Shh-Mediated Increase in ß-Catenin Levels Maintains Cerebellar Granule Neuron Progenitors in Proliferation.

Cerebellar granule neuron progenitors (CGNPs) give rise to the cerebellar granule neurons in the developing cerebellum. Generation of large number of these neurons is made possible by the high proliferation rate of CGNPs in the external granule layer (EGL) in the dorsal cerebellum. Here, we show that upregulation of ß-catenin can maintain murine CGNPs in a state of proliferation. Further, we show that ß-catenin mRNA and protein levels can be regulated by the mitogen Sonic hedgehog (Shh). Shh signaling led to an increase in the level of the transcription factor N-myc. N-myc was found to bind the ß-catenin promoter, and the increase in ß-catenin mRNA and protein levels could be prevented by blocking N-myc upregulation downstream of Shh signaling. Furthermore, blocking Wingless-type MMTV integration site (Wnt) signaling by Wnt signaling pathway inhibitor Dickkopf 1 (Dkk-1) in the presence of Shh did not prevent the upregulation of ß-catenin. We propose that in culture, Shh signaling regulates ß-catenin expression through N-myc and results in increased CGNP proliferation.

Chemical diversity and anti-proliferative activity of marine algae.

The chemical diversity of three macroalgae (Ulva reticulata, Sargassum wightii, Gracilaria sp) were determined using the GC-MS method with principal component analysis (PCA) and their potential efficacy against human pathogens and cervical carcinoma cells evaluated using MTT bioassay method. Our results showed that >30 metabolites were detected in three seaweeds, among these, steroids and fatty acids are the most dominant chemical group that highly contributes to discriminate this species. The PCA of GC-MS mass spectral variables showed a clear discrimination between three different species based on the phytochemical diversity of seaweeds. The extracts of U. reticulata exhibited anti-microbial activity with Pseudomonas aeruginosa (6.00 mm) and showed potential anti-proliferative activity against the HeLa cells (IC50 37 µmol/L) at concentration 1-50 µM treatment. Results of this study concluded that PCA analysis of mass spectral variables could be utilized as a reliable tool for species discrimination and chemotaxonomic classification of seaweeds.

miR-135a Regulates Synaptic Transmission and Anxiety-Like Behavior in Amygdala.

MicroRNAs are a class of non-coding RNAs with a growing relevance in the regulation of gene expression related to brain function and plasticity. They have the potential to orchestrate complex phenomena, such as the neuronal response to homeostatic challenges. We previously demonstrated the involvement of miR-135a in the regulation of early stress response. In the present study, we examine the role of miR-135a in stress-related behavior. We show that the knockdown (KD) of miR-135a in the mouse amygdala induces an increase in anxiety-like behavior. Consistently with behavioral studies, electrophysiological experiments in acute brain slices indicate an increase of amygdala spontaneous excitatory postsynaptic currents, as a result of miR-135a KD. Furthermore, we presented direct evidences, by in vitro assays and in vivo miRNA overexpression in the amygdala, that two key regulators of synaptic vesicle fusion, complexin-1 and complexin-2, are direct targets of miR-135a. In vitro analysis of miniature excitatory postsynaptic currents on miR-135a KD primary neurons indicates unpaired quantal excitatory neurotransmission. Finally, increased levels of complexin-1 and complexin-2 proteins were detected in the mouse amygdala after acute stress, accordingly to the previously observed stress-induced miR-135a downregulation. Overall, our results unravel a previously unknown miRNA-dependent mechanism in the amygdala for regulating anxiety-like behavior, providing evidences of a physiological role of miR-135a in the modulation of presynaptic mechanisms of glutamatergic neurotransmission.