JAK-STAT pathway inDrosophilamorphogenesis (original) (raw)

The Drosophila JAK-STAT pathway

JAK-STAT, 2013

The molecular characterization of the JAK-STAT pathway has recently celebrated its 20th birthday, a milestone that marks the discovery of the tyrosine kinases TYK2 and JAK1 and the STAT1 and STAT2 transcription factors as the key factors underlying the cellular response to type I interferons. The initial description of the first JAK-STAT pathway components sparked a flurry of activity in multiple labs, which rapidly characterized a wide range of ligands, receptors, four JAKs, and seven STATs present in vertebrate cells. Collectively these factors signal through fundamentally similar mechanisms; a JAK-STAT pathway that now serves as a textbook example of how extracellular ligands can act at the cell surface to modulate nuclear gene expression. Hopscotch-the fly JAK. In contrast to the key role played by the Drosophila system in identifying many other key cellular signaling cascades, the initial steps leading to the identification of the Drosophila JAK-STAT pathway components lagged pioneering work being undertaken in vertebrate cell-based systems. However, the ball was set rolling in 1994 when the Perrimon lab cloned a novel gene termed Hopscotch (Hop), which encodes a maternally supplied protein required for the patterning of the embryonic cuticle (for an example of the LOF phenotype see ) and the proliferation of diploid imaginal cells. 5,6 Cloning of Hop identified it as a 1177 amino acid non-receptor tyrosine kinase, expressed throughout development, with a kinase domain, sharing 39% identity with JAK1, JAK2, and Tyk2, and an overall identity of 27% to JAK2. While not necessarily apparent at the time, the identification of JAK and the characteristic segmentation phenotype associated with pathway mutants represented a key insight and the first step on the path toward identifying the rest of the pathway.

Drosophila SOCS36E negatively regulates JAK/STAT pathway signaling via two separable mechanisms

Molecular Biology of the Cell, 2013

Conserved from humans to Drosophila, the Janus kinase/signal transducer and activators of transcription (JAK/STAT) signaling cascade is essential for multiple developmental and homeostatic processes, with regulatory molecules controlling pathway activity also highly conserved. We characterize the Drosophila JAK/STAT pathway regulator SOCS36E and show that it functions via two independent mechanisms. First, we show that Drosophila Elongin B/C and Cullin-5 act via the SOCS-box of SOCS36E to reduce pathway activity specifically in response to ligand stimulation-a process that involves endocytic trafficking and lysosomal degradation of the Domeless (Dome) receptor. Second, SOCS36E also suppresses both stimulated and basal pathway activity via an Elongin/Cullinindependent mechanism that is mediated by the N-terminus of SOCS36E, which is required for the physical interaction of SOCS36E with Dome. Although some human SOCS proteins contain N-terminal kinase-inhibitory domains, we do not identify such a region in SOCS36E and propose a model wherein the N-terminal of SOCS36E blocks access to tyrosine residues in Dome. Our biochemical analysis of a SOCS-family regulator from a lower organism highlights the fundamental conserved roles played by regulatory mechanisms in signal transduction. . As a consequence, numerous regulators of pathway activity have emerged. Of these, the protein inhibitors of

The Fertile Field of Drosophila JAK/STAT Signalling

Current Biology, 2002

The JAK/STAT pathway plays important roles in vertebrate and invertebrate development. The recent cloning and characterisation of the receptor in Drosophila shows that the pathway is conserved across phyla. In this review we describe current knowledge of the pathway and use genome data to discuss what elements are present in Drosophila. We also summarise recent work describing the involvement of the JAK/STAT pathway in oogenesis and spermatogenesis. Interestingly, the JAK/STAT pathway maintains the niche required for germline stem cell maintenance in the testis, providing the first molecular characterisation of a stem cell niche. Drosophila's streamlined pathway offers a simple model to find new elements and analyse the function of existing ones. The JAK/STAT pathway is one of the main eukaryotic signalling pathways [1]. In Drosophila the pathway is required for segmentation, eye development, cell growth, haematopoiesis, sex determination (reviewed in [2]), and tracheal development [3].The first part of this review will describe the core signalling elements of the JAK/STAT pathway in Drosophila, and the second part will concentrate on new and exciting findings about the requirement for JAK/STAT signalling during spermatogenesis and oogenesis.

Identification of a Stat Gene That Functions in Drosophila Development

Cell, 1996

The receptors involved include both those that lack and those that possess intrinsic tyrosine kinase activity Charles R. Dearolf, § and James E. Darnell, Jr.* (Schindler and Darnell, 1995). *Laboratory of Molecular Cell Biology Such a pervasively used signaling mechanism Rockefeller University seemed likely to function in invertebrates as well as New York, New York 10021 vertebrates. In fact, the Drosophila protein encoded by † Department of Biology the hopscotch (hop) gene (Perrimon and Mahowald, New York University 1986) has been identified as a member of the JAK family New York, New York 10003 (Binari and Perrimon, 1994). Zygotic hop ϩ expression is ‡ Howard Hughes Medical Institute required for the proliferation of diploid imaginal cells in Rockefeller University larvae (Perrimon and Mahowald, 1986). When both the New York, New York 10021 maternal and zygotic contributions of hop ϩ are removed, § Developmental Genetics Group segmental defects, frequently deletions of denticle belts Dana Farber Cancer Institute from the fifth abdominal segment (Perrimon and Mahoand Cancer Biology Section wald, 1986), are observed as an imperfect expression of Joint Center for Radiation Therapy pair rule genes even skipped (eve) (Binari and Perrimon, Harvard Medical School 1994) and runt (run) (Harrison et al., 1995). Boston, Massachusetts 02115 A dominant, gain-of-function, temperature-sensitive hop mutation, hop Tumorous-lethal (hop Tum-l) (Hanratty and Dearolf, 1993), has a single amino acid substitution (Luo Summary et al., 1995), resulting in a hyperphosphorylated kinase (Harrison et al., 1995) that causes leukemia-like defects A Drosophila Stat gene (D-Stat) with a zygotic seg-(Hanratty and Ryerse, 1981). This mutation causes overmental expression pattern was identified. This protein proliferation of phagocytic plasmatocytes and aggregabecomes phosphorylated on Tyr-704 when coextion of these cells into large melanizing tumors in hemapressed in Schneider cells with a Drosophila janus topoietic and gut tissue. kinase (JAK), Hopscotch (HOP). The phosphorylated We now report a Drosophila STAT protein with high protein binds specifically to the consensus sequence amino acid identity to the mammalian STAT proteins. TTCCCGGAA. Suppressor mutations of hop Tum-l , a The gene for this protein, D-Stat, maps at 92E on chrodominant hyperactive allele of hop whose phenotype mosome 3 and is expressed in early embryos in a weak is hematocyte overproduction and tumor formation, seven-stripe pattern and at both terminal regions. A were selected. One of these mutants, stat HJ , mapped single tyrosine residue, 704, becomes phosphorylated, to the same chromosomal region (92E) as does D-Stat, and the activated D-STAT can bind DNA when D-Stat had an incompletely penetrant pair rule phenotype, is expressed in cells along with hop or if the D-Statand exhibited aberrant expression of the pair rule gene transfected cells are treated with vanadate to inhibit even skipped (eve) at the cellular blastoderm stage. phosphotyrosine phosphatases. To connect D-STAT to Two D-STAT-binding sites were identified within the development, we recovered a mutation in the stat locus eve stripe 3 enhancer region. Mutations in either of from a genetic screen for dominant suppressors of the STAT-binding sites greatly decreased the stripe 3 hop Tum-l lethality. This mutation, termed stat HiJak (stat HJ), expression in transgenic flies. Clearly, the JAK-STAT causes reduced viability when homozygous and exhibits pathway is connected to Drosophila early devela partially penetrant pair rule phenotype, one characteropment. istic of which is aberrant EVE expression at the cellular blastoderm stage.

Opposing roles for Drosophila JAK/STAT signalling during cellular proliferation

Oncogene, 2005

The JAK/STAT signalling pathway mediates both antiproliferative responses following interferon stimulation and cellular proliferation in response to cytokines such as interleukins and growth factors. Central to these responses are the seven vertebrate STAT molecules, misregulation of which is implicated in a variety of malignancies. We have investigated the proliferative role of the single Drosophila STAT92E, part of the evolutionarily conserved JAK/STAT cascade. During second instar larval wing disc development pathway activity is both necessary and sufficient to promote proliferation of this epithelial cell type. However by later stages, endogenous STAT92E is stimulated by a noncannonical mechanism to exert pronounced antiproliferative effects. Ectopic canonical activation is sufficient to further decrease proliferation and leads to the premature arrest of cells in the G2 phase of the cell cycle. The single STAT92E present in Drosophila therefore mediates both proproliferative functions analogous to vertebrate interleukin-stimulated STAT3 and antiproliferative functions analogous to interferon-stimulated STAT1. Pro-and antiproliferative roles therefore represent ancestral activities conserved through evolution and subsequently assigned to distinct molecules.

GFP reporters detect the activation of the Drosophila JAK/STAT pathway in vivo

Gene Expression Patterns, 2007

JAK/STAT signaling is essential for a wide range of developmental processes in Drosophila melanogaster. The mechanism by which the JAK/STAT pathway contributes to these processes has been the subject of recent investigation. However, a reporter that reXects activity of the JAK/STAT pathway in all Drosophila tissues has not yet been developed. By placing a fragment of the Stat92E target gene Socs36E, which contains at least two putative Stat92E binding sites, upstream of GFP, we generated three constructs that can be used to monitor JAK/STAT pathway activity in vivo. These constructs diVer by the number of Stat92E binding sites and the stability of GFP. The 2XSTAT92E-GFP and 10XSTAT92E-GFP constructs contain 2 and 10 Stat92E binding sites, respectively, driving expression of enhanced GFP, while 10XSTAT92E-DGFP drives expression of destabilized GFP. We show that these reporters are expressed in the embryo in an overlapping pattern with Stat92E protein and in tissues where JAK/STAT signaling is required. In addition, these reporters accurately reXect JAK/STAT pathway activity at larval stages, as their expression pattern overlaps that of the activating ligand unpaired in imaginal discs. Moreover, the STAT92E-GFP reporters are activated by ectopic JAK/STAT signaling. STAT92E-GFP Xuorescence is increased in response to ectopic upd in the larval eye disc and mis-expression of the JAK kinase hopscotch in the adult fat body. Lastly, these reporters are speciWcally activated by Stat92E, as STAT92E-GFP reporter expression is lost cell-autonomously in stat92E homozygous mutant tissue. In sum, we have generated in vivo GFP reporters that accurately reXect JAK/STAT pathway activation in a variety of tissues. These reporters are valuable tools to further investigate and understand the role of JAK/STAT signaling in Drosophila.

Localised JAK/STAT Pathway Activation Is Required for Drosophila Wing Hinge Development

PLoS ONE, 2013

Extensive morphogenetic remodelling takes place during metamorphosis from a larval to an adult insect body plan. These changes are particularly intricate in the generation of the dipteran wing hinge, a complex structure that is derived from an apparently simple region of the wing imaginal disc. Using the characterisation of original outstretched alleles of the unpaired locus as a starting point, we demonstrate the role of JAK/STAT pathway signalling in the process of wing hinge development. We show that differences in JAK/STAT signalling within the proximal most of three lateral folds present in the wing imaginal disc is required for fold morphology and the subsequent differentiation of the first and second auxiliary sclerites as well as the posterior notal wing process. Changes in these domains are consistent with the established fate map of the wing disc. We show that outstretched wing posture phenotypes arise from the loss of a region of Unpaired expression in the proximal wing fold and demonstrate that this results in a decrease in JAK/STAT pathway activity. Finally we show that reduction of JAK/STAT pathway activity within the proximal wing fold is sufficient to phenocopy the outstretched phenotype. Taken together, we suggest that localised Unpaired expression and hence JAK/STAT pathway activity, is required for the morphogenesis of the adult wing hinge, providing new insights into the link between signal transduction pathways, patterning and development.