Regulation of Axon Initial Segment Diameter by COUP-TFI Fine-tunes Action Potential Generation.

The axon initial segment (AIS) is a specialized structure that controls neuronal excitability via action potential (AP) generation. Currently, AIS plasticity with regard to changes in length and location in response to neural activity has been extensively investigated, but how AIS diameter is regulated remains elusive. Here we report that COUP-TFI (chicken ovalbumin upstream promotor-transcription factor 1) is an essential regulator of AIS diameter in both developing and adult mouse neocortex. Either embryonic or adult ablation of COUP-TFI results in reduced AIS diameter and impaired AP generation. Although COUP-TFI ablations in sparse single neurons and in populations of neurons have similar impacts on AIS diameter and AP generation, they strengthen and weaken, respectively, the receiving spontaneous network in mutant neurons. In contrast, overexpression of COUP-TFI in sparse single neurons increases the AIS diameter and facilitates AP generation, but decreases the receiving spontaneous network. Our findings demonstrate that COUP-TFI is indispensable for both the expansion and maintenance of AIS diameter and that AIS diameter fine-tunes action potential generation and synaptic inputs in mammalian cortical neurons.

PUPIL enables mapping and stamping of transient electrical connectivity in developing nervous systems.

Currently, many genetic methods are available for mapping chemical connectivity, but analogous methods for electrical synapses are lacking. Here, we present pupylation-based interaction labeling (PUPIL), a genetically encoded system for noninvasively mapping and stamping transient electrical synapses in the mouse brain. Upon fusion of connexin 26 (CX26) with the ligase PafA, pupylation yields tag puncta following conjugation of its substrate, a biotin- or fluorescent-protein-tagged PupE, to the neighboring proteins of electrical synapses containing CX26-PafA. Tag puncta are validated to correlate well with functional electrical synapses in immature neurons. Furthermore, puncta are retained in mature neurons when electrical synapses mostly disappear-suggesting successful stamping. We use PUPIL to uncover spatial subcellular localizations of electrical synapses and approach their physiological functions during development. Thus, PUPIL is a powerful tool for probing electrical connectivity patterns in complex nervous systems and has great potential for transient receptors and ion channels as well.

[Effect of miRNA from Glycyrrhiza uralensis decoction on gene expression of human immune cells].

MicroRNAs(miRNA) are small non-coding RNAs that regulate the expression of protein coding genes by repressing translation of protein coding mRNA or enhancing mRNA degradation. Its functions have attracted more and more attention from the public. In recent years, the cross-border regulation of miRNA has become a new research direction, and provides a new perspective for people to comprehensively understand the functions of miRNA. Plant miRNA is usually methylated and not easy to degrade. According to our previous researches, there were abundant small RNAs in the decoction of dried liquorice, which provides a new way to study the mechanism of action of licorice. In this study, small RNAs extracted from Glycyrrhiza uralensis decoction and synthesized miRNA mimics were used to treat peripheral blood mononuclear cells(PBMC) isolated from healthy volunteers. The gene expression of toll-like receptors(TLRs), some transcription factors, signal molecules and cytokines were analyzed by RT-PCR. The results showed that glycyrrhiza miRNA could significantly regulate PBMC by inhibiting the expression of genes involved in T cell differentiation, inflammation and apoptosis. The study brought new ideas to us in comprehensively studying the mechanism of licorice and developing the traditional Chinese medicine.