Retinoic Acid-Activated Ndrg1a Represses Wnt/β-catenin Signaling to Allow <i>Xenopus</i> Pancreas, Oesophagus, Stomach, and Duodenum Specification

<div><p>How cells integrate multiple patterning signals to achieve early endoderm regionalization remains largely unknown. Between gastrulation and neurulation, retinoic acid (RA) signaling is required, while Wnt/β-catenin signaling has to be repressed for the specification of the pancreas, oesophagus, stomach, and duodenum primordia in <i>Xenopus</i> embryos. In attempt to screen for RA regulated genes in <i>Xenopus</i> endoderm, we identified a direct RA target gene, N-myc downstream regulated gene 1a (<i>ndrg1a</i>) that showed expression early in the archenteron roof endoderm and late in the developing pancreas, oesophagus, stomach, and duodenum. Both antisense morpholino oligonucleotide mediated knockdown of <i>ndrg1a</i> in <i>Xenopus laevis</i> and the transcription activator-like effector nucleases (TALEN) mediated disruption of <i>ndrg1</i> in <i>Xenopus tropicalis</i> demonstrate that like RA signaling, Ndrg1a is specifically required for the specification of <i>Xenopus</i> pancreas, oesophagus, stomach, and duodenum primordia. Immunofluorescence data suggest that RA-activated Ndrg1a suppresses Wnt/β-catenin signaling in <i>Xenopus</i> archenteron roof endoderm cells. Blocking Wnt/β-catenin signaling rescued Ndrg1a knockdown phenotype. Furthermore, overexpression of the putative Wnt/β-catenin target gene Atf3 phenocopied knockdown of Ndrg1a or inhibition of RA signaling, while Atf3 knockdown can rescue Ndrg1a knockdown phenotype. Lastly, the pancreas/stomach/duodenum transcription factor Pdx1 was able to rescue Atf3 overexpression or Ndrg1a knockdown phenotype. Together, we conclude that RA activated Ndrg1a represses Wnt/β-catenin signaling to allow the specification of pancreas, oesophagus, stomach, and duodenum progenitor cells in <i>Xenopus</i> embryos.</p></div

Facile one-step chemical deposition process to fabricate superhydrophobic porous Cu films on Al alloy surface

<p>Herein, we demonstrated a facile one-step fabrication strategy combining both chemical deposition and self-assembly of stearic acid for the fabrication of superhydrophobic porous Cu films on the Al substrates. The scanning electron microscopy and white light interferometer showed that the multi-scale porous structures comprising micron-sized pores and nano-sized fishbone-like dendrites were formed on the sample. X-ray diffraction and Fourier-transform infrared spectrophotometer revealed the deposition of Cu and the grafting process of stearic acid on the films. In addition, the formation mechanism of the superhydrohobic surface was explained, and the processing conditions were investigated to determine their effects on the wettability. The resultant sample revealed superhydrophobicity with a water contact angle of 159 ± 1°, a sliding angle of ca. 4° and great bouncing behaviour of water droplets. Moreover, such a surface exhibited a stable superhydrophobicity even after six weeks of ambient air exposure.</p

Epicardial MAPD90/60/30 and triangulation (MAPD90 - MAPD30) recorded from the remote zone (basal).

<p><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031545#s2" target="_blank">Results</a> were means ± STD. There were no significant differences between groups.</p

Comparison of waveforms between the Sham (2-d) and Infarct (2-d) groups after bolus injection of epinephrine.

<p>The only morphological differences in peri-infarct MAP were identified in the Infarct (2-d) group. (<b>A</b>) ECG Lead II waveforms showing that both groups had a comparable degree of heart rate increase. (<b>B</b>) MAP recorded at the peri-infarct epicardial zone showing that after the adrenergic challenge, the MAP of the Infarct (2-d) group had a dramatic shortening of MAPD30, whereas the MAPD90 was only minimally changed. (<b>C</b>) Direct overlapping of MAP showing that the MAP of the Infarct (2-d) group demonstrates more prominent triangulation.</p

Divergent molecular mechanisms for potassium channel remodeling in animal models of heart disease.

<p>AV, atrioventricular; ICM, ischemic cardiomyopathy; ND, not determined; -, no change.</p><p>*Weak bands limited the reliability of the measurement.</p>‡<p>KCNQ1.2, a truncated isoform of canine KCNQ1, was increased and may suppress I_Ks in a dominant-negative fashion.</p

Comparison of ventricular premature beats and KCNQ1 expression between groups.

<p>(<b>A</b>) Comparison of the total premature ventricular beats (PVBs) between the groups within 10 min after bolus injection of epinephrine. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031545#s2" target="_blank">Results</a> are presented in a box plot format (n = 6–8) where boxes indicate the 25–75% interval along with the median of the data. * P<0.05 vs. the other groups. (<b>B</b>) Reverse transcription-polymerase chain reaction (RT-PCR) of KCNQ1 mRNA levels. Top: Examples of KCNQ1 mRNA with samples harvested from the peri-infarct zone and remote zone of the Healing (2-d; n = 6), Infarct (2-d; n = 8), Sham (2-d; n = 7), Healing (5-d; n = 7), Infarct (5-d; n = 7), and Sham (5-d; n = 8) groups of rabbit hearts. Bottom: mean KCNQ1 mRNA band intensities. (<b>C</b>) Western blot analysis of membrane-associated KCNQ1 protein levels. Top: Representative immunoblot results showing membrane KCNQ1 protein (∼75 kDa) with samples harvested from the peri-infarct zone and remote zone of the six groups of rabbit hearts. Bottom: mean membrane KCNQ1 protein band intensities. * P<0.05 vs. Sham (2-d) and Sham (5-d) respectively; # P<0.05 vs. Healing (2-d) and Healing (5-d) respectively; $ P<0.05 vs. Infarct (5-d).</p

Details of PCR.

<p>Details of PCR.</p

The P value of main effects and interaction effects of I/R or sham operation and L-768,673 or vehicle on MAPD and triangulation.

<p>I/R = Ischemia/reperfusion, interaction = interaction effect of ischemia/reperfusion and L-768,673, Triangulation = MAPD90–MAPD30.</p><p>P<0.05 highlighted by *.</p

Study protocol 1 of experiments.

<p>Monophasic action potentials were recorded after the equilibration at both the middle of the infarct zone and the unaffected zone of the epicardium. For L-768,673, The infusion rate of the initial dose was 0.5 µg/kg/h for 30 min, and the maintenance rate was 0.25 µg/kg/h for two hours. MAP duration data were expressed as MAPD90/60/30_{Baseline, Initial Dose, I5, I10, I15, I20, R5, R10, R15, R20, R25, R30, R45, R60, R75, R90, R105, R120}, which stood for MAPD90/60/30 recorded at baseline, after initial dose, at ischemia for 5 min, 10 min, 15 min, 20 min and at reperfusion for 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 45 min, 60 min, 75 min, 90 min, 105 min, 120 min, respectively.</p

MAPDs, triangulations and MAP waveforms comparison between the IR+L-768,673 and IR+vehicle groups.

<p>(<b>A</b>) Epicardial MAPDs and triangulation recorded from the ischemia/reperfusion zone (apical) in the IR+L-768,673 group and the IR+vehicle group. Triangulations of the IR+L-768,673 group were increased compared with those of the IR+vehicle group by 31.1%, 26.5%, and 19.3% at R45, R60, and R75 respectively. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031545#s2" target="_blank">Results</a> are mean ± standard deviation (STD). * P<0.05 vs. IR+vehicle. (<b>B</b>) Comparison of monophasic action potential (MAP) waveforms between the IR+L-768,673 and IR+vehicle groups at R45, R60, and R75.</p