Reviews & Analysis

Imaging technologies drive discovery in cell biology. Innovations in microscopy hardware, imaging methods and computational analysis of large-scale, complex datasets can increase imaging resolution, definition and allow access to new biology. We asked experts at the leading edge of biological imaging what they are most excited about when it comes to microscopy in cell biology and what challenges need to be overcome to reach these goals.

Primary cilia transduce cues, including Hedgehog (Hh) signals, and possess doublet microtubules that interact with kinesin motors. The kinesin KIF7 is important for Hh signalling and binds to GLI transcription factors. Haque et al. reveal that, surprisingly, GLI proteins bind a DNA-like part of KIF7 to promote their accumulation at the ciliary tip.

Intrinsically disordered regions are a ubiquitous class of protein domains that lack a fixed 3D structure. Here, an evolutionarily conserved family of disordered CO₂ sensors has been discovered, expanding the growing repertoire of disordered regions that respond to changes in the cellular environment.

In Caenorhabditis elegans, RNAi-initiated gene silencing can persist for multiple generations. A study shows that this heritable silencing requires parallel contributions of both a nuclear transcriptional silencing pathway and perinuclear condensate-localized poly(UG)-tailed transcripts to produce abundant germline siRNAs in adult progeny.

Multiple methods for deriving human cortical organoids have been established in the past decade. A study now systematically compares patterning strategies and shows that combined WNT and dual SMAD inhibition is superior to dual SMAD inhibition alone in inducing robust cortical identity in 3D human pluripotent stem-cell aggregates.

Human naive pluripotent stem cells are generally believed to possess an unrestricted capacity to differentiate into both embryonic and extraembryonic lineages. However, two new studies now uncover a role for the Polycomb repressive complex 2 (PRC2) as a lineage gatekeeper that shields the potency of these cells.

Le et al. review various technologies for imaging RNAs in fixed and live cells and the biological insights gained from these technologies.

The lysosome is an essential organelle that degrades extra- and intra-cellular components and acts as a signaling hub. A study in Caenorhabditis elegans now shows that the lysosome mediates inter-tissue communication from periphery to neurons to regulate lifespan via fatty acid breakdown and secretion.

The nuclear pore complex (NPC) regulates transport of macromolecules into and out of the nucleus. A study now shows that mechanical force applied on the nucleus affects the transport rates across the NPC diffusion barrier, modulating the nuclear localization of certain cargos.

Fibroblasts become activated during wound repair and rapidly return to a ‘resting’ state, and are thus critical for normal tissue homeostasis and tumour development. A new study now reveals an important pro-tumorigenic role for the stress response in cancer-associated fibroblasts that may offer a new opportunity to limit tumour progression.

Unfried and Ulitsky discuss recent advances in understanding how long noncoding RNAs expressed at much lower levels compared with their targets or cofactors overcome the stoichiometric disadvantages and exert their cellular functions.

Although cardiac cell therapy has been intensely studied, the high expectations are still an unmet goal. A study now characterizes the translational potential and mode of action of human ventricular progenitors (HVPs) derived from embryonic stem cells, as a source for cardiac cell therapy.

Cytosolic DNA sensing by the cGAS–STING pathway is critical for sustaining an innate immune defense program. A new study shows that the cGAS–STING pathway signals by a non-canonical mechanism to control protein translation through the unfolded protein response sensor PERK, and thereby contributes to cellular senescence and organ fibrosis.

Phosphoinositide signalling regulates cellular processes and is hijacked by pathogens. Classically, phosphoinositides are produced by kinase- and phosphatase-catalysed reactions. A study now reveals an unprecedented, kinase- and ATP-free synthesis of PtdIns(3,4)P₂ via a phosphotransferase mechanism during bacterial infection.

Organic acidurias are inherited disorders that can severely affect mitochondria. A study in Caenorhabditis elegans suggests that binding of a toxic metabolite to a factor crucial for mitochondrial structure may contribute to disease mechanisms.

Shi et al. discuss recent approaches for the discovery of small noncoding RNAs (sncRNAs), limitations associated with sncRNA expression analyses, and emerging methods for direct and simultaneous detection of multiple RNA modifications.

Overload of proteasomal clearance triggers formation of a large protein inclusion called the aggresome, which shares similarities with protein aggregates seen in neurodegenerative diseases such as Huntington’s. A new study uncovers how centrosome and centriolar satellite components facilitate stepwise assembly of aggresomes.

Biomolecular condensation has emerged as a fundamental mechanism for cellular organization, but less is known about the regulation of condensate subcellular location and size. A new study reports that membrane tethering of protein and RNA directly influences the assembly, size and material properties of ribonucleic condensates.

Epithelial to mesenchymal transitions (EMTs) drive cancer metastases. A series of single cell analyses now reveal this change in state is not binary and that two epigenetic complexes govern the convertibility of epithelial cells to mesenchymal states that are differentially conducive to metastasis.

Necrosomes formed by RIPK1–RIPK3 mediate necroptosis. Super-resolution microscopy identifies the architectural features of necrosomes and provides mechanistic insights into the signalling from RIPK1 to RIPK3 when RIPK1 is activated to mediate necroptosis, and from RIPK3 to RIPK1 when RIPK3 is inhibited to mediate apoptosis.