51
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Abstract
In Drosophila, the Jun amino-terminal kinase (JNK) homolog Basket (Bsk) is required for epidermal closure. Mutants for Src42A, a Drosophila c-src protooncogene homolog, are described. Src42A functions in epidermal closure during both embryogenesis and metamorphosis. The severity of the epidermal closure defect in the Src42A mutant depended on the amount of Bsk activity, and the amount of Bsk activity depended on the amount of Src42A. Thus, activation of the Bsk pathway is required downstream of Src42A in epidermal closure. This work confirms mammalian studies that demonstrated a physiological link between Src and JNK.
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Affiliation(s)
- M Tateno
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
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52
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Abstract
In recent years, Drosophila researchers have developed powerful genetic techniques that allow for the rapid identification and characterization of genes involved in tumor formation and development. The high level of gene and pathway conservation, the similarity of cellular processes and the emerging evidence of functional conservation of tumor suppressors between Drosophila and mammals, argue that studies of tumorigenesis in flies can directly contribute to the understanding of human cancer. In this review, we explore the historical and current roles of Drosophila in cancer research, as well as speculate on the future of Drosophila as a model to investigate cancer-related processes that are currently not well understood.
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Affiliation(s)
- C J Potter
- Howard Hughes Medical Institute, Department of Genetics, Yale University School of Medicine, Boyer Center for Molecular Medicine, NewHaven, CT 06536-0812,
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53
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Kramerova IA, Kramerov AA. Mucinoprotein is a universal constituent of stable intercellular bridges in Drosophila melanogaster germ line and somatic cells. Dev Dyn 1999; 216:349-60. [PMID: 10633855 DOI: 10.1002/(sici)1097-0177(199912)216:4/5<349::aid-dvdy4>3.0.co;2-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Intercellular bridges formed by incomplete cytokinesis may be important in a variety of processes, including synchronization of mitotic and meiotic divisions in animal cells. Using specific antibodies against a mucin-type glycoprotein (Kramerov et al. [1996] FEBS Lett. 378:213-218) from Drosophila melanogaster cultured embryonic cells, we showed that this glycoprotein is located in all cytoplasmic bridges found in various germline and somatic tissues. In the ovary, immunostaining of ring canals connecting germ cells can be detected in the very early stages at the germarium region 1 where first gonial divisions take place, and the immunostaining appears to persist through late stages when transport of cytoplasm from nurse cells to a growing oocyte occurs. Each ring canal is made up of an outer and an inner rim. Mucin glycoprotein appears to be one of the first proteins localized to the outer rim, which is a derivative of the arrested cleavage furrow. The known ring canal proteins, phosphotyrosine-containing protein(s), F-actin, hts- and kelch proteins, are localized to the inner rim at a later developmental time. Similarly, mucin glycoprotein is recruited early to ring canals connecting mitotic primary spermatocytes in both larval and adult testes. Mucin glycoprotein was found to be present in intercellular bridges (small ring canals) in somatic cells, including follicular epithelium in ovary and imaginal disc cells. Intercellular bridges were observed for the first time in a subset of cells in the larval brain. Thus, mucin glycoprotein is the only protein hitherto found in all known types of stable intercellular bridges and may be an important constituent of a backbone needed for assembly and preservation of this particular type of cell-cell contact.
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Affiliation(s)
- I A Kramerova
- Department of Animal Molecular Genetics, Institute of Molecular Genetics, Russian Academy of Sciences, Moscow, Russia
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54
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Sokol NS, Cooley L. Drosophila filamin encoded by the cheerio locus is a component of ovarian ring canals. Curr Biol 1999; 9:1221-30. [PMID: 10556087 DOI: 10.1016/s0960-9822(99)80502-8] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND The ring canals in the ovary of the fruit fly Drosophila provide a versatile system in which to study the assembly and regulation of membrane-associated actin structures. Derived from arrested cleavage furrows, ring canals allow direct communication between cells. The robust inner rim of filamentous actin that attaches to the ring-canal plasma membrane contains cytoskeletal proteins encoded by the hu-li-tao shao (hts) and kelch genes, and is regulated by the Src64 and Tec29 tyrosine kinases. Female sterile cheerio mutants fail to recruit actin to ring canals, disrupting the flow of cytoplasm to oocytes. RESULTS We have cloned cheerio and found that it encodes a member of the Filamin/ABP-280 family of actin-binding proteins, known to bind transmembrane proteins and crosslink actin filaments into parallel or orthogonal arrays. Antibodies to Drosophila Filamin revealed that Filamin is an abundant ring-canal protein and the first known component of both the outer and inner rims of the ring canal. The cheerio gene also encodes a new Filamin isoform that lacks the actin-binding domain. CONCLUSIONS Localization of Filamin to nascent ring canals is necessary for the recruitment of actin filaments. We propose that Filamin links filamentous actin to the plasma membrane of the ring canal. Although loss of Filamin in human cells supports a role for Filamin in organizing orthogonal actin arrays at the cell cortex, the cheerio mutant provides the first evidence that Filamin is required in membrane-associated parallel actin bundles, such as those found in ring canals, contractile rings and stress fibers.
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Affiliation(s)
- N S Sokol
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06510, USA
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55
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Jackson SM, Berg CA. Soma-to-germline interactions during Drosophila oogenesis are influenced by dose-sensitive interactions between cut and the genes cappuccino, ovarian tumor and agnostic. Genetics 1999; 153:289-303. [PMID: 10471713 PMCID: PMC1460760 DOI: 10.1093/genetics/153.1.289] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The cut gene of Drosophila melanogaster encodes a homeodomain protein that regulates a soma-to-germline signaling pathway required for proper morphology of germline cells during oogenesis. cut is required solely in somatic follicle cells, and when cut function is disrupted, membranes separating adjacent nurse cells break down and the structural integrity of the actin cytoskeleton is compromised. To understand the mechanism by which cut expression influences germline cell morphology, we determined whether binucleate cells form by defective cytokinesis or by fusion of adjacent cells. Egg chambers produced by cut, cappuccino, and chickadee mutants contained binucleate cells in which ring canal remnants stained with antibodies against Hu-li tai shao and Kelch, two proteins that are added to ring canals after cytokinesis is complete. In addition, defects in egg chamber morphology were observed only in middle to late stages of oogenesis, suggesting that germline cell cytokineses were normal in these mutants. cut exhibited dose-sensitive genetic interactions with cappuccino but not with chickadee or other genes that regulate cytoskeletal function, including armadillo, spaghetti squash, quail, spire, Src64B, and Tec29A. Genomic regions containing genes that cooperate with cut were identified by performing a second-site noncomplementing screen using a collection of chromosomal deficiencies. Sixteen regions that interact with cut during oogenesis and eight regions that interact during the development of other tissues were identified. Genetic interactions between cut and the ovarian tumor gene were identified as a result of the screen. In addition, the gene agnostic was found to be required during oogenesis, and genetic interactions between cut and agnostic were revealed. These results demonstrate that a signaling pathway regulating the morphology of germline cells is sensitive to genetic doses of cut and the genes cappuccino, ovarian tumor, and agnostic. Since these genes regulate cytoskeletal function and cAMP metabolism, the cut-mediated pathway functionally links these elements to preserve the cytoarchitecture of the germline cells.
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Affiliation(s)
- S M Jackson
- Department of Genetics, University of Washington, Seattle, Washington 98195-7360, USA.
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56
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Baba K, Takeshita A, Majima K, Ueda R, Kondo S, Juni N, Yamamoto D. The Drosophila Bruton's tyrosine kinase (Btk) homolog is required for adult survival and male genital formation. Mol Cell Biol 1999; 19:4405-13. [PMID: 10330180 PMCID: PMC104399 DOI: 10.1128/mcb.19.6.4405] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/1998] [Accepted: 02/23/1999] [Indexed: 11/20/2022] Open
Abstract
We isolated a Drosophila fickleP (ficP) mutant with a shortened copulatory duration and reduced adult-stage life span. The reduced copulatory duration is ascribable to incomplete fusion of the left and right halves of the apodeme that holds the penis during copulation. ficP is an intronic mutation occurring in the Btk gene, a gene which encodes two forms (type 1 and type 2) of a Bruton's tyrosine kinase (Btk) family cytoplasmic tyrosine kinase as a result of alternative exon usage. The ficP mutation prevents the formation of the type 2 isoform but leaves expression of the type 1 transcript intact. Ubiquitous overexpression of the wild-type cDNA by using a heat shock 70 promoter during the late larval or pupal stages rescued the life span and genital defects in the mutant, respectively, establishing the causal relationship between the ficP phenotypes and the Btk gene mutation. The stage specificity of the rescuing ability suggests that the Btk gene is required for the development of male genitalia and substrates required for adult survival.
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Affiliation(s)
- K Baba
- Developmental Genetics Group, Mitsubishi Kasei Institute of Life Sciences, Machida, Tokyo 194-8511, Japan
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57
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Yamadori T, Baba Y, Matsushita M, Hashimoto S, Kurosaki M, Kurosaki T, Kishimoto T, Tsukada S. Bruton's tyrosine kinase activity is negatively regulated by Sab, the Btk-SH3 domain-binding protein. Proc Natl Acad Sci U S A 1999; 96:6341-6. [PMID: 10339589 PMCID: PMC26883 DOI: 10.1073/pnas.96.11.6341] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Bruton's tyrosine kinase (Btk) is a cytoplasmic tyrosine kinase that is crucial for human and murine B cell development, and its deficiency causes human X-linked agammaglobulinemia and murine X-linked immunodeficiency. In this report, we describe the function of the Btk-binding protein Sab (SH3-domain binding protein that preferentially associates with Btk), which we reported previously as a newly identified Src homology 3 domain-binding protein. Sab was shown to inhibit the auto- and transphosphorylation activity of Btk, which prompted us to propose that Sab functions as a transregulator of Btk. Forced overexpression of Sab in B cells led to the reduction of B cell antigen receptor-induced tyrosine phosphorylation of Btk and significantly reduced both early and late B cell antigen receptor-mediated events, including calcium mobilization, inositol 1, 4,5-trisphosphate production, and apoptotic cell death, where the involvement of Btk activity has been demonstrated previously. Together, these results indicate the negative regulatory role of Sab in the B cell cytoplasmic tyrosine kinase pathway.
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Affiliation(s)
- T Yamadori
- Department of Molecular Medicine (formerly Department of Medicine III), Osaka University Medical School, 2-2 Yamadaoka, Suita City, Osaka 565-0871, Japan
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58
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Nisitani S, Kato RM, Rawlings DJ, Witte ON, Wahl MI. In situ detection of activated Bruton's tyrosine kinase in the Ig signaling complex by phosphopeptide-specific monoclonal antibodies. Proc Natl Acad Sci U S A 1999; 96:2221-6. [PMID: 10051622 PMCID: PMC26764 DOI: 10.1073/pnas.96.5.2221] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/29/1998] [Indexed: 11/18/2022] Open
Abstract
Bruton's tyrosine kinase (Btk) is a critical transducer of signals originating from the B cell antigen receptor (BCR). Dosage, sequential phosphorylation, and protein interactions are interdependent mechanisms influencing Btk function. Phosphopeptide-specific mAbs recognizing two distinct phosphotyrosine modifications were used to quantify Btk activation by immunofluorescent techniques during B cell stimulation. In a population of cultured B cells stimulated by BCR crosslinking and analyzed by flow cytometry, transient phosphorylation of the regulatory Btk tyrosine residues (551Y and 223Y) was detected. The kinetics of phosphorylation of the residues were temporally distinct. Tyrosine 551, a transactivating substrate site for Src-family kinases, was maximally phosphorylated within approximately 30 seconds of stimulation as monitored by flow cytometry. Tyrosine 223, an autophosphorylation site within the SH3 domain, was maximally phosphorylated at approximately 5 minutes. Btk returned to a low tyrosine phosphorylation level within 30 minutes, despite persistent elevation of global tyrosine phosphorylation. Colocalization of activated Btk molecules with the crosslinked BCR signaling complex was observed to coincide with the period of maximal Btk tyrosine phosphorylation when stimulated B cells were analyzed with confocal microscopy. The results of these in situ temporal and spatial analyses imply that Btk signaling occurs in the region of the Ig receptor signaling complex, suggesting a similar location for downstream targets of its activity.
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Affiliation(s)
- S Nisitani
- Department of Howard Hughes Medical Institute, University of California, Los Angeles, CA 90095, USA
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59
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Zhang Q, Zheng Q, Lu X. A genetic screen for modifiers of drosophila Src42A identifies mutations in Egfr, rolled and a novel signaling gene. Genetics 1999; 151:697-711. [PMID: 9927462 PMCID: PMC1460506 DOI: 10.1093/genetics/151.2.697] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Drosophila Src42A, a close relative of the vertebrate c-Src, has been implicated in the Ras-Mapk signaling cascade. An allele of Src42A, Su(Raf)1, dominantly suppresses the lethality of partial loss-of-function Raf mutations. To isolate genes involved in the same pathway where Src42A functions, we carried out genetic screens for dominant suppressor mutations that prevented Su(Raf)1 from suppressing Raf. Thirty-six mutations representing at least five genetic loci were recovered from the second chromosome. These are Drosophila EGF Receptor (Egfr), rolled, Src42A, and two other new loci, one of which was named semang (sag). During embryogenesis, sag affects the development of the head, tail, and tracheal branches, suggesting that it participates in the pathways of Torso and DFGF-R1 receptor tyrosine kinases. sag also disrupts the embryonic peripheral nervous system. During the development of imaginal discs, sag affects two processes known to require Egfr signaling: the recruitment of photoreceptor cells and wing vein formation. Thus sag functions in several receptor tyrosine kinase (RTK)-mediated processes. In addition, sag dominantly enhances the phenotypes associated with loss-of-function Raf and rl, but suppresses those of activated Ras1(V12) mutation. This work provides the first genetic evidence that both Src42A and sag are modulators of RTK signaling.
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Affiliation(s)
- Q Zhang
- Department of Molecular Biosciences, The University of Kansas, Lawrence, Kansas 66045, USA
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60
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Dodson GS, Guarnieri DJ, Simon MA. Src64 is required for ovarian ring canal morphogenesis during Drosophila oogenesis. Development 1998; 125:2883-92. [PMID: 9655810 DOI: 10.1242/dev.125.15.2883] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Src family of protein tyrosine kinases have been implicated as important regulators of cellular proliferation, differentiation and function. In order to understand further the role of Src family kinases, we have generated loss-of-function mutations in Src64, one of two Src family kinases known in Drosophila melanogaster. Animals with reduced Src64 function develop normally and are fully viable. However, Src64 female flies have reduced fertility, which is associated with the incomplete transfer of cytoplasm from nurse cells to the developing oocyte. Analysis of Src64 egg chambers showed defects in the ring canals that interconnect the oocyte and its 15 associated nurse cells. Src64 ring canals fail to accumulate the high levels of tyrosine phosphorylation that are normally present. Despite the reduced tyrosine phosphorylation, known ring canal components such as filamentous actin, a ring canal-specific product of the hu-li tai shao gene, and the kelch protein localize properly. However, Src64 ring canals are reduced in size and frequently degenerate. These results indicate that Src64 is required for the proper growth and stability of the ovarian ring canals.
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Affiliation(s)
- G S Dodson
- Department of Biological Sciences and Department of Genetics, Stanford University, Stanford, CA 94305, USA
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61
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Affiliation(s)
- L Cooley
- Department of Genetics, Yale Medical School, New Haven, Connecticut 06520-8005, USA
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62
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Roulier EM, Panzer S, Beckendorf SK. The Tec29 tyrosine kinase is required during Drosophila embryogenesis and interacts with Src64 in ring canal development. Mol Cell 1998; 1:819-29. [PMID: 9660965 DOI: 10.1016/s1097-2765(00)80081-7] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Tec29 encodes the only known Drosophila member of the Tec tyrosine kinases. By identifying the first mutations in Tec29 (formerly Src29A), we show that it is essential for head involution during embryogenesis and for ring canal development during oogenesis. Tec29 mutant egg chambers are defective in transfer of cytoplasm from the accessory nurse cells through the ring canals into the oocyte. Growth of the mutant ring canals is arrested, and they lack the strong phosphotyrosine localization seen in wild-type ring canals. Mutants lacking the Drosophila Src homolog Src64 show the same phenotype, and we show that Src64 is required for the localization of Tec29 to the ring canals. This interaction is similar to that between vertebrate Src and Tec kinases and suggests that Tec29 is an effector of Src64 that modifies ring canal components required for growth.
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Affiliation(s)
- E M Roulier
- Department of Molecular and Cell Biology, University of California, Berkeley 94720, USA
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