Heat resilience in embryonic zebrafish revealed using an in vivo stress granule reporter

Application of stress granule core element G3BP1 in various diseases: A review

Ras-GTPase-activating protein-binding protein 1 (G3BP1) is a core component and crucial regulatory switch in stress granules (SGs). When the concentration of free RNA within cells increases, it can trigger RNA-dependent liquid-liquid phase separation (LLPS) with G3BP1 as the core, thereby forming SGs that affect cell survival or death. In addition, G3BP1 interacts with various host proteins to regulate the expression of SGs. As a multifunctional binding protein, G3BP1 has diverse biological functions, influencing cell proliferation, differentiation, apoptosis, and RNA metabolism and serving as a crucial regulator in signaling pathways such as Rac1-PAK1, TSC-mTORC1, NF-κB, and STAT3. Therefore, it plays a significant role in the regulation of neurodegenerative diseases, myocardial hypertrophy, and congenital immunity, and is involved in the proliferation, invasion, and metastasis of cancer cells. G3BP1 is an important antiviral factor that interacts with viral proteins, and regulates SG assembly to exert antiviral effects. This article focuses on the recent discoveries and progress of G3BP1 in biology, including its structure and function, regulation of SG formation and dissolution, and its relationships with non-neoplastic diseases, tumors, and viruses.

Neurodevelopmental disorders: 2023 update

Several advances in the field of neurodevelopmental diseases (NDDs) have been reported by 2022. Of course, NDDs comprise a diverse group of disorders, most of which with different aetiologies. However, owing to the development and consolidation of technological approaches, such as proteomics and RNA-sequencing, and to the improvement of brain organoids along with the introduction of artificial intelligence (AI) for biodata analysis, in 2022 new aetiological mechanisms for some NDDs have been proposed. Here, we present hints of some of these findings. For instance, centrioles regulate neuronal migration and could be behind the aetiology of periventricular heterotopia; also, the accumulation of misfolded proteins could explain the neurological effects in COVID-19 patients; and, autism spectrum disorders (ASD) could be the expression of altered cortical arealization. We also cover other interesting aspects as the description of a new NDD characterized by deregulation of genes involved in stress granule (SG) assemblies, or the description of a newly discovered neural progenitor that explains the different phenotypes of tumours and cortical tubers in tuberous sclerosis complex (TSC) disease; and how it is possible to decipher the aetiology of sudden unexplained death in childhood (SUDC) or improve the diagnosis of cortical malformations using formalin-fixed paraffin-embedded samples.

De novo variants in genes regulating stress granule assembly associate with neurodevelopmental disorders

Stress granules (SGs) are cytoplasmic assemblies in response to a variety of stressors. We report a new neurodevelopmental disorder (NDD) with common features of language problems, intellectual disability, and behavioral issues caused by de novo likely gene-disruptive variants in UBAP2L, which encodes an essential regulator of SG assembly. Ubap2l haploinsufficiency in mouse led to social and cognitive impairments accompanied by disrupted neurogenesis and reduced SG formation during early brain development. On the basis of data from 40,853 individuals with NDDs, we report a nominally significant excess of de novo variants within 29 genes that are not implicated in NDDs, including 3 essential genes (G3BP1, G3BP2, and UBAP2L) in the core SG interaction network. We validated that NDD-related de novo variants in newly implicated and known NDD genes, such as CAPRIN1, disrupt the interaction of the core SG network and interfere with SG formation. Together, our findings suggest the common SG pathology in NDDs.

Monitoring Virus-Induced Stress Granule Dynamics Using Long-Term Live-Cell Imaging

The integrated stress response is a highly regulated signaling cascade that allows cells to react to a variety of external and internal stimuli. Activation of different stress-responsive kinases leads to the phosphorylation of their common downstream target, the eukaryotic translation initiation factor 2 alpha (eIF2α), which is a critical component of functional translation preinitiation complexes. As a consequence, stalled ribonucleoprotein complexes accumulate in the cytoplasm and condense into microscopically visible cytoplasmic stress granules (SGs). Over the past years, numerous microscopy approaches have been developed to study the spatiotemporal control of SG formation in response to a variety of stressors. Here, we apply long-term live-cell microscopy to monitor the dynamic cellular stress response triggered by infection with chronic hepatitis C virus (HCV) at single-cell level and study the behavior of infected cells that repeatedly switch between a stressed and unstressed state. We describe in detail the engineering of fluorescent SG-reporter cells expressing enhanced yellow fluorescent protein (YFP)-tagged T cell internal antigen 1 (TIA-1) using lentiviral delivery, as well as the production of mCherry-tagged HCV trans-complemented particles, which allow live tracking of SG assembly and disassembly, SG number and size in single infected cells over time.

Studying molecular interactions in the intact organism: fluorescence correlation spectroscopy in the living zebrafish embryo

Cell behaviour and function is determined through the interactions of a multitude of molecules working in concert. To observe these molecular dynamics, biophysical studies have been developed that track single interactions. Fluorescence correlation spectroscopy (FCS) is an optical biophysical technique that non-invasively resolves single molecules through recording the signal intensity at the femtolitre scale. However, recording the behaviour of these biomolecules using in vitro-based assays often fails to recapitulate the full range of variables in vivo that directly confer dynamics. Therefore, there has been an increasing interest in observing the state of these biomolecules within living organisms such as the zebrafish Danio rerio. In this review, we explore the advancements of FCS within the zebrafish and compare and contrast these findings to those found in vitro.

Light-triggered switching of liposome surface charge directs delivery of membrane impermeable payloads in vivo

Surface charge plays a fundamental role in determining the fate of a nanoparticle, and any encapsulated contents, in vivo. Herein, we describe, and visualise in real time, light-triggered switching of liposome surface charge, from neutral to cationic, in situ and in vivo (embryonic zebrafish). Prior to light activation, intravenously administered liposomes, composed of just two lipid reagents, freely circulate and successfully evade innate immune cells present in the fish. Upon in situ irradiation and surface charge switching, however, liposomes rapidly adsorb to, and are taken up by, endothelial cells and/or are phagocytosed by blood resident macrophages. Coupling complete external control of nanoparticle targeting together with the intracellular delivery of encapsulated (and membrane impermeable) cargos, these compositionally simple liposomes are proof that advanced nanoparticle function in vivo does not require increased design complexity but rather a thorough understanding of the fundamental nano-bio interactions involved.

First person – Ruiqi Wang

First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping early-career researchers promote themselves alongside their papers. Ruiqi Wang is first author on ‘Heat resilience in embryonic zebrafish revealed using an in vivo stress granule reporter’, published in JCS. Ruiqi is an assistant technologist in the lab of Jin Xu at Chinese Academy of Sciences, Shanghai, People's Republic of China, investigating non-invasive ways to cure neurodegenerative disease, and the relationships among circadian, stress granule and neurodegenerative diseases.