Relaxation processes in the ferrielectric and alpha phases of antiferroelectric liquid crystals

Dielectric measurements of a new antiferroelectric liquid crystal series exhibiting different phase sequences have been carried out as a function of frequency from 10 Hz to 10 MHz. Structural properties of SCα* and ferrielectric SCFI* phases were discussed on the basis of the experimental results of temperature and dc bias field dependencies of the dielectric modes. Besides the soft mode observed around the SA−SCα* phase transition, a Goldstone mode was detected in the SCα* phase indicating a helicoidal structure with small pitch values. In agreement with a bilayer ordering model, the dielectric absorption in the SCFI* phase was splitted up into two contributions: one related to a Goldstone mode and the other to an azimuthal antiphase mode

Propriétés orientationnelles et conductrices de polypyrroles mésomorphes

Des polypyrroles à groupes latéraux mésogènes ont été synthétisés dans le but d'avoir des matériaux conducteurs intrinsèquement anisotropes. Les conditions de polymérisation ont été adaptées pour obtenir des polymères mésomorphes. Ces polymères peuvent être orientés macroscopiquement, soit en cours de synthèse en phase orientée, soit à l'issue de la polymérisation. L'orientation est confirmée au niveau des mésogènes par diffraction des rayons X, et au niveau du squelette polymère par diffusion des neutrons aux petits angles. Les conductivités des polypyrroles mésomorphes obtenus sont de l'ordre de 10-3-10-4 S.cm-1. Des mesures effectuées sur des films orientés ont mis nettement en évidence une anisotropie de la conductivité statique

Paracrine regulation of neural crest EMT by placodal MMP28.

Epithelial-mesenchymal transition (EMT) is an early event in cell dissemination from epithelial tissues. EMT endows cells with migratory, and sometimes invasive, capabilities and is thus a key process in embryo morphogenesis and cancer progression. So far, matrix metalloproteinases (MMPs) have not been considered as key players in EMT but rather studied for their role in matrix remodelling in later events such as cell migration per se. Here, we used Xenopus neural crest cells to assess the role of MMP28 in EMT and migration in vivo. We show that a catalytically active MMP28, expressed by neighbouring placodal cells, is required for neural crest EMT and cell migration. We provide strong evidence indicating that MMP28 is imported in the nucleus of neural crest cells where it is required for normal Twist expression. Our data demonstrate that MMP28 can act as an upstream regulator of EMT in vivo raising the possibility that other MMPs might have similar early roles in various EMT-related contexts such as cancer, fibrosis, and wound healing

Rescue of Sox10 expression can occur in absence of a rescue of Six1 expression.

(a–f) In situ hybridization for Sox10 (a–c) and Six1 (d–f), in embryos injected with CMO (a, n = 29; d, n = 56), MMP28-MOspl (b, n = 40; e, n = 43), or co-injected with MMP28-MOspl and mRNA for MMP28wt-GFP (c, n = 31; f, n = 41). (g, h) Proportions of embryos with symmetrical or decreased expression of Sox10 (g) or Six1 (h) in each experimental condition. Contingency tables for comparison of proportions: Sox10 CMO vs. MOspl, T = 57.34 (***), MOspl vs. rescue condition, T = 36.65 (***); Six1 CMO vs. MOspl, T = 70.59 (***), MOspl vs. rescue condition, T = 7.7 (***), Rescue Sox10 vs. Rescue Six1, T = 19.5 (***). Asterisks on images indicate the injected side. Dotted lines mark the midline of each embryo. Brown arrows indicate the missing portion of Six1 expression domain in MMP28-MOspl and MMP28-MOspl+mRNA MMP28wt-GFP embryos. Scale, embryos are 500 μm wide on average. (TIF)</p

3D confocal imaging of neural crest cells expressing MMP28-GFP.

Neural crest cells express MMP28-GFP (green) and are counterstained with DAPI (blue). DAPI staining is used as a mask to sample the green channel, highlighting the amount of MMP28-GFP present in the nuclei. Related to Fig 4. (AVI)</p

Processing of MMP28 requires entry into the secretion pathway.

(a, b) Western blots using anti-GFP antibody after cell fractionation from embryos expressing MMP28-GFP (WT), MMP28-ΔSP (deletion of the secretion peptide), or MMP28-ΔSPNLS (deletion of the secretion peptide and insertion of a strong NLS in C-terminus) on the soluble (a) and chromatin-associated (b) nuclear fractions, representative image from 2 independent experiments. Lamin B1 and Histone H3 were used as controls for the soluble and chromatin-associated fractions, respectively. Note that the lower band of MMP28 (circa 70kDa) is not detected in the ΔSP and ΔSPNLS conditions indicating that the pro-domain of MMP28 is not removed if MMP28 is prevented from entering the secretion pathway. (TIF)</p

MMP28 is required for normal EMT and cell migration.

(a) Phenotype of CMO, MMP28-MOspl, and MMP28-MOatg-injected embryos (stage 25) analysed for twist and sox9 expression, scale bar, 250 μm. (b) Graph plotting the distance migrated by NC cells in CMO and MMP28-MO embryos. twist: nCMO = 32, nMOspl = 45, nMOatg = 49; sox9: nCMO = 53, nMOspl = 44, nMOatg = 7. ANOVA followed by multiple comparisons, **** p p = 0.0005; **, p = 0.0034. (c) Representative examples of explants at t0 (1 h after plating on fibronectin) and +7.5 h, scale bar, 100 μm. (d, e) Distribution of explant areas per hour for CMO (n = 24), MMP28-MOatg-8ng (n = 16), MOatg-8ng+MMP28wt-1200pg (n = 11), MMP28wt-1200pg (n = 12). Analysed by two-way ANOVA per time point, ***, p = 0.0003; ****, p mmp28, sox10, twist, cadherins E, N and 11, integrin α5, and β1 subunits, after injection of MMP28-MOspl or CMO. The values are normalised to eef1a1 and to the levels of expression in CMO. From 3 independent mRNA extractions. Two-way ANOVA, p values CMO vs. MMP28-MO: mmp28 = 0.0001 (***), sox10 twist e-cadherin 0.9498 (ns), n-cadherin 0.8943 (ns), cadherin-11 integrin-β1 0.9813 (ns), integrin-α5 0.0915 (ns). Numerical data from all graphs can be found in the supporting S1 Data file. CMO, control Morpholino; EMT, epithelial–mesenchymal transition; MMP, matrix metalloproteinase; NC, neural crest.</p

PCR after chromatin immunoprecipitation with GFP, MMP14-GFP, MMP28-GFP, and Twist-GFP.

PCR after chromatin immunoprecipitation with GFP, MMP14-GFP, MMP28-GFP, and Twist-GFP.</p

PCR after chromatin immunoprecipitation with GFP and MMP28-GFP.

(a, b) Original images for the 3 independent ChIP assays analysed in Fig 7G–7L. On each gel, the band located left to the marker of size is the positive control of PCR efficiency for each site on total chromatin extracts. (TIF)</p

3D confocal imaging of neural crest cells expressing MMP28-flag.

Flag was detected by immunostaining (grey) and cells are counterstained with DAPI (blue). DAPI staining is used as a mask to sample the grey channel, highlighting the amount of MMP28-flag present in the nuclei. Related to Fig 4. (AVI)</p