Myosin heavy chain like (Mhcl) agiert während der Embryonalentwicklung und Myogenese von Drosophila melanogaster in Redundanz zu Zipper, die Funktion des C2-Domänen-Proteins CG10737-P während der Muskelentwicklung bleibt unklar

The unconventional myosin Mhcl was originally identified as potential interaction partner of Rols7, which is essential for Drosophila myogenesis. During the fusion relevant stages, Mhcl transcript is detectable both in the somatic and the visceral mesoderm (Bonn, Diplomarbeit 2006). Here we could show via in situ hybridization that the gene is expressed founder cell specifically and regulated by the transcription factor DMef2. By analyzing different P element fly lines with the help of in situ hybridization, it became obvious that there are different isoforms of Mhcl established, most likely via differential splicing and the use of different promoters. Furthermore, RT-PCR products revealed the existence of a so far unpredicted 5´-UTR. We raised an antibody against a protein fragment of Mhcl, which detects ectopically expressed protein but showed only unspecific stainings on embryos. We were not able to verify the predicted interaction of Mhcl and Rols7, neither with genetic studies nor by doing co immunoprecipitation analysis. We could show that Mhcl works in redundancy to Zip during early morphogenetic processes. Here they are most likey responsible for the correct intercalation of cells during germ band elongation. Double mutant embryos for both zip and Mhcl stop myoblast fusion after the first fusion phase. Therefore we postulate that Mhcl regulates the migration of FCMs towards the growing myotubes or the migration of muscles towards their attachement sites. The implication of Mhcl in establishing the sarcomeres seems feasible. C2 domains are able to insert into membranes and thereby promote their fusion. The participation in myoblast fusion could not be shown for any of these fusogens, yet. Here we could show by in situ hybridization that CG10737, which codes for one of these domains, is expressed during myoblast fusion in the somatic as well as in the visceral mesoderm. Its expression is regulated by the transcription factor DMef2 and in the somatic mesoderm limited to the FCs. Immunhistological stainings on embryos could show, as well as western blot analysis, that the generated peptide antibody does not detect the protein specifically. Although deletion of CG10737 does not cause any myoblast fusion or attachement defects, we postulate a function for CG10737-P for signal transduction during myogenesis or for establishing neuromuscular junction.