Secreted dual reporter assay with Gaussia luciferase and the red fluorescent protein mCherry

Oct1 cooperates with the Smad family of transcription factors to promote mesodermal lineage specification

The transition between pluripotent and tissue-specific states is a key aspect of development. Understanding the pathways driving these transitions will facilitate the engineering of properly differentiated cells for experimental and therapeutic uses. Here, we showed that during mesoderm differentiation, the transcription factor Oct1 activated developmental lineage-appropriate genes that were silent in pluripotent cells. Using mouse embryonic stem cells (ESCs) with an inducible knockout of Oct1, we showed that Oct1 deficiency resulted in poor induction of mesoderm-specific genes, leading to impaired mesodermal and terminal muscle differentiation. Oct1-deficient cells exhibited poor temporal coordination of the induction of lineage-specific genes and showed inappropriate developmental lineage branching, resulting in poorly differentiated cell states retaining epithelial characteristics. In ESCs, Oct1 localized with the pluripotency factor Oct4 at mesoderm-associated genes and remained bound to those loci during differentiation after the dissociation of Oct4. Binding events for Oct1 overlapped with those for the histone lysine demethylase Utx, and an interaction between Oct1 and Utx suggested that these two proteins cooperate to activate gene expression. The specificity of the ubiquitous Oct1 for the induction of mesodermal genes could be partially explained by the frequent coexistence of Smad and Oct binding sites at mesoderm-specific genes and the cooperative stimulation of mesodermal gene transcription by Oct1 and Smad3. Together, these results identify Oct1 as a key mediator of mesoderm lineage-specific gene induction.

A Novel Potent Carrier for Unconventional Protein Export in Ustilago maydis

Recombinant proteins are ubiquitously applied in fields like research, pharma, diagnostics or the chemical industry. To provide the full range of useful proteins, novel expression hosts need to be established for proteins that are not sufficiently produced by the standard platform organisms. Unconventional secretion in the fungal model Ustilago maydis is an attractive novel option for export of heterologous proteins without N-glycosylation using chitinase Cts1 as a carrier. Recently, a novel factor essential for unconventional Cts1 secretion termed Jps1 was identified. Here, we show that Jps1 is unconventionally secreted using a fusion to bacterial β-glucuronidase as an established reporter. Interestingly, the experiment also demonstrates that the protein functions as an alternative carrier for heterologous proteins, showing about 2-fold higher reporter activity than the Cts1 fusion in the supernatant. In addition, Jps1-mediated secretion even allowed for efficient export of functional firefly luciferase as a novel secretion target which could not be achieved with Cts1. As an application for a relevant pharmaceutical target, export of functional bi-specific synthetic nanobodies directed against the SARS-CoV2 spike protein was demonstrated. The establishment of an alternative efficient carrier thus constitutes an excellent expansion of the existing secretion platform.

HMSC-Derived Exosome Inhibited Th2 Cell Differentiation via Regulating miR-146a-5p/SERPINB2 Pathway

Background

Allergic rhinitis (AR) is a global disease without specific treatment. Human mesenchymal stem cell- (HMSC-) derived exosomes (HMSC-exos) have been implicated for the amelioration of allergic inflammation by delivering miR-146a-5p in a mouse asthma model. However, the antiallergic activity and the underlying mechanism of HMSC-exos in AR remain unclear. The present study aimed to investigate the role of HMSC-exos in the pathogenesis of AR.

Materials and Methods

Blood specimens were collected from AR patients and healthy donators for investigation. HMSC and CD4⁺ T cells were used in the present study. Flow cytometry was used to characterize the population of Type 1 helper T (Th1) and Th2 cells. Specific siRNA and overexpressed plasmids were designed to silence or overexpress the expressions of miR-146a-5p and SERPINB2. Luciferase reporter assay was adopted to explore the binding site of miR-146a-5p and SERPINB2. Quantitative real-time PCR and immunoblots were performed to estimate the expression of target genes.

Results

The population of Th2 cells was significantly elevated in AR patients as compared with that in healthy donators. HMSC-exos could decrease the expression of SERPINB2 and the differentiation of Th2 cells. miR-146a-5p in HMSC-exos exhibited consistent effects and lowered the expression of SERPINB2 by binding on its 3′UTR region. Moreover, the differentiation of Th2 cells was promoted by SERPINB2 that could be reversed by HMSC-exos. Additionally, the miR-146a-5p expression was negatively associated with the SERPINB2 expression in the serum of AR patients.

Conclusion

HMSC-exos could inhibit the differentiation of Th2 cells via the regulation of the miR-146a-5p/SERPINB2 pathway. miR-146a-5p and SERPINB2 could be applied as potential targets for AR treatment.

Gaussia Luciferase as a Reporter for Quorum Sensing in Staphylococcus aureus

Gaussia luciferase (GLuc) is a secreted protein with significant potential for use as a reporter of gene expression in bacterial pathogenicity studies. To date there are relatively few examples of its use in bacteriology. In this study we show that GLuc can be functionally expressed in the human pathogen Staphylococcus aureus and furthermore show that it can be used as a biosensor for the agr quorum sensing (QS) system which employs autoinducing peptides to control virulence. GLuc was linked to the P3 promoter of the S. aureusagr operon. Biosensor strains were validated by evaluation of chemical agent-mediated activation and inhibition of agr. Use of GLuc enabled quantitative assessment of agr activity. This demonstrates the utility of Gaussia luciferase for in vitro monitoring of agr activation and inhibition.

Examining multiple cellular pathways at once using multiplex hextuple luciferase assaying

Sensitive simultaneous assessment of multiple signaling pathways within the same cells requires orthogonal reporters that can assay over large dynamic ranges. Luciferases are such genetically encoded candidates due to their sensitivity, versatility, and cost-effectiveness. We expand luciferase multiplexing in post-lysis endpoint luciferase assays from two to six. Light emissions are distinguished by a combination of distinct substrates and emission spectra deconvolution. All six luciferase reporter units are stitched together into one plasmid facilitating delivery of all reporter units through a process we termed solotransfection, minimizing experimental errors. We engineer a multiplex hextuple luciferase assay to probe pathway fluxes through five transcriptional response elements against a control constitutive promoter. We can monitor effects of siRNA, ligand, and chemical compound treatments on their target pathways along with the four other probed cellular pathways. We demonstrate the effectiveness and adaptiveness of multiplex luciferase assaying, and its broad application across different research fields.

Multiplexed detection of luciferase-based sensors in the same sample is challenging and limited by the substrates’ emission spectra. Here the authors establish a system based on three different luciferases and sequential detection to achieve measurements of up to six parameters within the same experiment.

Insect Transcription Factors: A Landscape of Their Structures and Biological Functions in Drosophila and beyond

Transcription factors (TFs) play essential roles in the transcriptional regulation of functional genes, and are involved in diverse physiological processes in living organisms. The fruit fly Drosophila melanogaster, a simple and easily manipulated organismal model, has been extensively applied to study the biological functions of TFs and their related transcriptional regulation mechanisms. It is noteworthy that with the development of genetic tools such as CRISPR/Cas9 and the next-generation genome sequencing techniques in recent years, identification and dissection the complex genetic regulatory networks of TFs have also made great progress in other insects beyond Drosophila. However, unfortunately, there is no comprehensive review that systematically summarizes the structures and biological functions of TFs in both model and non-model insects. Here, we spend extensive effort in collecting vast related studies, and attempt to provide an impartial overview of the progress of the structure and biological functions of current documented TFs in insects, as well as the classical and emerging research methods for studying their regulatory functions. Consequently, considering the importance of versatile TFs in orchestrating diverse insect physiological processes, this review will assist a growing number of entomologists to interrogate this understudied field, and to propel the progress of their contributions to pest control and even human health.