![]() ![]() The study shows that the fusion of myoblasts to existing muscle fibres, called myotubes, follows a set of distinct stages that requires communication between transmembrane elements and the actin cytoskeleton. "With the advent of RNAi technology, this problem was solved, and we were able to study the myoblast fusion process in great detail", says Dhanyasi. In spite of this, the study of myogenic processes in flight muscles has lagged behind, primarily because tools for the genetic manipulation of later developmental phases were lacking. This set the stage for addressing questions on vertebrate muscle regeneration in a Drosophila model system." The advantages of using Drosophila as a model are many-the tiny fly is easily grown and is amenable to a huge array of genetic manipulations. Rajesh established the presence of stem cells in Drosophila muscles similar to the satellite cells in vertebrate muscles. This work was also a collaboration with Drs. "Priyankana began this work by investigating the role of various fusion proteins using confocal microscopy in the myogenesis of flight muscles of Drosophila. "This work is actually a continuation of studies carried out by Vijay's earlier students-Priyankana Mukherkjee and Rajesh Gunage", says Nagaraju Dhanyasi, the first author of the paper. These muscles serve as a particularly attractive model, since their developmental program, and their muscle fibre organisation resemble key aspects of vertebrate skeletal myogenesis. This study focuses on the events occurring in myoblast fusion in Drosophila during the formation of flight muscles. However, the mechanisms governing myogenesis (formation of muscle fibres) in striated muscles of the skeletal musculature in vertebrates is not very clear. Most of our knowledge about the fusion of myoblasts to form multinucleate muscle fibers has been gleaned from studies on the development of tubular muscles of Drosophila larvae. The team's investigations have resulted in a description of the events during the merging of individual myoblast cells with muscle cells, and was published in the Oct. The work involved molecular biology and state-of-the-art electron microscopic techniques, which were carried out in collaboration with the EM facility of the Weizmann Institute. This allowed researchers to reconstruct the steps in the dynamic process of myoblast fusion, where the structure of the fusing membranes was closely examined. To study the process at a high resolution, it was necessary to generate electron microscope (EM) images. Eyal Schejter at the Weizmann Institute of Science, Israel, who are also investigating the processes governing myoblast fusion in flies and mice. ![]() ![]() Nagaraju Dhanyasi from Vijayraghavan's group, has collaborated with Prof. The mechanistic basis of myoblast fusion with muscle fibers is now clearer thanks to recent work from Vijayraghavan's group at the National Centre for Biological Sciences (NCBS). However, muscles do heal-a set of quiescent cells called myosatellite cells in muscles are activated by injury to divide and form myoblasts, which in turn fuse with muscle cells to repair damaged muscles. A sudden turn or an unusually vigorous bout of aerobics can leave one with a muscle tear that will effectively confine a person to bed for a few weeks. ![]() Credit: (c) 2015 Dhanyasi et al., Journal of Cell Biologyįor an avid exerciser, a muscle pull or tear is a painful and fairly common occurrence. suggest that contact sites (green) within the apposed surface membranes (pink) give rise to small pores (red), which then expand, leading to cytoplasmic continuity and complete fusion. A tomogram-derived scheme shows the interface between a Drosophila flight muscle myotube and a closely apposed myoblast as they fuse with one another. ![]()
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