Journal: bioRxiv

Article Title: p53 deletion rescues lethal microcephaly in a mouse model with neural stem cell abscission defects

doi: 10.1101/272393

Figure Lengend Snippet: A. Examples of E12.5 dissociated cortical NSCs at stages of mitosis and cytokinesis, labeled with PH3 (red) and AurkB (green). B. The mean percentages (+/- s.e.m.) of cycling NSCs(Ki67+) in mitosis or midbody stage are slightly reduced in Kif20b-/- cultures. C. Categorizing the dividing NSCs from B, there is a small increase of Kif20b-/- NSCs in anaphase/early telophase. For B and C, n = 3 coverslips from 3 embryos each, with 1499 control and 1421 Kif20b-/- Ki67+ cells. * p ≤ 0.05, Student’s t-test for (B), Chi Square and Fisher’s exact test for (C). All cultures dissociated from E12.5 cortices and fixed after 24 hours. Scale bar, 5 μ m.

Article Snippet: Antibodies used in this analysis were rabbit polyclonal anti-human cleaved-caspase 3 (Cell-Signaling 9661S, 1:250), mouse monoclonal anti-rat beta-III-tubulin (Tuj1) (BioLegend 801201, 1:500), rat monoclonal anti-mouse Tbr2 (ebioscience 14-4875, 1:200), rabbit polyclonal anti-mouse Pax6 (BioLegend PRB-278P, 1:200), Aurora B kinase mouse monoclonal anti-rat (BD Biosciences 611082, 1:300), rabbit polyclonal anti-human alpha-tubulin (Thermo Scientific RB-9281-P0, 1:300), rat monoclonal alpha-tubulin (Novus Biologicals NB600-506, 1:300), rabbit monoclonal anti-human PH3 (Cell Signaling 3458, 1:200), chicken polyclonal anti-mouse Nestin (Aves Labs NES, 1:600), rat monoclonal anti-human Ki67 (eBioscience 14-5698, 1:100), mouse monoclonal anti-human p53 (Millipore 05-224, 1:250), rabbit polyclonal anti-mouse p53 (Leica Biosystems NCL-L-p53-CM5p, 1:500), rabbit polyclonal anti-human Beta-Catenin (Sigma-Aldrich SAB4500545 1:1000), and polyclonal rabbit anti Zo-1 (rabbit, Invitrogen 61-7300,1:50).

Techniques: Labeling

Journal: eLife

Article Title: Actin foci facilitate activation of the phospholipase C-γ in primary T lymphocytes via the WASP pathway

doi: 10.7554/eLife.04953

Figure Lengend Snippet: ( A ) TCR-induced recruitment of NWASP and WAVE2 to IS. Mouse primary WT CD4 T cells were incubated with bilayer containing ICAM1 alone (−) or both ICAM1 and anti-CD3 (+) for 2 min at 37°C, fixed and immunostained for endogenous proteins. Stained cells were visualized using TIRF microscopy. The graph shows quantitation of antibody fluorescence at IS, where each point represents the value obtained from a single cell. n1 = 16, n2 = 54 (for WAVE2), n3 = 16, n4 = 78 (for NWASP); p1, p2 < 0.0001 . Each point represents average levels of indicated protein at synapse in a single cell. ( B ) The images shown are TIRF plane distributions of the indicated proteins. As elaborated in the magnified areas marked with white boundary in original ‘merge’ image, there is a lack of co-localization between either of these proteins and TCR MCs. Scale bar, 5 μm. Insets in ( B ) have been intensity scaled differently from original ‘Merge’ panel to highlight protein distribution with more clarity. DOI: http://dx.doi.org/10.7554/eLife.04953.007

Article Snippet: HS1 antibody (D5A9), Phospho-Y397 HS-1 antibody (D12C1), phospho-Y319 Zap70/Y352 Syk (affinity purified antisera #2704), PLCγ1 (D9H10), phospho-Y783 PLCγ1 (#2821), NFAT1 (D43B1), phospho-Y416 SFK (#6943), phospho-Y171 LAT (#3581) and WAVE2 (D2C8) antibodies were obtained from Cell Signaling Technology (Beverly, MA).

Techniques: Incubation, Staining, Microscopy, Quantitation Assay, Fluorescence

Journal: eLife

Article Title: Actin foci facilitate activation of the phospholipase C-γ in primary T lymphocytes via the WASP pathway

doi: 10.7554/eLife.04953

Figure Lengend Snippet: Human CD4 T cells were incubated with culture media containing lentiviral particles carrying WASP shRNA or non-specific (control) shRNA for 48 hr ( A ) T cells transduced with WASP shRNA or control shRNA carrying lentiviral particles were incubated with endothelial monolayer for 10 min, fixed and processed for Alexa594-phalloidin (pseudo-colored green) and phospho-HS1 (pseudo-colored red) immuno-staining. The conjugates were then imaged using an EMCCD-coupled spinning disc confocal microscope. Each image represents a single confocal plane of T cell synapse, where the planar endothelial interface is in focus. The area outlined in ‘merge’ panels was further scaled and magnified to show the details with more clarity (bottom panels). The top panels show the image of the field of view in DIC (left image) or fluorescence settings. ( B ) A reduction in WASP levels results in defective phospho-HS1 accumulation at T cell-endothelial cell synapse. The upper graph shows quantitation of phalloidin intensity in the synaptic plane, while the lower graph shows phospho-HS1 levels in the same plane. For both the upper and lower graphs, n1 = 68, n2 = 29, p1 = 0.071, p2 < 0.0001 . This experiment was repeated twice with similar results. ( C ) Model of temporal sequence of events leading to F-actin foci formation and PLCγ signaling at the immunological synapse. Multiple pathways can result in actin polymerization and remodeling at the synaptic interface, contributing to F-actin organization in different SMAC zones. One such pathway involves WAVE2 recruitment by activated LFA1, followed by WAVE2 dependent Arp2/3 complex activation resulting in thick lamellipodial (dSMAC) and lamellar (pSMAC) F-actin meshworks. WAVE2-dependent F-actin pool is required for calcium-dependent calcium entry via the CRAC channel. Additional pathways including MyosinII-mediated actin remodeling is required for maintaining lamellar actin flow and directional persistence of microclusters (MCs) towards the cSMAC, and formin-mediated nucleation of F-actin promotes MTOC docking and stability of synapse. Another pool of F-actin or ‘F-actin foci’ is generated by the activity of WASP protein in the p- and dSMAC zones. Following TCR triggering, WASP is recruited at TCR signalosome via several possible mechanisms – such as via Vav, via NCK, via Zap70 and CrkL mediated WIP release and other effector mechanisms, and, through Fyn or PIP2 or PTP-PEST-binding at the plasma membrane (PM). Once activated, WASP recruits Arp2/3 complex to the MC, which then leads to actin branch nucleation and polymerization at the MC, over and above the local background actin. This process continues even during MC movement in the lamellar region, with a high F-actin turnover at the foci until its delivery to the cSMAC. In the foci, HS1 is recruited via binding both the Arp2/3 complex as well as F-actin, and is subsequently phosphorylated. As a consequence of early TCR signaling, PLCγ1 is also recruited to the MC signalosome, where it is stabilized via interactions with both F-actin, and foci residing HS1. F-actin foci dynamics in the proximity of the plasma membrane further support PLCγ1 phosphorylation, potentially by facilitating its interaction with PM-bound, upstream activators such as Itk. Phosphorylation of PLCγ1 by Itk then triggers phosphoinositide signaling, which in turn initiates calcium ion flux and NFAT1 activation. WASP deficiency or failure to activate Arp2/3 complex by WASPΔC mutant leads to selective loss of nucleation of foci at the MC. As a result, early signaling is not affected, however, both HS1 and PLCγ1 levels are severely reduced at the microcluster sites. The remaining PLCγ1 at synapse allows cell spreading and synapse formation, however, it is not sufficient to achieve calcium flux comparable to the control cells. Direct pharmacological inhibition of Arp2/3 complex using CK666 yields similar results; early TCR signaling is preserved while PLCγ1 phosphorylation and late signaling are severely perturbed. As actin polymerizing processes other than WASP also utilize Arp2/3 Complex, CK666-treated cells show a general reduction in lamellipodial and lamellar actin as well. However, the remaining F-actin levels are sufficient to support early TCR signaling. In contrast, total F-actin depolymerization at the synapse using CytochalasinD results in defects in early as well as late signaling, as has been reported in earlier studies. The image on the bottom shows a maximum intensity projection of synaptic contact interface of a human primary CD4 T cell, acquired using spinning disc confocal microscope. This cell was activated on a bilayer reconstituted with Alexa568 tagged anti-CD3 (red) and ICAM1 (unlabeled), for 2 min, fixed and stained for F-actin (green), and imaged. DOI: http://dx.doi.org/10.7554/eLife.04953.031

Article Snippet: HS1 antibody (D5A9), Phospho-Y397 HS-1 antibody (D12C1), phospho-Y319 Zap70/Y352 Syk (affinity purified antisera #2704), PLCγ1 (D9H10), phospho-Y783 PLCγ1 (#2821), NFAT1 (D43B1), phospho-Y416 SFK (#6943), phospho-Y171 LAT (#3581) and WAVE2 (D2C8) antibodies were obtained from Cell Signaling Technology (Beverly, MA).

Techniques: Incubation, shRNA, Control, Transduction, Immunostaining, Microscopy, Fluorescence, Quantitation Assay, Sequencing, Activation Assay, Generated, Activity Assay, Binding Assay, Clinical Proteomics, Membrane, Phospho-proteomics, Mutagenesis, Inhibition, Staining