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Cilia
Kinds of Cilia Selected AbstractsCentrioles are freed from cilia by severing prior to mitosis,CYTOSKELETON, Issue 7 2010Jeremy D.K. Parker Abstract Cilia are necessary for normal tissue development and homeostasis and are generally present during interphase, but not in mitosis. The precise mechanism of premitotic ciliary loss has been controversial, with data supporting either sequential disassembly through the transition zone or, alternatively, a severing event at the base of the cilia. Here we show by live cell imaging and immunofluoresence microscopy that resorbing flagella of Chlamydomonas leave remnants associated with the mother cell wall. We postulated that the remnants are the product of severing of doublet microtubules between the basal bodies and the flagellar transition zone, thereby freeing the centrioles to participate in spindle organization. We show via TEM that flagellar remnants are indeed flagellar transition zones encased in vesicles derived from the flagellar membrane. This transition zone vesicle can be lodged within the cell wall or it can be expelled into the environment. This process is observable in Chlamydomonas, first because the released flagellar remnants can remain associated with the cell by virtue of attachments to the cell wall, and second because the Chlamydomonas transition zone is particularly rich with electron-dense structure. However, release of basal bodies for spindle-associated function is likely to be conserved among the eukaryotes. © 2010 Wiley-Liss, Inc. [source] Three types of cilia including a novel 9+4 axoneme on the notochordal plate of the rabbit embryoDEVELOPMENTAL DYNAMICS, Issue 12 2006Kerstin Feistel Abstract Motile monocilia play a pivotal role in left-right axis determination in mouse and zebrafish embryos. Cilia with 9+0 axonemes localize to the distal indentation of the mouse egg cylinder ("node"), while Kupffer's vesicle cilia in zebrafish show 9+2 arrangements. Here we studied cilia in a prototype mammalian embryo, the rabbit, which develops via a flat blastodisc. Transcription of ciliary marker genes Foxj1, Rfx3, lrd, polaris, and Kif3a initiated in Hensen's node and persisted in the nascent notochord. Cilia emerged on cells leaving Hensen's node anteriorly to form the notochordal plate. Cilia lengthened to about 5 ,m and polarized from an initially central position to the posterior pole of cells. Electron-microscopic analysis revealed 9+0 and 9+2 cilia and a novel 9+4 axoneme intermingled in a salt-and-pepper-like fashion. Our data suggest that despite a highly conserved ciliogenic program, which initiates in the organizer, axonemal structures may vary widely within the vertebrates. Developmental Dynamics 235:3348,3358, 2006. © 2006 Wiley-Liss, Inc. [source] Colloidal Films That Mimic CiliaADVANCED FUNCTIONAL MATERIALS, Issue 18 2010Fang Liu Abstract Cilia are wavy hair-like structures that extend outward from surfaces of various organisms. They are classified into two general categories, primary cilia, which exhibit sensing attributes, and motile cilia, which exert mechanical forces. A new poly(2-(N,N -dimethylamino)ethyl methacrylate- co -n-butyl acrylate- co - N,N -(dimethylamino) azobenzene acrylamide) (p(DMAEMA/nBA/DMAAZOAm) copolymer is prepared using colloidal synthesis, which, upon coalescence, form films capable of generating surfaces with cilia-like features. While film morphological features allow the formation of wavy whiskers, the chemical composition of the copolymer facilitates chemical, thermal, and electromagnetic responses manifested by simultaneous shape and color changes as well as excitation wavelength dependent fluorescence. These studies demonstrate that synthetically produced polymeric films can exhibit combined thermal, chemical, and electromagnetic sensing leading to locomotive and color responses, which may find numerous applications in sensing devices, intelligent actuators, defensive mechanisms, and others. [source] Caenorhabditis elegans DYF-11, an orthologue of mammalian Traf3ip1/MIP-T3, is required for sensory cilia formationGENES TO CELLS, Issue 1 2008Hirofumi Kunitomo Cilia and flagella play critical roles in cell motility, development and sensory perception in animals. Formation and maintenance of cilia require a conserved protein transport system called intraflagellar transport (IFT). Here, we show that Caenorhabditis elegans dyf-11 encodes an evolutionarily conserved protein required for cilium biogenesis. dyf-11 is expressed in most of the ciliated neurons and is regulated by DAF-19, a crucial transcription factor for ciliary genes in C. elegans. dyf-11 mutants exhibit stunted cilia, fluorescent dye-filling defects (Dyf) of sensory neurons, and abnormal chemotaxis (Che). Cell- and stage-specific rescue experiments indicated that DYF-11 is required for formation and maintenance of sensory cilia in cell-autonomous manner. Fluorescent protein-tagged DYF-11 localizes to cilia and moves antero- and retrogradely via IFT. Analysis of DYF-11 movement in bbs mutants further suggested that DYF-11 is likely associated with IFT complex B. Domain analysis using DYF-11 deletion constructs revealed that the coiled-coil region is required for proper localization and ciliogenesis. We further show that Traf3ip1/MIP-T3, the mammalian orthologue of DYF-11, localizes to cilia in the MDCK renal epithelial cells. [source] Cilia and the ciliopathies: An introduction,AMERICAN JOURNAL OF MEDICAL GENETICS, Issue 4 2009Helga V. Toriello No abstract is available for this article. [source] Ciliary assessment in bronchiectasisRESPIROLOGY, Issue 2 2000Kenneth Wt Tsang Objective: Bronchiectasis is a common condition among the Oriental population and affected patients suffer from chronic sputum production punctuated by recurrent infective exacerbations. Cilia are minute structures present on the surface of respiratory and other epithelial cells that beat continuously to maintain a sterile mucosal surface in the respiratory tract. Patients with primary ciliary dyskinesia could potentially develop recurrent sinotrachrobronchitis, bronchiectasis, serous otitis media, hydrocephalus, and male infertility. The assessment of cilia has, however, received little attention until recently and generally involves elaborate methods that require complex and expensive technology. This brief article discusses application of the saccharine test, light microscopy assessment of ciliary beat, and transmission electron microscopy assessment of the ultrastructure of cilia. The rationale and indications for ciliary assessment are also listed along with illustrations showing ciliary structure, equipment required for sampling and assessment of cilia, and transmission electron micrographs of ciliary ultrastructural abnormalities. [source] Development of olfactory epithelium in the human fetus: Scanning electron microscopic observationsCONGENITAL ANOMALIES, Issue 3 2009Mitsuhiro Kimura ABSTRACT Aims:, Human olfactory epithelium becomes functional at birth, but prenatal development remains unclear. In the present study, we aimed to clarify the development of human olfactory epithelium using scanning electron microscopy (SEM). Methods:, The development of human olfactory epithelium was observed in 24 externally normal fetuses, which were formalin-fixed and long-preserved, with a crown-rump length (CRL) of 102,336 mm (gestational week 14,38). The olfactory mucosa in the superior wall of the nasal septum near the choana were dissected and observed under SEM. We examined the number of olfactory vesicles per unit area, diameter of olfactory vesicles, and number and length of cilia on olfactory vesicles. Results:, At circa (ca) CRL 100 mm (ca 14 weeks), olfactory epithelium displayed several olfactory vesicles with 1,2 short cilia per unit area. At ca CRL 150 mm (ca 18 weeks), olfactory vesicles were present in small clusters, and cilia were longer. At CRL lager than 225 mm (ca 26 weeks), olfactory vesicles became located separately from each other, while length and number of cilia per olfactory vesicle were further increased. Conclusion:, The present findings suggest that fetal olfactory epithelium becomes morphologically almost the same as that in adults in late gestation, much later than previously thought. [source] Released nucleotides amplify the cilium-dependent, flow-induced [Ca2+]i response in MDCK cellsACTA PHYSIOLOGICA, Issue 3 2009H. A. Praetorius Abstract Aim:, Changes in perfusate flow produce increases in [Ca2+]i in renal epithelial cells. Cultured renal epithelia require primary cilia to sense subtle changes in flow. In perfused kidney tubules this flow response is caused by nucleotide signalling via P2Y2 receptors. It is, however, not known whether nucleotides are released by mechanical stress applied to renal primary cilia. Here we investigate whether nucleotides are released during the cilium-dependent flow response and contribute to the flow-induced, cilium-dependent [Ca2+]i signal. Methods:, MDCK cells loaded with Fluo-4-AM were observed at 37 °C in semi-open single or closed-double perfusion chambers. Results:, Our data suggest a purinergic component of the cilium-dependent flow-response: (1) ATP scavengers and P2 receptor antagonists reduced (55%) the cilium-dependent flow-response; (2) ATP added at subthreshold concentration sensitized the renal epithelia to flow changes; (3) increases in fluid flow transiently enhanced the ATP concentration in the superfusate (measured by biosensor-cells). To test if nucleotides were released in sufficient quantities to stimulate renal epithelia we used non-confluent MDCK cells without cilia as reporter cells. We confirmed that non-confluent cells do not respond to changes in fluid flow. Placing confluent, ciliated cells upstream in the in-flow path of the non-confluent cells made them responsive to fluid flow changes. This phenomenon was not observed if either non-confluent or de-ciliated confluent cells were placed upstream. The [Ca2+]i -response in the non-confluent cells with ciliated cells upstream was abolished by apyrase and suramin. Conclusion:, This suggests that subtle flow changes sensed by the primary cilium induces nucleotide release, which amplifies the epithelial [Ca2+]i -response. [source] Centrioles are freed from cilia by severing prior to mitosis,CYTOSKELETON, Issue 7 2010Jeremy D.K. Parker Abstract Cilia are necessary for normal tissue development and homeostasis and are generally present during interphase, but not in mitosis. The precise mechanism of premitotic ciliary loss has been controversial, with data supporting either sequential disassembly through the transition zone or, alternatively, a severing event at the base of the cilia. Here we show by live cell imaging and immunofluoresence microscopy that resorbing flagella of Chlamydomonas leave remnants associated with the mother cell wall. We postulated that the remnants are the product of severing of doublet microtubules between the basal bodies and the flagellar transition zone, thereby freeing the centrioles to participate in spindle organization. We show via TEM that flagellar remnants are indeed flagellar transition zones encased in vesicles derived from the flagellar membrane. This transition zone vesicle can be lodged within the cell wall or it can be expelled into the environment. This process is observable in Chlamydomonas, first because the released flagellar remnants can remain associated with the cell by virtue of attachments to the cell wall, and second because the Chlamydomonas transition zone is particularly rich with electron-dense structure. However, release of basal bodies for spindle-associated function is likely to be conserved among the eukaryotes. © 2010 Wiley-Liss, Inc. [source] Thinking about flagellar oscillationCYTOSKELETON, Issue 8 2009Charles J. Brokaw Abstract Bending of cilia and flagella results from sliding between the microtubular outer doublets, driven by dynein motor enzymes. This review reminds us that many questions remain to be answered before we can understand how dynein-driven sliding causes the oscillatory bending of cilia and flagella. Does oscillation require switching between two distinct, persistent modes of dynein activity? Only one mode, an active forward mode, has been characterized, but an alternative mode, either inactive or reverse, appears to be required. Does switching between modes use information from curvature, sliding direction, or both? Is there a mechanism for reciprocal inhibition? Can a localized capability for oscillatory sliding become self-organized to produce the metachronal phase differences required for bend propagation? Are interactions between adjacent dyneins important for regulation of oscillation and bend propagation? Cell Motil. Cytoskeleton 2008. © 2008 Wiley-Liss, Inc. [source] Centrioles to basal bodies in the spermiogenesis of Mastotermes darwiniensis (Insecta, Isoptera)CYTOSKELETON, Issue 5 2009Maria Giovanna Riparbelli Abstract In addition to their role in centrosome organization, the centrioles have another distinct function as basal bodies for the formation of cilia and flagella. Centriole duplication has been reported to require two alternate assembly pathways: template or de novo. Since spermiogenesis in the termite Mastotermes darwiniensis lead to the formation of multiflagellate sperm, this process represents a useful model system in which to follow basal body formation and flagella assembly. We present evidence of a possible de novo pathway for basal body formation in the differentiating germ cell. This cell also contains typical centrosomal proteins, such as centrosomin, pericentrin-like protein, ,-tubulin, that undergo redistribution as spermatid differentiation proceeds. The spermatid centrioles are long structures formed by nine doublet rather than triplet microtubules provided with short projections extending towards the surrounding cytoplasm and with links between doublets. The sperm basal bodies are aligned in parallel beneath the nucleus. They consist of long regions close to the nucleus showing nine doublets in a cartwheel array devoid of any projections; on the contrary, the short region close to the plasma membrane, where the sperm flagella emerge, is characterized by projections similar to those observed in the centrioles linking the basal body to the plasma membrane. It is hypothesized that this appearance is in connection with the centriole elongation and further with the flagellar axonemal organization. Microtubule doublets of sperm flagellar axonemes are provided with outer dynein arms, while inner arms are rarely visible. Cell Motil. Cytoskeleton 2009. © 2009 Wiley-Liss, Inc. [source] Functional studies of an evolutionarily conserved, cytochrome b5 domain protein reveal a specific role in axonemal organisation and the general phenomenon of post-division axonemal growth in trypanosomesCYTOSKELETON, Issue 1 2009Helen Farr Abstract Eukaryotic cilia and flagella are highly conserved structures composed of a canonical 9+2 microtubule axoneme. Several recent proteomic studies of cilia and flagella have been published, including a proteome of the flagellum of the protozoan parasite Trypanosoma brucei. Comparing proteomes reveals many novel proteins that appear to be widely conserved in evolution. Amongst these, we found a previously uncharacterised protein which localised to the axoneme in T. brucei, and therefore named it Trypanosome Axonemal protein (TAX)-2. Ablation of the protein using RNA interference in the procyclic form of the parasite has no effect on growth but causes a reduction in motility. Using transmission electron microscopy, various structural defects were seen in some axonemes, most frequently with microtubule doublets missing from the 9+2 arrangement. RNAi knockdown of TAX-2 expression in the bloodstream form of the parasite caused defects in growth and cytokinesis, a further example of the effects caused by loss of flagellar function in bloodstream form T. brucei. In procyclic cells we used a new set of vectors to ablate protein expression in cells expressing a GFP:TAX-2 fusion protein, which enabled us to easily quantify protein reduction and visualise axonemes made before and after RNAi induction. This establishes a useful generic technique but also revealed a specific observation that the new flagellum on the daughter trypanosome continues growth after cytokinesis. Our results provide evidence for TAX-2 function within the axoneme, where we suggest that it is involved in processes linking the outer doublet microtubules and the central pair. Cell Motil. Cytoskeleton 2008. © 2008 Wiley-Liss, Inc. [source] Protein kinase A RII-like (R2D2) proteins exhibit differential localization and AKAP interaction,CYTOSKELETON, Issue 7 2008Amy E. Hanlon Newell Abstract A-kinase anchoring proteins (AKAPs) bind to protein kinase A (PKA) via an amphipathic helix domain that interacts with a dimerization/docking domain on the regulatory (R) subunit of PKA. Four other mammalian proteins (ROPN1, ASP, SP17, and CABYR) also contain a highly conserved RII dimerization/docking (R2D2) domain, suggesting all four proteins may interact with all AKAPs in a manner similar to RII. All four of these proteins were originally detected in the flagellum of mammalian sperm. In this report, we demonstrate that all four R2D2 proteins are expressed in a wide variety of tissues and three of the proteins SP17, CABYR, and ASP are located in motile cilia of human bronchus and fallopian tubes. In addition, we detect SP17 in primary cilia. We also provide evidence that ROPN1 and ASP bind to a variety of AKAPs and this interaction can be disrupted with anchoring inhibitor peptides. The interaction of SP17 and CABYR with AKAPs appears to be much more limited. None of the R2D2 proteins appears to bind cAMP, a fundamental characteristic of the regulatory subunits of PKA. These observations suggest that R2D2 proteins utilize docking interactions with AKAPs to accomplish their function of regulating cilia and flagella. Based on location, affinity for AKAPs and lack of affinity for cAMP, it appears that each R2D2 protein has a unique role in this process. Cell Motil. Cytoskeleton 2008. © 2008 Wiley-Liss, Inc. [source] Evolution and persistence of the ciliumCYTOSKELETON, Issue 12 2007Peter Satir Abstract The origin of cilia, a fundamental eukaryotic organelle, not present in prokaryotes, poses many problems, including the origins of motility and sensory function, the origins of nine-fold symmetry, of basal bodies, and of transport and selective mechanisms involved in ciliogenesis. We propose the basis of ciliary origin to be a self-assembly RNA enveloped virus that contains unique tubulin and tektin precursors. The virus becomes the centriole and basal body, which would account for the self-assembly and self-replicative properties of these organelles, in contrast to previous proposals of spirochaete origin or endogenous differentiation, which do not readily account for the centriole or its properties. The viral envelope evolves into a sensory bud. The host cell supplies the transport machinery and molecular motors to construct the axoneme. Polymerization of cytoplasmic microtubules in the 9 + 0 axoneme completes the 9 + 2 pattern. Cell Motil. Cytoskeleton 2007. © 2007 Wiley-Liss, Inc. [source] Dynein light chain family in Tetrahymena thermophilaCYTOSKELETON, Issue 2 2007David E. Wilkes Abstract Dyneins are large protein complexes that produce directed movement on microtubules. In situ, dyneins comprise combinations of heavy, intermediate, light-intermediate, and light chains. The light chains regulate the locations and activities of dyneins but their functions are not completely understood. We have searched the recently sequenced Tetrahymena thermophila macronuclear genome to describe the entire family of dynein light chains expressed in this organism. We identified fourteen genes encoding putative dynein light chains and seven genes encoding light chain-like proteins. RNA-directed PCR revealed that all 21 genes were expressed. Quantitative real time reverse transcription PCR showed that many of these genes were upregulated after deciliation, indicating that these proteins are present in cilia. Using the nomenclature developed in Chlamydomonas, Tetrahymena expresses two isoforms each of LC2, LC4, LC7, and Tctex1, three isoforms of p28, and six LC8/LC8-like isoforms. Tetrahymena also expresses two LC3-like genes. No Tetrahymena orthologue was found for Chlamydomonas LC5 or LC6. This study provides a complete description of the different genes and isoforms of the dynein light chains that are expressed in Tetrahymena, a model organism in which the targeted manipulation of genes is straightforward. Cell Motil. Cytoskeleton 2006. © 2006 Wiley-Liss, Inc. [source] An electro-optic monitor of the behavior of Chlamydomonas reinhardtii ciliaCYTOSKELETON, Issue 2 2005Keith Josef Abstract The unicellular green alga Chlamydomonas reinhardtii steers through water with a pair of cilia (eukaryotic flagella). Long-term observation of the beating of its cilia with controlled stimulation is improving our understanding of how a cell responds to sensory inputs. Here we describe how to record ciliary motion continuously for long periods. We also report experiments on the network of intracellular signaling that connects the environment inputs with response outputs. Local spatial changes in ciliary response on the time scale of the underlying biochemical dynamics are observed. Near-infrared light monitors the cells held by a micropipette. This condition is tolerated well for hours, not interfering with ciliary beating or sensory transduction. A computer integrates the light stimulation of the eye of Chlamydomonas with the ciliary motion making possible long-term correlations. Measures of ciliary responses include the beating frequency, stroke velocity, and stroke duration of each cilium, and the relative phase of the cis and trans cilia. The stationarity and dependence of the system on light intensity was investigated. About 150,000,000 total beat cycles and up to 8 h on one cell have been recorded. Each beat cycle is resolved so that each asynchronous beat is detected. Responses extend only a few hundred milliseconds, but there is a persistence of momentary changes that last much longer. Interestingly, we see a response that is linear with absolute light intensity as well as different kinds of response that are clearly nonlinear, implying two signaling pathways from the cell body to the cilia. Cell Motil. Cytoskeleton 61:83,96, 2005. © 2005 Wiley-Liss, Inc. [source] Glutamylated tubulin: Diversity of expression and distribution of isoformsCYTOSKELETON, Issue 1 2003Marie-Louise Kann Abstract Glutamylation of , and , tubulin isotypes is a major posttranslational modification giving rise to diversified isoforms occurring mainly in neurotubules, centrioles, and axonemes. Monoglutamylated tubulin isoforms can be differentially recognized by two mAbs, B3 and GT335, which both recognize either polyglutamylated isoforms. In the present study, immunoelectron microscopy and immunofluorescence analyses were performed with these two mAbs to determine the expression and distribution of glutamylated tubulin isoforms in selected biological models whose tubulin isotypes are characterized. In mouse spermatozoa, microtubules of the flagellum contain polyglutamylated isoforms except in the tip where only monoglutamylated isoforms are detected. In spermatids, only a subset of manchette microtubules contain monoglutamylated tubulin isoforms. Cytoplasmic microtubules of Sertoli cells are monoglutamylated. Mitotic and meiotic spindles of germ cells are monoglutamylated whereas the HeLa cell mitotic spindle is polyglutamylated. Three models of axonemes are demonstrated as a function of the degree and extent of tubulin glutamylation. In lung ciliated cells, axonemes are uniformly polyglutamylated. In sea urchin sperm and Chlamydomonas, flagellar microtubules are polyglutamylated in their proximal part and monoglutamylated in their distal part. In Paramecium, cilia are bi- or monoglutamylated only at their base. In all cells, centrioles or basal bodies are polyglutamylated. These new data emphasize the importance of glutamylation in all types of microtubules and strengthen the hypothesis of its role in the regulation of the intracellular traffic and flagellar motility. Cell Motil. Cytoskeleton 55:14,25, 2003. © 2003 Wiley-Liss, Inc. [source] Asymmetric formation and possible function of the primary pore canal in plutei of Temnopleurus hardwickiDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 4 2003Yoshinobu Hara The development and possible function of the primary pore canal (PPC) in plutei of the sea urchin Temnopleurus hardwicki was examined by immunochemistry, electron microscopy and microsurgery. Left and right PPC that extended from coelomic sacs in plutei contained a bundle of cilia with a 9 + 2 structure that was initially detected as a group of anti-acetylated tubulin antibody-binding granules in the epithelium of coelomic sacs in 28 h postfertilization (PF) prism larvae. The granules extended to be a bundle of fibers toward the larval dorsal surface, concurrent with formation of the PPC on both sides, over the next 4 h. The cilia in both PPC beat actively. However, the PPC on the right side disappeared by approximately 55 h PF, establishing left,right asymmetry by 60 h PF (the four-arm pluteus stage). The numbers of cilia in the left and right PPC in 56 h PF plutei were five and eight, respectively. Microsurgical removal of the coelomic sac from both sides or the left side only from 26 h PF prism larvae decreased body width to 64 and 91% of normal width by 50 h PF pluteus stage, respectively, whereas that of the right PPC did not. These observations suggest that PPC contribute to the maintenance of normal body width, and that there is asymmetrical activity between the left and right PPC. [source] Oda16/Wdr69 is essential for axonemal dynein assembly and ciliary motility during zebrafish embryogenesisDEVELOPMENTAL DYNAMICS, Issue 8 2010Chunlei Gao Abstract In the alga Chlamydomonas reinhardtii, Oda16 functions during ciliary assembly as an adaptor for intraflagellar transport of outer arm dynein. Oda16 orthologs only occur in genomes of organisms that use motile cilia; however, such cilia play multiple roles during vertebrate development and the contribution of Oda16 to their assembly remains unexplored. We demonstrate that the zebrafish Oda16 ortholog (Wdr69) is expressed in organs with motile cilia and retains a role in dynein assembly. Antisense morpholino knockdown of Wdr69 disrupts ciliary motility and results in multiple phenotypes associated with vertebrate ciliopathies. Affected cilia included those in Kupffer's vesicle, where Wdr69 plays a role in generation of asymmetric fluid flow and establishment of organ laterality, and otic vesicles, where Wdr69 is needed to develop normal numbers of otoliths. Analysis of cilium ultrastructure revealed loss of outer dynein arms in morphant embryos. These results support a remarkable level of functional conservation for Oda16/Wdr69. Developmental Dynamics 239:2190,2197, 2010. © 2010 Wiley-Liss, Inc. [source] Planar cell polarity effector gene Fuzzy regulates cilia formation and Hedgehog signal transduction in mouseDEVELOPMENTAL DYNAMICS, Issue 12 2009Westley Heydeck Abstract Precise planar cell polarity (PCP) is critical for the development of multiple organ systems in animals. A group of core-PCP proteins are recognized to play crucial roles in convergent extension and other PCP-related processes in mammals. However, the functions of another group of PCP-regulating proteins, the PCP-effector proteins, are yet to be fully studied. In this study, the generation and characterization of a mouse mutant for the PCP effector gene Fuzzy (Fuz) is reported. Fuz homozygous mutants are embryonically lethal, with multiple defects including neural tube defects, abnormal dorsal/ventral patterning of the spinal cord, and defective anterior/posterior patterning of the limb buds. Fuz mutants also exhibit abnormal Hedgehog (Hh) signaling and inefficient proteolytic processing of Gli3. Finally, a significant decrease in cilia was found in Fuz homozygous mutants. In conclusion, Fuz plays an important role in cilia formation, Hh signal transduction, and embryonic development in mammals. Developmental Dynamics 238:3035,3042, 2009. © 2009 Wiley-Liss, Inc. [source] Morphogenesis of the node and notochord: The cellular basis for the establishment and maintenance of left,right asymmetry in the mouseDEVELOPMENTAL DYNAMICS, Issue 12 2008Jeffrey D. Lee Abstract Establishment of left,right asymmetry in the mouse embryo depends on leftward laminar fluid flow in the node, which initiates a signaling cascade that is confined to the left side of the embryo. Leftward fluid flow depends on two cellular processes: motility of the cilia that generate the flow and morphogenesis of the node, the structure where the cilia reside. Here, we provide an overview of the current understanding and unresolved questions about the regulation of ciliary motility and node structure. Analysis of mouse mutants has shown that the motile cilia must have a specific structure and length, and that they must point posteriorly to generate the necessary leftward fluid flow. However, the precise structure of the motile cilia is not clear and the mechanisms that position cilia on node cells have not been defined. The mouse node is a teardrop-shaped pit at the distal tip of the early embryo, but the morphogenetic events that create the mature node from cells derived from the primitive streak are only beginning to be characterized. Recent live imaging experiments support earlier scanning electron microscopy (SEM) studies and show that node assembly is a multi-step process in which clusters of node precursors appear on the embryo surface as overlying endoderm cells are removed. We present additional SEM and confocal microscopy studies that help define the transition stages during node morphogenesis. After the initiation of left-sided signaling, the notochordal plate, which is contiguous with the node, generates a barrier at the embryonic midline that restricts the cascade of gene expression to the left side of the embryo. The field is now poised to dissect the genetic and cellular mechanisms that create and organize the specialized cells of the node and midline that are essential for left,right asymmetry. Developmental Dynamics 237:3464,3476, 2008. © 2008 Wiley-Liss, Inc. [source] The primary cilium as a gravitational force transducer and a regulator of transcriptional noiseDEVELOPMENTAL DYNAMICS, Issue 8 2008Stephen J. Moorman Abstract Circumstantial evidence has suggested that the primary cilium might function as a gravity sensor. Direct evidence of its gravity-sensing function has recently been provided by studies of rohon beard neurons. These neurons showed changes in the variability of gene expression levels that are linked to the cyclic changes in the Earth's gravitational field due to the Sun and Moon. These cyclic changes also cause the tides. Rohon beard neurons, after the primary cilia have been selectively destroyed, no longer show changes in gene expression variability linked to the cyclic changes in Earth's gravitational field. After the neurons regrow their primary cilia, the link between variability in gene expression levels and the Earth's changing gravitational field returns. This suggests two new functions for the primary cilia, detecting the cyclical changes in the Earth's gravitational field and transducing those changes into changes in the variability (stochastic nature) of gene expression. Developmental Dynamics 237:1955,1959, 2008. © 2008 Wiley-Liss, Inc. [source] Characterization of primary cilia and Hedgehog signaling during development of the human pancreas and in human pancreatic duct cancer cell linesDEVELOPMENTAL DYNAMICS, Issue 8 2008Sonja K. Nielsen Abstract Hedgehog (Hh) signaling controls pancreatic development and homeostasis; aberrant Hh signaling is associated with several pancreatic diseases. Here we investigated the link between Hh signaling and primary cilia in the human developing pancreatic ducts and in cultures of human pancreatic duct adenocarcinoma cell lines, PANC-1 and CFPAC-1. We show that the onset of Hh signaling from human embryogenesis to fetal development is associated with accumulation of Hh signaling components Smo and Gli2 in duct primary cilia and a reduction of Gli3 in the duct epithelium. Smo, Ptc, and Gli2 localized to primary cilia of PANC-1 and CFPAC-1 cells, which may maintain high levels of nonstimulated Hh pathway activity. These findings indicate that primary cilia are involved in pancreatic development and postnatal tissue homeostasis. Developmental Dynamics 237:2039,2052, 2008. © 2008 Wiley-Liss, Inc. [source] Role for primary cilia in the regulation of mouse ovarian functionDEVELOPMENTAL DYNAMICS, Issue 8 2008Ellen T. Johnson Abstract Ift88 is a component of the intraflagellar transport complex required for formation and maintenance of cilia. Disruption of Ift88 results in depletion of cilia. The goal of the current study was to determine the role of primary cilia in ovarian function. Deletion of Ift88 in ovary using Cre-Lox recombination in mice resulted in a severe delay in mammary gland development including lack of terminal end bud structures, alterations in the estrous cycle, and impaired ovulation. Because estrogen drives the formation of end buds and Cre was expressed in the granulosa cells of the ovary, we tested the hypothesis that addition of estradiol to the mutant mice would compensate for defects in ovarian function and rescue the mammary gland phenotype. Mammary gland development including the formation of end bud structures resumed in mutant mice that were injected with estradiol. Together the results suggest that cilia are required for ovarian function. Developmental Dynamics 237:2053,2060, 2008. © 2008 Wiley-Liss, Inc. [source] Three types of cilia including a novel 9+4 axoneme on the notochordal plate of the rabbit embryoDEVELOPMENTAL DYNAMICS, Issue 12 2006Kerstin Feistel Abstract Motile monocilia play a pivotal role in left-right axis determination in mouse and zebrafish embryos. Cilia with 9+0 axonemes localize to the distal indentation of the mouse egg cylinder ("node"), while Kupffer's vesicle cilia in zebrafish show 9+2 arrangements. Here we studied cilia in a prototype mammalian embryo, the rabbit, which develops via a flat blastodisc. Transcription of ciliary marker genes Foxj1, Rfx3, lrd, polaris, and Kif3a initiated in Hensen's node and persisted in the nascent notochord. Cilia emerged on cells leaving Hensen's node anteriorly to form the notochordal plate. Cilia lengthened to about 5 ,m and polarized from an initially central position to the posterior pole of cells. Electron-microscopic analysis revealed 9+0 and 9+2 cilia and a novel 9+4 axoneme intermingled in a salt-and-pepper-like fashion. Our data suggest that despite a highly conserved ciliogenic program, which initiates in the organizer, axonemal structures may vary widely within the vertebrates. Developmental Dynamics 235:3348,3358, 2006. © 2006 Wiley-Liss, Inc. [source] Monocilia on chicken embryonic endocardium in low shear stress areasDEVELOPMENTAL DYNAMICS, Issue 1 2006Kim Van der Heiden Abstract During cardiovascular development, fluid shear stress patterns change dramatically due to extensive remodeling. This biomechanical force has been shown to drive gene expression in endothelial cells and, consequently, is considered to play a role in cardiovascular development. The mechanism by which endothelial cells sense shear stress is still unidentified. In this study, we postulate that primary cilia function as fluid shear stress sensors of endothelial cells. Such a function already has been attributed to primary cilia on epithelial cells of the adult kidney and of Hensen's node in the embryo where they transduce mechanical signals into an intracellular Ca2+ signaling response. Recently, primary cilia were observed on human umbilical vein endothelial cells. These primary cilia disassembled when subjected to high shear stress levels. Whereas endocardial,endothelial cells have been reported to be more shear responsive than endothelial cells, cilia are not detected, thus far, on endocardial cells. In the present study, we use field emission scanning electron microscopy to show shear stress-related regional differences in cell protrusions within the cardiovasculature of the developing chicken. Furthermore, we identify one of these cell protrusions as a monocilium with monoclonal antibodies against acetylated and detyrosinated alpha-tubulin. The distribution pattern of the monocilia was compared to the chicken embryonic expression pattern of the high shear stress marker Krüppel-like factor-2. We demonstrate the presence of monocilia on endocardial,endothelial cells in areas of low shear stress and postulate that they are immotile primary cilia, which function as fluid shear stress sensors. Developmental Dynamics 235:19,28, 2006. © 2005 Wiley-Liss, Inc. [source] Light and electron microscopic study of the anterior oesophagus of Bulla striata (Mollusca, Opisthobranchia)ACTA ZOOLOGICA, Issue 2 2010Alexandre Lobo-da-Cunha Abstract Lobo-da-Cunha, A., Oliveira, E., Alves, Â., Coelho, R. and Calado, G. 2010. Light and electron microscopic study of the anterior oesophagus of Bulla striata (Mollusca, Opisthobranchia). ,Acta Zoologica (Stockholm) 91: 125,138. The anterior oesophagus of Bulla striata was investigated with light and electron microscopy. In the most anterior region, the ridges of the oesophageal wall are covered by a ciliated columnar epithelium forming large apical blebs which are released into the lumen, an activity that is particularly intense in the oesophageal pouch. In the last two-thirds of the anterior oesophagus, the epithelium is covered with microvilli embedded in a cuticle, but apocrine secretion and cilia are absent. Subepithelial secretory cells are very abundant in the oesophageal wall, except in the roof of the pouch. They have a long neck that crosses the epithelium, whereas the cell body containing the nucleus is embedded in the connective tissue. Large electron-lucent secretory vesicles and many Golgi stacks fill most of their cytoplasm. The histochemical and cytochemical assays show that these cells secrete acid mucopolysaccharides. With the current and future studies we aim to obtain data for the establishment of relationships between morphofunctional features of the digestive system and food types in cephalaspideans. Additionally, the new data about the oesophageal pouch of B. striata may be useful for the establishment of eventual homologies with the oesophageal diverticula of other opisthobranchs. [source] The evolution of the protonephridial terminal organ across Rotifera with particular emphasis on Dicranophorus forcipatus, Encentrum mucronatum and Erignatha clastopis (Rotifera: Dicranophoridae)ACTA ZOOLOGICA, Issue 2 2010Ole Riemann Abstract Riemann, O. and Ahlrichs, W.H. 2009. The evolution of the protonephridial terminal organ across Rotifera with particular emphasis on Dicranophorus forcipatus, Encentrum mucronatum and Erignatha clastopis (Rotifera: Dicranophoridae). ,Acta Zoologica (Stockholm) 91: 199,211 We report on the ultrastructure of the protonephridial terminal organ in three species of dicranophorid rotifers (Dicranophorus forcipatus, Encentrum mucronatum and Erignatha clastopis). Differences between the three species relate to shape and size, the morphology of the filter region and the number of microvilli and cilia inside the terminal organ. A comparison across Rotifera indicates that the terminal organs in D. forcipatus display a number of plesiomorphic characters, but are modified in E. mucronatum and Er. clastopis. This is in accordance with the results of phylogenetic analyses suggesting a basal position of D. forcipatus compared with the more derived species E. mucronatum and Er. clastopis. Moreover, we survey available data on the terminal organ in Rotifera and discuss its evolutionary transformations. The protonephridial terminal organ in the common ancestor of Rotifera consisted of a cytoplasmic cylinder with cilia united into a vibratile flame and a single circle of circumciliary microvilli. Depending on the topology on which characters are optimized, the site of ultrafiltration was formed by longitudinal cytoplasmic columns spanned by a fine filter diaphragm or by pores in the wall of the terminal organ. In several taxa of Rotifera, the terminal organ , probably independently , lost its circumciliary microvilli. [source] The eye of the freshwater prosobranch gastropod Viviparus viviparus: ultrastructure, electrophysiology and behaviourACTA ZOOLOGICA, Issue 1 2006Valery V. Zhukov Abstract We used light and electron microscopy to study the retinal organization of the eye of Viviparus viviparus. Electroretinogram (ERG) recordings were used to investigate the electrophysiological responsiveness to flashes of light of varying intensity and colour, behavioural observations were made of phototactic reactions, and optical measurements and calculations related to the path of light rays in the eye were made. The retina contains principally two types of cells: first, photoreceptor cells with both microvilli and cilia, and second, cells, often strongly pigmented, that are supportive in nature. The ERGs obtained were essentially similar in form, amplitude and duration to those known from other gastropods that have exclusively rhabdomeric photoreceptors. Spectral sensitivity curves closely fitted the absorption spectrum of a rhodopsin-like pigment. The spectral sensitivity peak was at 475 nm. Measurements of the refractive indices of the lens gave values of 1.55 for the outer layer and 1.57 for the lens core. None of the snails tested exhibited a ,defensive reflex' and although no preference between light and dark regions was expressed, we nevertheless argue that, on the basis of optical measurements and calculations, the eye of V. viviparus is well-adapted for seeing under water. Our main conclusion is that in the eye of V. viviparus with its ,mixed photoreceptor' cell type, there is an equal probability for microvilli and cilia to function as principal photoreceptive elements. [source] Ultrastructure of an integumental organ with probable sensory function in Paragordius varius (nematomorpha)ACTA ZOOLOGICA, Issue 1 2004Andreas Schmidt-Rhaesa Abstract The cuticle of late parasitic stages of Paragordius varius (Leidy, 1851) is composed of a layer with large fibres and a second layer (often named the areolar layer) distal from it. In this paper, organs are described that start at the basal side of the epidermis, pass the epidermis and the fibrous layer of the cuticle and merge with large, cushion-like structures in the distal layer of the cuticle. The epidermal part of the organs is composed of darkly stained cells, which are probably in contact with the basi-epidermal nervous system. Up to four processes of this cell traverse the cuticle. These processes might include cilia, because they contain microtubule-like structures. The probable connection to nerve cells and the connection to the cushion-like structures in the outer cuticular layer make it likely that the organs described here are sensory in function. [source] | ||||||||||||||||||||||||||||||||||||||||