The transcription factor Foxg1 regulates telencephalic progenitor proliferation cell autonomously, in part by controlling Pax6 expression levels

<p>Abstract</p> <p>Background</p> <p>The transcription factor Foxg1 is an important regulator of telencephalic cell cycles. Its inactivation causes premature lengthening of telencephalic progenitor cell cycles and increased neurogenic divisions, leading to severe hypoplasia of the telencephalon. These proliferation defects could be a secondary consequence of the loss of Foxg1 caused by the abnormal expression of several morphogens (Fibroblast growth factor 8, bone morphogenetic proteins) in the telencephalon of <it>Foxg1 </it>null mutants. Here we investigated whether Foxg1 has a cell autonomous role in the regulation of telencephalic progenitor proliferation. We analysed <it>Foxg1^+/+</it>↔<it>Foxg1^-/-</it>chimeras, in which mutant telencephalic cells have the potential to interact with, and to have any cell non-autonomous defects rescued by, normal wild-type cells.</p> <p>Results</p> <p>Our analysis showed that the <it>Foxg1^-/-</it>cells are under-represented in the chimeric telencephalon and the proportion of them in S-phase is significantly smaller than that of their wild-type neighbours, indicating that their under-representation is caused by a cell autonomous reduction in their proliferation. We then analysed the expression of the cell-cycle regulator Pax6 and found that it is cell-autonomously downregulated in <it>Foxg1^-/-</it>dorsal telencephalic cells. We went on to show that the introduction into <it>Foxg1^-/-</it>embryos of a transgene designed to reverse Pax6 expression defects resulted in a partial rescue of the telencephalic progenitor proliferation defects.</p> <p>Conclusions</p> <p>We conclude that Foxg1 exerts control over telencephalic progenitor proliferation by cell autonomous mechanisms that include the regulation of Pax6, which itself is known to regulate proliferation cell autonomously in a regional manner.</p

A nanomechanical resonator shuttling single electrons at radio frequencies

We observe transport of electrons through a metallic island on the tip of a nanomechanical pendulum. The resulting tunneling current shows distinct features corresponding to the discrete mechanical eigenfrequencies of the pendulum. We report on measurements covering the temperature range from 300 K down to 4.2 K. We explain the I-V curve, which differs from previous theoretical predictions, with model calculations based on a Master equation approach.Comment: 5 pages, 4 jpeg-figure

Variation of Heat Input and Its Influence on Residual Stresses and Coating Properties in Arc Spraying with Different Gas Mixtures

This work is about the influence of heat input on arc-sprayed coatings, caused by varying spraying patterns. The highly cavitation erosion-resistant alloys CuAl9Ni5Fe4Mn and CuMn13Al8Fe3Ni2 were arc-sprayed with a spiral-shaped pattern, using both pressurized air and a mixture of nitrogen and hydrogen. Process temperatures were recorded by thermographic imaging, and residual stresses were measured by modified hole-drilling method. Moreover, analyses of the cavitation erosion behavior and other properties were performed. Compared to previous own works, in which a meander-shaped spray pattern was used, most importantly the thermal loads, for example the maximum temperatures, during the coating buildup were lowered up to approx. 20 °C. Moreover, a more even heating of the specimens and reduced tensile stresses for both atomizing gases and materials were achieved. Furthermore, also the course of the residual stresses was changed. Hence, the dominance of the quenching stresses regarding residual stresses and coating properties, especially when spraying with pressurized air, was found to be reduced. In addition, the cavitation erosion resistance was improved severely, i.e., erosion depth was decreased up to 57%. In contrast to the aforementioned positive effects, the deposition efficiency, Young’s moduli and hardness were reduced, but still sufficient considering the application