Tbx6 Regulates Left/Right Patterning in Mouse Embryos through Effects on Nodal Cilia and Perinodal Signaling

Background: The determination of left/right body axis during early embryogenesis sets up a developmental cascade that coordinates the development of the viscera and is essential to the correct placement and alignment of organ systems and vasculature. Defective left-right patterning can lead to congenital cardiac malformations, vascular anomalies and other serious health problems. Here we describe a novel role for the T-box transcription factor gene Tbx6 in left/right body axis determination in the mouse. Results: Embryos lacking Tbx6 show randomized embryo turning and heart looping. Our results point to multiple mechanisms for this effect. First, Dll1, a direct target of Tbx6, is down regulated around the node in Tbx6 mutants and there is a subsequent decrease in nodal signaling, which is required for laterality determination. Secondly, in spite of a lack of expression of Tbx6 in the node, we document a profound effect of the Tbx6 mutation on the morphology and motility of nodal cilia. This results in the loss of asymmetric calcium signaling at the periphery of the node, suggesting that unidirectional nodal flow is disrupted. To carry out these studies, we devised a novel method for direct labeling and live imaging cilia in vivo using a genetically-encoded fluorescent protein fusion that labels tubulin, combined with laser point scanning confocal microscopy for direct visualization of cilia movement. Conclusions: We conclude that the transcription factor gene Tbx6 is essential for correct left/right axis determination in th

Cartographie du remplissage glaciaire passé de Valles Marineris, Mars

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Extensive glaciation of Valles Marineris (Mars) revealed by sackung, trimlines and ablation tills

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Formation et accumulation de sulfates dans les calottes polaires actuelles et dans les glaciers équatoriaux anciens de Mars

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Staphylococcal <i>α</i>-toxin was cytotoxic for DDADs.

<p>DDAD cells were treated with various concentrations of α-toxin for 24 h. The Cell Titer 96® Aqueous One Solution Proliferation Assay and propidium iodine were used to assess the cellular toxicity and damage. (a) At 5 ug/ml and 10 ug/ml of α-toxin significant cell death occurred, while no effect was observed at lower concentrations (below 1 ug/ml). (b) Consistent with the cytotoxic effect, significant amounts of PI were incorporated into DDADs at 5 ug/ml and 10 ug/ml of α-toxin, but not at lower concentrations (*represents p<0.05, Students t-test).</p

Expression of adipocyte markers in differentiated cells.

<p>NPADs and DPADs (white bars) were differentiated into NDADs and DDADs (black bars), respectively. The expression of adipocyte markers was examined by quantitative reverse transcriptase PCR (q-RT-PCR). (A) Peroxisome proliferator-activated receptor gamma (PPARγ); (B) CCAAT/enhancer binding protein-alpha (C/EBPα); (C) lipoprotein lipase (LPL); (D) fatty acid binding protein 4 (FABP-4); (E) adipsin; (F) adiponectin; and (G) leptin were all induced to high levels upon differentiation. (H) A marker of pre-adipocytes termed C-C motif chemokine 2 (CCL2) was expressed in the undifferentiated DPAD and NPAD cells but reduced upon differentiation. Values were normalized to GAPDH and made relative to undifferentiated NPADs and represent 3 replicates. All transcript level changes in differentiated cells as compared to undifferentiated cells were statistically significant (*represents p<0.05; **represents p<0.01, Students t-test). For all genes except leptin, differences between DDADs and NDADs were significant (#p<0.05, Students t-test).</p

α-toxin failed to induce IL-6 and IL-8 production in DDADs.

<p>DDADs were treated with low concentrations of α-toxin for 24 h. The culture supernates were collected for IL-6 (a) and IL-8 (b) quantification by ELISA.</p

TSST-1 and SEB induced IL-6 and Il-8 production in DDADs and NDADs.

<p>Differentiated adipocytes were treated with 50/ml and 100 ug/ml of TSST-1 or SEB for 24 h. The culture supernates were collected from DDADs for IL-6 (a) and IL-8 (b) and NDADs IL-6 (c) and IL-8 (d) for quantification by ELISA (*represents p<0.05; **p<0.01, Students t-test). Fold changes in IL-6 (e) and IL-8 (f) production were calculated in DDADs and NDADs after TSST-1 and SEB exposure. Values represent fold changes relative to PBS-treated controls.</p

Genes that were analyzed by q-RT-PCR with respective primers.

<p>Genes that were analyzed by q-RT-PCR with respective primers.</p