Live-Cell Imaging of Endogenous RNA with a Genetically Encoded Fluorogenic Allosteric Aptamer.

Imaging and tracking tools for natural cellular RNA with improved biocompatibility, specificity, and sensitivity are critical to understanding RNA function and providing insights into disease therapeutics. We developed a new genetically encoded sensor using fluorogenic allosteric aptamer (FaApt) for the sensitive imaging of the localization and dynamics of RNA targets in live cells. Target RNAs can be specifically recognized with our sensor by forming perfectly complementary duplexes, which in turn can induce allosteric structural changes of the sensor to refold the native conformation of fluorogenic RNA aptamers. We demonstrated the ability of the sensor to monitor the effect of tumor necrosis factor and small-molecule inhibitor on the expression abundance of CXCL1 and survivin mRNA in human cancer cells, respectively. The asymmetrical distribution of endogenous Squint mRNA was confirmed in developing zebrafish embryos through microinjection of FaApt probes. This study provides an effective molecular tool for sensitive imaging and tracking endogenous RNA in living cells. Due to the high specificity and small size of our sensor system, it is expected to be applied to early diagnosis of RNA marker-related diseases and real-time evaluation of the treatment process.

Dopey2 and Pcdh7 orchestrate the development of embryonic neural stem cells/ progenitors in zebrafish.

DOPEY2 has been shown to be associated with Down syndrome and PCDH7 might be involved in Rett syndrome and MECP2 duplication syndrome. The mechanism how both proteins play roles in these syndromes are largely unknown. Here, we show that Dopey2 and Pcdh7 balance the proliferation and differentiation of neural stem cells and progenitors during embryonic neurogenesis to generate proper size and architecture of zebrafish brains. Dopey2 and Pcdh7 mutually restricted expression of each other in zebrafish embryos. Dopey2 was responsible for the proliferation of neural stem cells/progenitors, whereas Pcdh7 was responsible for the differentiation of neural stem cells/progenitors. Both proteins were shown to orchestrate the proper development and arrangement of neural cells in zebrafish embryonic brains. The results provide an insight into mechanisms to understand how the embryonic brain is constituted and how developmental defects occur in the brains of patients with Down syndrome, Rett syndrome, or MECP2 duplication syndrome.

A genetically encoded fluorescent biosensor for monitoring ATP in living cells with heterobifunctional aptamers.

Visualizing the dynamics of ATP in living cells is key to understanding cellular energy metabolism and related diseases. However, the live-cell applications of current methods are still limited due to challenges in biological compatibility and sensitivity to pH. Herein, a novel label-free fluorescent " turn-on " biosensor for monitoring ATP in living bacterias and mammalian cells was developed. This biosensor (Broc-ATP) employed heterobifunctional aptamers to detect ATP with high sensitivity in vitro. In our system, a very useful tandem method was established by combining four Broc-ATPs with 3 × F30 three-way junction scaffold to construct an intracellular biosensor that achieves sufficient fluorescence to respond to intracellular ATP. This intracellular biosensor can be used for sensitive and specific dynamic imaging of ATP in mammalian cells. Hence, this genetically encoded biosensor provides a robust and efficient tool for the detection of intracellular ATP dynamics and 3 × F30 tandem method expands the application of heterobifunctional aptamers in mammalian cells.

An integrated map of fibroblastic populations in human colon mucosa and cancer tissues.

Fibroblasts and myofibroblasts are major mesenchymal cells in the lamina propria of colon mucosa and in colon cancer tissues. Detailed insight into the highly specific populations of fibroblasts and myofibroblasts is required to understand the integrity and homeostasis of human colon mucosa and colon cancer. Based on gene expression profiles of single cells, we identified fibroblast populations that produce extracellular matrix components, Wnt ligand- and BMP-secreting fibroblasts, chemokine- and chemokine ligand-generating fibroblasts, highly activated fibroblasts, immune-modulating fibroblasts, epithelial cell-modulating myofibroblasts, stimuli-responsive myofibroblasts, proliferating myofibroblasts, fibroblast-like myofibroblasts, matrix producing myofibroblasts, and contractile myofibroblasts in human colon mucosa. In colon cancer tissue, the compositions of fibroblasts and myofibroblasts were highly altered, as were the expressing patterns of genes including BMPs, Wnt ligands, chemokines, chemokine ligands, growth factors and extracellular matrix components in fibroblasts and myofibroblasts. Our work expands the working atlas of fibroblasts and myofibroblasts and provides a framework for interrogating the complexity of stromal cells in human healthy colon mucosa and colon cancer tissues.