RESUMEN

Using constitutive GRF1/2 knockout mice, we showed previously that GRF2 is a key regulator of nuclear migration in retinal cone photoreceptors. To evaluate the functional relevance of that cellular process for two putative targets of the GEF activity of GRF2 (RAC1 and CDC42), here we compared the structural and functional retinal phenotypes resulting from conditional targeting of RAC1 or CDC42 in the cone photoreceptors of constitutive GRF2KO and GRF2WT mice. We observed that single RAC1 disruption did not cause any obvious morphological or physiological changes in the retinas of GRF2WT mice, and did not modify either the phenotypic alterations previously described in the retinal photoreceptor layer of GRF2KO mice. In contrast, the single ablation of CDC42 in the cone photoreceptors of GRF2WT mice resulted in clear alterations of nuclear movement that, unlike those of the GRF2KO retinas, were not accompanied by electrophysiological defects or slow, progressive cone cell degeneration. On the other hand, the concomitant disruption of GRF2 and CDC42 in the cone photoreceptors resulted, somewhat surprisingly, in a normalized pattern of nuclear positioning/movement, similar to that physiologically observed in GRF2WT mice, along with worsened patterns of electrophysiological responses and faster rates of cell death/disappearance than those previously recorded in single GRF2KO cone cells. Interestingly, the increased rates of cone cell apoptosis/death observed in single GRF2KO and double-knockout GRF2KO/CDC42KO retinas correlated with the electron microscopic detection of significant ultrastructural alterations (flattening) of their retinal ribbon synapses that were not otherwise observed at all in single-knockout CDC42KO retinas. Our observations identify GRF2 and CDC42 (but not RAC1) as key regulators of retinal processes controlling cone photoreceptor nuclear positioning and survival, and support the notion of GRF2 loss-of-function mutations as potential drivers of cone retinal dystrophies.

Asunto(s)

Factor 2 Liberador de Guanina Nucleótido , Células Fotorreceptoras Retinianas Conos , Animales , Ratones , Ratones Noqueados , Retina , Células Fotorreceptoras Retinianas Conos/ultraestructura , Sinapsis/ultraestructura

RESUMEN

Fission yeast undergoes premeiotic nuclear oscillation, which is dependent on microtubules and is driven by cytoplasmic dynein. Although the molecular mechanisms have been analyzed, how a robust oscillation is generated despite the dynamic behaviors of microtubules has yet to be elucidated. Here, we show that the oscillation exhibits cell length-dependent frequency and requires a balance between microtubule and viscous drag forces, as well as proper microtubule dynamics. Comparison of the oscillations observed in living cells with a simulation model based on microtubule dynamic instability reveals that the period of oscillation correlates with cell length. Genetic alterations that reduce cargo size suggest that the nuclear movement depends on viscous drag forces. Deletion of a gene encoding Kinesin-8 inhibits microtubule catastrophe at the cell cortex and results in perturbation of oscillation, indicating that nuclear movement also depends on microtubule dynamic instability. Our findings link numerical parameters from the simulation model with cellular functions required for generating the oscillation and provide a basis for understanding the physical properties of microtubule-dependent nuclear movements.

Asunto(s)

Schizosaccharomyces , Schizosaccharomyces/metabolismo , Dineínas/genética , Microtúbulos/metabolismo , Núcleo Celular/metabolismo , Tamaño de la Célula

RESUMEN

Nuclear movement is crucial for the development of many cell types and organisms. Nuclear movement is highly conserved, indicating its necessity for cellular function and development. In addition to mononucleated cells, there are several examples of cells in which multiple nuclei exist within a shared cytoplasm. These multinucleated cells and syncytia have important functions for development and homeostasis. Here, we review a subset of the developmental contexts in which the regulation of the movement and positioning of multiple nuclei are well understood, including pronuclear migration, the Drosophila syncytial blastoderm, the Caenorhabditis elegans hypodermis, skeletal muscle and filamentous fungi. We apply the principles learned from these models to other systems.

Asunto(s)

Caenorhabditis elegans , Núcleo Celular , Animales , Núcleo Celular/metabolismo , Caenorhabditis elegans/metabolismo , Transporte Biológico , Citoplasma/metabolismo , Células Gigantes , Drosophila

RESUMEN

In 1975, the death of dictator Francisco Franco opened the door to a turbulent period known as the "Spanish Transition." In the wake of the 1973 oil crisis, national politics, political violence and social demands were interwoven with international shifts in science and technology and global debates on "energy transitions." In close dialogue with foreign environmental groups, the anti-nuclear movement in Spain deployed a large repertoire of collective action; it ranged from pleasant activities to violent direct actions against nuclear technologies, but also included the making of technological alternatives. Counter-culture activists and counter-experts opposed nuclear energy and promoted renewable energy as two sides of the same coin.This paper explores the pioneering (and networked) initiatives of an anarchist-oriented group called Self-Managed Radical Alternative Technologies, created in 1976, and a group of young engineers who founded the cooperative Ecotècnia, which was behind the construction of the first commercial wind turbine in Catalonia in 1984. The paper focuses on the transnational circulation of grassroots knowledge, the epistemics of resistance, and the development of wind energy technologies as "technologies of protest." Technologies of protest illuminate how the social construction of technology is intertwined with what I call the "social destruction of technology."

Asunto(s)

Política , Tecnología , Energía Renovable , España , Violencia

RESUMEN

MAIN CONCLUSION: Actin polarization and actin-driven host nuclear movement towards the fungal penetration site facilitates successful host colonization during compatible pea-Erysiphe pisi interactions. Proper nuclear positioning in plant cells is crucial for developmental processes and response to (a)biotic stimuli. During plant-fungal interactions, the host nucleus moves toward the infection site, a process regulated by the plant cytoskeleton. Notably, rearrangement of the plant cytoskeleton is one of the earliest cellular responses to pathogen invasion and is known to impact penetration efficiency. Yet, the connection between host nuclear movement and fungal ingress is still elusive, particularly in legumes. Here, we investigated the host nuclear dynamics during compatible interactions between Pisum sativum (pea) and the adapted powdery mildew (PM) fungus Erysiphe pisi to gain insights into the functional relevance of PM-induced nuclear movement in legumes. We show that the host nucleus moves towards the fungal appressorium before penetration and becomes associated with the primary haustorium. However, the nucleus migrates away from the primary infection site as the infection progresses toward colony expansion and sporulation. Treatment of pea leaves with the actin-polymerization inhibitor, cytochalasin D, abolished host nuclear movement towards the fungal penetration site and restricted PM growth. In contrast, treatment with oryzalin, a microtubule-polymerization inhibitor, had no effect. In addition to nuclear movement, strong polarization of host actin filaments towards the site of appressorial contact was evident at early infection stages. Our results suggest that actin focusing mediates host nuclear movement to the fungal penetration site and facilitates successful colonization during compatible pea-PM interactions.

Asunto(s)

Ascomicetos , Pisum sativum , Actinas , Ascomicetos/fisiología , Erysiphe , Pisum sativum/microbiología , Enfermedades de las Plantas/microbiología , Plantas

RESUMEN

Nuclear migration during growth and development is a conserved phenomenon among many eukaryotic species. In Arabidopsis, movement of the nucleus is important for root hair growth, but the detailed mechanism behind this movement is not well known. Previous studies in different cell types have reported that the myosin XI-I motor protein is responsible for this nuclear movement by attaching to the nuclear transmembrane protein complex WIT1/WIT2. Here, we analyzed nuclear movement in growing root hairs of wild-type, myosin xi-i, and wit1 wit2 Arabidopsis lines in the presence of actin and microtubule-disrupting inhibitors to determine the individual effects of actin filaments and microtubules on nuclear movement. We discovered that forward nuclear movement during root hair growth can occur in the absence of myosin XI-I, suggesting the presence of an alternative actin-based mechanism that mediates rapid nuclear displacements. By quantifying nuclear movements with high temporal resolution during the initial phase of inhibitor treatment, we determined that microtubules work to dampen erratic nuclear movements during root hair growth. We also observed microtubule-dependent backwards nuclear movement when actin filaments were impaired in the absence of myosin XI-I, indicating the presence of complex interactions between the cytoskeletal arrays during nuclear movements in growing root hairs.

Asunto(s)

Proteínas de Arabidopsis , Arabidopsis , Citoesqueleto de Actina/metabolismo , Actinas/metabolismo , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Microtúbulos/metabolismo , Miosinas/metabolismo , Raíces de Plantas/metabolismo

RESUMEN

As cells move from two-dimensional surfaces into complex 3D environments, the nucleus becomes a barrier to movement due to its size and rigidity. Therefore, moving the nucleus is a key step in 3D cell migration. In this review, we discuss how coordination between cytoskeletal and nucleoskeletal networks is required to pull the nucleus forward through complex 3D spaces. We summarize recent migration models which utilize unique molecular crosstalk to drive nuclear migration through different 3D environments. In addition, we speculate about the role of proteins that indirectly crosslink cytoskeletal networks and the role of 3D focal adhesions and how these protein complexes may drive 3D nuclear migration.

Asunto(s)

Citoesqueleto , Adhesiones Focales , Transporte Biológico , Movimiento Celular , Núcleo Celular/metabolismo , Citoesqueleto/metabolismo

RESUMEN

Movement of the cell nucleus typically involves the cytoskeleton and either polymerization-based pushing forces or motor-based pulling forces. In the fission yeast Schizosaccharomyces pombe, nuclear movement and positioning are thought to depend on microtubule polymerization-based pushing forces. Here, we describe a novel, microtubule-independent, form of nuclear movement in fission yeast. Microtubule-independent nuclear movement is directed towards growing cell tips, and it is strongest when the nucleus is close to a growing cell tip, and weakest when the nucleus is far from that tip. Microtubule-independent nuclear movement requires actin cables but does not depend on actin polymerization-based pushing or myosin V-based pulling forces. The vesicle-associated membrane protein (VAMP)-associated proteins (VAPs) Scs2 and Scs22, which are critical for endoplasmic reticulum-plasma membrane contact sites in fission yeast, are also required for microtubule-independent nuclear movement. We also find that in cells in which microtubule-based pushing forces are present, disruption of actin cables leads to increased fluctuations in interphase nuclear positioning and subsequent altered septation. Our results suggest two non-exclusive mechanisms for microtubule-independent nuclear movement, which may help illuminate aspects of nuclear positioning in other cells.

Asunto(s)

Proteínas de Schizosaccharomyces pombe , Schizosaccharomyces , Núcleo Celular , Interfase , Microtúbulos , Proteínas de Schizosaccharomyces pombe/genética

RESUMEN

The nuclear position in eukaryotes is controlled by a nucleo-cytoskeletal network, critical in cell differentiation, division, and movement. Forces are transmitted through conserved Linker of Nucleoskeleton and Cytoskeleton (LINC) complexes that traverse the nuclear envelope and engage on either side of the membrane with diverse binding partners. Nesprin-2-giant (Nes2G), a LINC element in the outer nuclear membrane, connects to the actin directly as well as through FHOD1, a formin primarily involved in actin bundling. Here, we report the crystal structure of Nes2G bound to FHOD1 and show that the presumed G-binding domain of FHOD1 is rather a spectrin repeat (SR) binding enhancer for the neighboring FH3 domain. The structure reveals that SR binding by FHOD1 is likely not regulated by the diaphanous-autoregulatory domain helix of FHOD1. Finally, we establish that Nes1G also has one FHOD1 binding SR, indicating that these abundant, giant Nesprins have overlapping functions in actin-bundle recruitment for nuclear movement.

Asunto(s)

Proteínas del Citoesqueleto/metabolismo , Proteínas Fetales/química , Proteínas Fetales/metabolismo , Forminas/química , Forminas/metabolismo , Proteínas de Microfilamentos/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Secuencias de Aminoácidos , Animales , Cristalografía por Rayos X , Proteínas del Citoesqueleto/química , Proteínas del Citoesqueleto/genética , Células HEK293 , Humanos , Ratones , Proteínas de Microfilamentos/química , Proteínas de Microfilamentos/genética , Modelos Moleculares , Células 3T3 NIH , Proteínas del Tejido Nervioso/química , Proteínas del Tejido Nervioso/genética , Unión Proteica , Conformación Proteica , Dominios Proteicos

RESUMEN

At gastrulation, a subpopulation of epiblast cells constitutes a transient posteriorly located structure called the primitive streak, where cells that undergo epithelial-mesenchymal transition make up the mesoderm and endoderm lineages. Mouse embryo epiblast cells were labelled ubiquitously or in a mosaic fashion. Cell shape, packing, organization and division were recorded through live imaging during primitive streak formation. Posterior epiblast displays a higher frequency of rosettes, some of which associate with a central cell undergoing mitosis. Cells at the primitive streak, in particular delaminating cells, undergo mitosis more frequently than other epiblast cells. In pseudostratified epithelia, mitosis takes place at the apical side of the epithelium. However, mitosis is not restricted to the apical side of the epiblast, particularly on its posterior side. Non-apical mitosis occurs specifically in the streak even when ectopically located. Posterior non-apical mitosis results in one or two daughter cells leaving the epiblast layer. Cell rearrangement associated with mitotic cell rounding in posterior epiblast, in particular when non-apical, might thus facilitate cell ingression and transition to a mesenchymal phenotype.

Asunto(s)

Gastrulación , Estratos Germinativos , Animales , Transición Epitelial-Mesenquimal/genética , Mesodermo , Ratones , Mitosis

RESUMEN

The nucleus is specifically positioned within a cell in diverse biological contexts. There are multiple connections between the nuclear envelope and the cytoskeleton and these connections are involved in nuclear positioning. During cell polarization prior to cell migration, nuclear envelope proteins bind to the actin cytoskeleton and get organized into linear arrays, known as transmembrane actin-associated nuclear (TAN) lines to move the nucleus away from the leading edge. Here we describe methods to study perinuclear actin dynamics, including measurement of the thickness of actin cables coupled to TAN lines, measurement of the number of perinuclear actin cables, and ablation of perinuclear actin cables. These methods are used to identify mechanisms of nuclear positioning.

Asunto(s)

Actinas/metabolismo , Movimiento Celular , Núcleo Celular/metabolismo , Citoesqueleto de Actina/metabolismo , Transporte Activo de Núcleo Celular , Animales , Biomarcadores , Técnica del Anticuerpo Fluorescente , Ratones , Células 3T3 NIH , Membrana Nuclear/metabolismo

RESUMEN

Mispositioned nuclei are a hallmark of skeletal muscle disease. Many of the genes that are linked to Emery-Dreifuss muscular dystrophy (EDMD) encode proteins that are critical for nuclear movement in various cells, suggesting that disruptions in nuclear movement and position may contribute to disease progression. However, how these genes are coordinated to move nuclei is not known. Here, we focussed on two different emerin proteins in Drosophila, Bocksbeutel and Otefin, and their effects on nuclear movement. Although nuclear position was dependent on both, elimination of either Bocksbeutel or Otefin produced distinct phenotypes that were based in differential effects on the KASH-domain protein Klarsicht. Specifically, loss of Bocksbeutel reduced Klarsicht localization to the nucleus and resulted in a disruption in nuclear separation. Loss of Otefin increased the transcription of Klarsicht and led to premature separation of nuclei and their positioning closer to the edge of the muscle. Consistent with opposing functions, nuclear position is normal in otefin; bocksbeutel double mutants. These data indicate emerin-dependent regulation of Klarsicht levels in the nuclear envelope is a critical determinant of nuclear position.

Asunto(s)

Proteínas de Drosophila/metabolismo , Proteínas de la Membrana/metabolismo , Proteínas de Transporte de Membrana/metabolismo , Músculos/metabolismo , Membrana Nuclear/metabolismo , Proteínas Nucleares/metabolismo , Animales , Proteínas de Drosophila/genética , Drosophila melanogaster , Proteínas de la Membrana/genética , Proteínas de Transporte de Membrana/genética , Membrana Nuclear/genética , Proteínas Nucleares/genética

RESUMEN

Calcium is a secondary messenger that regulates and coordinates the cellular responses to environmental cues. Despite calcium being a key player during fertilization in plants, little is known about its role during the development of the endosperm. For this reason, the distribution, abundance, and dynamics of cytosolic calcium during the first stages of endosperm development of Agave tequilana and Agave salmiana were analyzed. Cytosolic calcium and actin filaments detected in the embryo sacs of Agave tequilana and A. salmiana revealed that they play an important role during the division and nuclear migration of the endosperm. After fertilization, a relatively high concentration of cytosolic calcium was located in the primary nucleus of the endosperm, as well as around migrating nuclei during the development of the endosperm. Cytosolic calcium participates actively during the first mitosis of the endosperm mother cell and interacts with the actin filaments that generate the motor forces during the migration of the nuclei through the large cytoplasm of the central cell.

Asunto(s)

Agave/crecimiento & desarrollo , Calcio/metabolismo , Citosol/metabolismo , Endospermo/crecimiento & desarrollo , Citoesqueleto de Actina/metabolismo , Agave/citología , Agave/metabolismo , Endospermo/citología , Endospermo/metabolismo , Mitosis , Células Vegetales/metabolismo

RESUMEN

Studies of the accelerated aging disorder Hutchinson-Gilford progeria syndrome (HGPS) can potentially reveal cellular defects associated with physiological aging. HGPS results from expression and abnormal nuclear envelope association of a farnesylated, truncated variant of prelamin A called "progerin." We surveyed the diffusional mobilities of nuclear membrane proteins to identify proximal effects of progerin expression. The mobilities of three proteins-SUN2, nesprin-2G, and emerin-were reduced in fibroblasts from children with HGPS compared with those in normal fibroblasts. These proteins function together in nuclear movement and centrosome orientation in fibroblasts polarizing for migration. Both processes were impaired in fibroblasts from children with HGPS and in NIH 3T3 fibroblasts expressing progerin, but were restored by inhibiting protein farnesylation. Progerin affected both the coupling of the nucleus to actin cables and the oriented flow of the cables necessary for nuclear movement and centrosome orientation. Progerin overexpression increased levels of SUN1, which couples the nucleus to microtubules through nesprin-2G and dynein, and microtubule association with the nucleus. Reducing microtubule-nuclear connections through SUN1 depletion or dynein inhibition rescued the polarity defects. Nuclear movement and centrosome orientation were also defective in fibroblasts from normal individuals over 60 y, and both defects were rescued by reducing the increased level of SUN1 in these cells or inhibiting dynein. Our results identify imbalanced nuclear engagement of the cytoskeleton (microtubules: high; actin filaments: low) as the basis for intrinsic cell polarity defects in HGPS and physiological aging and suggest that rebalancing the connections can ameliorate the defects.

Asunto(s)

Envejecimiento/genética , Lamina Tipo A/genética , Proteínas de la Membrana/genética , Proteínas de Microfilamentos/genética , Proteínas Asociadas a Microtúbulos/genética , Proteínas del Tejido Nervioso/genética , Proteínas Nucleares/genética , Progeria/genética , Envejecimiento/patología , Animales , Núcleo Celular/genética , Polaridad Celular/genética , Dineínas/química , Dineínas/genética , Fibroblastos/metabolismo , Regulación de la Expresión Génica , Humanos , Lamina Tipo A/química , Proteínas de la Membrana/química , Ratones , Proteínas de Microfilamentos/química , Células 3T3 NIH , Proteínas del Tejido Nervioso/química , Membrana Nuclear/genética , Proteínas Nucleares/química , Progeria/fisiopatología , Prenilación de Proteína

RESUMEN

A fundamental issue in developmental biology and in organ homeostasis is understanding the molecular mechanisms governing the balance between stem cell maintenance and differentiation into a specific lineage. Accumulating data suggest that cell cycle dynamics play a major role in the regulation of this balance. Here we show that the G2/M cell cycle regulator CDC25B phosphatase is required in mammals to finely tune neuronal production in the neural tube. We show that in chick neural progenitors, CDC25B activity favors fast nuclei departure from the apical surface in early G1, stimulates neurogenic divisions and promotes neuronal differentiation. We design a mathematical model showing that within a limited period of time, cell cycle length modifications cannot account for changes in the ratio of the mode of division. Using a CDC25B point mutation that cannot interact with CDK, we show that part of CDC25B activity is independent of its action on the cell cycle.

Asunto(s)

Ciclo Celular/genética , Modelos Estadísticos , Células-Madre Neurales/enzimología , Tubo Neural/enzimología , Neurogénesis/genética , Fosfatasas cdc25/genética , Animales , Proteína Quinasa CDC2/genética , Proteína Quinasa CDC2/metabolismo , Diferenciación Celular , Embrión de Pollo , Pollos , Embrión de Mamíferos , Regulación del Desarrollo de la Expresión Génica , Humanos , Proteínas Inmediatas-Precoces/genética , Proteínas Inmediatas-Precoces/metabolismo , Ratones , Ratones Noqueados , Células-Madre Neurales/citología , Tubo Neural/citología , Tubo Neural/crecimiento & desarrollo , Neuronas/citología , Neuronas/enzimología , Factor de Transcripción PAX7/genética , Factor de Transcripción PAX7/metabolismo , Mutación Puntual , Factores de Transcripción SOXB1/genética , Factores de Transcripción SOXB1/metabolismo , Médula Espinal/citología , Médula Espinal/enzimología , Médula Espinal/crecimiento & desarrollo , Imagen de Lapso de Tiempo , Proteínas Supresoras de Tumor/genética , Proteínas Supresoras de Tumor/metabolismo , Fosfatasas cdc25/metabolismo

RESUMEN

Skeletal muscle cells (myofibers) are rod-shaped multinucleated cells surrounded by an extracellular matrix (ECM) basal lamina. In contrast to other cell types, nuclei in myofibers are positioned just below the plasma membrane at the cell periphery. Peripheral nuclear positioning occurs during myogenesis and is driven by myofibril crosslinking and contraction. Here we show that peripheral nuclear positioning is triggered by local accumulation of fibronectin secreted by myofibroblasts. We demonstrate that fibronectin via α5-integrin mediates peripheral nuclear positioning dependent on FAK and Src activation. Finally, we show that Cdc42, downstream of restricted fibronectin activation, is required for myofibril crosslinking but not myofibril contraction. Thus we identify that local activation of integrin by fibronectin secreted by myofibroblasts activates peripheral nuclear positioning in skeletal myofibers.

Asunto(s)

Núcleo Celular/metabolismo , Fibronectinas/metabolismo , Integrina alfa5/metabolismo , Fibras Musculares Esqueléticas/metabolismo , Miofibroblastos/metabolismo , Proteína de Unión al GTP cdc42/metabolismo , Animales , Células Cultivadas , Activación Enzimática/fisiología , Quinasa 1 de Adhesión Focal/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Proteína de Unión al GTP cdc42/genética , Proteínas de Unión al GTP rac/metabolismo , Proteínas de Unión al GTP rho/metabolismo , Familia-src Quinasas/metabolismo

RESUMEN

BACKGROUND: A strength of Drosophila as a model system is its utility as a tool to screen for novel regulators of various functional and developmental processes. However, the utility of Drosophila as a screening tool is dependent on the speed and simplicity of the assay used. METHODS: Here, we use larval locomotion as an assay to identify novel regulators of skeletal muscle function. We combined this assay with muscle-specific depletion of 82 genes to identify genes that impact muscle function by their expression in muscle cells. The data from the screen were supported with characterization of the muscle pattern in embryos and larvae that had disrupted expression of the strongest hit from the screen. RESULTS: With this assay, we showed that 12/82 tested genes regulate muscle function. Intriguingly, the disruption of five genes caused an increase in muscle function, illustrating that mechanisms that reduce muscle function exist and that the larval locomotion assay is sufficiently quantitative to identify conditions that both increase and decrease muscle function. We extended the data from this screen and tested the mechanism by which the strongest hit, fascin, impacted muscle function. Compared to controls, animals in which fascin expression was disrupted with either a mutant allele or muscle-specific expression of RNAi had fewer muscles, smaller muscles, muscles with fewer nuclei, and muscles with disrupted myotendinous junctions. However, expression of RNAi against fascin only after the muscle had finished embryonic development did not recapitulate any of these phenotypes. CONCLUSIONS: These data suggest that muscle function is reduced due to impaired myoblast fusion, muscle growth, and muscle attachment. Together, these data demonstrate the utility of Drosophila larval locomotion as an assay for the identification of novel regulators of muscle development and implicate fascin as necessary for embryonic muscle development.

Asunto(s)

Proteínas Portadoras/fisiología , Drosophila/genética , Drosophila/fisiología , Proteínas de Microfilamentos/fisiología , Desarrollo de Músculos/fisiología , Mioblastos/fisiología , Interferencia de ARN , Animales , Proteínas Portadoras/genética , Fusión Celular , Femenino , Regulación de la Expresión Génica , Larva/fisiología , Masculino , Proteínas de Microfilamentos/genética , Movimiento/fisiología , Desarrollo de Músculos/genética , Músculo Esquelético/fisiología , Tendones/fisiología

RESUMEN

During muscle development, myonuclei undergo a complex set of movements that result in evenly spaced nuclei throughout the muscle cell. In Drosophila, two separate pools of Kinesin and Dynein work in synchrony to drive this process. However, how these two pools are specified is not known. Here, we investigate the role of Aplip1 (the Drosophila homolog of JIP1, JIP1 is also known as MAPK8IP1), a known regulator of both Kinesin and Dynein, in myonuclear positioning. Aplip1 localizes to the myotendinous junction and has genetically separable roles in myonuclear positioning and muscle stability. In Aplip1 mutant embryos, there was an increase in the percentage of embryos that had both missing and collapsed muscles. Via a separate mechanism, we demonstrate that Aplip1 regulates both the final position of and the dynamic movements of myonuclei. Aplip1 genetically interacts with both Raps (also known as Pins) and Kinesin to position myonuclei. Furthermore, Dynein and Kinesin localization are disrupted in Aplip1 mutants suggesting that Aplip1-dependent nuclear positioning requires Dynein and Kinesin. Taken together, these data are consistent with Aplip1 having a function in the regulation of Dynein- and Kinesin-mediated pulling of nuclei from the muscle end.This article has an associated First Person interview with the first author of the paper.

Asunto(s)

Proteínas Portadoras/metabolismo , Núcleo Celular/metabolismo , Proteínas de Drosophila/metabolismo , Drosophila/metabolismo , Desarrollo de Músculos , Músculos/metabolismo , Animales , Proteínas Portadoras/genética , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Núcleo Celular/genética , Drosophila/genética , Drosophila/crecimiento & desarrollo , Proteínas de Drosophila/genética , Dineínas/genética , Dineínas/metabolismo , Cinesinas/genética , Cinesinas/metabolismo

RESUMEN

Skeletal muscle cells possess a unique cellular architecture designed to fulfill their contractile function. Muscle cells (also known as myofibers) result from the fusion of hundreds of myoblasts and grow into a fiber of several centimeters in length. Cellular structures gradually become organized during muscle development to raise a mature contractile cell. A hallmark of this singular cell architecture is the position of nuclei at the periphery of the myofiber, below the plasma membrane. Nuclei in myofibers are evenly distributed except in specialized regions like the neuromuscular or myotendinous junctions. Disruption of nuclear positioning results in hindered muscle contraction and occurs in a multitude of muscle disorders as well as in regenerative myofibers. We will explore in this review the step by step nuclear migrations during myogenesis for nuclei to reach their evenly distributed anchored position at the periphery.

Asunto(s)

Núcleo Celular/metabolismo , Músculo Esquelético/metabolismo , Humanos

RESUMEN

The positioning and movement of the nucleus has recently emerged as an important aspect of cell migration. Understanding of nuclear positioning and movement has reached an apogee in studies of fibroblast migration. Specific nuclear positioning and movements have been described in the polarization of fibroblast for cell migration and in active migration in 2D and 3D environments. Here, we review recent studies that have uncovered novel molecular mechanisms that contribute to these events in fibroblasts. Many of these involve a connection between the nucleus and the cytoskeleton through the LINC complex composed of outer nuclear membrane nesprins and inner nuclear membrane SUN proteins. We consider evidence that appropriate nuclear positioning contributes to efficient fibroblast polarization and migration and the possible mechanism through which the nucleus affects cell migration.

Asunto(s)

Núcleo Celular/metabolismo , Fibroblastos/metabolismo , Transporte Biológico , Movimiento Celular