Differential Expressions of Nodal-Signal Transducers and Global Transcriptional Repression Commit Vegetal Cells in Eleutherodactylus Coqui to Form Nutritional Endoderm

The vegetal core cells of a Xenopus laevis embryo commit to mesendoderm via the Nodal-signaling pathway. In Eleutherodactylus coqui, a direct developing frog, mesendoderm is specified at the marginal zone of the early gastrulae and vegetal core cells transform into nutritional endoderm. It is a novel tissue consisting of transient, yolk rich cells that provide nutrition, but do not differentiate into adult tissues. We hypothesized that a disruption of Nodal-signaling is responsible for committing vegetal core cells to nutritional endoderm. I report a dual regulation involved in the generation of nutritional endoderm. First, differential expression of Nodal-signaling components like Smad2 and Smad4 was observed during early gastrulation between cells in the marginal zone and in the vegetal core. Although EcSmad2 RNA, as well as both native and the active forms of EcSmad2, were detected in the vegetal core by qPCR and western blot respectively, western analysis revealed that Smad4 isoforms were expressed at a low level during early gastrulation. Immunostaining showed that only 12% and 50% of vegetal core cells were positive for nuclear Smad2 and Smad4 signals, respectively, compared to 100% in marginal zone cells. These differential expressions may indicate a signaling blockade in vegetal core cells. Second, I found global transcription repression in vegetal core cells by immunostaining. At late blastula, both the marginal zone and vegetal core cell were transcriptionally silent. At the onset of gastrulation, marginal zone cells, but not vegetal core ones, became transcriptionally active. This indicates the occurrence of a mid-blastula transition in the marginal zone by early gastrulation. Global transcriptional repression prevails in the vegetal core through development. A combination of differential Nodal-signaling and global transcriptional repression in vegetal core cells may account for its lack of differentiation

HMN: Generalization of Heterogeneous and Multi-layered Network

A network may have different types of entities and their relations. Further, there could be additional layers of ties. The former is referred to as Heterogeneous networks, while the latter is known as Multi-layer networks. The present paper provides a generalized network model, namely, a Heterogeneous Multi-layered Network (HMN), which can simultaneously be multi-layered and heterogeneous. The model can represent homogeneous networks as well. We define different structural measures in an HMN. We proved that the sets of all homogeneous, heterogeneous and multi-layered networks are subsets of the set of all HMNs. Accordingly, we established the equivalency of the proposed structural measures of HMNs with that of homogeneous, heterogeneous, and multi-layered networks. Following that, we show how our proposed HMN is more efficient in tasks such as link prediction. In addition, we present a novel parameterized algorithm (with complexity analysis) for generating synthetic HMNs. The networks generated from our proposed algorithm are more consistent in modelling the layer-wise degree distribution of a real-world Twitter network (represented as HMN) than those generated by existing models. Moreover, we also show that our algorithm is more effective in modelling an air-transportation multiplex network when compared to an algorithm designed specifically for the task

The visibility based Tapered Gridded Estimator (TGE) for the redshifted 21-cm power spectrum

We present the improved visibility based Tapered Gridded Estimator (TGE) for the power spectrum of the diffuse sky signal. The visibilities are gridded to reduce the computation, and tapered through a convolution to suppress the contribution from the outer regions of the telescope's field of view. The TGE also internally estimates the noise bias, and subtracts this out to give an unbiased estimate of the power spectrum. An earlier version of the 2D TGE for the angular power spectrum $C_{\ell}$ is improved and then extended to obtain the 3D TGE for the power spectrum $P({\bf k})$ of the 21-cm brightness temperature fluctuations. Analytic formulas are also presented for predicting the variance of the binned power spectrum. The estimator and its variance predictions are validated using simulations of $150 \, {\rm MHz}$ GMRT observations. We find that the estimator accurately recovers the input model for the 1D Spherical Power Spectrum $P(k)$ and the 2D Cylindrical Power Spectrum $P(k_\perp,k_\parallel)$, and the predicted variance is also in reasonably good agreement with the simulations.Comment: 19 pages, 13 figures. Accepted for publication in MNRAS. The definitive version will be available at http://mnrasl.oxfordjournals.org