either fuse to each other to form the multinucleated muscles or differentiate into cardiomyocytes. At late stages during muscle morphogenesis, final differentiation of the muscles takes place by the assembly of myofibrils (Schejter and Baylies, 2010; Schweitzer et al, 2010).
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