ABSTRACT
The vertebrate adapter protein termed Crk was initially identified from the chicken CT10 retrovirus on the basis of its transforming activity (Mayer et al., 1988. Nature 332, 272-275). We have identified a Drosophila protein with homology to vertebrate Crk, termed dCRK, by interaction with the protein encoded by the Drosophila myoblast city (mbc) gene. The dCRK protein has extensive homology to the both the Crk-II form of vertebrate Crk and the Crk-related protein CRKL, and includes one SH2 domain followed by two SH3 domains. A single protein of approx. 37kDa is detected in extracts from embryos, and Northern analysis revealed a single transcript of 1.3kb. The dCrk mRNA is abundant throughout embryogenesis, declines during the larval stages, and reappears during pupation. In addition, maternally-provided transcripts have been detected. During embryogenesis, the spatial distribution of this transcript is relatively broad and appears to include all germ layers. Finally, dCrk is located on the fourth chromosome, approximately at cytological position 101F-102A.
Subject(s)
Adaptor Proteins, Signal Transducing , Cytoskeletal Proteins , Drosophila Proteins , Drosophila/genetics , Insect Proteins/metabolism , Proto-Oncogene Proteins/genetics , Vertebrates/genetics , Amino Acid Sequence , Animals , Blotting, Western , Chromosome Mapping , DNA, Complementary/chemistry , DNA, Complementary/genetics , DNA, Complementary/isolation & purification , Drosophila/chemistry , Drosophila/embryology , Embryo, Nonmammalian/metabolism , Embryonic Development , Gene Expression Regulation, Developmental , Molecular Sequence Data , Nuclear Proteins/genetics , Protein Kinases/genetics , Proto-Oncogene Proteins/metabolism , Proto-Oncogene Proteins c-crk , RNA, Messenger/genetics , RNA, Messenger/metabolism , Sequence Analysis, DNA , Sequence Homology, Amino Acid , Tissue Distribution , src Homology Domains/geneticsABSTRACT
The Drosophila myoblast city (mbc) locus was previously identified on the basis of a defect in myoblast fusion (Rushton et al., 1995. Development [Camb.]. 121:1979-1988). We describe herein the isolation and characterization of the mbc gene. The mbc transcript and its encoded protein are expressed in a broad range of tissues, including somatic myoblasts, cardial cells, and visceral mesoderm. It is also expressed in the pole cells and in ectodermally derived tissues, including the epidermis. Consistent with this latter expression, mbc mutant embryos exhibit defects in dorsal closure and cytoskeletal organization in the migrating epidermis. Both the mesodermal and ectodermal defects are reminiscent of those induced by altered forms of Drac1 and suggest that mbc may function in the same pathway. MBC bears striking homology to human DOCK180, which interacts with the SH2-SH3 adapter protein Crk and may play a role in signal transduction from focal adhesions. Taken together, these results suggest the possibility that MBC is an intermediate in a signal transduction pathway from the rho/rac family of GTPases to events in the cytoskeleton and that this pathway may be used during myoblast fusion and dorsal closure.
