Desensitisation of Notch signalling through dynamic adaptation in the nucleus

Chemogenetic Manipulation of Endogenous Proteins in Fission Yeast Using a Self-Localizing Ligand-Induced Protein Translocation System

Cells sense extracellular stimuli through membrane receptors and process information through an intracellular signaling network. Protein translocation triggers intracellular signaling, and techniques such as chemically induced dimerization (CID) have been used to manipulate signaling pathways by altering the subcellular localization of signaling molecules. However, in the fission yeast Schizosaccharomyces pombe, the commonly used FKBP-FRB system has technical limitations, and therefore, perturbation tools with low cytotoxicity and high temporal resolution are needed. We here applied our recently developed self-localizing ligand-induced protein translocation (SLIPT) system to S. pombe and successfully perturbed several cell cycle-related proteins. The SLIPT system utilizes self-localizing ligands to recruit binding partners to specific subcellular compartments such as the plasma membrane or nucleus. We optimized the self-localizing ligands to maintain the long-term recruitment of target molecules to the plasma membrane. By knocking in genes encoding the binding partners for self-localizing ligands, we observed changes in the localization of several endogenous molecules and found perturbations in the cell cycle and associated phenotypes. This study demonstrates the effectiveness of the SLIPT system as a chemogenetic tool for rapid perturbation of endogenous molecules in S. pombe, providing a valuable approach for studying intracellular signaling and cell cycle regulation with an improved temporal resolution.

Synthetic developmental biology: New tools to deconstruct and rebuild developmental systems

Technological advances have driven many recent advances in developmental biology. Light sheet imaging can reveal single-cell dynamics in living three-dimensional tissues, whereas single-cell genomic methods open the door to a complete catalogue of cell types and gene expression states. An equally powerful but complementary set of approaches are also becoming available to define development processes from the bottom up. These synthetic approaches aim to reconstruct the minimal developmental patterns, signaling processes, and gene networks that produce the basic set of developmental operations: spatial polarization, morphogen interpretation, tissue movement, and cellular memory. In this review we discuss recent approaches at the intersection of synthetic biology and development, including synthetic circuits to deliver and record signaling stimuli and synthetic reconstitution of pattern formation on multicellular scales.

A novel program of infiltrative control in astrocytomas: ADAM23 depletion promotes cell invasion by activating -secretase complex

Background

Infiltration is a life-threatening growth pattern in malignant astrocytomas and a significant cause of therapy resistance. It results in the tumor cell spreading deeply into the surrounding brain tissue, fostering tumor recurrence and making complete surgical resection impossible. We need to thoroughly understand the mechanisms underlying diffuse infiltration to develop effective therapies.

Methods

We integrated in vitro and in vivo functional assays, RNA sequencing, clinical, and expression information from public data sets to investigate the role of ADAM23 expression coupling astrocytoma's growth and motility.

Results

ADAM23 downregulation resulted in increased infiltration, reduced tumor growth, and improved overall survival in astrocytomas. Additionally, we show that ADAM23 deficiency induces γ-secretase (GS) complex activity, contributing to the production and deposition of the Amyloid-β and release of NICD. Finally, GS ablation in ADAM23-low astrocytomas induced a significant inhibitory effect on the invasive programs.

Conclusions

Our findings reveal a role for ADAM23 in regulating the balance between cell proliferation and invasiveness in astrocytoma cells, proposing GS inhibition as a therapeutic option in ADAM23 low-expressing astrocytomas.

Analysis of Slow-Cycling Variants of the Light-Inducible Nuclear Protein Export System LEXY in Mammalian Cells

The optogenetic tool LEXY consists of the second light oxygen voltage (LOV) domain of Avena sativa phototropin 1 mutated to contain a nuclear export signal. It allows exporting from the nucleus with blue light proteins of interest (POIs) genetically fused to it. Mutations slowing the dark recovery rate of the LOV domain within LEXY were recently shown to allow for better depletion of some POIs from the nucleus in Drosophila embryos and for the usage of low light illumination regimes. We investigated these variants in mammalian cells and found they increase the cytoplasmic localization of the proteins we tested after illumination, but also during the dark phases, which corresponds to higher leakiness of the system. These data suggest that, when aiming to sequester into the nucleus a protein with a cytoplasmic function, the original LEXY is preferable. The iLEXY variants are, instead, advantageous when wanting to deplete the nucleus of the POI as much as possible.

Design and engineering of light-sensitive protein switches

Engineered, light-sensitive protein switches are used to interrogate a broad variety of biological processes. These switches are typically constructed by genetically fusing naturally occurring light-responsive protein domains with functional domains from other proteins. Protein activity can be controlled using a variety of mechanisms including light-induced colocalization, caging, and allosteric regulation. Protein design efforts have focused on reducing background signaling, maximizing the change in activity upon light stimulation, and perturbing the kinetics of switching. It is common to combine structure-based modeling with experimental screening to identify ideal fusion points between domains and discover point mutations that optimize switching. Here, we introduce commonly used light-sensitive domains and summarize recent progress in using them to regulate protein activity.

Optogenetic control of NOTCH1 signaling

The Notch signaling pathway is a crucial regulator of cell differentiation as well as tissue organization, whose deregulation is linked to the pathogenesis of different diseases. NOTCH1 plays a key role in breast cancer progression by increasing proliferation, maintenance of cancer stem cells, and impairment of cell death. NOTCH1 is a mechanosensitive receptor, where mechanical force is required to activate the proteolytic cleavage and release of the Notch intracellular domain (NICD). We circumvent this limitation by regulating Notch activity by light. To achieve this, we have engineered an optogenetic NOTCH1 receptor (optoNotch) to control the activation of NOTCH1 intracellular domain (N1ICD) and its downstream transcriptional activities. Using optoNotch we confirm that NOTCH1 activation increases cell proliferation in MCF7 and MDA-MB-468 breast cancer cells in 2D and spheroid 3D cultures, although causing distinct cell-type specific migratory phenotypes. Additionally, optoNotch activation induced chemoresistance on the same cell lines. OptoNotch allows the fine-tuning, ligand-independent, regulation of N1ICD activity and thus a better understanding of the spatiotemporal complexity of Notch signaling. Video Abstract.

Optogenetic control of the Bicoid morphogen reveals fast and slow modes of gap gene regulation

Developmental patterning networks are regulated by multiple inputs and feedback connections that rapidly reshape gene expression, limiting the information that can be gained solely from slow genetic perturbations. Here we show that fast optogenetic stimuli, real-time transcriptional reporters, and a simplified genetic background can be combined to reveal the kinetics of gene expression downstream of a developmental transcription factor in vivo. We engineer light-controlled versions of the Bicoid transcription factor and study their effects on downstream gap genes in embryos. Our results recapitulate known relationships, including rapid Bicoid-dependent transcription of giant and hunchback and delayed repression of Krüppel. In addition, we find that the posterior pattern of knirps exhibits a quick but inverted response to Bicoid perturbation, suggesting a noncanonical role for Bicoid in directly suppressing knirps transcription. Acute modulation of transcription factor concentration while recording output gene activity represents a powerful approach for studying developmental gene networks in vivo.

Notch-dependent and -independent transcription are modulated by tissue movements at gastrulation

Cells sense and integrate external information from diverse sources that include mechanical cues. Shaping of tissues during development may thus require coordination between mechanical forces from morphogenesis and cell-cell signalling to confer appropriate changes in gene expression. By live-imaging Notch-induced transcription in real time, we have discovered that morphogenetic movements during Drosophila gastrulation bring about an increase in activity-levels of a Notch-responsive enhancer. Mutations that disrupt the timing of gastrulation resulted in concomitant delays in transcription up-regulation that correlated with the start of mesoderm invagination. As a similar gastrulation-induced effect was detected when transcription was elicited by the intracellular domain NICD, it cannot be attributed to forces exerted on Notch receptor activation. A Notch-independent vnd enhancer also exhibited a modest gastrulation-induced activity increase in the same stripe of cells. Together, these observations argue that gastrulation-associated forces act on the nucleus to modulate transcription levels. This regulation was uncoupled when the complex linking the nucleoskeleton and cytoskeleton (LINC) was disrupted, indicating a likely conduit. We propose that the coupling between tissue-level mechanics, arising from gastrulation, and enhancer activity represents a general mechanism for ensuring correct tissue specification during development and that Notch-dependent enhancers are highly sensitive to this regulation.

[Inhibition of the Notch1/Jagged1 pathway promotes homing of bone mesenchymal stem cells to improve asthma in rats]

OBJECTIVE

To explore the association of the Notch1/Jagged1 pathway with the homing of mesenchymal stem cells (BMSCs) to regulate Th1/Th2 drift in asthma.

METHODS

Twenty SD rats were randomly divided into normal control group, model group, BMSC transplantation group, and BMSC+Notch inhibitor group. Ovalbumin sensitization was used to establish rat models of asthma, and BMSCs were transplanted via the tail vein. The pathology of the lung tissue was examined with HE staining, and the contents of interleukin (IL)-5, IL-13, and interferon-γ (IFN-γ) in lung tissue homogenate were determined with enzyme-linked immunosorbent assay. The expressions of Notch1 and Jagged1 mRNA were detected with RT-PCR, and CXCR4 expression in the bronchial epithelial cells was examined using immunofluorescence staining; Western blotting was used to detect the protein expressions of T-bet, GATA-3, Notch1, and Jagged1 in the lung tissue.

RESULTS

Compared with those in the control group, the expressions of IFN-γ and T-bet proteins decreased significantly and the pulmonary expressions of IL-5, IL-13, and GATA-3 proteins as well as Notch1 and Jagged1 mRNA and protein expressions all increased significantly in the model group (P < 0.05 or 0.01). Compared with those in the model group, CXCR4, IFN-γ, and T-bet protein expressions in BMSC group and BMSCs+Notch inhibitor group all increased significantly, and Notch1 and Jagged1 protein expressions in BMSCs group and IL-5, IL-13, Notch1, and Jagged1 mRNA and protein expressions in BMSCs + Notch inhibitor group all decreased significantly (P < 0.05 or 0.01). The expressions of CXCR4 and IFN-γ were significantly higher and the expressions of IL-13 and Notch1 mRNA were significantly lower in BMSCs+Notch inhibitor group than in BMSC group (P < 0.05).

CONCLUSION

In asthmatic rats, the homing of the BMSCs to the lung tissue has a regulatory effect on Th1/Th2 drift, and the Notch1/Jagged1 pathway may participate in the homing of the BMSCs.