Dynamics of cell shape inheritance in fission yeast.

Every cell has a characteristic shape key to its fate and function. That shape is not only the product of genetic design and of the physical and biochemical environment, but it is also subject to inheritance. However, the nature and contribution of cell shape inheritance to morphogenetic control is mostly ignored. Here, we investigate morphogenetic inheritance in the cylindrically-shaped fission yeast Schizosaccharomyces pombe. Focusing on sixteen different 'curved' mutants--a class of mutants which often fail to grow axially straight--we quantitatively characterize their dynamics of cell shape inheritance throughout generations. We show that mutants of similar machineries display similar dynamics of cell shape inheritance, and exploit this feature to show that persistent axial cell growth in S. pombe is secured by multiple, separable molecular pathways. Finally, we find that one of those pathways corresponds to the swc2-swr1-vps71 SWR1/SRCAP chromatin remodelling complex, which acts additively to the known mal3-tip1-mto1-mto2 microtubule and tea1-tea2-tea4-pom1 polarity machineries.This is the published manuscript. It has been published by PLoS in PLoS ONE and is available online here: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0106959

Piezo2 channel regulates RhoA and actin cytoskeleton to promote cell mechanobiological responses

Actin polymerization and assembly into stress fibers (SFs) is central to many cellular processes. However, how SFs form in response to the mechanical interaction of cells with their environment is not fully understood. Here we have identified Piezo2 mechanosensitive cationic channel as a transducer of environmental physical cues into mechanobiological responses. Piezo2 is needed by brain metastatic cells from breast cancer (MDA-MB-231-BrM2) to probe their physical environment as they anchor and pull on their surroundings or when confronted with confined migration through narrow pores. Piezo2-mediated Ca2+ influx activates RhoA to control the formation and orientation of SFs and focal adhesions (FAs). A possible mechanism for the Piezo2-mediated activation of RhoA involves the recruitment of the Fyn kinase to the cell leading edge as well as calpain activation. Knockdown of Piezo2 in BrM2 cells alters SFs, FAs, and nuclear translocation of YAP; a phenotype rescued by overexpression of dominant-positive RhoA or its downstream effector, mDia1. Consequently, hallmarks of cancer invasion and metastasis related to RhoA, actin cytoskeleton, and/or force transmission, such as migration, extracellular matrix degradation, and Serpin B2 secretion, were reduced in cells lacking Piezo2

The p25 subunit of the dynactin complex is required for dynein–early endosome interaction

The p25 subunit of the dynactin complex is required for the interaction between cytoplasmic dynein and early endosomes but is not required for dynein-mediated nuclear distribution

A Complete Cross Section Data Set for Electron Scattering by Pyridine: Modelling Electron Transport in the Energy Range 0–100 eV

Electron scattering cross sections for pyridine in the energy range 0–100 eV, which we previously measured or calculated, have been critically compiled and complemented here with new measurements of electron energy loss spectra and double differential ionization cross sections. Experimental techniques employed in this study include a linear transmission apparatus and a reaction microscope system. To fulfill the transport model requirements, theoretical data have been recalculated within our independent atom model with screening corrected additivity rule and interference effects (IAM-SCAR) method for energies above 10 eV. In addition, results from the R-matrix and Schwinger multichannel with pseudopotential methods, for energies below 15 eV and 20 eV, respectively, are presented here. The reliability of this complete data set has been evaluated by comparing the simulated energy distribution of electrons transmitted through pyridine, with that observed in an electron-gas transmission experiment under magnetic confinement conditions. In addition, our representation of the angular distribution of the inelastically scattered electrons is discussed on the basis of the present double differential cross section experimental results

Frequency (proportion of incidences) of each of the six types of cell shape division outcome over the entire cell lineages analysed for the sixteen curved mutants and the wild-type.

<p>Measurements are based on the phenotype of progenitors before cell septation and progeny immediately after cell septation at birth. 1–6 are represented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0106959#pone-0106959-g001" target="_blank">Fig. 1D</a>. The frequencies are separated and normalized in two groups based on the progenitor’s shape: 1–3, straight progenitor; 4–6, curved progenitor.</p><p>Frequency (proportion of incidences) of each of the six types of cell shape division outcome over the entire cell lineages analysed for the sixteen curved mutants and the wild-type.</p

Emerg Infect Dis

The amazing structural variety of cells is matched only by their functional diversity, and reflects the complex interplay between biochemical and mechanical regulation. How both regulatory layers generate specifically shaped cellular domains is not fully understood. Here, we report how cell growth domains are shaped in fission yeast. Based on quantitative analysis of cell wall expansion and elasticity, we develop a model for how mechanics and cell wall assembly interact and use it to look for factors underpinning growth domain morphogenesis. Surprisingly, we find that neither the global cell shape regulators Cdc42-Scd1-Scd2 nor the major cell wall synthesis regulators Bgs1-Bgs4-Rgf1 are reliable predictors of growth domain geometry. Instead, their geometry can be defined by cell wall mechanics and the cortical localization pattern of the exocytic factors Sec6-Syb1-Exo70. Forceful re-directioning of exocytic vesicle fusion to broader cortical areas induces proportional shape changes to growth domains, demonstrating that both features are causally linked

Active modulation of cell shape throughout generations.

<p><b>A</b>. Percentage of septating curved cells resulting from divisions of curved (blue) and straight (grey) mothers, for each mutant and the wild-type. Strains exhibiting a ratio between the first and the second percentages higher than 1.3 are highlighted by a yellow box. <b>B</b>. Percentage of septating curved cells resulting from curved (blue) and straight (grey) grandmothers. Strains exhibiting a ratio between the first and the second percentages higher than 1.3 are highlighted by a yellow box. <b>C</b>. Image sequences showing the inheritance, during two cell cycle rounds, of the Qdot-tagged cell wall (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0106959#s4" target="_blank">Materials and Methods</a>) of a <i>tea1Δ</i> and a <i>mal3Δ</i> cell lineage. Images are Z-stack maximal intensity projections of the medial 2 µm of cells. In both cases, curved cell wall segments (arrows) are transmitted practically unaltered from mother cells to their progeny, influencing not only their initial but also their final morphology. Note that the bottom <i>tea1Δ</i> cell shown rotated slightly. Such rotations were exceptional and rotating cells were not included in the quantitative analysis. <b>D</b>. Percentage of granddaughter cells (G2) that retain more than a third (light grey) or than 45% (dark grey) of the cell wall of their grandmother, for two monopolar mutants (<i>tea1Δ</i> and <i>tea4Δ</i>) and the bipolarly growing mutant <i>mal3Δ</i>. <b>E</b>. A <i>mal3Δ</i> cell that divides asymmetrically (red asterisk) predisposing one of its daughters to grow curved from the newly generated cell end. <b>F</b>. A ‘curved’ <i>mgr2Δ</i> cell (red asterisk) with two seemingly straight segments joined at an angle of 22<b>°</b> that, after division, produces two straight descendants (orange asterisks). <b>G</b>. Straight-to-curved (StoC) transition of a growing <i>swc2Δ</i> cell. <b>H</b>. Curved-to-straight (CtoS) transition of an initially curved <i>tea1Δ</i> cell (red asterisk) that ‘corrects’ its shape dynamically by growing. All bars represent 10 µm.</p

Cell shape inheritance rules predict the existence of multiple pathways controlling axial cell growth.

<p><b>A–C</b>. Clustergrams of all ‘curved’ mutants based on different inheritance frequencies quantitated: cell shape inheritance comparing the phenotype of mothers before septation with that of daughters before septation (<b>A</b>; using the six frequencies described in Fig. 1D); shape changes during growth (<b>B</b>; 1–4 represent, respectively, the frequencies of straight cells that remain straight after growth, straight cells that become curved, curved cells that straighten and curved cells that continue being curved); and cell shape inheritance comparing the phenotype of mothers before septation with that of daughters directly after septation, when they are born (<b>C</b>; the frequencies 1–6 follow the same logics as in A). The clustergrams display in a colour scale (black: average, red/green: higher/lower than the average) the different frequencies for each and order them hierarchically in a dendrogram based on their level of similarity. <b>D</b>. <i>Superdendrogram</i> grouping the sixteen curved mutants based on their similarities in cell shape inheritance pattern, combining all features quantitated (including cell shape and growth pattern, inheritance pattern over two generations, cytokinesis defects and cell shape changes during growth, see text for details). Three distinctive groups - ‘mitochondrial/ribosomal’, ‘cell polarity/microtubule cytoskeleton’ (‘pol’) and ‘chromatin remodelling’ (‘chr’) - and the wild-type are obtained using a cut-off at a distance of 0.24 (arbitrary units). <b>E</b>. Comparison of the overall penetrances of single (‘chr’: <i>swc2Δ</i>, <i>swr1Δ</i> and <i>vps71Δ</i>; ‘pol’: <i>tea1Δ</i>, <i>tea2Δ</i>, <i>tip1Δ</i> and <i>tea4Δ</i>) and double curved mutants (‘chr×chr’, ‘pol×pol’ and ‘chr×pol’; generated by the combination of each of the aforementioned single mutants). Penetrances of single and double mutants of the same group were not significantly different (p = 0.348 for the ‘chr’ group; p = 0.209 for the ‘pol’ group). By contrast, penetrances of double mutants from different groups were significantly different from the former (p = 0.023 for ‘chr×chr’ against ‘pol×pol’; p = 0.001 for the other two). <b>F</b>. Schematic representation of the different machineries that control axial cell growth in <i>S. pombe</i>.</p

Dynamics of cell shape inheritance of curved and straight cells from genotypically identical <i>S. pombe</i> populations.

<p><b>A</b>. Visual classification of curved (C) and straight (S) cells in the ‘curved’ mutant <i>tea4Δ</i>. The overall penetrance percentage was calculated by dividing the number of cells visually classified as curved (18) by the total number of cells (44). Bar, 10 µm. <b>B</b>. Quantitative classification of curved and straight cells. The radius of curvature of each cell was quantitatively estimated by calculating the inverted radius of a circle crossing the cell centre and two ends. Cells with an inverted radius of curvature greater than radius⁻¹ = 0.028 µm⁻¹ were considered curved. <b>C</b>. Time-lapse image sequence showing the lineage of a single <i>tip1Δ</i> cell over two rounds of cell division. Images were taken every 10 minutes and curvature was measured for each cell after birth and before septation. Unique name identifiers were given to each daughter and grand-daughter cell to indicate its origins, e.g. the daughters of 1 are 1.1 and 1.2. For cells selected as ‘curved’, a circle of radius equal to the cell’s radius of curvature is drawn around it. See also Electronic <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0106959#pone.0106959.s011" target="_blank">Movie S1</a>. Bar, 10 µm. <b>D</b>. The six types of morphological cell division outcomes observed in a mixed population containing curved and straight cells. <b>E</b>. The frequencies of those six outcomes over the entire cell lineage were calculated for four curved mutants and the wild-type, based on the phenotype of progenitors and progeny before cell septation. The penetrance at septation for each strain is shown. <b>F</b>. Duration of cell cycle and cell length, at birth and before septation, of curved (blue) and straight (grey) cells belonging to each of the indicated strains.</p