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Development (Cambridge, England) Oct 2012Many epithelia have a common planar cell polarity (PCP), as exemplified by the consistent orientation of hairs on mammalian skin and insect cuticle. One conserved system...
Many epithelia have a common planar cell polarity (PCP), as exemplified by the consistent orientation of hairs on mammalian skin and insect cuticle. One conserved system of PCP depends on Starry night (Stan, also called Flamingo), an atypical cadherin that forms homodimeric bridges between adjacent cells. Stan acts together with other transmembrane proteins, most notably Frizzled (Fz) and Van Gogh (Vang, also called Strabismus). Here, using an in vivo assay for function, we show that the quintessential core of the Stan system is an asymmetric intercellular bridge between Stan in one cell and Stan acting together with Fz in its neighbour: such bridges are necessary and sufficient to polarise hairs in both cells, even in the absence of Vang. By contrast, Vang cannot polarise cells in the absence of Fz; instead, it appears to help Stan in each cell form effective bridges with Stan plus Fz in its neighbours. Finally, we show that cells containing Stan but lacking both Fz and Vang can be polarised to make hairs that point away from abutting cells that express Fz. We deduce that each cell has a mechanism to estimate and compare the numbers of asymmetric bridges, made between Stan and Stan plus Fz, that link it with its neighbouring cells. We propose that cells normally use this mechanism to read the local slope of tissue-wide gradients of Fz activity, so that all cells come to point in the same direction.
Topics: Animals; Animals, Genetically Modified; Body Patterning; Cadherins; Cell Polarity; Drosophila; Drosophila Proteins; Embryo, Nonmammalian; Frizzled Receptors; Gene Expression Regulation, Developmental; Membrane Proteins; Models, Biological; Pleura; Signal Transduction; Tissue Distribution
PubMed: 22949620
DOI: 10.1242/dev.083550 -
Developmental Cell Aug 2002Interactions between the actin and microtubule cytoskeletons occur during cell polarization. Two papers in a recent issue of the Journal of Cell Biology use fluorescent... (Review)
Review
Interactions between the actin and microtubule cytoskeletons occur during cell polarization. Two papers in a recent issue of the Journal of Cell Biology use fluorescent speckle microscopy (FSM) to analyze the relationship between actin and microtubule movements in migrating epithelial cells and in polarizing neuronal growth cones.
Topics: Actins; Animals; Cell Movement; Cell Polarity; Epithelial Cells; Growth Cones; Humans; Microtubules; Models, Animal; Polymers; Pseudopodia
PubMed: 12194844
DOI: 10.1016/s1534-5807(02)00227-7 -
Current Biology : CB Jun 2004The anterior-posterior axis of Drosophila is established before fertilisation when the oocyte becomes polarised to direct the localisation of bicoid and oskar mRNAs to... (Review)
Review
The anterior-posterior axis of Drosophila is established before fertilisation when the oocyte becomes polarised to direct the localisation of bicoid and oskar mRNAs to opposite poles of the egg. Here we review recent results that reveal that the oocyte acquires polarity much earlier than previously thought, at the time when it acquires its fate. The oocyte arises from a 16-cell germline cyst, and its selection and the initial cue for its polarisation are controlled by the asymmetric segregation of a germline specific organelle called the fusome. Several different downstream pathways then interpret this asymmetry to restrict distinct aspects of oocyte identity to this cell. Mutations in any of the six conserved Par proteins disrupt the early polarisation of the oocyte and lead to a failure to maintain its identity. Surprisingly, mutations affecting the control of the mitotic or meiotic cell cycle also lead to a failure to maintain the oocyte fate, indicating crosstalk between the nuclear and cytoplasmic events of oocyte differentiation. The early polarity of the oocyte initiates a series of reciprocal signaling events between the oocyte and the somatic follicle cells that leads to a reversal of oocyte polarity later in oogenesis, which defines the anterior-posterior axis of the embryo.
Topics: Animals; Body Patterning; Cell Differentiation; Cell Division; Cell Nucleus; Cell Polarity; Cytoplasm; Drosophila; Female; Mutation; Oocytes; Oogenesis; Organelles; RNA Interference; Signal Transduction; Spindle Apparatus; Xenopus
PubMed: 15182695
DOI: 10.1016/j.cub.2004.05.040 -
Cell and Tissue Banking Jun 2016To investigate the de-orientation effect of DSAEK grafts by observing the cross patterns and polarization power of human donor corneas using a polarizing device...
To investigate the de-orientation effect of DSAEK grafts by observing the cross patterns and polarization power of human donor corneas using a polarizing device (Lumaxis(®)). Forty human donor corneas were placed in small petri-plates with epithelial side facing up. Polarizing power (arbitrary unit) and crosses were monitored and recorded by the software. The tissue was marked at 'Superior' position to ensure that the base and the polarizer are in alignment with each other after the cut. The anterior lamellar cut was performed using microkeratome. The lenticule was placed back in the same position as marked to mimic the alignment. The tissue was further rotated by 45° ensuring that the base of the cornea and the polarizer were in alignment. The polarization power and 'crosses' were identified at each step. The average of forty corneas from pre-cut to post-45° angular change showed statistically significant difference (p < 0.05) in terms of polarizing power. The cross-shaped pattern deformed and lost the sharpness towards 45° angle. However, multiple variances in terms of 'cross-patterns' were observed throughout the study. Lumaxis(®) was able to determine the worst quality tissue in terms of polarization (no black zone and crosses). Despite the quality of cross pattern which can be used as an additional objective parameter to evaluate the optical properties of the corneal tissue, this preliminary study needs to be further justified in terms of clinical relevance whether polarization changes with oriented or de-oriented grafts have any effects and consequences on the visual acuity.
Topics: Cornea; Humans; Image Processing, Computer-Assisted; Microscopy, Polarization; Tissue Donors
PubMed: 26920874
DOI: 10.1007/s10561-016-9546-9 -
Nanomaterials (Basel, Switzerland) Aug 2022We propose versatile integrated polarizers based on geometric metasurfaces. Metasurface polarizer consists of an L-shaped hole array etched on a silver film, and it can...
We propose versatile integrated polarizers based on geometric metasurfaces. Metasurface polarizer consists of an L-shaped hole array etched on a silver film, and it can simultaneously generate several polarization states, including linear polarization, circular polarization, elliptical polarization, or even hybrid polarization. Meanwhile, the combination of output polarization states changes with the illumination polarization type. The theoretical analysis provides a detailed explanation for the generation of the integrated polarization states. The well-designed metasurface polarizers may generate more complex polarization modes, including vector beams and vector vortex beams. The theoretical and simulated results confirm the polarization performance of the proposed integrated metasurface polarizers. The compact design of metasurface polarizers and the controllable generation of versatile polarization combinations are a benefit to the applications of polarization light in optical imaging, biomedical sensing, and material processing.
PubMed: 36014681
DOI: 10.3390/nano12162816 -
Physical Review Letters May 2022The ability to control the light polarization state is critically important for diverse applications in information processing, telecommunications, and spectroscopy....
The ability to control the light polarization state is critically important for diverse applications in information processing, telecommunications, and spectroscopy. Here, we propose that a stack of anisotropic van der Waals materials can facilitate the building of optical elements with Jones matrices of unitary, Hermitian, non-normal, singular, degenerate, and defective classes. We show that the twisted stack with electrostatic control can function as arbitrary-birefringent wave-plate or arbitrary polarizer with tunable degree of non-normality, which in turn give access to plethora of polarization transformers including rotators, pseudorotators, symmetric and ambidextrous polarizers. Moreover, we discuss an electrostatic-reconfigurable stack which can be tuned to operate as four different polarizers and be used for Stokes polarimetry.
PubMed: 35622026
DOI: 10.1103/PhysRevLett.128.193902 -
Developmental Cell Jun 2021Interfaces between cells with distinct genetic identities elicit signals to organize local cell behaviors driving tissue morphogenesis. The Drosophila embryonic axis...
Interfaces between cells with distinct genetic identities elicit signals to organize local cell behaviors driving tissue morphogenesis. The Drosophila embryonic axis extension requires planar polarized enrichment of myosin-II powering oriented cell intercalations. Myosin-II levels are quantitatively controlled by GPCR signaling, whereas myosin-II polarity requires patterned expression of several Toll receptors. How Toll receptors polarize myosin-II and how this involves GPCRs remain unknown. Here, we report that differential expression of a single Toll receptor, Toll-8, polarizes myosin-II through binding to the adhesion GPCR Cirl/latrophilin. Asymmetric expression of Cirl is sufficient to enrich myosin-II, and Cirl localization is asymmetric at Toll-8 expression boundaries. Exploring the process dynamically, we reveal that Toll-8 and Cirl exhibit mutually dependent planar polarity in response to quantitative differences in Toll-8 expression between neighboring cells. Collectively, we propose that the cell surface protein complex Toll-8/Cirl self-organizes to generate local asymmetric interfaces essential for planar polarization of contractility.
Topics: Animals; Cell Polarity; Cytoskeletal Proteins; Drosophila Proteins; Drosophila melanogaster; Embryonic Development; Gene Expression Regulation, Developmental; Membrane Proteins; Morphogenesis; Multiprotein Complexes; Muscle Contraction; Myosin Type II; Receptors, G-Protein-Coupled; Receptors, Peptide; Toll-Like Receptor 8
PubMed: 33932333
DOI: 10.1016/j.devcel.2021.03.030 -
Scientific Reports Jan 2020Neonatal sepsis is accompanied by impaired apoptotic depletion of monocytes and macrophages (MΦ), aberrant cytokine production, impaired cell metabolism, and sustained...
Neonatal sepsis is accompanied by impaired apoptotic depletion of monocytes and macrophages (MΦ), aberrant cytokine production, impaired cell metabolism, and sustained inflammation. Macrophage-colony stimulating factor (M-CSF) triggers the differentiation from monocytes into MΦ (MΦ-0). Interleukin-10 (IL10) and Interferon-gamma (IFNy) further differentiate MΦ subpopulations, the anti-inflammatory MΦ-IL10 and the pro-inflammatory MΦ-IFNy subtype. We previously have shown significant differences between adult (PBMΦ) and cord blood (CBMΦ) in the metabolism of all subtypes. To test the hypothesis whether the competence to differentiate monocytes into MΦ-0 and to polarise into MΦ-IFNy and MΦ-IL10 was diminished in CBMΦ as compared to PBMΦ, we polarised monocytes by cultivation with M-CSF for 72 h, followed by stimulation with IFNy or IL10, for 48 h. After flow cytometry based immunotyping, we tested four functions: Phagocytosis of GFP-E. coli, uptake of erythrocytes, T-cell proliferation, induction of regulatory T-cells as well as phosphorylation analysis of AKT and STAT1/STAT3. Phosphorylation of STAT-1 and STAT-3, obligatory to differentiate into MΦ-IFNγ, MΦ-0 and MΦ-IL10, was found to be aberrant in CBMΦ. Whereas infected MΦ-0 showed identical phagocytic indices and intracellular degradation, TLR4-expression, NFkB up-regulation, IL10-, IL6-, and TNFα production of CBMΦ-0 were reduced. In addition, the capacity to bind aged erythrocytes and the consecutive IL10 production was lower in CBMΦ-IL10. Polarised PBMΦ-IFNy and PBMΦ-IL10 expressed higher levels of co-stimulatory receptors (CD80, CD86), had a higher capacity to stimulate T-cells and induced higher amounts of regulatory T-cells (all p < 0.05 vs. corresponding CBMΦ). Hypoxia-inducible-factor-1α (HIF-1α) was stronger expressed in CBMΦ-IFNy and upregulated in infected CBMΦ-0, whereas heme-oxygenase 1 (HO-1) expression was similar to adult PBMΦ. Neonatal MΦ-0, MΦ-IFNy and MΦ-IL10 polarisation is impaired with respect to phenotype and functions tested which may contribute to sustained inflammation in neonatal sepsis.
Topics: Adult; Cell Polarity; Cells, Cultured; Female; Flow Cytometry; Gene Expression Regulation; Humans; Infant, Newborn; Interferon-gamma; Interleukin-10; Macrophage Colony-Stimulating Factor; Macrophages; Male; Models, Biological; Monocytes; Sepsis
PubMed: 31953452
DOI: 10.1038/s41598-019-56928-4 -
Microscopy Research and Technique Jan 2000Neurons begin to polarize when one of the neurites becomes the axon. Hippocampal neurons in cell culture have a sharp transition between their unpolarized and polarized... (Review)
Review
Neurons begin to polarize when one of the neurites becomes the axon. Hippocampal neurons in cell culture have a sharp transition between their unpolarized and polarized stage revealed by the rapid growth of the future axon. Recent progress shows that both a cytoplasmic membrane flow and actin dynamics govern axon formation, and thereby initial neuronal polarization. We here review these mechanisms, evaluate their physiological role, and show similarities to the transient polarization of migrating fibroblasts. Finally, we present a model how actin dynamics and vectorial membrane flow may interact to achieve axon formation.
Topics: Actins; Animals; Axons; Cell Membrane; Cell Polarity; Cells, Cultured; Hippocampus; Neurites; Neurons; Rats
PubMed: 10620780
DOI: 10.1002/(SICI)1097-0029(20000101)48:1<3::AID-JEMT2>3.0.CO;2-O -
Biophysical Journal May 2008Motile eukaryotic cells polarize in response to external signals. Numerous mechanisms have been suggested to account for this symmetry breaking and for the ensuing...
Motile eukaryotic cells polarize in response to external signals. Numerous mechanisms have been suggested to account for this symmetry breaking and for the ensuing robust polarization. Implicated in this process are various proteins that are recruited to the plasma membrane and segregate at an emergent front or back of the polarizing cell. Among these are PI3K, PTEN, and members of the Rho family GTPases such as Cdc42, Rac, and Rho. Many such proteins, including the Rho GTPases, cycle between active membrane-bound forms and inactive cytosolic forms. In previous work, we have shown that this property, together with appropriate crosstalk, endows a biochemical circuit (Cdc42, Rac, and Rho) with the property of inherent polarizability. Here we show that this property is present in an even simpler system comprised of a single active/inactive protein pair with positive feedback to its own activation. The simplicity of this minimal system also allows us to explain the mechanism using insights from mathematical analysis. The basic idea resides in a well-known property of reaction-diffusion systems with bistable kinetics, namely, propagation of fronts. However, it crucially depends on exchange between active and inactive forms of the chemicals with unequal rates of diffusion, and overall conservation to pin the waves into a stable polar distribution. We refer to these dynamics as wave-pinning and we show that this phenomenon is distinct from Turing-instability-generated pattern formation that occurs in reaction-diffusion systems that appear to be very similar. We explain the mathematical basis of the phenomenon, relate it to spatial segregation of Rho GTPases, and show how it can account for spatial amplification and maintenance of polarity, as well as sensitivity to new stimuli typical in polarization of eukaryotic cells.
Topics: Cell Polarity; Diffusion; Eukaryotic Cells; Feedback, Physiological; Kinetics; Mathematics; Models, Biological; rho GTP-Binding Proteins
PubMed: 18212014
DOI: 10.1529/biophysj.107.120824