RESUMEN
Epithelial remodeling of the Drosophila retina depends on the pulsatile contraction and expansion of apical contacts between the cells that form its hexagonal lattice. Phosphoinositide PI(3,4,5)P3 (PIP3) accumulates around tricellular adherens junctions (tAJs) during contact expansion and dissipates during contraction, but with unknown function. Here, we found that manipulations of Pten or PI3-kinase (PI3K) that either decreased or increased PIP3 resulted in shortened contacts and a disordered lattice, indicating a requirement for PIP3 dynamics and turnover. These phenotypes are caused by a loss of branched actin, resulting from impaired activity of the Rac1 Rho GTPase and the WAVE regulatory complex (WRC). We additionally found that during contact expansion, PI3K moves into tAJs to promote the cyclical increase of PIP3 in a spatially and temporally precise manner. Thus, dynamic control of PIP3 by Pten and PI3K governs the protrusive phase of junctional remodeling, which is essential for planar epithelial morphogenesis.
Asunto(s)
Actinas , Uniones Adherentes , Proteínas de Drosophila , Morfogénesis , Fosfohidrolasa PTEN , Fosfatidilinositol 3-Quinasas , Fosfatos de Fosfatidilinositol , Retina , Animales , Fosfohidrolasa PTEN/metabolismo , Fosfohidrolasa PTEN/genética , Proteínas de Drosophila/metabolismo , Proteínas de Drosophila/genética , Actinas/metabolismo , Fosfatos de Fosfatidilinositol/metabolismo , Fosfatidilinositol 3-Quinasas/metabolismo , Uniones Adherentes/metabolismo , Retina/metabolismo , Retina/citología , Drosophila melanogaster/metabolismo , Proteína de Unión al GTP rac1/metabolismo , Proteína de Unión al GTP rac1/genéticaRESUMEN
Lattice cells (LCs) in the developing Drosophila retina change shape before attaining final form. Previously, we showed that repeated contraction and expansion of apical cell contacts affect these dynamics. Here, we describe another factor, the assembly of a Rho1-dependent medioapical actomyosin ring formed by nodes linked by filaments that contract the apical cell area. Cell area contraction alternates with relaxation, generating pulsatile changes in cell area that exert force on neighboring LCs. Moreover, Rho1 signaling is sensitive to mechanical changes, becoming active when tension decreases and cells expand, while the negative regulator RhoGAP71E accumulates when tension increases and cells contract. This results in cycles of cell area contraction and relaxation that are reciprocally synchronized between adjacent LCs. Thus, mechanically sensitive Rho1 signaling controls pulsatile medioapical actomyosin contraction and coordinates cell behavior across the epithelium. Disrupting the kinetics of pulsing can lead to developmental errors, suggesting this process controls cell shape and tissue integrity during epithelial morphogenesis of the retina.
Asunto(s)
Actomiosina , Drosophila , Ojo , Animales , Citoesqueleto de Actina/fisiología , Actomiosina/fisiología , Citocinesis , Drosophila/embriología , Morfogénesis , Ojo/embriología , Proteínas de Unión al GTP rho/fisiología , Proteínas de Drosophila/fisiología , Retina/citologíaRESUMEN
Epithelial remodeling of the Drosophila retina depends on the pulsatile contraction and expansion of apical contacts between the cells that form its hexagonal lattice. Phosphoinositide PI(3,4,5)P 3 (PIP 3 ) accumulates around tricellular adherens junctions (tAJs) during contact expansion and dissipates during contraction, but with unknown function. Here we found that manipulations of Pten or Pi3K that either decreased or increased PIP 3 resulted in shortened contacts and a disordered lattice, indicating a requirement for PIP 3 dynamics and turnover. These phenotypes are caused by a loss of protrusive branched actin, resulting from impaired activity of the Rac1 Rho GTPase and the WAVE regulatory complex (WRC). We additionally found that during contact expansion, Pi3K moves into tAJs to promote the cyclical increase of PIP 3 in a spatially and temporally precise manner. Thus, dynamic regulation of PIP 3 by Pten and Pi3K controls the protrusive phase of junctional remodeling, which is essential for planar epithelial morphogenesis.
RESUMEN
Lattice cells (LCs) in the developing Drosophila retina constantly move and change shape before attaining final forms. Previously we showed that repeated contraction and expansion of apical cell contacts affect these dynamics. Here we describe a second contributing factor, the assembly of a medioapical actomyosin ring composed of nodes linked by filaments that attract each other, fuse, and contract the LCs' apical area. This medioapical actomyosin network is dependent on Rho1 and its known effectors. Apical cell area contraction alternates with relaxation, generating pulsatile changes in apical cell area. Strikingly, cycles of contraction and relaxation of cell area are reciprocally synchronized between adjacent LCs. Further, in a genetic screen, we identified RhoGEF2 as an activator of these Rho1 functions and RhoGAP71E/C-GAP as an inhibitor. Thus, Rho1 signaling regulates pulsatile medioapical actomyosin contraction exerting force on neighboring cells, coordinating cell behavior across the epithelium. This ultimately serves to control cell shape and maintain tissue integrity during epithelial morphogenesis of the retina.
RESUMEN
Contractile actomyosin and protrusive branched F-actin networks interact in a dynamic balance, repeatedly contracting and expanding apical cell contacts to organize the epithelium of the developing fly retina. Previously we showed that the immunoglobulin superfamily protein Sidekick (Sdk) contributes to contraction by recruiting the actin binding protein Polychaetoid (Pyd) to vertices. Here we show that as tension increases during contraction, Sdk progressively accumulates at vertices, where it toggles to recruit the WAVE regulatory complex (WRC) to promote actin branching and protrusion. Sdk alternately interacts with the WRC and Pyd using the same C-terminal motif. With increasing protrusion, levels of Sdk and the WRC decrease at vertices while levels of Pyd increase paving the way for another round of contraction. Thus, by virtue of dynamic association with vertices and interchangeable associations with contractile and protrusive effectors, Sdk is central to controlling the balance between contraction and expansion that shapes this epithelium.
Asunto(s)
Citoesqueleto de Actina , Actinas , Proteínas de Drosophila , Proteínas del Ojo , Moléculas de Adhesión de Célula Nerviosa , Citoesqueleto de Actina/metabolismo , Actinas/genética , Actinas/metabolismo , Actomiosina/metabolismo , Animales , Proteínas de Drosophila/metabolismo , Drosophila melanogaster , Epitelio/metabolismo , Proteínas del Ojo/metabolismo , Morfogénesis , Moléculas de Adhesión de Célula Nerviosa/metabolismo , Proteínas de Uniones Estrechas/metabolismoRESUMEN
Tricellular adherens junctions are points of high tension that are central to the rearrangement of epithelial cells. However, the molecular composition of these junctions is unknown, making it difficult to assess their role in morphogenesis. Here, we show that Sidekick, an immunoglobulin family cell adhesion protein, is highly enriched at tricellular adherens junctions in Drosophila. This localization is modulated by tension, and Sidekick is itself necessary to maintain normal levels of cell bond tension. Loss of Sidekick causes defects in cell and junctional rearrangements in actively remodeling epithelial tissues like the retina and tracheal system. The adaptor proteins Polychaetoid and Canoe are enriched at tricellular adherens junctions in a Sidekick-dependent manner; Sidekick functionally interacts with both proteins and directly binds to Polychaetoid. We suggest that Polychaetoid and Canoe link Sidekick to the actin cytoskeleton to enable tricellular adherens junctions to maintain or transmit cell bond tension during epithelial cell rearrangements.
Asunto(s)
Uniones Adherentes/metabolismo , Proteínas de Drosophila/metabolismo , Proteínas del Ojo/metabolismo , Moléculas de Adhesión de Célula Nerviosa/metabolismo , Citoesqueleto de Actina/metabolismo , Animales , Adhesión Celular , Línea Celular , Proteínas de Drosophila/genética , Drosophila melanogaster , Células Epiteliales/metabolismo , Células Epiteliales/fisiología , Proteínas del Ojo/genética , Moléculas de Adhesión de Célula Nerviosa/genética , Unión Proteica , Proteínas de Uniones Estrechas/genética , Proteínas de Uniones Estrechas/metabolismoRESUMEN
Contractile forces eliminate cell contacts in many morphogenetic processes. However, mechanisms that balance contractile forces to promote subtler remodeling remain unknown. To address this gap, we investigated remodeling of Drosophila eye lattice cells (LCs), which preserve cell contacts as they narrow to form the edges of a multicellular hexagonal lattice. We found that during narrowing, LC-LC contacts dynamically constrict and expand. Similar to other systems, actomyosin-based contractile forces promote pulses of constriction. Conversely, we found that WAVE-dependent branched F-actin accumulates at LC-LC contacts during expansion and functions to expand the cell apical area, promote shape changes, and prevent elimination of LC-LC contacts. Finally, we found that small Rho GTPases regulate the balance of contractile and protrusive dynamics. These data suggest a mechanism by which WAVE regulatory complex-based F-actin dynamics antagonize contractile forces to regulate cell shape and tissue topology during remodeling and thus contribute to the robustness and precision of the process.
Asunto(s)
Citoesqueleto de Actina/metabolismo , Actinas/metabolismo , Drosophila melanogaster/crecimiento & desarrollo , Ojo/citología , Morfogénesis/fisiología , Familia de Proteínas del Síndrome de Wiskott-Aldrich/metabolismo , Actomiosina/metabolismo , Animales , Forma de la Célula , Células Cultivadas , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/metabolismo , Epitelio/crecimiento & desarrollo , Epitelio/metabolismo , Ojo/metabolismo , Femenino , Masculino , Contracción Muscular/fisiología , Proteínas de Unión al GTP rho/metabolismoRESUMEN
Epithelial morphogenesis generates the shape of tissues, organs and embryos and is fundamental for their proper function. It is a dynamic process that occurs at multiple spatial scales from macromolecular dynamics, to cell deformations, mitosis and apoptosis, to coordinated cell rearrangements that lead to global changes of tissue shape. Using time lapse imaging, it is possible to observe these events at a system level. However, to investigate morphogenetic events it is necessary to develop computational tools to extract quantitative information from the time lapse data. Toward this goal, we developed an image-based computational pipeline to preprocess, segment and track epithelial cells in 4D confocal microscopy data. The computational pipeline we developed, for the first time, detects the adherens junctions of epithelial cells in 3D, without the need to first detect cell nuclei. We accentuate and detect cell outlines in a series of steps, symbolically describe the cells and their connectivity, and employ this information to track the cells. We validated the performance of the pipeline for its ability to detect vertices and cell-cell contacts, track cells, and identify mitosis and apoptosis in surface epithelia of Drosophila imaginal discs. We demonstrate the utility of the pipeline to extract key quantitative features of cell behavior with which to elucidate the dynamics and biomechanical control of epithelial tissue morphogenesis. We have made our methods and data available as an open-source multiplatform software tool called TTT (http://github.com/morganrcu/TTT).
Asunto(s)
Uniones Adherentes/fisiología , Uniones Adherentes/ultraestructura , Células Epiteliales/citología , Células Epiteliales/fisiología , Imagenología Tridimensional/métodos , Morfogénesis/fisiología , Animales , Adhesión Celular/fisiología , Rastreo Celular/métodos , Drosophila , Microscopía Confocal/métodos , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
Elongation and invagination of epithelial tissues are fundamental developmental processes that contribute to the morphogenesis of embryonic and adult structures and are dependent on coordinated remodeling of cell-cell contacts. The morphogenesis of Drosophila leg imaginal discs depends on extensive remodeling of cell contacts and thus provides a useful system with which to investigate the underlying mechanisms. The small Rho GTPase regulator RhoGAP68F has been previously implicated in leg morphogenesis. It consists of on an N-terminal Sec14 domain and a C-terminal GAP domain. Here we examined the molecular function and role of RhoGAP68F in epithelial remodeling. We find that depletion of RhoGAP68F impairs epithelial remodeling from a pseudostratified to simple, while overexpression of RhoGAP68F causes tears of lateral cell-cell contacts and thus impairs epithelial integrity. We show that the RhoGAP68F protein localizes to Rab4 recycling endosomes and forms a complex with the Rab4 protein. The Sec14 domain is sufficient for localizing to Rab4 endosomes, while the activity of the GAP domain is dispensable. RhoGAP68F, in turn, inhibits the scission and movement of Rab4 endosomes involved in transport the adhesion proteins Fasciclin3 and E-cadherin back to cell-cell contacts. Expression of RhoGAP68F is upregulated during prepupal development suggesting that RhoGAP68F decreases the transport of key adhesion proteins to the cell surface during this developmental stage to decrease the strength of adhesive cell-cell contacts and thereby facilitate epithelial remodeling and leg morphogenesis.
Asunto(s)
Proteínas de Drosophila/metabolismo , Drosophila/embriología , Extremidades/embriología , Proteínas Activadoras de GTPasa/metabolismo , Discos Imaginales/embriología , Modelos Biológicos , Morfogénesis/fisiología , Animales , Cadherinas/metabolismo , Adhesión Celular/genética , Adhesión Celular/fisiología , Moléculas de Adhesión Celular Neuronal/metabolismo , Endosomas/fisiología , Técnica del Anticuerpo Fluorescente , Inmunoprecipitación , Proteínas Luminiscentes , Transporte de Proteínas/fisiología , Interferencia de ARN , Proteínas de Unión al GTP rab4/metabolismo , Proteína Fluorescente RojaRESUMEN
The Drosophila wing imaginal disc is subdivided along the proximodistal axis into the distal pouch, the hinge, the surrounding pleura, and the notum. While the genetic pathways that specify the identity of each of these domains have been well studied, the mechanisms that coordinate the relative expansion of these domains are not well understood. Here we investigated the role of the stat92E signal transducer and activator of transcription in wing proximodistal development. We find that stat92E is active ubiquitously in early wing imaginal discs, where it acts to inhibit the induction of ectopic wing fields. Subsequently, stat92E activity is down regulated in the notum and distal pouch. These dynamics coincide with and contribute to the proportional subdivision and expansion of these primordia. As development proceeds, stat92E activity becomes restricted to the hinge, where it promotes normal expansion of the hinge, and restricts expansion of the notum. We also find that stat92E is required autonomously to specify dorsal pleura identity and inhibit notum identity to properly subdivide the body wall. Our data suggest that stat92E activity is regulated along the proximodistal axis to pattern this axis and control the relative expansion of the pouch, hinge, and notum.
Asunto(s)
Proteínas de Drosophila/fisiología , Drosophila melanogaster/embriología , Regulación del Desarrollo de la Expresión Génica , Discos Imaginales/embriología , Factores de Transcripción STAT/fisiología , Alas de Animales/embriología , Alelos , Animales , Tipificación del Cuerpo , Proliferación Celular , Proteínas de Drosophila/genética , Proteínas Fluorescentes Verdes/metabolismo , Janus Quinasa 1/metabolismo , Microscopía Fluorescente , Mutación , Factores de Transcripción STAT/genética , Transducción de Señal , Factores de Transcripción/metabolismo , TransgenesRESUMEN
The growth and patterning of Drosophila wing and notum primordia depend on their subdivision into progressively smaller domains by secreted signals that emanate from localized sources termed organizers. While the mechanisms that organize the wing primordium have been studied extensively, those that organize the notum are incompletely understood. The genes odd-skipped (odd), drumstick (drm), sob, and bowl comprise the odd-skipped family of C(2)H(2) zinc finger genes, which has been implicated in notum growth and patterning. Here we show that drm, Bowl, and eyegone (eyg), a gene required for notum patterning, accumulate in nested domains in the anterior notum. Ectopic drm organized the nested expression of these anterior notum genes and downregulated the expression of posterior notum genes. The cell-autonomous induction of Bowl and Eyg required bowl, while the non-autonomous effects were independent of bowl. The homeodomain protein Bar is expressed along the anterior border of the notum adjacent to cells expressing the Notch (N) ligand Delta (Dl). bowl was required to promote Bar and repress Dl expression to pattern the anterior notum in a cell-autonomous manner, while lines acted antagonistically to bowl posterior to the Bowl domain. Our data suggest that the odd-skipped genes act at the anterior notum border to organize the notum anterior-posterior (AP) axis using both autonomous and non-autonomous mechanisms.
Asunto(s)
Tipificación del Cuerpo/genética , Proteínas de Unión al ADN/genética , Proteínas de Drosophila/genética , Drosophila melanogaster/citología , Drosophila melanogaster/embriología , Genes de Insecto/genética , Factores de Transcripción/genética , Alas de Animales/anatomía & histología , Alas de Animales/embriología , Animales , Células Clonales , Proteínas de Unión al ADN/metabolismo , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/genética , Regulación del Desarrollo de la Expresión Génica , Larva/genética , Modelos Biológicos , Factores de Transcripción/metabolismoRESUMEN
The Drosophila leg imaginal disc consists of a peripheral region that contributes to adult body wall, and a central region that forms the leg proper. While the patterning signals and transcription factors that determine the identity of adult structures have been identified, the mechanisms that determine the shape of these structures remain largely unknown. The family of Rho GTPases, which consists of seven members in flies, modulates cell adhesion, actomyosin contractility, protrusive membrane activity, and cell-matrix adhesion to generate mechanical forces that shape adult structures. The Rho GTPases are ubiquitously expressed and it remains unclear how they orchestrate morphogenetic events. The Rho guanine nucleotide exchange factors (RhoGEFs) and Rho GTPase activating proteins (RhoGAPs), which respectively activate and deactivate corresponding Rho GTPases, have been proposed to regulate the activity of Rho signaling cascades in specific spatiotemporal patterns to orchestrate morphogenetic events. Here we identify restricted expression of 12 of the 20 RhoGEFs and 10 of the 22 Rho RhoGAPs encoded in Drosophila during metamorphosis. Expression of a subset of each family of RhoGTPase regulators was restricted to motile cell populations including tendon, muscle, trachea, and peripodial stalk cells. A second subset was restricted either to all presumptive joints or only to presumptive tarsal joints. Depletion of individual RhoGEFs and RhoGAPs in the epithelium of the disc proper identified several joint-specific genes, which act downstream of segmental patterning signals to control epithelial morphogenesis. Our studies provide a framework with which to understand how Rho signaling cascades orchestrate complex morphogenetic events in multi-cellular organisms, and evidence that patterning signals regulate these cascades to control apical constriction and epithelial invagination at presumptive joints.
Asunto(s)
Drosophila melanogaster/crecimiento & desarrollo , Drosophila melanogaster/genética , Extremidades/crecimiento & desarrollo , Proteínas Activadoras de GTPasa/metabolismo , Regulación del Desarrollo de la Expresión Génica , Factores de Intercambio de Guanina Nucleótido/metabolismo , Morfogénesis/genética , Animales , Tipificación del Cuerpo/genética , Movimiento Celular/genética , Drosophila melanogaster/citología , Proteínas Activadoras de GTPasa/genética , Factores de Intercambio de Guanina Nucleótido/genética , Articulaciones/citología , Articulaciones/metabolismo , Especificidad de Órganos , Factores de Intercambio de Guanina Nucleótido RhoRESUMEN
The Drosophila leg imaginal disc provides a paradigm with which to understand the fundamental developmental mechanisms that generate an intricate appendage structure. Leg formation depends on the subdivision of the leg proximodistal (PD) axis into broad domains by the leg gap genes. The leg gap genes act combinatorially to initiate the expression of the Notch ligands Delta (Dl) and Serrate (Ser) in a segmental pattern. Dl and Ser induce the expression of a set of transcriptional regulators along the segment border, which mediate leg segment growth and joint morphogenesis. Here we show that Lines accumulates in nuclei in the presumptive tarsus and the inter-joints of proximal leg segments and governs the formation of these structures by destabilizing the nuclear protein Bowl. Across the presumptive tarsus, lines modulates the opposing expression landscapes of the leg gap gene dachshund (dac) and the tarsal PD genes, bric-a-brac 2 (bab), apterous (ap) and BarH1 (Bar). In this manner, lines inhibits proximal tarsal fates and promotes medial and distal tarsal fates. Across proximal leg segments, lines antagonizes bowl to promote Dl expression by relief-of-repression. In turn, Dl signals asymmetrically to stabilize Bowl in adjacent distal cells. Bowl, then, acts cell-autonomously, together with one or more redundant factors, to repress Dl expression. Together, lines and bowl act as a binary switch to generate a stable Notch signaling interface between Dl-expressing cells and adjacent distal cell. lines plays analogous roles in developing antennae, which are serially homologous to legs, suggesting evolutionarily conserved roles for lines in ventral appendage formation.
Asunto(s)
Tipificación del Cuerpo , Proteínas Portadoras/metabolismo , Proteínas de Drosophila/metabolismo , Drosophila/embriología , Receptores Notch/metabolismo , Transducción de Señal , Animales , Proteínas Portadoras/genética , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Drosophila/metabolismo , Proteínas de Drosophila/genética , Extremidades/embriología , Extremidades/crecimiento & desarrollo , Regulación del Desarrollo de la Expresión Génica , Genes de Insecto , Extremidad Inferior/embriología , Extremidad Inferior/crecimiento & desarrollo , Factores de Transcripción/genética , Factores de Transcripción/metabolismoRESUMEN
Central to embryonic development is the generation of molecular asymmetries across fields of undifferentiated cells. The Drosophila wing imaginal disc provides a powerful system with which to understand how such asymmetries are generated and how they contribute to formation of a complex structure. Early in development, the wing primordium is subdivided into a thin layer of peripodial epithelium (PE) and an apposing thickened layer of pseudostratified columnar epithelium (CE), known as the disc proper (DP). The DP gives rise to the wing blade, hinge and dorsal mesothorax, whereas the PE makes only a minor contribution to the ventral hinge and pleura. The mechanisms that generate this major asymmetry and its contribution to wing development are poorly understood. The Lines protein destabilizes the nuclear protein Bowl in ectodermal structures. Here, we show that Bowl accumulates in the PE from early stages of wing development and is absent from the DP. Broad inhibition of Bowl in the PE resulted in the replacement of the PE with a mirror image duplication of the DP. The failure to generate the PE severely compromised wing growth and the formation of the notum. Conversely, the activation of bowl in the DP (by removal or inhibition of lines function) resulted in the transformation of the DP into PE. Thus, we provide evidence that bowl and lines act as a binary switch to subdivide the wing primordium into PE and DP, and assign crucial roles for this asymmetry in wing growth and patterning.
Asunto(s)
Proteínas Portadoras/fisiología , Proteínas de Unión al ADN/fisiología , Proteínas de Drosophila/fisiología , Drosophila/fisiología , Epitelio/crecimiento & desarrollo , Factores de Transcripción/fisiología , Alas de Animales/crecimiento & desarrollo , Animales , Proteínas Portadoras/genética , Proteínas Portadoras/metabolismo , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Drosophila/embriología , Drosophila/genética , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Embrión no Mamífero , Epitelio/metabolismo , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Alas de Animales/embriología , Alas de Animales/fisiologíaRESUMEN
Hedgehog and Wingless signaling in the Drosophila embryonic epidermis represents one paradigm for organizer function. In patterning this epidermis, Hedgehog and Wingless act asymmetrically, and consequently otherwise equivalent cells on either side of the organizer follow distinct developmental fates. To better understand the downstream mechanisms involved, we have investigated mutations that disrupt dorsal epidermal pattern. We have previously demonstrated that the gene lines contributes to this process. Here we show that the Lines protein interacts functionally with the zinc-finger proteins Drumstick (Drm) and Bowl. Competitive protein-protein interactions between Lines and Bowl and between Drm and Lines regulate the steady-state accumulation of Bowl, the downstream effector of this pathway. Lines binds directly to Bowl and decreases Bowl abundance. Conversely, Drm allows Bowl accumulation in drm-expressing cells by inhibiting Lines. This is accomplished both by outcompeting Bowl in binding to Lines and by redistributing Lines to the cytoplasm, thereby segregating Lines away from nuclearly localized Bowl. Hedgehog and Wingless affect these functional interactions by regulating drm expression. Hedgehog promotes Bowl protein accumulation by promoting drm expression, while Wingless inhibits Bowl accumulation by repressing drm expression anterior to the source of Hedgehog production. Thus, Drm, Lines, and Bowl are components of a molecular regulatory pathway that links antagonistic and asymmetric Hedgehog and Wingless signaling inputs to epidermal cell differentiation. Finally, we show that Drm and Lines also regulate Bowl accumulation and consequent patterning in the epithelia of the foregut, hindgut, and imaginal discs. Thus, in all these developmental contexts, including the embryonic epidermis, the novel molecular regulatory pathway defined here is deployed in order to elaborate pattern across a field of cells.
Asunto(s)
Tipificación del Cuerpo/fisiología , Proteínas Portadoras/metabolismo , Diferenciación Celular/fisiología , Proteínas de Unión al ADN/metabolismo , Proteínas de Drosophila/metabolismo , Drosophila/metabolismo , Regulación del Desarrollo de la Expresión Génica/fisiología , Transducción de Señal/fisiología , Factores de Transcripción/metabolismo , Animales , Sistema Digestivo/metabolismo , Drosophila/embriología , Drosophila/genética , Epidermis/fisiología , Epitelio/metabolismo , Técnica del Anticuerpo Fluorescente , Proteínas Hedgehog , Inmunohistoquímica , Hibridación in Situ , Proteínas Proto-Oncogénicas/metabolismo , Transducción de Señal/genética , Transgenes/genética , Proteína Wnt1RESUMEN
Elongation of the Drosophila embryonic hindgut epithelium occurs by a process of oriented cell rearrangement requiring the genes drumstick (drm) and lines (lin). The elongating hindgut becomes subdivided into domains -- small intestine, large intestine and rectum -- each characterized by a specific pattern of gene expression dependent upon normal drm and lin function. We show that drm encodes an 81 amino acid (10 kDa) zinc finger protein that is a member of the Odd-skipped family. drm expression is localized to the developing midgut-hindgut junction and is required to establish the small intestine, while lin is broadly expressed throughout the gut primordium and represses small intestine fate. lin is epistatic to drm, suggesting a model in which localized expression of drm blocks lin activity, thereby allowing small intestine fate to be established. Further supporting this model, ectopic expression of Drm throughout the hindgut produces a lin phenotype. Biochemical and genetic data indicate that the first conserved zinc finger of Drm is essential for its function. We have thus defined a pathway in which a spatially localized zinc finger protein antagonizes a globally expressed protein, thereby leading to specification of a domain (the small intestine) necessary for oriented cell rearrangement.