Microtubules are key components of the eukaryotic cytoskeleton. These stiff polymers often span the entire cell, provide structural support, and act as tracks for long-distance transport and force generators. Their organisation underlies the logistics of intracellular cargo transport, resistance to compressive loads, and polarity factor signalling. Microtubules are intrinsically dynamic and many factors that bind to the inside, outside, and ends of the microtubule modulate their properties. Passive crosslinkers can bundle two microtubules or align microtubules to the cell cortex and other cytoskeletal filaments, while molecular motors slide microtubules relative to each other, generating extensile or contractile forces, coalesce microtubule ends into asters, position and move microtubule superstructures within the cell, or drive bulk cytoplasmic flows. This review will summarise recent progress in our understanding of how microtubule organisers function and are regulated, which has been made possible through technical advances in structural biology and optical microscopy, increasingly complex reconstituted systems and insights from diverse cellular systems.
Adult stem cells reside within specialized niches that provide the local instructions needed to sustain regenerative fitness. Since the recognition that stem cells are not autonomous, the concept of the niche has widened from a local collection of supportive cells into a landscape of combinatorial microenvironments that stem cells help build rather than simply inhabit. Advances in molecular, genetic and deep imaging approaches and engineered organoid systems have shown these microenvironments to be far more diverse and dynamic than once appreciated. In this review, we consider how diverse cellular components build the stem cell niche across tissues, and how a growing set of non-cellular factors, from mechanical forces to metabolites, work alongside them to govern stem cell fate and regenerative capacity. We then ask how combinatorial niche interactions, spatial organization and reciprocal communication with stem cells support the diverse functions stem cells carry out across the lifespan. Understanding the niche as a dynamic and evolving system, rather than a fixed anatomical unit, promises insight into the fundamental mechanisms of developmental, regenerative, and pathologic stem cell function, with substantial implications for regenerative medicine.
The survival of sexually reproducing species depends on the production of competent germ cells. Before meiotic entry, the expansion of specialized totipotent cells is essential for establishing a sufficient germ cell pool during gametogenesis. Growing evidence suggests that the mechanisms guiding the earliest stages of germ cell development are evolutionarily conserved across invertebrate and vertebrate species. A defining feature of germ cell maturation is the formation of germline cysts, interconnected groups of germ cells that undergo mitotic divisions to expand the gamete progenitor pool. A second characteristic now emerging is the formation of a specialized, yet still enigmatic organelle known as the fusome. First characterized in insects and more recently identified in vertebrates, the fusome represents an underexplored component of germline development. Here, we review recent advances in fusome biology with particular focus on insights from female Drosophila, where its structure and function have been most extensively characterized.
Stem cell identity has traditionally been viewed through the lens of transcriptional and metabolic programs. Recent work has revealed an additional layer of complexity: the plasma membrane and intracellular organelles maintain compartment-specific membrane potentials, pH gradients, and ion dynamics that can influence stemness and fate. In this review, we synthesize recent advances identified across diverse stem cell populations to highlight convergent and divergent bioelectric mechanisms driving cell fate decisions. We explore how plasma membrane mechanosensors convert physical cues into internal ionic signals. We next examine the influence of lysosomal pH on metabolic programming to support cell transitions. We then discuss how differences in mitochondrial membrane potentials (MMPs) and inheritance, endoplasmic reticulum (ER)-calcium handling, and ER-mitochondrial coupling influence lineage commitment. Finally, we consider how nuclear ionic and mechano-osmotic conditions may shape chromatin organization and transcriptional competence. Collectively, these studies position the plasma membrane and organelles as coupled nodes within an integrated bioelectric network. This emerging framework identifies new questions about how compartment-specific ionic states are coordinated and suggests potential strategies for therapeutically redirecting cell fate.
Recent studies have revealed that cytokinetic abscission is developmentally regulated in a wide range of stem cell systems. Rather than a constitutive endpoint of cell division, abscission can be delayed, accelerated, or arrested altogether depending on developmental context. In this review, we highlight recent advances from Drosophila and mammalian models showing how stem cells modulate their link with daughter cells to regulate cell fate decisions and tissue development. Work in Drosophila germline and neural stem cells has uncovered how conserved regulators of cytokinesis, including endosomal sorting complex required for transport (ESCRT) proteins, mitotic kinases, and ubiquitin-dependent pathways, control intercellular bridge stability, midbody dynamics, and cell fate specification. In parallel, studies in mammalian embryonic and neural stem cells have linked delayed abscission to the maintenance of pluripotency, symmetric fate outcomes, and the regulation of differentiation. Emerging evidence also suggests that persistent intercellular bridges and postabscission midbody remnants can contribute to developmental signalling and stem cell behaviour. Together, these findings support a model in which stem cells actively regulate abscission to coordinate cell-cycle progression, fate transitions, and tissue organization.
