Excessive Myosin activity in mbs mutants causes photoreceptor movement out of the Drosophila eye disc epithelium.
Neuronal cells must extend a motile growth cone while maintaining the cell body in its original position. In migrating cells, myosin contraction provides the driving force that pulls the rear of the cell toward the leading edge. We have characterized the function of myosin light chain phosphatase, which down-regulates myosin activity, in Drosophila photoreceptor neurons. Mutations in the gene encoding the myosin binding subunit of this enzyme cause photoreceptors to drop out of the eye disc epithelium and move toward and through the optic stalk. We show that this phenotype is due to excessive phosphorylation of the myosin regulatory light chain Spaghetti squash rather than another potential substrate, Moesin, and that it requires the nonmuscle myosin II heavy chain Zipper. Myosin binding subunit mutant cells continue to express apical epithelial markers and do not undergo ectopic apical constriction. In addition, mutant cells in the wing disc remain within the epithelium and differentiate abnormal wing hairs. We suggest that excessive myosin activity in photoreceptor neurons may pull the cell bodies toward the growth cones in a process resembling normal cell migration.
Lee
Arnold
A
Skirball Institute for Biomolecular Medicine and Department of Cell Biology, New York University School of Medicine, New York, New York 10016, USA.
Treisman
Jessica E
JE
D000818:Animals; D004330:Drosophila / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D005123:Eye / Q000378:metabolism / Q000648:ultrastructure; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D018995:Myosin Heavy Chains / Q000378:metabolism; D024462:Myosin Type II / Q000378:metabolism; D043263:Myosin-Light-Chain Phosphatase / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D009218:Myosins / Q000378:metabolism*; D010766:Phosphorylation; D010786:Photoreceptor Cells / Q000002:abnormalities* / Q000254:growth & development; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D054460:rho-Associated Kinases
D029721:Drosophila Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C495593:Sqh protein, Drosophila; C097862:Zip protein, Drosophila; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; C495592:Mbs protein, Drosophila; D043263:Myosin-Light-Chain Phosphatase; D024462:Myosin Type II; D018995:Myosin Heavy Chains; D009218:Myosins