Biophysical characteristics reveal neural stem cell differentiation potential

Background

Distinguishing human neural stem/progenitor cell (huNSPC) populations that will predominantly generate neurons from those that produce glia is currently hampered by a lack of sufficient cell type-specific surface markers predictive of fate potential. This limits investigation of lineage-biased progenitors and their potential use as therapeutic agents. A live-cell biophysical and label-free measure of fate potential would solve this problem by obviating the need for specific cell surface markers.

Methodology/Principal Findings

We used dielectrophoresis (DEP) to analyze the biophysical, specifically electrophysiological, properties of cortical human and mouse NSPCs that vary in differentiation potential. Our data demonstrate that the electrophysiological property membrane capacitance inversely correlates with the neurogenic potential of NSPCs. Furthermore, as huNSPCs are continually passaged they decrease neuron generation and increase membrane capacitance, confirming that this parameter dynamically predicts and negatively correlates with neurogenic potential. In contrast, differences in membrane conductance between NSPCs do not consistently correlate with the ability of the cells to generate neurons. DEP crossover frequency, which is a quantitative measure of cell behavior in DEP, directly correlates with neuron generation of NSPCs, indicating a potential mechanism to separate stem cells biased to particular differentiated cell fates.

Conclusions/Significance

We show here that whole cell membrane capacitance, but not membrane conductance, reflects and predicts the neurogenic potential of human and mouse NSPCs. Stem cell biophysical characteristics therefore provide a completely novel and quantitative measure of stem cell fate potential and a label-free means to identify neuron- or glial-biased progenitors.     

Digest: Possible solutions for the joint estimation of divergence times and shared demographic changes*

Can we simultaneously infer divergence times and shared demographic events? Oaks et al. introduce a full-likelihood Bayesian method based on genomic data and show that this endeavor remains challenging. Their exercise also reveals some promising avenues for future modeling attempts.     

Tetra-acetylenic metabolites from Mycena viridimarginata

The structures of two new acetylenic compounds from Mycena viridimarginata were elucidated by spectroscopic methods and some chemical transformations. The major metabolite was 10-hydroxyundeca-2,4,6,8-tetraynamide and the minor one was 3,4,13-trihydroxytetradeca-5,7,9,11-tetraynoic acid γ-lactone. Another compound, methyl-3,4,13-trihydroxytetradeca-5,7,9,11-tetraynoate, was found to be an artifact from the γ-lactone produced on the Sephadex LH-20 column. Furthermore, model compounds were prepared to establish the chromophoric system of the major metabolite.     

Sexually dichromatic hybrids between two monochromatic duck species,the Chiloé wigeon and the Philippine duck

Captive bird hybrids can provide important data on certain traits, such as hybrid viability and fertility. In this paper, we describe four hybrids between the Chiloé wigeon (Anas sibilatrix) and the Philippine duck (Anas luzonica). These two species diverged about 13 million years ago and are found on different continents, making the occurrence of wild hybrids extremely unlikely. Hence, these captive hybrids provide a unique opportunity to learn more about the outcome of hybridization between these highly divergent species. One pair of hybrids mated and produced six unfertilized eggs, suggesting that hybrids between these species are infertile. Morphologically, the hybrids were slightly larger than the parental species, but had intermediate bill lengths. With regard to plumage patterns, the hybrids displayed characteristics of both parental species: Males developed the iridescent green head pattern of the Chiloé wigeon, whereas the females showed the dark crown and eye stripe of the Philippine duck. Interestingly, Chiloé wigeon and Philippine duck are both sexually monochromatic whereas the hybrids showed clear sexual dimorphism. These hybrids can thus lead to novel insights into the genetic and developmental basis of sexual mono‐ and dichromatism in ducks.     

Digest: How the snowshoe hare got its brown coat: Convergent evolution or gene flow?*

The winter-brown phenotype of snowshoe hares in the Pacific Northwest was acquired through hybridization with black-tailed jackrabbits. Some snowshoe hares in more northern boreal populations exhibit the same phenotype, but how did they acquire it? Jones and colleagues show that the phenotype in the boreal populations is the outcome of convergent evolution, highlighting the importance of understanding the genetic basis of a trait in reconstructing its evolution.     

Digest: The interplay between imprinting,mimicry, and multimodal signaling can lead to sympatric speciation†

Mimicry can directly affect the evolutionary history of models, mimics, and signal receivers. Mimics often use multimodal signaling to deceive receivers. Jamie et al. showed that brood parasitic birds display multimodal signaling of mimetic traits triggered by sexual and filial imprinting on host species. These resulting adaptations can interact with premating isolation barriers to strengthen reproductive isolation and potentially drive sympatric speciation.     

Weitere acetylenverbindungen aus Centaurea ruthenica

Reinvestigation of the polar fractions of the aerial parts of Centaurea ruthenica afforded, in addition to known compounds, more than 20 new ones, mostly in very small quantities, which in many cases could only partly be separated even after acetylation. The structures, however, could be elucidated by spectroscopic methods. Besides additional C₁₃-acetylenes, several new C₁₄- and C₁₀-acetylenes are present. The compounds isolated are of special interest in view of the proposed biosynthetic scheme of acetylenic compounds of this type.     

Antibiotics from basidiomycetes XVI. Antimicrobial and cytotoxic polyines from Mycena viridimarginata karst

Two new biologically active polyines were isolated from cultures of the fungus Mycena viridimarginata. Their structures were elucidated by spectroscopic and chemical methods as 10-hydroxy-undeca-2,4,6,8-tetraynamide (1) and 3,4,13-trihydroxy-tetradeca-5,7,9,11-tetraynoic acid--lactone (2). The main component (1) is highly antibiotically active and cytotoxic.Antibiotika aus Basidiomyceten XV. T. Anke, B.-M. Giannetti and W. Steglich: 1-Hydroxy-2-nonin-4-on, ein antifungischer und cytotoxischer Metabolit aus Ischnoderma benzoinum (Wahl.) Karst. Z. Naturforsch. 37c: 1–4 (1982)