The expression pattern and cellular localisation of Myosin VI during the Drosophila melanogaster life cycle.

Myosin VI is a motor protein which is necessary for the morphogenesis of epithelial tissues during Drosophila development. The spatial and temporal expression of Myosin VI was examined by expressing a GFP (Green Fluorescent Protein) tagged Myosin VI molecule (PGM), under the control of a Myosin VI-Gal4 line. PGM was present in tissues that were shown previously to express Myosin VI, such as the ovarian follicle epithelium, and the individualization complex; and in other tissues, including the trachea, the midgut, the salivary glands and the imaginal discs. The GFP-tagged Myosin V1 rescued the male sterile phenotype of Jaguar showing it is functional in vivo. Within individual cells, the role of the head and neck domain and the tail domain in targeting of the Myosin V1 molecule was examined by investigating the localisation of the separate domains tagged to GFP. In salivary glands and follicle cells the head and neck domains were concentrated in the cell nucleus, where the minus end of each actin filament is located. We found that the tail domain anchors the whole molecule outside of the nucleus. Similarly, in the individualization complex in the testes, the tail anchors the whole molecule to the base of the complex while the separated head with neck domain becomes scattered along the entire actin molecule suggesting the cellular location may be determined by cargo proteins that bind to the tail domain rather than by the movement of Myosin VI along the actin filaments.